Microbiologically extracted poly(hydroxyalkanoates) and its amalgams as therapeutic nano-carriers in anti-tumor therapies.

Requisite of contriving strategies for mitigating polymeric waste generated in Nature via synthetic polymers has conceded in development of biopolymers like poly(hydroxybutyrate) (PHB), poly(hydroxyvalerate) (PHV), poly(lactic acid) (PLA) etc. Amongst all these biopolymers, PHB and its assorted homologues have sought more attention from scientific researchers due to their non-toxic nature coupled with their intrinsic biodegradability as well as biocompatibility. Concurrently, they also demonstrate ease of production via microbial fermentation and closely analogous physical traits against their synthetic counterparts utilized in biomedical sector. Researchers have extensively exploited PHB and its amalgams for an array of biomedical functions extending from carriers for drug delivery to scaffolds in tissue engineering to resorbable medical devices like cardiovascular grafts and so on. Additionally, advancement of science and technology in recent times has realized in utilization of PHB and its various derivatives as chemoembolizing agents as well as carriers of encapsulated drugs in nanomedicine sector for cancer treatment functions. PHB and its derivative polymeric systems have been extensively explored and probed, however, no amalgamated information on their effective utilization in cancer treatment applications is available as such. Within this review, we consolidate and discuss current progress and strategies of PHB and its copious amalgams from available literature, while concurrently outlining their future potential for implementation in cancer treatment as nano-carriers for therapeutic agents.

Biocompatible PHB Production from Bacillus Species Under Submerged and Solid-State Fermentation and Extraction Through Different Downstream Processing.

Catastrophic global accumulation of non-biodegradable plastic has led to efforts for production of alternative eco-friendly biopolymer. Here, we attempted to produce a biodegradable, cytocompatible and eco-friendly polyhydroxy-butyrate (PHB) from a pigmented Bacillus sp. C1 (2013) (KF626477) through submerged (SmF) and solid-state fermentation (SSF). Under SmF and SSF, 0.60 g l-1 and 1.56 g l-1 of PHB with 0.497 g l-1 of yellow fluorescent pigment (YFP) was produced. Fourier transform infrared (FTIR) absorption bands at 1719-1720 cm-1 indicate the presence of C=O group of PHB. Nuclear magnetic resonance (NMR) exhibited the typical chemical shift patterns of PHB, and crystallinity was confirmed from X-ray diffraction (XRD). The melting temperature (Tm), degradation temperature (Td) and crystallinity (Xc) of extracted PHB were found to be 171 °C, 288 °C and 35%, respectively. FACS (Fluorescence-activated cell sorting) confirmed cytocompatibility of PHB at 400 µg ml-1 in mouse fibroblast line. Moreover, biodegradability and elevated cytocompatibility of the PHB produced through SSF make them highly potential biomaterials to be used as a drug delivery carrier in future.

Biosynthesis and characterization of polyhydroxyalkanoate from marine Bacillus cereus MCCB 281 utilizing glycerol as carbon source.

Polyhydroxyalkanoates (PHAs) are aliphatic polyesters produced by bacteria from renewable resources which serve as a substitute of synthetic plastics. In the present study isolation, screening, identification of PHA producing bacteria from marine water samples and optimization of process variables for increased PHA production were accomplished. The potent isolate identified as Bacillus cereus MCCB 281 synthesized PHA co-polymer with 13 mol% 3-hydroxyvalerate in presence of glycerol. Process parameters optimized using central composite design for enhanced PHA production showed 1.5 fold higher PHA yield. Cell dry weight of 3.72 ±â€¯0.04 g L-1, PHA yield 2.54 ±â€¯0.07 g L-1 and PHA content of 68.27 ±â€¯1.2% (w/w) was achieved in fermenter at the optimized conditions. Purified polymer was characterized by Fourier-transform infrared spectroscopy, Nuclear magnetic resonance spectroscopy, Gas chromatography-Mass spectrometry, X-ray powder diffraction techniques and molecular weight of PHA was found to be 2.56 × 105 Da. PHA nanoparticles with average particle size 179 nm were synthesized for medical applications and biocompatibility analysis was performed with L929 mouse fibroblast cell line. This is the first report of a moderately halophilic B. cereus, which utilizes glycerol as the sole carbon source for PHA co-polymer production.

