Aggregation enhances catecholamine secretion in cultured cells.

Transplanted cells and tissues have potential uses in the treatment of genetic, geriatric, and metabolic disorders, but optimal conditions for transplantation are not yet known. In this report, PC12 cells were aggregated in rotary and microgravity culture, using serum-free or serum-supplemented medium, and using a multifunctional polymer-peptide aggregation factor. Aggregates and single cells were then encapsulated and cultured within agarose gels, and the dopamine secretion in response to a depolarization buffer was measured using high-performance liquid chromatography combined with electrochemical detection (HPLC-ECD).

Materials for protein delivery in tissue engineering.

The ability of protein agents to modulate cellular behaviors, such as motility, proliferation, adhesion and function, is the subject of intense research; new therapies involving proteins will likely result. Unfortunately, many proteins have short half-lives and the potential for toxicity after systemic delivery, so traditional routes of administration are not appropriate. Alternate methods for sustained delivery of these agents to the desired cells and tissues in biologically active conformations and concentrations are necessary.

Synthesis and characterization of polymer-(multi)-peptide conjugates for control of specific cell aggregation.

A new synthetic approach has been applied to obtain novel di-, tetra-, and (multi)-peptide containing polymer conjugates in quantitative yields with a high degree of conjugation. Bis-(N-hydroxysuccinimidyl) esters of PEG (Mw = 200, 600, 1400, 2000, and 3400) were synthesized and studied in a condensation reaction with synthetic peptides: glycine-glycine-tyrosine-arginine (GGYR), a model peptide, and glycine-arginine-glycine-aspartic acid-tyrosine (GRGDY), a sequence known to promote cell adhesion and aggregation. Tetra-substituted derivatives of PEG-based conjugates were synthesized by coupling L-aspartic acid and L-aspartyl-L-phenylalanine through a condensation procedure in organic media.

PC12 cell aggregation and neurite growth in gels of collagen, laminin and fibronectin.

PC12 cells form aggregates when suspended within three-dimensional, self-assembled, type I collagen gels; these aggregates increase in size over time. In addition, when the cells are cultured in the presence of nerve growth factor, they express neurites, which extend through the three-dimensional matrix. In this report, the roles of fibronectin, laminin and nerve growth factor in PC12 cell aggregation and neurite growth following suspension in collagen matrices were evaluated.