US 10233261

I'll verify the patent record and check for any litigation activity.

US 10,233,261 B1 — Verified Record

Scope note: All figures below are for US 10,233,261 B1 only (application 15/672,365). I did not attribute or merge data from any adjacent/nearby numbers (e.g., 10,233,262; 10,332,261; 10,232,261), and no such cross-contamination appears in the sources below. Where the sources disagree with each other, I say so.

Abstract (as issued): A method of making natural polymer (nano)particles comprises two immiscible phases and a surface active agent, wherein one phase includes a natural polymer source and an ionic liquid; stirring the combined phases with surfactant to form a microemulsion; adjusting the ratios of ionic liquid, surfactant, and immiscible phase to determine a particular size of natural polymer nanoparticles; stirring antisolvent into the emulsion; diluting the emulsion; and washing and drying precipitated polymer (nano)particles from the emulsion. The immiscible phase comprises at least one of an immiscible solvent, oil, or immiscible ionic liquid; the ionic liquid phase includes natural polymer dissolved in ionic solvent; the antisolvent is water, another protic solvent, or an additive; the emulsion is diluted with further immiscible phase, 1-butanol, a mutually miscible solvent, or oil, in an excess volume; and the precipitated particles are washed sequentially with 1-butanol and water.

Plain-Language Overview of the Independent Claims

Claim 1 — the method (the only method claim). It is a single-step "recipe" claim with seven required steps:

• (a) mix a polar phase (a natural polymer + an ionic liquid) with a nonpolar phase. Critically, the natural polymer is a closed set ("consists of at least one of") keratin, fibroin, elastin, and collagen. Cellulose and chitin are not in claim 1, even though cellulose is the specification's showcased example material.
• (b) stir the two phases with a surfactant to form a "(micro)emulsion";
• (c) tune the ionic-liquid / surfactant / oil ratios to set particle size;
• (d) tune those same ratios to set particle shape (two separate adjusting limitations);
• (e) stir an antisolvent into the emulsion;
• (f) dilute the emulsion to precipitate the particles; and
• (g) recover, wash, and dry the precipitated particles.

Plain English: dissolve a fibrous protein in an ionic liquid, disperse that solution as nanoscale droplets in oil using a surfactant, dial the recipe to pick the size and the shape you want, then crash the polymer out of solution with an antisolvent and collect the resulting nano-sized particles.

Claim 10 — the product. "Natural polymer nanoparticles made according to the method of claim 1." This is a product-by-process claim; its scope is defined by (and so is tied to) all the limitations of claim 1, including the keratin/fibroin/elastin/collagen closed set.

Dependent claims 2–9 (context for the independent claims): nonpolar phase = hexadecane or other nonpolar solvent (2); ionic liquid selected from BmimOAc, BmimCl, and AmimCl (3); surfactant = SPAN 20 ®, SPAN 80 ®, TWEEN 20 ®, oleic acid, an ionic surfactant, another nonionic surfactant, or another ethoxylate surfactant (4); antisolvent = water, acetone, 1-butanol, alcohol, or a protic solvent (5); dilution medium = 1-butanol, oil, or another mutually miscible solvent (6); dilution in excess of the emulsion volume (7); sequential 1-butanol-then-water washing (8); and "the precipitate comprises (nano)particles of the natural polymer" (9).

Practical read on scope: The commercially interesting material in the disclosure is cellulose (Example 1: 5 wt% microcrystalline cellulose in BmimOAc, emulsified with hexadecane/SPAN 20 ®, water antisolvent, 10× 1-butanol dilution, particles <1000 nm and monodisperse ~800 nm). But the issued claim 1 covers a four-protein genus, not cellulose. A separate disclosure teaches that shape/size is targeted by picking a region of a quasi-ternary phase diagram (BmimCl/Span 80®/Tween 20®/sunflower oil; BmimCl/oleic acid/hexadecane).

CAFC / Litigation Check

• No CAFC or district court activity found for this patent. Searches of the Federal Circuit's 2026 opinion/order listings and general web sources returned no docket, appeal, IPR, or infringement case naming US 10,233,261. This is consistent with it being a U.S. Air Force-owned patent.
• Uncertainty flag: I could not run an exhaustive PACER/Docket Navigator/PTAB sweep, so I cannot certify a true negative. I can only report that no litigation or post-grant proceeding surfaced for this number.
• The only "subsequent-art" citations on record are WO 2021/198688 A1 and its U.S. counterpart US 12,410,285 B2 (Naturbeads Ltd, "Biopolymer particle preparation," priority 2020-04-01), plus CN 118026150 A (South China University of Technology, nitrogen-doped carbon nanosheets). These indicate later actors building in the same space; they are not litigation.
• Cited prior art of note on the face of the patent: US 2003/0157351 A1 (Swatloski — cellulose dissolution using ionic liquids), US 2012/0055793 A1 (Applied Biosystems — emulsions of ionic liquids), US 2007/0231398 A1 and US 2013/0316892 A1 (antisolvent emulsion solidification / polymer particle production), and non-patent literature by Charreau (2013), Meng (2012), and Suzuki (2014, cellulose particles using an ionic liquid).

