US 6858222

Here's a concise summary of US patent 6858222:

• Title: Fabrication of drug loaded biodegradable polymer fibers
• Assignee: University of Texas System
• Inventors: Kevin D Nelson, Andres A. Romero-Sanchez, George M. Smith, Nadir Alikacem, Delia Radulescu, Paula Waggoner, Zhibing Hu
• Filing Date: 2003-05-02
• Issue Date: 2005-02-22
• Abstract: The invention provides tissue engineering compositions and methods wherein three-dimensional matrices for growing cells are prepared for in vitro and in vivo use. The matrices comprise biodegradable polymer fibers capable of the controlled delivery of therapeutic agents. The spatial and temporal distribution of released therapeutic agents is controlled by use of defined nonhomogeneous patterns of therapeutic agents in the matrices.

Plain-language Overview of Independent Claims:
The claims section for US patent 6858222 was not included in the provided patent text. Therefore, a plain-language overview of each independent claim cannot be provided.

Legal Status and Litigation:
According to the provided patent document, the patent's legal status is "Expired - Lifetime", with an anticipated expiration date of 2020-08-04. The patent family is noted as having litigation. Searches of the USPTO database and CAFC 2026 dockets did not yield specific active litigation for US6858222 as of April 26, 2026.

As of April 26, 2026, there is no known litigation directly involving US Patent 6858222.

It is important to note that a related patent, U.S. Patent No. 6,596,296, owned by the Board of Regents of the University of Texas System (UT), was involved in litigation against Boston Scientific Corporation (BSC). In that case, which concluded with a precedential decision from the U.S. Court of Appeals for the Federal Circuit (CAFC) on July 27, 2026, the Federal Circuit reversed a jury verdict and found the '296 patent invalid as anticipated by prior art and also found non-infringement. While this case involves a related patent and the same assignee, it does not directly concern US Patent 6858222.

Proceedings overview

There are no AIA trial proceedings on file for US Patent 6858222.

Strategic summary

As of today, 2026-07-28, US Patent 6858222 has not been challenged through any AIA trial proceedings such as Inter Partes Review (IPR), Post-Grant Review (PGR), or Covered Business Method (CBM) review. This means that all claims of the patent remain untested by the USPTO's Patent Trial and Appeal Board (PTAB). For a potential defendant, this implies that no claims have been invalidated or confirmed as patentable through these specific administrative processes, and the full scope of the patent's claims is theoretically available for assertion. The estoppel provisions of 35 U.S.C. § 315(e)(2) are not applicable as no proceedings have been instituted.

The absence of PTAB activity could suggest several things. It might indicate that the patent has not been extensively asserted or that potential challengers have opted for other defensive strategies, such as district court litigation or licensing agreements. Alternatively, the patent's claims might be considered sufficiently robust against common prior art challenges, or perhaps the patent's commercial relevance hasn't yet reached a point where PTAB challenges are deemed worthwhile by potential infringers or defensive aggregators.

Recommended next steps

There are no PTAB proceedings on file for US Patent 6858222. If faced with an assertion of this patent, a potential defendant would have the full range of PTAB trial options available, including filing an IPR, PGR (if eligible), or CBM (if eligible), to challenge the validity of the patent's claims.

Inventors

The named inventors and their employer at the time of filing are:

• Kevin D Nelson (University of Texas System)
• Andres A. Romero-Sanchez (University of Texas System)
• George M. Smith (University of Texas System)
• Nadir Alikacem (University of Texas System)
• Delia Radulescu (University of Texas System)
• Paula Waggoner (University of Texas System)
• Zhibing Hu (University of Texas System)

All inventors were affiliated with the original assignee, the University of Texas System, at the time of filing.

Original assignee

The original assignee named on the issued patent is the University of Texas System. As a university system, their primary line of business is education and research. While they engage in technology transfer, they are not typically a product-shipping entity in the commercial sense of the patented technology. The University of Texas System is currently operating.

Assignment timeline

As of July 28, 2026, a search of the USPTO Assignment Center for patent US6858222 shows no recorded assignments beyond the original assignment to the University of Texas System. This indicates that the University of Texas System remains the current owner of the patent.

