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Nicholas A. Peppas

Bio: Nicholas A. Peppas is an academic researcher from University of Texas at Austin. The author has contributed to research in topics: Self-healing hydrogels & Drug delivery. The author has an hindex of 141, co-authored 825 publications receiving 90533 citations. Previous affiliations of Nicholas A. Peppas include National Technical University & University of Texas System.


Papers
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Journal ArticleDOI
TL;DR: In this article, a theoretical model was developed to describe solute transport through moderately swollen networks, which is an extension of the previous analysis of Peppas and Reinhart (1983), and it describes the normalized effective diffusion coefficient of the solute through the network as a function of the equilibrium degree of swelling.
Abstract: A theoretical model was developed to describe solute transport through moderately swollen networks. The model is an extension of the previous analysis of Peppas and Reinhart (1983), and it describes the normalized effective diffusion coefficient of the solute through the network as a function of the equilibrium degree of swelling, Q, the hydrodynamic radius of the solute, rs, the number average molecular weight between crosslinks, M¯c, and a function f(ξ) of the mesh size ξ, which takes into consideration barriers due to crosslinks, entanglements, etc. For the development of this model, the Cohen–Turnbull (1958) free volume theory was modified to incorporate topological and mobility characteristics from de Gennes' analysis (1979).

51 citations

Journal ArticleDOI
24 Feb 2014-ACS Nano
TL;DR: Knockdown experiments using polycationic nanoparticles to deliver siRNA demonstrated evidence of knockdown, thus demonstrating potential as an alternative route to creating polycationing nanoparticles.
Abstract: In this work, we develop and evaluate polycationic nanoparticles for the delivery of small interfering RNA (siRNA). Delivery remains a major challenge for translating siRNA to the clinic, and overcoming the delivery challenge requires effective siRNA delivery vehicles that meet the demands of the specific delivery strategy. Cross-linked polycationic nanoparticle formulations were synthesized using ARGET ATRP or UV-initiated polymerization. The one-step, one-pot, surfactant-stabilized monomer-in-water synthesis technique may provide a simpler and faster alternative to complicated, multistep techniques and an alternative to methods that rely on toxic organic solvents. The polymer nanoparticles were synthesized using the cationic monomer 2-(diethylamino)ethyl methacrylate, the hydrophobic monomer tert-butyl methacrylate to tune pH responsiveness, the hydrophilic monomer poly(ethylene glycol) methyl ether methacrylate to improve biocompatibility, and cross-linking agent tetraethylene glycol dimethacrylate to enhance colloidal stability. Four formulations were evaluated for their suitability as siRNA delivery vehicles in vitro with the human embryonic kidney cell line HEK293T or the murine macrophage cell line RAW264.7. The polycationic nanoparticles demonstrated efficient and rapid loading of the anionic siRNA following complexation. Confocal microscopy as well as flow cytometry analysis of cells treated with polycationic nanoparticles loaded with fluorescently labeled siRNA demonstrated that the polycationic nanoparticles promoted cellular uptake of fluorescently labeled siRNA. Knockdown experiments using polycationic nanoparticles to deliver siRNA demonstrated evidence of knockdown, thus demonstrating potential as an alternative route to creating polycationic nanoparticles.

51 citations

Journal ArticleDOI
TL;DR: In this paper, a constitutive relation is used to describe the effect of macromolecular relaxations on the rate of volume expansion as the polymer swells, and the penetrant fractional uptake, solute fractional release, sample dimensions, swelling front position, and instantaneous swelling interface number are determined and related to the nature of the swelling process.
Abstract: Penetrant transport through and solute release from continuously swelling polymers is viewed as a process associated with major structural changes in the polymer morphology. Changes in the diffusivities of penetrant and solute reflect a free volume mechanism for transport. The polymer is initially glassy with a uniform dispersion of solute. After the system is placed in contact with a thermodynamically good penetrant, a glassy/rubbery phase transition occurs at a well defined swelling interface. The Fickian equations with concentration-dependent diffusivities and moving boundaries are solved simultaneously in polymer-fixed coordinates. A constitutive relation is used to describe the effect of macromolecular relaxations on the rate of volume expansion as the polymer swells. The penetrant fractional uptake, solute fractional release, sample dimensions, swelling front position, and instantaneous swelling interface number are determined and related to the nature of the swelling process.