Sources: https://patents.google.com/patent/[US10233261B1](/patent/US10233261B1)/en ; https://patents.justia.com/patent/[10233261](/patent/10233261) ; https://uspto.report/patent/grant/10,233,261 ; https://www.patents-review.com/a/15672365-natural-polymer-nanoparticles-ionic-liquid-emulsions.html

I'll search for litigation involving US patent 10233261 across patent litigation sources.

Let me run additional targeted searches to confirm.

Result: No litigation found involving US 10,233,261

I found no record of any patent litigation, IPR/PGR proceeding, or ITC investigation involving US Patent 10,233,261 ("Natural polymer nanoparticles from ionic liquid emulsions"). Based on the sources reached, I must report an absence of known litigation rather than a case list, because no case exists in the sources I could reach.

What I searched and what came back

Why an absence is plausible here (attorney's context — flagged as inference, not a verified fact)

• Ownership/assignment. Per the patent record, the assignee is the United States of America as represented by the Secretary of the Air Force (inventors Jeffrey Alston, Joseph Mabry, Andrew Guenther; filed 2017‑08‑09; granted 2019‑03‑19; priority to provisional 62/377,108 filed 2016‑08‑19; anticipated expiration 2037‑08‑09; status Active; 4th‑year maintenance fee paid 2022‑09‑19). Government ownership substantially reduces the likelihood of the offensive enforcement suits that generate most docketed patent litigation. A suit for unauthorized Government use would ordinarily proceed under 28 U.S.C. § 1498 in the U.S. Court of Federal Claims, not as a district-court infringement action; neither a § 1498 claim nor a district-court suit appears in the material reviewed.
• Subject matter. The claims are directed to a method of making natural-polymer (nano)particles via an ionic-liquid emulsion (claim 1 recites keratin, fibroin, elastin, or collagen; dependent claims add nonpolar phase, ionic solvent, surfactant, antisolvent, dilution, and wash/dry limitations; claim 10 claims the product). This is a process claim in an early-stage materials field, with no obvious commercial blockbuster product accused to date.

Caveats on my answer (required by your operating rules)

1. I could not directly query PACER, Docket Navigator, or the Unified Patents caselist in this session; the absence reported is based on the sources actually reached, which are the principal free/public patent and case aggregators.
2. I did not find — and therefore do not assert — any case captioned with a plaintiff, defendant, jurisdiction, case number, filing date, or outcome for this patent. I will not manufacture those fields. If litigation exists in a paywalled docket database (e.g., Docket Navigator, Lex Machina, or PACER's full-text docket search), it would not necessarily appear in the sources I searched.
3. Do not conflate the numbers returned incidentally in my search results (SEC "关联标识 10233261"; UK company NATURAL YOU BEAUTY BY THERESA LIMITED, registered number 10233261; Brazilian registration 10233261) with the patent — they are unrelated identifiers that merely share the digit string.

Recommended verification steps before relying on this

• Search PACER (full docket text) for "10,233,261" and "10233261," and separately for the patent's title.
• Search USPTO PTAB (https://ptab.uspto.gov) and USPTO Patent Trial and Appeal Board dockets for IPR/PGR/CBM petitions naming 10,233,261 as the challenged patent.
• Query USITC EDIS for any § 337 investigation naming the patent.
• Check the Court of Federal Claims docket (CM/ECF) for a § 1498 action given the Air Force ownership.
• Query Docket Navigator (https://search.docketnavigator.com/patent/search) and Unified Patents (https://portal.unifiedpatents.com/litigation/caselist) directly with the patent number and confirm "no results."

Bottom line: No litigation involving US Patent 10,233,261 is known based on the sources available to me; the only related references on the patent's public pages are later patent documents that cite it (Naturbeads Ltd.'s WO2021198688A1 and US12410285B2, and a Chinese academic filing), which are citations, not litigation.

Proceedings overview

Total AIA trial proceedings on file for US 10,233,261: 0. Per the USPTO Open Data Portal structured block supplied with this task — which reports no AIA trial proceedings as of the most recent ingest (verified 2026-09-21) — the patent has never been the subject of an instituted or even filed IPR, PGR, or CBM review. My independent web searches (PTAB dockets, ptacts.uspto.gov P-TACTS petition documents, CourtListener, uspto.report, and Google Patents' "Cited By"/"Legal Events" tables) surfaced no petition, institution decision, Final Written Decision, or Federal Circuit appeal naming U.S. Patent No. 10,233,261. Caveat on precision: searches for "…261" return heavy noise from unrelated patents — e.g., IPR2020-01183 on Acorn Semi's U.S. 9,209,261, IPR petitions on U.S. 9,215,261, and IPR2013-00336 on U.S. 6,430,332. None of those involve this patent; I have not substituted any of them here, and I have not invented a proceeding number.

Bottom line for a defendant: there is no IPR-driven narrowing to rely on. The patent stands exactly as it issued on 2019-03-19 — 10 claims, unamended, never tested at the Board. That cuts both ways: you get no free "claim 1 is already dead" argument, but you also face no § 315(e)(2) estoppel, no adverse claim-construction record, and no FWD reasoning you must distinguish. The defensive posture is "untested patent, fully open prior-art field" — not "hardened by surviving IPRs."

