Polyhydroxyalkanoates: opening doors for a sustainable future

Abstract

Polyhydroxyalkanoates (PHAs) comprise a group of natural biodegradable polyesters that are synthesized by microorganisms. However, several disadvantages limit their competition with traditional synthetic plastics or their application as ideal biomaterials. These disadvantages include their poor mechanical properties, high production cost, limited functionalities, incompatibility with conventional thermal processing techniques and susceptibility to thermal degradation. To circumvent these drawbacks, PHAs need to be modified to ensure improved performance in specific applications. In this review, well-established modification methods of PHAs are summarized and discussed. The improved properties of PHA that blends with natural raw materials or other biodegradable polymers, including starch, cellulose derivatives, lignin, poly(lactic acid), polycaprolactone and different PHA-type blends, are summarized. The functionalization of PHAs by chemical modification is described with respect to two important synthesis approaches: block copolymerization and graft copolymerization. The expanded utilization of the modified PHAs as engineering materials and the biomedical significance in different areas are also addressed.

Advances in drug delivery systems based on synthetic poly(hydroxybutyrate) (co)polymers

“…The recent interest in stimuli-responsive polymers [162][163][164] and the unique properties of micelles containing a PHB core promoted the development of PHB-based stimuliresponsive drug carriers [57,165,166]. Indeed, thermo-or pH-responsive copolymers enable to tune the physico-chemical properties of the micelles and also to modify the drug release profile [167][168][169][170][171].…”

“…Most self-assembled systems using PHB are based on bacterial semi-crystalline poly((R)-3-hydroxybutyrate) P(R)-HB [43,[45][46][47][48][49][50][51][52][53][54][55][56][57]. Indeed, industrial production of bacterial PHB, and generally of PHAs (poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-4HB)), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(3-hydroxybutyrate-co-3-hydroxyhexanoate (PHBHH), etc.…”

“…Furthermore, polyester nanoparticulate DDSs can be formed from either naturally occurring polymers such as chitosan [41] or PHAs [42][43][44], or from synthetic macromolecules such as PLA, PEG, PCL or PHAs. Indeed, PHAs can be advantageously both naturally (microbial PHAs) or synthetically (chemically) produced [43,[45][46][47][48][49][50][51][52][53][54][55][56][57]. Among the numerous PHAs, the ubiquitous biocompatible and biodegradable poly(3-hydroxybutyrate) (PHB) can be obtained from bacteria as isotactic PHB, while ROP of substituted -lactones provides a valuable entry into PHBs featuring various tunable microstructures (atactic, syndiotactic, isotactic) [58][59][60].…”

“…The stereoregularity of the enchainment of -lactone units within PHB dictates its thermomechanical properties. In particular, microbial isotactic PHB is a stiff and rather brittle polymer of high crystallinity, and consequently not easily processable, thus impeding its applications such as in packaging, implantable devices, or also drug delivery applications [57,61]. Therefore, the possibility to access various PHBs with different stereochemistries from ROP opens new venues in PHBbased DDSs [62].…”

Latest Advances in Antibacterial Materials

“…From the environmental standpoint, it is also useful to develop biodegradable antibacterial polymers. With regards to biodegradable antibacterial compounds, there is also potential to use polyesters such as poly[(R)-3-hydroxybutyrate], [74][75][76][77][78][79][80][81][82][83] poly(lactic acid), 84,85 poly(e-caprolactone) [86][87][88] or even polycarbonates. 89,90 These polyesters have been extensively used for the development of biomaterials and future work can focus on these polymer backbones and their subsequent modi¯cations.…”