Zeke Barnard

PHEMA Hydrogels Modified through the Grafting of Phosphate Groups by ATRP Support the Attachment and Growth of Human Corneal Epithelial Cells

Converting the surface of poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel into a cell-adhesive surface has been successfully achieved through a method based on atom transfer radical polymerization (ATRP) grafting. Following activation of the surface hydroxyl groups of PHEMA by bromination, surface-initiated ATRP of mono(2-methacryloyloxyethyl) phosphate (MMEP) was conducted in a methanol—water system with Cu(I)Br as catalyst at room temperature. The conversion of PHEMA hydroxyl groups to brominated isobutyryl groups and the occurrence of grafting of PMMEP were confirmed by infrared and X-ray photoelectron spectroscopies. Cell attachment experiments were conducted by culturing human corneal limbal epithelial cells on the PMMEP-grafted PHEMA, and on unmodified PHEMA and tissue culture plastic for comparison. The results showed that the grafted PMMEP was homogeneously distributed, and the phosphate groups appeared to significantly promote the attachment, spreading and growth of cells, at a level comparable to the tissue culture plastic.

Reconstruction of the ocular surface using biomaterials

Abstract This chapter discusses the effect on our vision of a large group of disorders, known as ocular surface disorders (OSDs), and presents the therapeutic strategies to reconstruct the afflicted ocular surface. If left untreated, OSDs lead to partial or total loss of eyesight. An overview of various treatment strategies is presented, with the emphasis on the development of the ex vivo expansion of corneal limbal epithelial cells (presumed to be stem or progenitor cells) and the creation of transplantable epithelial constructs. The use of naturally derived biomaterials (collagen, fibrin, etc.) or synthetic polymers (polylactides, thermoresponsive polymers, etc.) as substrata in these constructs is critically analyzed. Emphasis is placed on the substrata from silk fibroin, currently being developed by the authors.

Degradable hydrogels for tissue engineering-part II: Responses of fibroblasts and macrophages to Linear PHEMA

A series of linear poly(2-hydroxyethyl methacrylate) (PHEMA) with defined molecular weights (MW) and narrow molecular distributions were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization using cumyl dithiobenzoate (CDB) as a chain transfer agent. Murine fibroblasts (3T3) were exposed to eluates from various PHEMA samples, washed or unwashed, and with or without dithioester end groups. After 72 hrs in cell culture, no cytotoxic response was elicited by the polymer samples devoid of dithioester end groups, and which also underwent a thorough washing regime. Specimens throughout the entire MW range were internalized by a macrophage (cell line Raw 264), suggesting that such polymers can be used as models for studying the biodegradation of PHEMA.