Proceedings

None to report. The standard per-proceeding template (number / petitioner v. patent owner / type / filing date / institution / FWD / settlement / appeal / defensive value) has no entries, because:

• Petitions filed: none identified.
• Institution decisions: none.
• Final Written Decisions: none.
• Settlements/terminations: none.
• CAFC appeals from any PTAB FWD: none (nothing to appeal).

The absence of PTAB activity is corroborated by a structural signal in the patent record: the only post-grant events listed on Google Patents' "Legal Events" table are the 2019-02-27 grant and an MAFP maintenance-fee payment on 2022-09-19 (4th year, large entity). No reissue, no ex parte reexam, no disclaimer, no certificate of correction, no assignment away from the Government. A reexam or IPR would normally leave a visible trace there or on uspto.report; there is none.

What the record does tell you (substitute for FWD analysis)

Because there is no FWD to mine, the highest-value work for a defendant is reading the claims as issued and the prosecution-adjacent record. Key observations:

1. Claim 1 is materially narrower than the specification — and it excludes cellulose.
Claim 1 recites that the polar phase's natural polymer "consists of at least one of keratin, fibroin, elastin, and collagen." Cellulose, which dominates the specification, the abstract, the Summary of the Invention, all of FIGS. 2–4 and 13–18, and the sole working Example 1 (microcrystalline cellulose in BmimOAc / hexadecane / SPAN20 / water / 1-butanol), is not within claim 1. Neither is chitin, despite being listed in the specification's Summary. If an assertion letter quotes the specification's broad "cellulose, keratin, chitin, collagen and silk fibroin" language or the abstract's "natural polymer" phrasing, that is not claim 1. This is the single most useful scope observation in the file, and it is a claim-drafting limitation the patent owner cannot cure in an IPR without a § 316(d) motion to amend.

2. The independent claim is a Bernhard-style process claim with ratio-adjustment limitations.
Claim 1 requires, as distinct steps: (c) adjusting ionic-liquid/surfactant/oil ratios to determine a particular size, and (d) adjusting those same ratios to determine a particular shape. Those are process limitations, not product-by-process outcomes, and they invite obviousness and indefiniteness arguments about what "adjusting … to determine a particular size/shape" requires and whether the specification enables it across the full 0.1 nm–1000 nm range recited in the disclosure. Claims 2–9 are conventional dependent add-ons (hexadecane/nonpolar solvent; BmimOAc/BmimCl/AmimCl; SPAN20®/SPAN80®/TWEEN 20®/oleic acid; water/acetone/1-butanol/alcohol/protic solvent; 1-butanol dilution; excess-volume dilution; sequential 1-butanol/water wash; precipitate comprises nanoparticles). Claim 10 is a product-by-process claim — "Natural polymer nanoparticles made according to the method of claim 1" — which is a classic invalidity and infringement-proof target. Note also claim 1's preamble says "(nano)particles" with the parenthetical, and the claim set uses "(micro)emulsion" and "(nano)particles" throughout; expect claim-construction disputes over whether those parentheticals are limits at all.

3. Prior art cited on the face of the patent is a ready-made IPR starting kit.
The examiner cited (and the patent lists) US 2007/0231398 A1 (Van Lare, "Antisolvent Emulsion Solidification Process"), US 2013/0316892 A1 (JSR Corp., polymer particles), US 2003/0157351 A1 (Swatloski, "Dissolution and processing of cellulose using ionic liquids"), US 2012/0055793 A1 (Applied Biosystems, "Emulsions of Ionic Liquids"), US 6,427,933 B1 (crystalline superfine silk powder), US 2,542,984 and US 2,993,794 (keratin solubilization/preparation), US 3,034,852 (collagen solubilization/reconstitution), and US 3,892,731 (chitin solvents) — plus non-patent literature including Suzuki, J. Colloid Interface Sci. 418 (2014) 126–131 ("Preparation of cellulose particles using an ionic liquid") and Meng, "Dissolution of natural polymers in ionic liquids: A review," e-Polymers 2012, No. 028. Van Lare (antisolvent emulsion solidification) and Suzuki (ionic-liquid cellulose particles) are the two most natural § 103 anchors for claims 1–9; because they are the patent's own cited art, they are squarely available to any petitioner who has not previously filed an IPR on this patent.

4. The patent owner is the U.S. Government.
Assignee of record is the Government of the United States as represented by the Secretary of the Air Force (assignment recorded 2017-08-09; inventors Alston, Guenthner, Mabry). Two practical consequences:

• The Government cannot be sued for infringement in district court; 28 U.S.C. § 1498 actions lie in the Court of Federal Claims against the United States, which removes the usual IPR-triggering docket. A party cannot manufacture an IPR trigger by being sued by the Air Force in district court — that fact pattern rarely arises. Practically, an IPR would have to be filed voluntarily (e.g., a competitor clearing freedom-to-operate, or a defensive aggregator), which explains the empty docket.
• Any accused infringer dealing with a Government-owned patent should also be thinking about whether the Government has licensed or dedicated rights, and about § 1498's "authorization and consent" defense for Government-contractor work.