Timeline diagram

timeline
    title Ownership of US 6858222
    2003 : Filed by University of Texas System
    2005 : Issued to University of Texas System

NPE / troll-pattern signals

1. Shell-entity transfer — not present. There are no recorded transfers of the patent to any shell entities.
2. Known asserter in the chain — not present. The patent remains with the original assignee, the University of Texas System, which is not a known NPE.
3. Repeat correspondent across the chain — not present. There are no multiple recorded assignments to demonstrate a recurring correspondent.
4. Cascading transfers — not present. There are no recorded transfers.
5. Pre-litigation transfer — not present. There are no recorded transfers and no direct litigation involving this patent.
6. Bankruptcy fire-sale — not present. The University of Texas System is an operating entity and there is no indication of bankruptcy.
7. Privateering — not present. There is no evidence of the University of Texas System transferring the patent to an NPE for assertion.
8. Defensive aggregator (anti-NPE) — not present. The patent has not been acquired by a defensive aggregator.

Verdict

Insufficient data. As there are no recorded assignments for US6858222 beyond its initial issuance to the University of Texas System, there is insufficient data to determine any NPE or troll patterns. The patent appears to remain with its original assignee.

For verification, you can search the USPTO Assignment Center at https://assignmentcenter.uspto.gov/.

Most Relevant Prior Art for US Patent 6858222

To identify the most relevant prior art for US patent 6858222, a search of the USPTO database was conducted. The patent itself lists several prior art references, both patent and non-patent literature. Prior art, in patent law, refers to any public information that existed before the filing date of a patent application and can be used to determine if an invention is novel and non-obvious.

As the claims section for US patent 6858222 was not provided in the initial text, a detailed analysis of which claims each prior art reference potentially anticipates under 35 U.S.C. § 102 cannot be performed at this time. However, I can provide the full citations and brief descriptions of the prior art explicitly mentioned in the patent.

Prior Art References Mentioned in US6858222:

The patent text for US6858222 specifically incorporates by reference several publications for their descriptions of drugs and angiogenic factors. It also references prior art related to biodegradable polymer matrices.

Non-Patent Literature:

• "The Physicians Desk Reference," 471st edition, pages 101-321:
  • Publication/Filing Date: The 471st edition would predate the priority date of US6858222 (1999-08-06).
  • Brief Description: This reference is incorporated to define "drug" and provides a listing of recognized pharmaceuticals.
  • Potential Anticipation: Without specific claims, it's difficult to pinpoint direct anticipation, but this reference broadly informs the scope of therapeutic agents mentioned in the invention.
• "Goodman and Gilman's The Pharmacological Basis of Therapeutics" 8th Edition (1990), pages 84-1614 and 1655-1715:
  • Publication/Filing Date: 1990 (predates priority date of US6858222).
  • Brief Description: Similar to the Physicians Desk Reference, this book is incorporated by reference for its comprehensive listing and description of pharmacological substances, contributing to the definition of "drug."
  • Potential Anticipation: Provides general knowledge of therapeutic agents.
• "The United States Pharmacopeia, The National Formulary", USP XXII NF XVII (1990):
  • Publication/Filing Date: 1990 (predates priority date of US6858222).
  • Brief Description: This official compendium provides standards for drug substances and dosage forms, further supporting the definition and scope of "drug."
  • Potential Anticipation: General reference for pharmaceutical compositions.
• Peppas and Langer, 1994 (referring to biodegradable polymer matrices):
  • Publication/Filing Date: 1994 (predates priority date of US6858222).
  • Brief Description: This reference is cited for its discussion of biodegradable polymer matrices, specifically mentioning polyanhydrides, polyorthoesters, and poly(amino acids).
  • Potential Anticipation: This reference potentially anticipates aspects of the invention related to the use of these specific biodegradable polymers for matrices, which are also listed as preferred polymers in US6858222.
• Folkman and Klagsbrun, 1987 (and references cited therein, each incorporated herein in their entirety by reference) (referring to induction of angiogenesis):
  • Publication/Filing Date: 1987 (predates priority date of US6858222).
  • Brief Description: This work is cited for the induction of angiogenesis, mediated by various factors. The patent states that "any of which may be used in conjunction with the present invention."
  • Potential Anticipation: This reference, and those cited within it, would be highly relevant to claims involving the use of angiogenic factors in the fibers. The specific mention of various angiogenic factors (e.g., VEGF, FGF family, IL-8, EGF, PDGF, TGF-α, TGF-β, TNF-α, HGF, GM-CSF, IGF-1, angiogenin, angiotropin, fibrin, and nicotinamide) indicates prior knowledge of these agents for promoting angiogenesis.
• Folkman, 1986, 1995; Auerbach and Auerbach, 1994; Fidler and Ellis, 1994; Folkman and Klagsbrun, 1987; Nagy et al. (referring to angiogenic factors):
  • Publication/Filing Dates: Various dates, all preceding the priority date of US6858222.
  • Brief Description: These references are cited in relation to specific angiogenic factors, further demonstrating the existing knowledge in the field.
  • Potential Anticipation: Similar to the previous Folkman and Klagsbrun reference, these publications would be strong prior art for claims related to the use and function of angiogenic factors in tissue engineering.
• Sambrook et al. (1989; incorporated herein by reference) (referring to promoters for protein expression):
  • Publication/Filing Date: 1989 (predates priority date of US6858222).
  • Brief Description: This is a standard molecular biology reference, incorporated for its general knowledge regarding promoters to achieve protein expression.
  • Potential Anticipation: Relevant for claims involving the incorporation and expression of polynucleotides or genes within the fibers.

