Prolastin polymer

Upon dn ing from solution or treatment witli a nonsolvent such as ethanol most SELF polymer materials are converted to water stable products. Presumably, once induced to crystallize, the cohesion of the silklike blocks dominates the solubility properties of the block copolymer. Tbis property of ProLastin polymers allows them to be processed or formulated rith other compounds in aqueous, physiological solution and then converted to a water stable material by simply diying, lyophilizing, or treating the formulation wdth alcohol. 

Our protein polymers are generally not soluble in organic solvents. In fact, common organic solvents such as methanol and acetone can be used as nonsolvents which will induce the cr stallization and precipitation of polymers containing silklike blocks. Except for SELPO, once ciy stallization is induced they are no longer soluble in water. These properties are used in the preparation of water stable materials from ProLastin polymers. 

A number of solvents and coagulants have been used for wet spinning fibers composed of BetaSilk and ProLastin polymers. Solvents include 98% formic acid. 

ProLastin polymers are a family of protein-based materials w hose resorption rate in vivo can be controlled by adjusting the sequence and not just the composition of the polymer (Cappello et al, 1995). These adjustments can be made so as to cause little change in the formulation characteristics of the materials, their physical forms, or their mechanical properties. They have good mechanical integrity with no need for chemical crosslinking. They degrade by enzymatic proteolysis and are presumed to resorb by surface erosion. Their breakdowm products are peptides or amino acids w hich are electroneutral at physiological pH and cause no undue inflammation or tissue response. 

A family of protein polymers, ProLastins, were produced consisting of silklike (S) and elastinlike (E) peptide blocks in various block lengths and compositional ratios (Ferrari et al, 1986, and Cappello et al, 1990). The elastinlike block consists of the five amino add sequence, GVG T (Urn 1984, Urry et al., 1976, and Uriy 1988). As a family, silk-elastinlike copolymers (SELP s) consist of exact periodic alternation of silk and elastinlike domains. Individual members of the family vary in the number of silk or elastin blocks within the repeating domains. Table 2 displays the compositional structures of some ProLastin monomers. 

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