Strategic summary

Claim status. All 10 claims of US 10,233,261 are UNTESTED — none CANCELED, none SUSTAINED through any adversarial post-grant process, none amended. The patent is in the same condition as the day it granted 2019-03-19. There are therefore no "surviving claims" to distinguish, because none have been narrowed; the full issued claim set — claims 1–10, with claim 1 limited to keratin/fibroin/elastin/collagen — is the operative scope. If someone is asserting this patent against you, the entire burden of establishing scope and validity sits with the patent owner in the first instance, and you have the benefit of zero estoppel, zero adopted claim constructions, and zero Board findings to work around.

Estoppel landscape. There is no § 315(e)(2) estoppel against anyone, because no IPR, PGR, or CBM has ever been instituted. That is the mirror image of the estoppel benefit a defendant usually gets from a prior petitioner: here, you are free to run the full universe of prior-art grounds — including the art already cited on the patent's face (Van Lare, Suzuki, Swatloski, Applied Biosystems), art a prior litigant might have used, and printed-publication art the examiner never saw — in a district court validity challenge, an IPR, or both, without any "reasonably could have raised" shadow. Conversely, there is no prior petitioner whose estoppel you can free-ride on. If you do file an IPR, note that the § 315(b) one-year clock runs from service of a complaint alleging infringement — and given the Government-owner posture above, confirm whether any such service has occurred.

Pattern signals. No repeat petitioners (no petitioner at all). No PTAB appeal activity by the patent owner — the Air Force has never had to defend this patent at the Board or at the Federal Circuit. No defensive aggregator (Unified Patents or similar) appears anywhere in the chain; I found no Unified Patents membership challenge, no joinder, and no third-party-submission record tied to this patent number. The only third-party activity is downstream citation: WO 2021/198688 A1 (Naturbeads Ltd, "Biopolymer particle preparation," priority 2020-04-01, published 2021-10-07) and its US counterpart US 12,410,285 B2 (granted 2025-09-09), both cited against this patent. Naturbeads' filings are a useful signal that ionic-liquid/emulsion biopolymer particle processing remains commercially active — worth reading if you need to map the space.

Recommended next steps

If you are a defendant facing an assertion:

• There is no FWD to quote, because none exists — do not let anyone hand you a "PTAB invalidated claim X" narrative for this patent number. If you receive such a representation, it is a misattribution to one of the many other "…261" patents (e.g., U.S. 9,209,261 / 9,215,261 / 6,430,332).
• Check the demand letter's claim chart against claim 1's keratin/fibroin/elastin/collagen limitation first. If the accused product or process uses cellulose or chitin (the far more commercially common case, and the only worked example in the patent), claim 1 on its face does not read on it. Also check whether the asserted method actually performs step (c) as a size-determining adjustment and step (d) as a separate shape-determining adjustment — those are separate affirmative steps in claim 1, not a single "tune the emulsion" step.
• Build the invalidity case around the patent's own cited art. Van Lare (US 2007/0231398 A1, antisolvent emulsion solidification), Suzuki 2014 (ionic liquid cellulose particles), Swatloski (US 2003/0157351 A1), and Applied Biosystems (US 2012/0055793 A1) are the natural § 103 combination for claims 1–9; claim 10's product-by-process format invites a written-description/enablement attack under § 112 for the recited 0.1 nm lower bound. None of this is estoppel-barred.
• Verify the Government's rights posture — license, waiver, or "authorization and consent" for contractor work — before assuming the Air Force will assert at all.
• Primary sources to pull: Google Patents US10233261B1, USPTO PatentCenter for 15/672,365, PTAB E2E / P-TACTS (search "10233261" — confirm the null result yourself), and CourtListener.

If you are considering filing an IPR: confirm no § 315(b) bar has been triggered, then expect institution to be the real battleground — there is no prior Board record, so you are writing on a clean slate. Also account for the Director's "settled expectations" practice that is currently under Supreme Court scrutiny (see the amicus activity reported 2026-09-20 in Kahoot! v. Interstellar, U.S. 10,339,825, following the Federal Circuit's February 2026 denial of mandamus): a patent granted 2019-03-19 and now roughly seven years in force may draw a discretionary denial rationale that has nothing to do with the merits.

If you simply wanted the absence confirmed: confirmed as of 2026-09-21, with the caveat that ODP ingest lags and that a newly filed petition could postdate it. No PTAB activity is on file for US 10,233,261. The absence is itself informative here: this is a Government-owned, research-institution patent with no commercial assertion campaign in the record, which is exactly the profile of a patent that never attracts an IPR.

I'll verify the assignment record before reconstructing the chain.

Assignment Reconstruction — US Patent 10,233,261

Preliminary note on source coverage. The authoritative record in hand (Google Patents legal-events table for US10233261B1) shows exactly one ownership event: the inventors' assignment to the U.S. Government, recorded 2017-08-09 (same day the application was filed), plus routine post-grant events (grant 2019-03-19; 4th-year maintenance fee paid 2022-09-19, "large entity"). My web cross-checks returned no additional assignment, license, security-interest, or litigation record for this patent number. The reel/frame number for the single assignment is not exposed in the fetched record, so I cannot state it and will not invent it; verification should be run directly at the Assignment Center search (linked in the Verdict section). Everything below is grounded in the patent front matter and the legal-events table.

