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M R Mariappan

Publications and source records attributed to M R Mariappan.

3 recordsLinked to original sources
PubMed2000

Enhancing hepatocyte adhesion by pulsed plasma deposition and polyethylene glycol coupling.

Decreased hepatocyte adhesion to polymeric constructs limits the function of tissue engineered hepatic assist devices. We grafted adhesion peptides (RGD and YIGSR) to polycaprolactone (PCL) and poly-L-lactic acid (PLLA) in order to mimic the in vivo extracellular matrix and thus enhance hepatocyte adhesion. Peptide grafting was done by a novel technique in which polyethylene glycol (PEG)-adhesion peptide was linked to allyl-amine coated on the surface of PCL and PLLA by pulsed plasma deposition (PPD). Peptide grafting density, quantified by radio-iodinated tyrosine in YIGSR, was 158 fmol/cm(2) on PLLA and 425 fmol/cm(2) on PCL surfaces. The adhesion of hepatocytes was determined by plating 250,000 hepatocytes/well (test substrates were coated on 12 well plates) and quantifying the percentage of adhered cells after 6 h by MTT assay. Adhesion on PCL surfaces was significantly enhanced (p < 0.05) by both YIGSR (percentage of adhered cells = 53 +/- 7%) and RGD (53 +/- 12%) when compared to control surfaces (31 +/- 8%). Hepatocyte adhesion on PLLA was significantly (p < 0.05) enhanced on PLLA-PEG-RGD surfaces (76 +/- 14%) compared to control surfaces (42 +/- 19%) and more (68 +/- 25%) but not statistically significant (p = 0.15) on PLLA-PEG-YIGSR surfaces compared to control surfaces. These results indicate that hepatocyte adhesion to PCL and PLLA based polymeric surfaces can be enhanced by a novel adhesion peptide grafting technique using pulsed plasma deposition and PEG cross-linking.

Animals↗
PubMedDate not supplied

Chitosan and chitosan sulfate have opposing effects on collagen-fibroblast interactions.

Soon after injury, hyaluronan is prominent in granulation tissue. As hyaluronan wanes, sulfated glycosaminoglycans predominate. The temporal relationship between the transition from unsulfated to sulfated glycosaminoglycans and the phenotypic changes in fibroblasts in the wound bed suggest that these two events are interrelated. This possibility was investigated using chitosan and its sulfated product as model compounds. The ability of cultured human foreskin fibroblasts to bind and to contract lattices of collagen, collagen-chitosan, and collagen-chitosan sulfate was determined. Fibroblast adherence to substrates after 24 hours was determined by the MTT assay at A570. Adherence to the collagen-chitosan substrate was markedly reduced (mean A570 +/- SD; 0.16 +/- 0.05, n = 6) (p < 0.01) compared to collagen alone (0.92 +/- 0.04) or to collagen-chitosan sulfate (0.84 +/- 0.05). Kinetics of contraction of lattices by enmeshed fibroblasts was determined by planimetric measurements, 0-48 hours after loosening the lattices. Contraction of the collagen-chitosan lattices (n = 5) was less at all time points than for the other two lattices. After 48 hours, the collagen- chitosan lattices contracted significantly (p < 0.01) less (30.0% +/- 4.4) compared to collagen alone (66.9% +/- 4.7) and collagen-chitosan sulfate (71.6% +/- 7.7). Scanning electron microscopy of the acellular lattices showed fibers of the collagen-chitosan mixture to be the thickest and with altered organization. These results show that chitosan sulfation markedly enhances fibroblast adhesion and promotes contraction of a collagen lattice compared to the unsulfated material. By analogy to the in vivo sequence of hyaluronan followed by sulfated glycosaminoglycans in wounds, the results suggest that glycosaminoglycan sulfation may be a contributing signal for phenotypic transformation during wound healing.

Biopolymers↗