In JoVE (1)

Other Publications (2)

Articles by Ramya Bhuthalingam in JoVE

Other articles by Ramya Bhuthalingam on PubMed

Quantification of Aldehyde Terminated Heparin by SEC-MALLS-UV for the Surface Functionalization of Polycaprolactone Biomaterials

Colloids and Surfaces. B, Biointerfaces. Aug, 2015  |  Pubmed ID: 26052108

A straight forward strategy of heparin surface grafting employs a terminal reactive-aldehyde group introduced through nitrous acid depolymerization. An advanced method that allows simultaneously monitoring of both heparin molar mass and monomer/aldehyde ratio by size exclusion chromatography, multi-angle laser light scattering and UV-absorbance (SEC-MALLS-UV) has been developed to improve upon heparin surface grafting. Advancements over older methods allow quantitative characterization by direct (aldehyde absorbance) and indirect (Schiff-based absorbance) evaluation of terminal functional aldehydes. The indirect quantitation of functional aldehydes through labeling with aniline (and the formation of a Schiff-base) allows independent quantitation of both polymer mass and terminal functional groups with the applicable UV mass extinction coefficients determined. The protocol was subsequently used to synthesize an optimized heparin-aldehyde that had minimal polydispersity (PDI<2) and high reaction yields (yield >60% by mass). The 8 kDa weight averaged molar mass heparin-aldehyde was then grafted on polycaprolactone (PCL), a common implant material. This optimized heparin-aldehyde retained its antithrombin activity, assessed in freshly drawn blood or surface immobilized on PCL films. Anticoagulant activity was equal to or better than the 24 kDa unmodified heparin it was fragmented from.

Smooth Muscle Cell Alignment and Phenotype Control by Melt Spun Polycaprolactone Fibers for Seeding of Tissue Engineered Blood Vessels

International Journal of Biomaterials. 2015  |  Pubmed ID: 26413093

A method has been developed to induce and retain a contractile phenotype for vascular smooth muscle cells, as the first step towards the development of a biomimetic blood vessel construct with minimal compliance mismatch. Melt spun PCL fibers were deposited on a mandrel to form aligned fibers of 10 μm in diameter. The fibers were bonded into aligned arrangement through dip coating in chitosan solution. This formed a surface of parallel grooves, 10 μm deep by 10 μm across, presenting a surface layer of chitosan to promote cell surface interactions. The aligned fiber surface was used to culture cells present in the vascular wall, in particular fibroblasts and smooth muscle cells. This topography induced "surface guidance" over the orientation of the cells, which adopted an elongated spindle-like morphology, whereas cells on the unpatterned control surface did not show such orientation, assuming more rhomboid shapes. The preservation of VSMC contractile phenotype on the aligned scaffold was demonstrated by the retention of α-SMA expression after several days of culture. The effect was assessed on a prototype vascular graft prosthesis fabricated from polylactide caprolactone; VSMCs aligned longitudinally along a fiberless tube, whereas, for the aligned fiber coated tubes, the VSMCs aligned in the required circumferential orientation.

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