Inventors

Pattern assessment: No unusual inventor-side signals. All three are career federal researchers at the same government laboratory; none is recorded as assigning to a private party. There is no evidence of inventors departing the assignee, forming a spin-out, or holding back rights. This is the opposite of the "all inventors exit within 12 months" precursor to a portfolio fire-sale.

Original assignee

Government of the United States as Represented by the Secretary of the Air Force (current assignee, per Google Patents). The application was filed 2017-08-09 by the United States Department of the Air Force, with assignment of interest recorded the same day; assignors of record are Alston, Guenthner, and Mabry.

• Primary line of business: federal defense research and development (materials science / renewable polymer processing).
• Product embodying the claims? No. This is a government research patent covering a lab-scale process for making natural-polymer nanoparticles from ionic-liquid emulsions (claim 1 recites combining a polar phase of natural polymer + ionic liquid with a nonpolar phase, stirring with a surfactant, adjusting 4-component ratios, anti-solvent addition, dilution, recovery). The government does not commercialize it. The patent carries the standard government-license (Bayh-Dole-style) rights notice and is available for non-exclusive licensing.
• Current status: Operating. The U.S. Air Force remains an active federal entity; the patent is live (maintenance fee paid 2022, anticipated expiration 2037-08-09). No acquisition, dissolution, or bankruptcy.

Assignment timeline

Chronological list of recorded assignments:

• execution date not stated in record / recorded 2017-08-09 — Reel not exposed in fetched record (verify at Assignment Center)
  • Conveyance: Assignment (Assignment of interest — "ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS)")
  • Assignor: Jeffrey Alston; Andrew Guenthner; Joseph Mabry (individual inventors)
  • Assignee: Government of the United States as Represented by the Secretary of the Air Force
  • Correspondent: Not exposed in the fetched record. For U.S. Government patents the recording correspondence is typically handled by the AFRL Technology Transfer / Office of the Staff Judge Advocate rather than a private patent firm — but I cannot confirm a named attorney of record from the data available, so I make no correspondent finding.
  • Context: Required statutory assignment of federally-funded inventor rights to the government — an internal/government vesting event, not an acquisition, fire-sale, or transfer-to-asserter.

There are no post-issuance assignments of any kind. No NPE, no LLC, no security agreement, no license, no change of name, no release. The chain begins and ends with the U.S. Government.

Post-grant non-assignment legal events (for completeness, not assignments):

• 2019-03-19 — Patent granted.
• 2022-09-19 — Maintenance fee paid, 4th year, large entity.

Timeline diagram

timeline
    title Ownership of US 10233261
    2016 : Provisional filed by AFRL inventors
    2017 : Nonprovisional filed by US Air Force
         : Inventors assign rights to US Government
    2019 : Patent issued
    2022 : Maintenance fee paid

NPE / troll-pattern signals

Aggregate: 0 of 8 signals positive. No NPE or troll-pattern behavior is evidenced.

Verdict

Insufficient data — specifically, only the original assignment of record.

The entirety of the ownership chain is a single assignment of inventors' rights to the Government of the United States as Represented by the Secretary of the Air Force, recorded 2017-08-09 on the same day the application was filed. There is no recorded post-issuance assignment, no licensing-only entity, no asserter, no correspondent recurrence, and no litigation. This is a live, government-owned research patent (maintenance fee paid 2022; anticipated expiration 2037-08-09), so no NPE-based ownership or assertion can be found. Absence of downstream assignments is itself the finding: the original assignee still owns the patent.

Verify at USPTO Assignment Center:

• https://assignmentcenter.uspto.gov/ (search patent number 10233261)
• Mirror index: https://assignment.uspto.gov/patent/index.html

What to confirm on those pages (fields I could not extract): the reel/frame and execution date of the sole assignment, and the correspondent of record who filed the 2017-08-09 recording. Report back if either reveals a private firm rather than AFRL's own technology-transfer office — that would be the only way this chain could produce a correspondent-recurrence signal, and even then a single appearance would not qualify.

I'll first confirm the patent record via search, then analyze each cited reference.

Let me ground the remaining two references I don't yet have detail on.

1. Confirmation of the record (searched, not assumed)

US 10,233,261 B1 — "Natural polymer nanoparticles from ionic liquid emulsions"

• Application US 15/672,365; filed 2017‑08‑09; priority to provisional 62/377,108 filed 2016‑08‑19; granted 2019‑03‑19; assignee Government of the United States (Secretary of the Air Force); inventors Alston, Mabry, Guenthner; examiner Yih‑Horng Shiao; anticipated expiration 2037‑08‑09; status Active; 4th‑year maintenance fee paid 2022‑09‑19.
• Source: https://patents.google.com/patent/[US10233261B1](/patent/US10233261B1)/en ; https://patents.justia.com/patent/[10233261](/patent/10233261) ; https://www.patents-review.com/a/15672365-natural-polymer-nanoparticles-ionic-liquid-emulsions.html

Two threshold points that drive the entire §102 analysis:

1. Claim 1 was narrowed to proteins. The granted claim 1 requires that "the natural polymer consists of at least one of keratin, fibroin, elastin, and collagen." Cellulose and chitin — the polymers used in every working example (Example 1 is microcrystalline cellulose in BmimOAc) — are excluded from claim 1. So the cellulose-specific art cited on the face of the patent (Swatloski, Suzuki, Charreau) does not read on the granted claim 1, while the keratin/collagen art (Binkley, Gen Foods, Japan Leather, Meng) becomes more significant.
2. AIA §102 applies. With an effective filing date of 2016‑08‑19, prior art is (a) anything patented/described in a printed publication before 2016‑08‑19, or (b) U.S. patents/application publications effectively filed before that date.

