Biodegradable Hydrogels (biodegradable + hydrogel)

Distribution by Scientific Domains

Selected Abstracts

Photopolymerizable Hydrogels Made from Polymer-Conjugated Albumin for Affinity-Based Drug Delivery,

Liat Oss-Ronen
As a drug delivery vehicle, biodegradable albumin hydrogels can combine the high binding capacity of albumin with the structural stability of a polymeric hydrogel network to enable controlled release of small molecules based on both binding affinity and physical interactions. In the present study, we report on the development of a hybrid hydrogel composed of albumin conjugated to poly(ethylene glycol) (PEG) for drug delivery applications where controlled release is accomplished using the natural affinity of the drugs to the serum albumin. Bovine serum albumin was conjugated to PEG-diacrylate having a molecular weight of 1.5, 4, or 10,kDa to form a PEGylated albumin macromolecule (mono-PEGylated or multi-PEGylated). Biodegradable hydrogels were formed from the PEGylated albumin using photopolymerization. Two model drugs, Warfarin and Naproxen, were used for equilibrium dialysis and release experiments from the hydrogels, both having relatively low molecular weights and a known high affinity for albumin. Equilibrium dialysis experiments showed that multi-PEGylation of albumin significantly decreased the drug affinity to the protein compared to non-PEGylated controls, irrespective of the PEG molecular weight. However, the results from drug release experiments showed that mono-PEGylation of albumin did not change its natural affinity to the drug. Comparing the release profiles with a Fickian diffusion model provided strong evidence that hydrogels containing mono-PEGylated albumin exhibited sub-diffusive drug release properties based on the affinity of the drug to the tethered protein. [source]

Biodegradable Water Absorbent Synthesized from Bacterial Poly(amino acid)s

Masao Kunioka
Abstract Summary: Biodegradable hydrogels prepared by , -irradiation from microbial poly(amino acid)s have been studied. pH-Sensitive hydrogels were prepared by the , -irradiation of poly(, -glutamic acid) (PGA) produced by Bacillus subtilis and poly(, -lysine) (PL) produced by Streptomyces albulus in aqueous solutions. When the , -irradiation dose was 19 kGy or more, and the concentration of PGA in water was 2 wt.-% or more, transparent hydrogels could be produced. For the 19 kGy dose, the produced hydrogel was very weak, however, the specific water content (wt. of absorbed water/wt. of dry hydrogel) of this PGA hydrogel was approximately 3,500. The specific water content decreased to 200, increasing when the , -irradiation dose was over 100 kGy. Under acid conditions or upon the addition of electrolytes, the PGA hydrogels shrunk. The PGA hydrogel was pH-sensitive and the change in the volume of the hydrogel depended on the pH value outside the hydrogel in the swelling medium. This PGA hydrogel was hydrodegradable and biodegradable. A new novel purifier reagent (coagulant), made from the PGA hydrogels, for contaminated turbid water has been found and developed by Japanese companies. A very small amount of this coagulant (only 2 ppm in turbid water) with poly(aluminum chloride) can be used for the purification of turbid water. A PL aqueous solution also can change into a hydrogel by , -irradiation. The specific water content of the PL hyrdogel ranged from 20 to 160 depending on the preparation conditions. Under acid conditions, the PL hydrogel swelled because of the ionic repulsion of the protonated amino groups in the PL molecules. The rate of enzymatic degradation of the respective PL hydrogels by a neutral protease was much faster than the rate of simple hydrolytic degradation. [source]

Poly(glutamic acid) poly(ethylene glycol) hydrogels prepared by photoinduced polymerization: Synthesis, characterization, and preliminary release studies of protein drugs

Zhiqiang Yang
Abstract A class of new biodegradable hydrogels based on poly(ethylene glycol) methacrylate-graft-poly(glutamic acid) and poly(ethylene glycol) dimethacrylate was synthesized by photoinduced polymerization. Because all the polymeric constituents were highly hydrophilic, crosslinking could be performed in aqueous solutions. This type of crosslinked hydrogel was prepared by modifying a select number of acidic side-groups on poly(glutamic acid) with poly(ethylene glycol) methacrylate. These modified chains were then crosslinked in the presence of poly(ethylene glycol) dimethacrylate under a photoinduced polymerization at a wavelength of 365 nm. Swelling experiments were conducted to study the crosslinking density, pH-responsive behavior, and degradation of the hydrogel. Results showed that the degree of swelling of this type of hydrogels increased as the crosslinker concentration (or density) was reduced. Because of the presence of acidic side chains on poly(glutamic acid), swelling behavior was found to be pH-responsive, increasing at high pH in response to the increase in the amount of ionized acidic side chains. The degradation rate of these hydrogels also varied with pH. More rapid degradation was observed under stronger alkaline conditions because of the hydrolysis of the ester bonds between the crosslinker and the polymer backbone. Practically useful degradation rates could be achieved for such hydrogels under physiological conditions. Drug release rates from these hydrogels were found to be proportional to the protein molecular weight and the crosslinker density; increasing at lower protein molecular weight or crosslinker density. The preliminary findings presented in this article suggest that this class of biodegradable hydrogels could be an attractive avenue for drug delivery applications. The specific photoinduced crosslinking chemistry used would permit hydrogels to be synthesized in existence of the entrapped macromolecular drugs including peptides, proteins, and cells. In addition, the rapid feature of this polymerization procedure along with the ability to perform hydrogel synthesis and drug loading in an aqueous environment would offer great advantages in retaining drug activity during hydrogel synthesis. 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 14,21, 2002 [source]