## 2 PHA in Biotechnology
### Drug Carriers
[66] demonstrated results that point to the nanocomposite composed of PHBV as an alternative to improve breast cancer treatment through the loading of the hydrophobic drug docetaxel. The drug-pumping system applied to fight cancer using docetaxel has also been shown to be effective using a thermogel based on poly[(R)-3-hydroxybutyrate-(R)-3-hydroxyhexanoate] copolymerized with poly(ethylene glycol) and polypropylene glycol. The application of this drug, combined with the carrier, proved to be effective in treating melanomas without causing damage to healthy tissues, proving to be a promising carrier for anticancer drugs [67]. The incorporation of PHA in conjunction with other polymers offers a promising alternative to drug-pumping systems. The junction between PHA and polyvinyl alcohol (PVA) is an example where the specificities of both polymers complement each other, reducing the degradation rate of PVA. Additionally, the PHA membrane supports water-soluble PVA fibers. The efficacy of this combination was demonstrated in the transportation of levofloxacin, resulting in highly efficient bactericidal results against Gram-negative strains of _E. coli_ and Gram-positive strains of _S. aureus_[68]. Furthermore, the incorporation of compounds can also serve to modulate the release of the drug by the carrier, as well as the incorporation of superparamagnetic nanoparticles. A carrier with a thermal responsive property regulated by magnetic oscillation was demonstrated to be a promising candidate for veterinary application when PHA copolymers were combined with nanomagnette to achieve controlled progesterone release [69]. [PERSON] et al. [70] also described an effective combination in encapsulating hydrophobic drugs, which is the copolymer formed by combining hyaluronic acid and PHA. _Bacillus subtilis_ was able to produce PHA from a culture medium containing orange peel as a way to reduce the cost of polymer production. This PHA produced was proved effective in administering levofloxacin, with the release of the drug reaching up to 99.12% [71]. The bacterium _Pseudomonas mendocina_ CH50 showed positive results for the production of poly(3-hydroxyoctanoate-co-3-hydroxydecananoate-co-3-hydroxydodecanoate) or P(3 HO-co-3 HD-co-3 HDD). This polymer was used as a film and submitted to a coating process based on the chemical used by mussels to adhere to wet surfaces, thus allowing it to overcome the main barrier for the targeted application of drugs in the oral mucosa. The polydopamine lining showed positive results, increasing film adhesion in in vitro cell proliferation and in in vivo neovascularization [72]. [PERSON] et al. [73] showed that poly(3-hydroxybutriato-co-butylene adipate) can produce drug nanocarriers. The formation of PHA nanoparticles can also be performed using the interaction of the polymer with the phasins. PHBHx was combined with PhaP phasin modified with a targeting peptide that recognizes an epidermal growth factor receptor to develop a targeting system for tumors, proving to be suitable as a drug carrier [74]. The spray-drying technique was used with efficiency in the production of drug carriers. Microparticles of P3 HB and P3 HB were combined with polyethylene glycol(PEG) for the paclitaxel(PTX) and 5-Fluoroucail(5-FU) drugs carriage. The method showed improvement in yield and greater incorporation of drugs into microparticles, and extended release of drugs led to inhibition of tumor cell growth [75]. PHA was also utilized as an inhaled drug carrier for the lungs; however, additional research is required to determine the viability of these carriers [76]. As drug carriers, the PHA microspheres that were previously mentioned as scaffolds also demonstrated promising results. [PERSON] et al. [77] showed the feasibility of using MCL-PHA in microspheres to transport antifungal drugs to combat candidiasis.