Showing papers by "Nicholas A. Peppas published in 1998"
TL;DR: It was concluded that drug diffusion may be impeded by associated drug binding, especially in IPN hydrogels containing high amounts of PAA.
153 citations
TL;DR: The swelling behavior of these gels in deionized water at 37 °C indicated that the gels prepared from PEG star Poly(ethylene glycol) star polymers with a small number of long arms swelled to a greater extent than those prepared fromPEG star polymer with a large number of short arms.
Abstract: Poly(ethylene glycol) (PEG) star polymer hydrogels were prepared by γ-irradiation of aqueous solutions of star PEG polymers The swelling behavior of these gels in deionized water at 37 °C indicated that the gels prepared from PEG star polymers with a small number of long arms swelled to a greater extent than those prepared from PEG star polymers with a large number of short arms PEG star polymers and branched PEG polymers were modified to incorporate acrylate groups on the ends of the polymer arms These acrylated star or branched polymers were copolymerized with poly(ethylene glycol) diacrylate in the presence of UV light The ensuing materials swelled to a greater extent than hydrogels prepared without acrylated star or branched PEG polymers Number-average molecular weights were calculated using several rubber elasticity-based theories
125 citations
TL;DR: In this paper, a new class of poly(ethylene glycol)-grafted, cationic hydrogels was prepared by copolymerization and simultaneous crosslinking of diethylaminoethyl methacrylate (DEAEM) and poly (ethylene gels) monomethacrylated (PEGMA), which exhibited a strong swelling ratio dependence on pH.
70 citations
Patent•
02 Apr 1998TL;DR: In this paper, a composition and method for the oral administration of bioactive components to vertebrates is described, which comprises the step of orally administering the vertebrate a composition comprising a swellable hydrogel matrix and a bioactive composition contained within the hydrastic matrix.
Abstract: A composition and method are described for the oral administration of bioactive components to vertebrates. The method comprises the step of orally administering the vertebrate a composition comprising a swellable hydrogel matrix and a bioactive composition contained within the hydrogel matrix.
37 citations
TL;DR: In this article, a series of novel copolymerization and/or crosslinking techniques using polyvinyl alcohol (PVA) moieties modified by the incorporation of olefinic structures.
Abstract: Biodegradable polyacrylates were produced by a series of novel copolymerization and/or crosslinking techniques using poly(vinyl alcohol) (PVA) moieties modified by the incorporation of olefinic structures. PVA was modified by a tosylation and/or detosylation reaction. The functionalized PVA was copolymerized and/or crosslinked with acrylic acid or its partially neutralized form to give crosslinked polyacrylates that could swell in water. Their swelling behavior was determined under load. Degradation studies were performed in α-chymotrypsin, trypsin, and papain solutions. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 817–829, 1998
32 citations
TL;DR: The transport of poly(ethylene glycol) chains than can promote mucoadhesion across the interface between lightly cross-linked poly(acrylic acid) and mucin may be analyzed as a function of molecular characteristics using theories of chain penetration in a dilute network.
Abstract: The transport of poly(ethylene glycol) chains than can promote mucoadhesion across the interface between lightly cross-linked poly(acrylic acid) and mucin may be analyzed as a function of molecular characteristics using theories of chain penetration in a dilute network. The fracture energy for the ensuing adhesive bond is proportional to the number of polymer chains crossing the interface, which, in turn, is related to the polymer volume fraction, the chain diffusion coefficient, and the degree of polymerization. Relevant calculations were performed for a number of cross-linked poly(acrylic acid) gels and three different types of poly(ethylene glycol) chains.
21 citations
TL;DR: Nuclear magnetic resonance microscopy has been used to monitor the hydration of poly(vinyl alcohol) (PVA) samples of varying molecular weight, providing supporting evidence for the hypothesis that phenomena such as reptation are important near the glassy/rubbery interface of polymers during dissolution.
19 citations
01 Dec 1998
18 citations
TL;DR: Modifications of the coating permeability introduce a further possibility of modulating drug-release kinetics and lead to a reduced dependence of swellable matrix tablet release on environmental conditions.
18 citations
01 Dec 1998
16 citations
01 Jan 1998
01 Jan 1998
TL;DR: A new type of hydrogel composed of poly(methacrylic acid) grafted with poly(ethylene glycol) which can be used as drug delivery carriers for salmon calcitonin which was developed and Calcitonin release was achieved.
Abstract: Major challenges in oral delivery of peptides include the need to overcome gastric and intestinal degradation. pH -Sensitive hydrogels are suitable candidates for oral drug delivery of peptides due to their ability to respond to their environment. We have developed a new type of hydrogel composed of poly(methacrylic acid) grafted with poly(ethylene glycol) which can be used as drug delivery carriers for salmon calcitonin. These hydrogels were prepared by free radical solution polymerization and were molecularly designed to contain poly(ethylene glycol) tethered chains promoting mucosal adhesion and providing calcitonin protection, as well as methacrylic acid moieties, which act as calcium binders leading to epithelial cell junction opening. Solutions of approximately 0.1 mg/ml of salmon calcitonin were used to load the protein into the gels at pH = 7 and constant ionic strength of 0.1 M. In vitro release studies were performed at pH=7 and 37 °C, while keeping an ionic strength of 0.1 M. Calcitonin release was achieved. The release behavior was explained in terms of diffusional theories.