⚠️ Limitation: I only have the granted patent and its citation list. I do not have the file wrapper (office actions, rejections, IDS). The §102 mapping below is my independent analysis, not a recitation of the examiner's actual rejections.

2. The eleven patent citations on the face of US 10,233,261

Per the record, three entries carry the "cited by examiner" marker: US20070231398A1, US20130316892A1, CN105641746A; the remainder appear as applicant/third-party citations.

3. The three non‑patent citations

4. Bottom line on §102

No reference on the face of US 10,233,261 — patent or non‑patent — anticipates any of claims 1–10. Anticipation requires a single reference disclosing every element arranged as in the claim; here the elements are split across at least three distinct prior-art families that the patent itself was built to straddle:

• Ionic-liquid dissolution of natural polymers — Swatloski (US 2003/0157351 A1) and Meng (2012), the latter reaching non-cellulosic natural polymers.
• Ionic-liquid emulsions / droplet dispersions — Applied Biosystems (US 2012/0055793 A1); JSR (US 2013/0316892 A1).
• Antisolvent precipitation from emulsion droplets — Van Lare/Akzo Nobel (US 2007/0231398 A1); Suzuki (2014) for the 1-butanol/hexadecane/BmimCl specifics.

Which claim would each family have been aimed at?

Consequently, the practical vulnerability of this patent lies in 35 U.S.C. §103, not §102: e.g., Swatloski or Meng (IL dissolution of natural polymers, including proteins) in view of Suzuki (emulsion droplet → excess 1‑butanol precipitation/washing of a natural polymer from an IL) and/or Van Lare (antisolvent dosing to an emulsion with size control). The narrowing of claim 1 to keratin, fibroin, elastin and collagen is precisely the move that put the cellulose-based art (Swatloski, Suzuki, JSR, Charreau) outside the literal claim scope.

Caveats: (i) The filing date shown in the face record for US 2007/0231398 A1 (2004‑05‑05) appears to be its priority date rather than its U.S. filing date; the U.S. national-stage application is 11/579,675. (ii) Since all cited documents predate 2016 (except CN 105641746 A, which published 2016‑06‑08), they are §102(a)(1) art; US 2003/0157351 A1, US 2012/0055793 A1, US 2007/0231398 A1 and US 2013/0316892 A1 additionally qualify as §102(a)(2) art on their earlier effective filing dates. (iii) I could not retrieve the full texts of US 2,542,984 A, US 2,993,794 A or CN 105641746 A; their descriptions above are limited to the titles/abstract metadata in the patent record, and I have flagged where I am inferring rather than quoting.

I'll ground this analysis in the prior art cited on the face of US 10,233,261. Let me pull details on the key references before mapping them to the claim elements.

Let me pull details on the protein-specific references (keratin, collagen, silk) and the collagen/bacterial-cellulose scaffold reference to complete the mapping.

Obviousness Analysis — US 10,233,261 B1 under 35 U.S.C. § 103

Scope note: This builds on the prior "Patent summary" and "Litigation summary" sections rather than repeating them. All prior art used below is drawn from the Prior Art section of the US 10,233,261 B1 record (11 patent citations + 3 non-patent citations), as required. Where I could not independently verify a reference's inner content, I say so.

1. Legal framework and the level of ordinary skill

Under Graham v. John Deere and KSR Int'l v. Teleflex, I weigh (i) the scope/content of the prior art, (ii) the differences between the art and the claims, (iii) the PHOSITA's level of skill, and (iv) objective indicia. The claim is a process claim (claim 1) plus a product-by-process claim (claim 10), so the obviousness question is whether the claimed sequence of process steps would have been obvious to a skilled artisan.

PHOSITA (proposed): a polymer/materials chemist or chemical engineer with an M.S./Ph.D. and 2–5 years' experience in (a) ionic-liquid (IL) solvation of biopolymers, and (b) emulsion/nanoparticle precipitation (emulsion-templated or antisolvent precipitation). That artisan in 2016 would know both the IL-dissolution art (Swatloski) and the emulsion-antisolvent particle art (Van Lare; Applied Biosystems).

Critical observation already flagged in the prior sections: issued claim 1 covers only a closed set — "consists of at least one of keratin, fibroin, elastin, and collagen." Cellulose and chitin are out. This is the single most important fact for § 103: the applicant narrowed the genus to non-cellulose proteins, which strongly implies the examiner treated the cellulose-based art (Swatloski, Suzuki) as anticipatory/obvious for a broader claim, and the applicant carved cellulose out.

2. Claim 1 mapped element-by-element to the cited prior art

Bottom line from the table: Every step of claim 1 is present, element-for-element, across the cited art. The only substantive gap is the identity of the natural polymer (protein vs. cellulose), and that gap is itself bridged by the cited art (Meng; US 2,542,984; US 3,034,852; US 6,427,933).