Patent Literature:

• U.S. Pat. No. 5,270,300 (referring to angiogenic factor administration):
  • Publication/Filing Date: This patent issued on December 14, 1993, well before the priority date of US6858222.
  • Brief Description: This patent is explicitly referenced in US6858222 as disclosing an angiogenic factor that could be delivered along with nucleic acids.
  • Potential Anticipation: This patent would be highly relevant to any claims in US6858222 concerning the delivery or administration of angiogenic factors.

It's crucial to obtain the full text of the claims of US6858222 to conduct a thorough anticipation analysis for each of these prior art references. Without the claims, a definitive statement about anticipation is not possible.

To analyze the obviousness of US patent 6858222 under 35 U.S.C. § 103, we need to consider the claims of the patent, the identified prior art, and whether a person having ordinary skill in the art (PHOSITA) would have been motivated to combine the prior art references to arrive at the claimed invention, with a reasonable expectation of success.

First, it is important to note that the independent claims for US patent 6858222 were not included in the provided patent text, which limits the specificity of this obviousness analysis. However, based on the patent's abstract and detailed description, the core of the invention lies in:

• Three-dimensional matrices for tissue engineering.
• Comprising biodegradable polymer fibers.
• These fibers are capable of controlled delivery of therapeutic agents.
• The spatial and temporal distribution of these agents is controlled by using defined nonhomogeneous patterns of polymer fibers.

A PHOSITA in this field would likely have a background in biomedical engineering, materials science, or pharmaceutical sciences, with knowledge of drug delivery systems, polymer science, and tissue engineering.

Prior Art References:

From the "Prior art keywords" section of US6858222, we have: "fibers", "fiber", "chitosan", "polymer", "concentration". While these are keywords, they point to general areas of relevant prior art.

The "Description of Related Art" section of US6858222 also explicitly mentions:

• Three-dimensional polymer networks, often composed of biodegradable fibers, used as scaffolds for growing cells in vitro.
• Empty three-dimensional, biodegradable polymer scaffolds directly implanted to induce host cell migration and vascularization.
• The use of biodegradable matrices that allow cells to create their own extracellular matrix as the exogenous matrix degrades.
• A limitation in current methodologies is the lack of specific means to actively assist the incorporation of blood vessels throughout the polymer matrix.

Let's consider how a PHOSITA might combine these known concepts, as supported by the provided patent information and general knowledge in the field at the time of the invention (priority date 1999-08-06).

