# Poly(lactic acid)-Based Electrospun Fibrous Structures for Biomedical Applications
## 8 Biomedical Applications of PLA-Based Nanofibrous Structures
### Drug Delivery  
In recent years, a lot of research has been done for discovering nanotechnology procedures (especially nanofibers) as a drug delivery system for transdermal uses by different scientists. Nanofibers are used to deliver drugs and are able to release the drugs under controlled conditions for a long period of time. In these cases, PLA is one of the well-known synthetic polymers in biomedical usage since it has good biodegradability and biocompatibility. PLA, which is a liner aliphatic polyester can be synthesized from 100% renewable materials, such as rice and wheat through fermentation and polymerization. The FDA has accepted PLA as a biomaterial application, such as, for instance, sutures, bone plates, abdominal mesh, and drug delivery systems [71]. There are some mechanisms, such as coating, embedding, or encapsulating for drug loading and drug releasing from nanofibers to achieve control over drug release kinetics [92; 93; 94]. It is possible to dissolve the drug and the polymer directly in the polymer solution if they both are soluble in the same solution [85]. On the other hand, when drugs and polymers are not soluble in the same solvent, the drug can be dissolved in another solvent and then added to the polymer solution [95]. There is another method for dissolving drugs and polymers which are not soluble in the same solvent: in this method, the drug is dissolved in a solvent that is immiscible with the solvent in which the polymer is dissolved, and both solutions are loaded in different capillaries to be electrospun coaxially, or both solutions can be mixed and the emulsion electrospun [96]; this method is an encapsulation tactic of the drug in the polymer matrix [97]. Another method has been suggested for loading the drug in nanofibers after the nanofiber was made; in this method, the nanofiber is immersed in a drug solution and the drug is absorbed by nanofibers through capillary property [84; 98; 99]. Figure 12: TEM images of core–shell nanofibers: (**a**) with compact core structure; (**b**) with porous core structure Reproduced with permission from [6] (License number: 523520656228), (**c**) SEM image of coaxial PLA-PVA-CTGF membranes, reproduced from an open access paper [91] distributed under the terms of the Creative Commons Attribution—Non-Commercial (v3.0) License. Several mechanisms are involved in the release of drugs from nanofibers, including desorption from the nanofiber surface layer, diffusion through the canals and pores of nanofibers, or matrix degradation [100; 101]. The drug release kinetics can be changed with the type of polymer, geometry, control over the diameter of nanofibers, porosity, morphology, and adjustment of multiple processing variables during the production of nanofibers [92; 102]. Figure 13 shows a scheme image of the different methods for loading the drug into nanofibers. PLA-based nanofiber structures have been investigated as drug carriers in different types of systems, such as nanofibers containing chemical drugs, nanofibers coated with drugs, porous nanofibers combined with growth factors, and core-shell fibrous structure containing drugs in the core [84; 103; 104]. Table 2 shows different studies in which electrospinning has been used for the production of drug-loaded PLA fibers for drug delivery application. Figure 13: The scheme image of the different methods for loading the drug in nanofibers, reproduced from an open access paper [71], under the terms of Creative Commons Attribution 4.0 International (CC BY 4.0) License. \begin{table}
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[PERSON] et al. [107] investigated the possibility of loading the hydrophilic doxorubicin hydrochloride (Dox-HCl) and hydrophobic free doxorubicin (Dox-base) in a PLA carrier matrix. Drug-polymer miscibility, fiber wettability, and fiber degradability were investigated as a function of the drug release profile of the fibers.