51 citations

Journal ArticleDOI
TL;DR: Investigating the effect of drug type on the degradation of P(DL)LGA 53/47 films and their ultimate release profiles found complete release of metoclopramide monohydrochloride was achieved much earlier than paclitaxel.
Abstract: Many factors affect the rate of drug release from biodegradable polymers. Here, we focus on investigating the effect of drug type on the degradation of P(DL)LGA 53/47 films and their ultimate release profiles. A freely water-soluble drug (metoclopramide monohydrochloride) exhibited an initial burst, whereas a water-insoluble drug (paclitaxel) exhibited an initial latent period with very little drug release. The onset of the second-stage release of the hydrophobic drug was delayed as compared with the hydrophilic drug. Overall, complete release of metoclopramide monohydrochloride was achieved much earlier than paclitaxel. In addition, the hydrophobic drug exhibited an extra stage of release when compared with the two-stage release for the hydrophilic drug. A novel model was developed to describe the underlying drug release mechanisms and kinetics. The model postulated that the total fraction of drug release from bulk-degrading polymer is a summation of three mechanisms: burst release, relaxation induced/drug-dissolution controlled release, and diffusional release. All the three steps are important for hydrophobic drugs. However, for hydrophilic drugs, burst and diffusional release steps are sufficient to account for the whole release process. The proposed model showed very good match with the experimental data. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009

50 citations

Journal ArticleDOI
TL;DR: In this paper, a dual drug-loaded core-shell nanoparticles (DLTPT) consisting of CD44-targeting hyaluronic acid shells decorated with doxorubicin (HA-DOX) and mitochondria-targeted triphenylphosphonium derivative nanoparticle cores loaded with lonidamine (LND) dimers (LTPT).
Abstract: Nanoparticle-based drug delivery faces challenges from the imprecise targeted delivery and the low bioavailability of drugs due to complex biological barriers. Here, we designed cascade-targeting, dual drug-loaded, core-shell nanoparticles (DLTPT) consisting of CD44-targeting hyaluronic acid shells decorated with doxorubicin (HA-DOX) and mitochondria-targeting triphenylphosphonium derivative nanoparticle cores loaded with lonidamine (LND) dimers (LTPT). DLTPT displayed prolonged blood circulation time and efficiently accumulated at the tumor site due to the tumor-homing effect and negatively charged hyaluronic acid. Subsequently, the HA-DOX shell was degraded by extracellular hyaluronidase, resulting in decreased particle size and negative-to-positive charge reversal, which would increase tumor penetration and internalization. The degradation of HA-DOX further accelerated the release of DOX and exposed the positively charged LTPT core for rapid endosomal escape and mitochondria-targeted delivery of LND. Notably, when DLTPT was used in combination with anti-PD-L1, the tumor growth was inhibited, which induced immune response against tumor metastasis.

50 citations


Cited by
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28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal Article
TL;DR: This book by a teacher of statistics (as well as a consultant for "experimenters") is a comprehensive study of the philosophical background for the statistical design of experiment.
Abstract: THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

13,333 citations

Journal ArticleDOI
TL;DR: The 11th edition of Harrison's Principles of Internal Medicine welcomes Anthony Fauci to its editorial staff, in addition to more than 85 new contributors.
Abstract: The 11th edition of Harrison's Principles of Internal Medicine welcomes Anthony Fauci to its editorial staff, in addition to more than 85 new contributors. While the organization of the book is similar to previous editions, major emphasis has been placed on disorders that affect multiple organ systems. Important advances in genetics, immunology, and oncology are emphasized. Many chapters of the book have been rewritten and describe major advances in internal medicine. Subjects that received only a paragraph or two of attention in previous editions are now covered in entire chapters. Among the chapters that have been extensively revised are the chapters on infections in the compromised host, on skin rashes in infections, on many of the viral infections, including cytomegalovirus and Epstein-Barr virus, on sexually transmitted diseases, on diabetes mellitus, on disorders of bone and mineral metabolism, and on lymphadenopathy and splenomegaly. The major revisions in these chapters and many

6,968 citations

Journal ArticleDOI
TL;DR: This review discusses the synthetic chemistry, fluid stabilization and surface modification of superparamagnetic iron oxide nanoparticles, as well as their use for above biomedical applications.

6,207 citations

Journal ArticleDOI
TL;DR: Probing the various interfaces of nanoparticle/biological interfaces allows the development of predictive relationships between structure and activity that are determined by nanomaterial properties such as size, shape, surface chemistry, roughness and surface coatings.
Abstract: Rapid growth in nanotechnology is increasing the likelihood of engineered nanomaterials coming into contact with humans and the environment. Nanoparticles interacting with proteins, membranes, cells, DNA and organelles establish a series of nanoparticle/biological interfaces that depend on colloidal forces as well as dynamic biophysicochemical interactions. These interactions lead to the formation of protein coronas, particle wrapping, intracellular uptake and biocatalytic processes that could have biocompatible or bioadverse outcomes. For their part, the biomolecules may induce phase transformations, free energy releases, restructuring and dissolution at the nanomaterial surface. Probing these various interfaces allows the development of predictive relationships between structure and activity that are determined by nanomaterial properties such as size, shape, surface chemistry, roughness and surface coatings. This knowledge is important from the perspective of safe use of nanomaterials.

6,075 citations