Biodegradable Polyphosphazene Biomaterials for Tissue Engineering and Delivery of Therapeutics

Table 1

Summary of in vitro degradation studies of poly(amino acid ester)phosphazenes and their cosubstituted polyphosphazenes. The ester refers to the chain attached to the carboxyl terminus of the amino acid. The detailed degradation profiles can be found in the cited papers.

Amino acid	Ester	Cosubstituents	Study length	Reference(s)
Glycine	Methyl		35 days	[37]
	Ethyl		35–120 days	[22, 37, 38]
		Alanine ethyl ester (50%)	7 weeks	[23]
		p-Methyl phenoxy (25–90%)	7 weeks	[56]
		Ethyl-2-(O-glycyl)lactate (0–25%) and phenylalanine ethyl ester (70%)	120 days	[22]
	t-Butyl		5 weeks	[37]
	Benzyl		5 weeks	[37]
Alanine	Methyl		5 weeks	[37]
	Ethyl		7 weeks	[23, 38]
		p-Methyl phenoxy (50%)	7 weeks	[23]
		p-Phenyl phenoxy (50%)	7 weeks	[23]
	Benzyl		7 weeks	[38]
Valine	Methyl		5 weeks	[37]
Phenylalanine	Ethyl		5 weeks	[37]