## 5 Drug Delivery Systems
### Poly(D,L-lactic-co-glycolic) Acid (PLGA)  
PLGA is a copolymer that is composed of lactic and glycolic acid. The endogenous nature of these substances and the fact that the organism easily metabolizes the polymer itself contribute to its very low toxicity and safe biodegradability profile. There have been studies that assessed its release profile, which are summarized in [PERSON] et al. [80]. Since then, studies have researched its possible applications outside the food industry. PLGA has been used, among other things, to increase the shelf life of drugs at their final site of action, as such compounds include anastrozole (an aromatase inhibitor), a compound administered to treat breast cancer in postmenopausal women. In 2006, [PERSON] et al. [116] published the first paper showing the encapsulation of this drug through the use of biodegradable microparticles based on lactic-co-glycolic acid copolymers (PLGA-poly[lactic-co-glycolic acid]).  
PLGA has been studied extensively as a polymeric carrier for biodegradable microspheres. PLGA microparticles have proven to be an effective way to deliver drugs belonging to various classes, including non-steroidal anticancer drugs--including anastrozole--and non-steroidal anti-inflammatory drugs, peptides, and steroid hormones [117]. In addition, another paper documented that electrospun PLGA ultrafine fibers loaded with fusidic acid with antimicrobial activity have found their application in wound healing as a wound dressing material [118]. PLGA was selected as a Food and Drug Administration-approved biodegradable and biocompatible copolymer compound. PLGA with different ratios of glycolic acid to lactic acid produces fibers with suitable mechanical properties and a wide range of diameters and degradation rates. Due to its hydrophobicity, PLGA is electrospun from organic solvents. The developed electrospun fibrous mats were used to test in vitro interactions with the following three strains of bacteria found on wounds: _P. aeruginosa_; methicillin-resistant _S. aureus_ (MRSA) reference strain; and MRSA clinical isolate. This study investigated the effect of wound bacteria on the structural integrity and function of the ultrathin fibrous mat, mainly in terms of matrix degradation and drug release properties, as well as the effect of mat properties containing fatty acids on in vitro antimicrobial activity. This study confirmed that biodegradable polymeric ultrathin fibrous wound dressing materials, in addition to providing structural support for wound healing and antimicrobial reservoir function for wound infection control, are actively involved in dynamic interaction with the wound environment [119].  
Two studies conducted by [PERSON] et al. [119; 120] used thyme EO encapsulated in PLGA to treat skin inflammation and acne. Their results indicate that such a strategy may be viable. In one of the works, the authors showed that _C Antibacterium acnes_ viability decreased after 2 h of application, while the healthy skin microbiota was unaffected [121]. The second work has also shown that this formulation could promote wound healing, probably due to its antimicrobial and anti-inflammatory effects [119; 120]. However, it is worth emphasizing that those studies were conducted on relatively few participants (12). The participants had no skin conditions, and the authors stressed the need to evaluate the long-term effects of this application method. However, there are severe limitations to the use of PLGA nanosystems. Various authors have noticed that their loading capacity is quite low, and their production cost is high and difficult to scale up [80].