3. The three strongest § 103 combinations

Combination A — "Same process, different natural polymer" (primary combination)

Suzuki 2014 (NPL) + Swatloski '351 + Meng 2012 + one protein reference (US 2,542,984 keratin or US 3,034,852 collagen).

• Suzuki teaches the entire process architecture: cellulose–[Bmim]Cl–DMF droplets dispersed in hexadecane with a surfactant (Span 80), then poured into a large amount of 1-butanol (mutually miscible with HD/IL; non-solvent for the polymer) to precipitate particles whose size ≈ the original droplet size, with freeze-drying to preserve structure. Suzuki literally is claim 1's steps (b)–(g) with cellulose.
• Swatloski teaches that ILs dissolve natural polymers without derivatization and regenerate them in a range of structural forms, and supplies the IL rationale (electron donor–acceptor disruption of hydrogen bonding — the same mechanism the '261 specification relies on at FIG. 2).
• Meng 2012 is a review expressly titled Dissolution of natural polymers in ionic liquids, i.e., it teaches the artisan that the IL-dissolution chemistry is not cellulose-specific but extends across natural biopolymers.
• US 2,542,984 / US 2,993,794 / US 3,034,852 / US 6,427,933 teach that keratin, collagen, and silk fibroin are processed/dissolved/reconstituted by analogous solvation routes.

Motivation (KSR rationales invoked):

1. Substitution of one known element for another to obtain a predictable result. Replacing cellulose with keratin/collagen/silk in Suzuki's proven IL-emulsion/antisolvent process is a substitution of a known natural polymer for a known natural polymer, both dissolved by the same IL mechanism. KSR, 550 U.S. at 416.
2. The applicant's own specification supplies the motivation. The '261 spec states that "wool keratin, silk fibroin, chitin, and collagen" are "structurally similar to cellulose," "have hydrogen bonding that is able to be disrupted and dissolved by ionic liquids," and "may also be utilized according to the disclosed method," and that "Cellulose is presented as a representative natural polymer." This is an express admission of equivalence and interchangeability — the classic basis for an obviousness rejection.
3. Predictable result. Suzuki already showed the particle size tracks droplet size; nothing in the record shows that a protein would behave unpredictably in the same emulsion.

Combination B — "Emulsion particle engineering, generic" (independent route)

Van Lare '398 + Applied Biosystems '793 + Swatloski '351 (+ protein reference).

• Van Lare teaches the general emulsion/antisolvent particle-formation method: form an emulsion with the compound in the dispersed phase, then dose an antisolvent to force solidification, expressly to gain "control over the size and shape of the produced particles" by "tuning the average droplet size." It lists the exact surfactants (Span 20/40/80, Tween 20/80, sorbitan monooleate) and antisolvents (water, alcohol) recited in dependent claims 4–5. Van Lare states applicability to "a variety of compounds," including proteins and fatty acids (its claim 7 genus lists "proteins").
• Applied Biosystems teaches ionic-liquid microemulsions stabilized by surfactant, with sub-100 nm droplets and a microemulsion regime, and solidifying the emulsion droplets into beads — i.e., it supplies the "(micro)emulsion of an ionic liquid" element that Van Lare's generic process does not.
• Swatloski supplies the IL-solubilized natural polymer as the dispersed phase.

Motivation: Both Van Lare and Applied Biosystems are in the same field of endeavor (controlled particle/bead formation from emulsions) and address the same problem (controlling particle size/morphology). A PHOSITA seeking to make natural-polymer nanoparticles would combine the IL-dissolution chemistry (Swatloski) with the IL-microemulsion platform (Applied Biosystems) and the antisolvent solidification step (Van Lare) — a combination of familiar elements according to known methods, yielding a predictable result. KSR.

Combination C — the "all-elements stack"

Swatloski '351 + Applied Biosystems '793 + Van Lare '398 + Suzuki 2014 + Meng 2012 + a keratin/collagen/silk reference. This is Combination A with the generic emulsion/antisolvent teachings added to reinforce each individual step. Because each step appears in at least two independent references, an obviousness finding does not hinge on any single reference.

4. Dependent claims 2–9 — largely mechanical

Given Combination A/B, the dependents add little:

• Claim 2 (hexadecane / other nonpolar solvent): Suzuki uses hexadecane; Van Lare lists alkanes.
• Claim 3 (BmimOAc, BmimCl, AmimCl): Suzuki uses [Bmim]Cl; the IL art (Swatloski; the spec's FIG. 12) teaches imidazolium halides/acetates. BmimOAc is the '261 spec's own Example-1 solvent — a known IL from the same class.
• Claim 4 (SPAN 20/80, TWEEN 20, oleic acid, ionic/nonionic/ethoxylate): Van Lare expressly lists Span 20/40/80, Tween 20/80; Suzuki uses Span 80; the '261 FIG. 11 uses oleic acid. Strongly taught.
• Claim 5 (water, acetone, 1-butanol, alcohol, protic solvent antisolvent): Van Lare lists water, methanol, ethanol; Suzuki uses 1-butanol.
• Claim 6 (dilute with 1-butanol/oil/miscible solvent): Suzuki pours into 1-butanol. Taught directly.
• Claim 7 (dilute in excess of emulsion volume): Suzuki pours into "a large amount of 1-butanol." Taught.
• Claim 8 (sequential 1-butanol then water wash): Suzuki washes; the two-solvent sequence is routine optimization (the '261 spec itself says water removes IL while 1-butanol removes oil).
• Claim 9 ("precipitate comprises (nano)particles"): inherent result of the process.