Potential Combinations and Motivation for a PHOSITA:

1. Basic concept of drug-loaded biodegradable fibers for tissue engineering:

   • The patent itself acknowledges that "tissue engineering is a discipline wherein living cells are used to replace functional loss because of injury, disease, or birth defect" and that "scaffolds are typically three-dimensional polymer networks, often composed of biodegradable fibers." The general idea of biodegradable polymers for medical applications, including drug delivery, was well-established. For instance, biodegradable polymers like poly(glycolic acid) (PGA) were known for forming bioabsorbable sutures that could be safely absorbed by the body. Additionally, the use of polymeric carriers in injectable drug delivery systems requires biodegradable polymers that degrade into non-toxic and safe products. PLGA and PLLA were used to encapsulate drugs in the form of microparticles or nanoparticles to increase circulation time and bioavailability.
   • Motivation: A PHOSITA would inherently understand the benefit of combining drug delivery with biodegradable scaffolds to promote tissue regeneration. The problem of ensuring appropriate cell types migrate into a scaffold and maintaining mechanical and biological properties to meet physiological needs, as outlined in the "Background of the Invention" of US6858222, would strongly motivate efforts to integrate therapeutic agents directly into the scaffold material.

2. Controlled release of therapeutic agents from fibers:

   • The patent highlights the advantage of fibers as a drug delivery platform over other slow drug-releasing agents like microspheres, porous plugs, or patches. The patent also describes that therapeutic agents are encapsulated into individual fibers and released slowly and in a controlled manner.
   • Motivation: Given the known utility of biodegradable polymers in drug delivery, and the desire for localized and sustained therapeutic effects in tissue engineering, a PHOSITA would be motivated to develop controlled release mechanisms from the fiber scaffolds. The patent explicitly states, "The advances in micro- and nano-fabrication technology have enhanced the tools available to create clinically important therapeutic applications. Microfabrication technology has been applied to the successful fabrication of a variety of implantable and oral drug delivery devices based on silicon, glass, silicone elastomer, or plastic materials." The control over drug release kinetics through polymer type and processing conditions, as mentioned in the patent, would be an obvious design choice for optimizing therapeutic outcomes.

3. Spatial and temporal distribution of therapeutic agents via nonhomogeneous patterns:

   • This is presented as a key inventive aspect of US6858222. The patent describes controlling spatial and temporal distribution through "defined nonhomogeneous patterns of polymer fibers, which are capable of releasing one or more therapeutic agents as a function of time." It also mentions "coaxial layers within a fiber" for temporal control and concentration gradients along the longitudinal axis of fibers for spatial control.
   • Motivation: The "Background of the Invention" in US6858222 explicitly states a "major problem is that there is currently no way to ensure that the appropriate cell types will migrate into the scaffold, and that the mechanical and biological properties will be maintained to provide the patient's physiological need." The patent further states, "Most current methodologies provide no specific means of actively assisting the incorporation of blood vessels into and throughout the polymer matrix." This clearly identifies the problems. A PHOSITA would be motivated to find ways to actively guide cell behavior and vascularization within a scaffold. The concept of using patterned release to direct cell migration and differentiation, mimicking natural extracellular matrix signals during embryological development, would be a logical extension of existing knowledge in tissue engineering. The idea of "smart fabric" to induce specific cell types to migrate to specific regions due to chemotactic factors is also explicitly mentioned in the patent. The US7033603B2 patent, which shares some inventors with US6858222 and has a similar title, also discusses controlling spatial and temporal concentration of therapeutic agents within a fiber-scaffold implant. It further notes that this is achieved by "designing the fiber scaffold such that fibers with specific therapeutic agents and specific release profiles are placed at specific locations within the scaffold."

Conclusion on Obviousness (General):

While a detailed claim-by-claim analysis is not possible without the independent claims, the overarching concepts of US6858222 appear to be an integration of known principles in biodegradable polymers, drug delivery, and tissue engineering. The motivation for a PHOSITA to combine these elements would stem from the recognized challenges in existing tissue engineering approaches, particularly the need for better control over cell migration, differentiation, and vascularization within implanted scaffolds. The patent itself highlights these unmet needs, and the proposed solutions (drug-loaded biodegradable fibers, controlled release, and spatial/temporal patterning) represent logical advancements given the state of the art in the late 1990s.

The novelty of US6858222 likely resides in the specific implementation of these principles, such as the detailed methods for fabricating fibers with specific gradients, coaxial layers, or patterns, rather than the broad concepts themselves. However, without the exact wording of the claims, it's challenging to pinpoint where the inventive step might precisely lie against a combination of general prior art. For instance, if the claims specify particular dimensions of fibers or specific types of nonhomogeneous patterns, those details would need to be compared against prior art teaching similar features.