Biomedical subjects

K G Marra

Publications and source records attributed to K G Marra.

5 recordsLinked to original sources

PubMed2001

The influence of polymer blend composition on the degradation of polymer/hydroxyapatite biomaterials.

The in vitro degradation of biodegradable polymer/ceramic composites was assessed in two different environments under both static and pseudodynamic conditions. The blends, consisting of polycaprolactone, poly(lactic-co-glycolic acid), and hydroxyapatite, have potential use in bone tissue engineering applications, thus it is essential to establish a standardized method of characterizing the degradation of new biomaterials. In this study, the variation in polymer blend ratio was examined to observe a change in degradation rate. The porous blends were degraded in water and serum-containing media. A previous study examined in vitro degradation in serum-free buffer. Molecular weight loss, gravimetric weight loss, pH changes and morphological changes were evaluated. The changes in porosity were observed with scanning electron microscopy and quantitatively assessed using image analysis. There was a significant difference in molecular weight loss and gravimetric weight loss between the blends after 10 weeks in vitro. Blends containing the greatest amount of poly(lactic-co-glycolic acid) degraded most rapidly.

Journal Article↗

PubMed2001

Controlled release from coated polymer microparticles embedded in tissue-engineered scaffolds.

The controlled release of proteins in tissue-engineered implants is being examined with the potential application to improve vascularization and hasten tissue growth. Bovine serum albumin (BSA), was encapsulated within poly(D,L-lactic-co-glycolic acid) [PLGA] microparticles. The microparticles were coated with poly(vinyl alcohol) and incorporated into PLGA tissue-engineered scaffolds during fabrication. The release of BSA from PLGA microparticles, coated PLGA microparticles, and microparticles embedded in a porous PLGA scaffold was measured. We have developed a novel approach that will permit incorporation of coated polymeric microparticles during PLGA scaffold fabrication. Growth factors or drugs could be incorporated into the microparticles resulting in a long-term, controlled release.

Animals↗

PubMed2000

Characterization of osteoblast-like behavior of cultured bone marrow stromal cells on various polymer surfaces.

The creation of novel bone substitutes requires a detailed understanding of the interaction between cells and materials. This study was designed to test certain polymers, specifically poly(caprolactone) (PCL), poly(D,L-lactic-CO-glycolic acid) (PLGA), and combinations of these polymers for their ability to support bone marrow stromal cell proliferation and differentiation. Bone marrow stromal cells were cultured from New Zealand White rabbits and were seeded onto glass slides coated with a thin layer of PCL, PLGA, and combinations of these two polymers in both a 40:60 and a 10:90 ratio. Growth curves were compared. At the end of 2 weeks, the cells were stained for both matrix mineralization and alkaline phosphatase activity. There was no statistically significant difference in growth rate of the cells on any polymer or polymer combination. However, there was a striking difference in Von Kossa staining and alkaline phosphatase staining. Cells on PCL did not show Von Kossa staining or alkaline phosphatase staining. However, in the 40:60 and 10:90 blends, there was both positive Von Kossa and alkaline phosphatase staining. These data indicate that PCL alone may not be a satisfactory material for the creation of a bone substitute. However, it may be used in combination with PLGA for the creation of a bone substitute material.

Animals↗

PubMed1999

In vitro analysis of biodegradable polymer blend/hydroxyapatite composites for bone tissue engineering.

Blends of biodegradable polymers, poly(caprolactone) and poly(D, L-lactic-co-glycolic acid), have been examined as scaffolds for applications in bone tissue engineering. Hydroxyapatite granules have been incorporated into the blends and porous discs were prepared. Mechanical properties and degradation rates in vitro of the composites were determined. The discs were seeded with rabbit bone marrow or cultured bone marrow stromal cells and incubated under physiological conditions. Polymer/ceramic scaffolds supported cell growth throughout the scaffold for 8 weeks. Scanning and transmission electron microscopy, and histological analyses were used to characterize the seeded composites. This study suggests the feasibility of using novel polymer/ceramic composites as scaffold in bone tissue engineering applications.

Animals↗

PubMed1999

Cytomimetic biomaterials. 3. Preparation and transport studies of an alginate/amphiphilic copolymer/polymerized phospholipid film.

The significance of molecular design methodologies based upon membrane-mimetic systems lies in the ability to engineer robust materials of varying geometry with a high degree of reproducibility and molecular control over surface order and chemistry. However, non-covalently associated assemblies, in and of themselves, are often insufficiently robust for many applications. We have previously reported the in situ polymerization of a single phospholipid monolayer on a self-assembled film of octadecyltrichrolosilane (OTS) on glass, as well as the polymerization of phospholipids on an amphiphilic, dialkyl-containing terpolymer bound to a gold-coated silicon wafer. We now report the polymerization of a phospholipid monolayer assembly onto an alkylated hydrogel substrate with significant alteration in both surface chemistry and mass transport properties at the hydrogel-water interface. A general platform is thereby created for enhancing the control of either the local delivery of specific macromolecules or the immunoisolation barrier for many cell based therapies.

Alginates↗