Claim 10 ("Natural polymer nanoparticles made according to the method of claim 1") is a product-by-process claim; its patentability rises and falls with claim 1's process (the process limitations are treated as part of the product definition for patentability purposes, In re Thorpe). If claim 1 is obvious, claim 10 is too.

5. Where the § 103 attack is weakest — and what the patent owner will argue

To be balanced, the following are the genuine bulwarks:

1. The closed "consists of keratin, fibroin, elastin, and collagen" genus. The strongest cited cellulose/IL-emulsion references (Swatloski; Suzuki) are cellulose-centric and do not themselves form nanoparticles of these proteins. The patent owner will argue no single reference, and no combination, expressly names protein nanoparticles from an IL microemulsion. This is why the examiner likely insisted on the cellulose carve-out.
2. "(Nano)" limitation / particle size. Suzuki 2014 reports micron-sized particles via its "solvent releasing method"; the '261 claim is directed to "(nano)particles." The owner may argue the prior art does not reach the nanoscale. However, claim 1 does not recite a numeric size limit — "(nano)" is parenthetical and definitional — and Van Lare expressly teaches sub-500 nm, sub-300 nm, and sub-100 nm particles via the same droplet-size control, so this distinction is weak.
3. "Adjusting ratios to determine a particular shape" (step d). The shape-control limitation is arguably the best non-obviousness talking point, but Van Lare teaches morphology control and the '261 spec itself attributes shape to routine phase-diagram targeting (FIGS. 3–6), which is optimization of a result-effective variable.
4. Elastin. Among the four proteins, elastin has the least direct support in the cited art (the protein-specific refs cover keratin, collagen, silk; Meng's review coverage of elastin could not be verified here). A hypothetical claim narrowed to elastin alone would be more defensible than the current genus.
5. Objective indicia. U.S. Air Force ownership means there is no commercial product and no nexus to secondary considerations — so the patent owner cannot rebut with unexpected results or commercial success on this record. Conversely, the specification's FIG. 16/17 (lower MW → narrower size distribution) shows only predictable effects of a known MW-reduction pretreatment.

6. Bottom line

• Claim 1 would likely be held obvious under § 103 over Suzuki 2014 in view of Swatloski '351 and Meng 2012 (and a keratin/collagen/silk reference), and alternatively over Van Lare '398 in view of Applied Biosystems '793 and Swatloski '351. Each element appears in the cited art, and the only real difference — the natural-polymer identity — is bridged by the cited art and admitted to be an equivalent by the applicant's own specification.
• Claims 2–9 and 10 are very strong obviousness targets, since their added limitations are taught expressly (Span 80, Tween 20, hexadecane, [Bmim]Cl, 1-butanol, excess dilution) primarily by Suzuki 2014 and Van Lare.
• The best defense is the closed four-protein genus combined with the "(nano)" and "particular shape" language — but this is a narrowing defense, not a strong validity position, because the patent's own disclosure characterizes those four proteins as interchangeable with cellulose in the very IL-emulsion process claimed.

7. Uncertainty flags (per my operating rules)

• I verified the content of Swatloski '351, Applied Biosystems '793 / US 7,578,916, Van Lare '398, and Suzuki 2014 through web sources (URLs below). Their teachings as quoted are from those sources.
• I could not independently verify the inner disclosure of US 2,542,984 (keratin), US 2,993,794 (keratin), US 3,034,852 (collagen), US 6,427,933 (silk), US 3,892,731 (chitin), CN 105641746 A (collagen/bacterial-cellulose scaffold), or the Meng 2012 review — my tool access was exhausted before I could confirm their specific examples. I therefore rely on their titles as listed in the '261 Prior Art section and on the '261 specification's own statements about these polymers. If those references do not actually teach IL dissolution of the named proteins, Combination A's bridging rationale weakens and the analysis would shift toward Combination B (Van Lare + Applied Biosystems, which expressly list "proteins").
• JSR '892 ("Method for producing polymer particles") is cited by the examiner but its specific antisolvent/emulsion content was only partially visible in the available snippet; I did not rely on it for any essential element.
• This is an ex ante validity assessment based on the face-of-record prior art; it is not a litigation opinion, does not account for claim-construction positions a court might adopt, and does not consider art that a challenger might find outside the cited references.

Key URLs: Swatloski — https://patents.google.com/patent/US20030157351A1/en ; Applied Biosystems — https://patents.google.com/patent/US20120055793A1/en (parent US 7,578,916 — https://www.freepatentsonline.com/y2012/0055793.html) ; Van Lare — https://patents.google.com/patent/US20070231398A1/en ; Suzuki 2014 — https://pubmed.ncbi.nlm.nih.gov/24461827/ and https://www.sciencedirect.com/science/article/abs/pii/S0021979713010916 ; patent record — https://patents.google.com/patent/[US10233261B1](/patent/US10233261B1)/en