Biomedical subjects

Venkatram Prasad Shastri

Publications and source records attributed to Venkatram Prasad Shastri.

3 recordsLinked to original sources

PubMed2004

A preliminary report on the biocompatibility of photopolymerizable semi-interpenetrating anhydride networks.

A new family of poly(anhydrides) (PA) has been developed which can be cured photochemically to produce degradable networks. These degradable anhydride networks may be useful in orthopaedics as bone cements and as matrices for drug delivery. This system, which is a semi-interpenetrating network (semi-IPN), has been evaluated for biocompatibility in subcutaneous tissue in rats and appears to undergo degradation primarily by surface erosion. The inflammatory response to the semi-IPN implants was minimal at both short (3 and 6 weeks) and long (28 weeks) time points and the fibrotic response was largely absent throughout the duration of this study. Furthermore, the OrthoCure implant material integrated well with the surrounding tissue and was invaded with vascularized connective tissue. For reference, linear PA controls were tested and showed a foreign body response culminating in the formation of relatively avascular fibrous capsule several cell layers thick, which became thicker over time, a response similar to what is typically observed in FDA approved implantable polymeric device systems.

Absorbable Implants↗

PubMed2003

A method to protect sensitive molecules from a light-induced polymerizing environment.

Systems that can be polymerized in situ upon exposure to light radiation may have significant applications in tissue engineering and drug delivery. However, the light-induced polymerization step, which is the requisite for this technology, could be potentially deleterious to sensitive bioactive agents (e.g., enzymes, cytokines, matrix metalloproteinases) being entrapped. In this study, a method to protect sensitive molecules from a light-induced polymerizing environment is proposed. This method is based on the idea that nonaccessible substances cannot interact with the polymerizing species. To examine this concept, two model enzymes-namely, horseradish peroxidase and alpha-glucosidase-were protected by gelatin-based wet granulation and incorporated within a cured polyethylene glycol dimethacrylate, a photocurable monomer, under different conditions. Unprotected enzymes were used as controls. Enzymes were then allowed to diffuse out of the polymerized matrices. The activity and total enzyme recovered from these matrices by passive diffusion were compared to ascertain the extent of activity retention. Matrix assisted laser desorption ionization mass spectrometry combined with time of flight mass spectrometry (MALDI-TOF) was used to determine changes in enzyme molecular weight. During the first 24 h of diffusion from the polymerized matrices, unprotected enzymes consistently showed a loss of activity ranging from 10-66%, depending on the matrix composition and enzyme properties. In contrast, protected enzymes retained over 94% of their activity irrespective of the experimental setting. The loss of activity appears to be a direct consequence of the polymerizing environment.

Acrylates↗

PubMed2003

In situ pore formation in a polymer matrix by differential polymer degradation.

A new approach for the in situ formation of porosity in a matrix based on differential polymer degradation has been studied. This approach exploits the differences in polymer properties such as molecular weight, hydrophilicity (hydrophobicity), and degradation to induce preferential degradation of one phase in a biphasic polymer system. Biphasic polymer systems polymers derived from alpha-hydroxy acids and poly(anhydrides), which vary in their erosion characteristics (surface vs. bulk) and hydrophobicities were studied. In addition to examining the generality of the approach, potential advantages of such systems in the context of tissue engineering and drug delivery are briefly discussed.

Anhydrides↗