Which of the following is NOT a biodegradable polymer?

Polyphospho-esters (PPEs) are indeed known for their biocompatibility and potential use in biomedical applications, but they may not necessarily be classified as biodegradable in the same context as the other polymers listed. Although they can exhibit some degree of degradation under specific conditions, their overall behavior does not match the established biodegradability criteria typically associated with the other materials mentioned.

In contrast, poly(lactic acid), poly(glycolic acid), and poly(ε-caprolactone) are well-documented biodegradable polymers. Poly(lactic acid) and poly(glycolic acid) are particularly prevalent in tissue engineering due to their predictable degradation characteristics into non-toxic lactic acid and glycolic acid, respectively. Poly(ε-caprolactone) is also utilized for its slow degradation rate, making it suitable for various applications in tissue scaffolding.

By focusing on the known degradation properties, polyphospho-esters stand out as less commonly recognized for biodegradability compared to the well-established biodegradable profiles of the other polymers listed.