Structural and thermal characterization of PHAs produced by Lysinibacillus sp. through submerged fermentation process.

In this investigation an attempt has been made to characterize and identify Lysinibacillus sp. 3HHX by 16S-rDNA sequencing. The bacterium exhibited occurrence of PHAs granules on an average 11±1 per cell of 1.0µm length and breadth 0.72µm, revealed from TEM studies. Under optimized condition, 4.006gm/L of PHAs was extracted using hypochlorite digestion and multi-solvent extraction process. PhaC gene of ∼540bp and higher PHA synthase activity was detected at 48h of cultivation. The extracted PHAs was structurally characterized by GC-MS and 1H NMR reported to be P(3HB-co-3HDD-co-3HTD) and amorphous in nature with 112°C melting point, -11.0°C glass transition point and 114.76°C decomposition temperature detected by DSC & TGA respectively. The C/O of biopolymer disc was 1:65 as revealed from C1s and O1s spectra of XPS, that was completely biodegradable within 30 days. This biopolymer was observed to be non-cytotoxic to NIH 3T3 mouse fibroblast cells. The report is of its kind in establishing the abilities of Lysinibacillus sp. 3HHX for non-growth associated PHA co-polymer production. Moreover the biocompatible and biodegradable nature of the biopolymer conferred to its substantial biomedical applications.

Facile synthesis of multicompartment micelles based on biocompatible poly(3-hydroxyalkanoate).

In this paper, a straightforward method to produce poly(3-hydroxyalkanoate)-based multicompartment micelles (MCMs) is presented. Thiol-ene addition is used to graft sequentially perfluorooctyl chains and poly(ethylene glycol) oligomers onto poly(3-hydroxyoctanoate-co-hydroxyundecenoate) oligomers backbone. Well-defined copolymers are obtained as shown by ¹H NMR and size-exclusion chromatography. After nanoprecipitation in water, novel PHA-based MCMs are evidenced by cryo-transmission electron microscopy. Moreover, the cytocompatibility of MCMs is demonstrated in vitro via cell viability assay.

An assessment of the risks of carcinogenicity associated with polyhydroxyalkanoates through an analysis of DNA aneuploid and telomerase activity.

Polyhydroxyalkanoates (PHA) are aliphatic polyesters synthesized by many bacteria. Because of their flexible mechanical strengths, superior elastic property, biodegradability and biocompatibility, PHA have been developed for applications as medical implants, drug delivery matrices, and devices to support cell growth. Lots of studies showed that PHA matrices improved cell proliferation and tissue regeneration. However, the possibility of whether rapid cell proliferation on PHA matrices will induce tumor formation is unclear. Here we confirmed that proliferating rat osteoblasts grown on films of various PHA including PHB, PHBV, P3HB4HB, PHBHHx and PHBVHHx did not lead to cancer induction at least for p8th. Cell proliferation was evaluated by the incorporation of 5-bromodeoxyuridine (BrdU), the transcript expression of cancer related genes Ki67, p53 and c-Fos was monitored by quantitative Real-time PCR, the results showed the cells proliferating on the PHA films were under normal cell cycle regulation. Moreover, DNA aneuploid and telomerase activity were only detected in the positive control UMR-108 cells; compared with cells grown on films, UMR-108 cells had longer telomeres, further demonstrated the normal status of cells proliferating on the PHA films. It indicated that the above PHA family members could be used to support cell growth without indication of susceptibility to tumor induction. These results will be important for promoting the application of PHA as new members of biomaterials.