## 5 Additives in Melt Electrospinning
### Pharmaceutical Additives
[21] developed a PP and high-density polyethylene (HDPE) blend loaded with chloroxididine dihydrochloride (CHDH) fibrous membrane for medical and filtration applications. CHDH is a common ingredient in oral rinse and toothpastes due to its antibacterial, antifungal and antiviral properties [132]. The main advantage is that its toxicity to mammals is very low [133]. In this experiment, the fibrous membrane had a porosity of 77%, with a mean flow pore size of 10 \(\upmu\)m. CHDH-loaded PP/HDPE melt electrospun fibers proved to be effective and efficient as the bacterial cell reduction was that of 99.9% in only 4 h [21]. Drug delivery of anththrombotic and anthromogenic agents like dipyridamole (DPD) is also possible. DPD was blended with PLA and polyhydroxy butyrate (PHB) in a work by [PERSON], [PERSON], et al. [134] to obtain a melt electrospun drug delivery system. PHB is a nontoxic polymer obtained from a natural source. It presents biocompatibility and controlled biodegradability, which makes it suitable for biological applications [135]. However, they can be limited by its brittleness and poor thermostability. Nevertheless, as it has been previously mentioned, polymer blends and additives may enhance the properties of materials at different concentrations. In this case, two different proportions of PLA/PHB were tested (9:1 and 7:3) and whilst the first showed a higher resistance to polymer hydrolysis, the latter presented a rate of diffusion transport of DPD twice as high as the 9:1 system. Different content of DPD was also tested and it was observed that the addition of the drug reduced the melting temperature of the blend. DPD-free fibers showed a smooth surface with a relatively constant diameter, whereas fibers with DPD had a rough surface with varying diameter within a single fiber. It should be noted, though, that the drug release profile is not constant because both polymers of this blend are sensitive to hydrolysis and so the drug was released to the medium not only by diffusion but also because of surface degradation of the fibers. Thus, this system should be further studied. Figure 8: PCL/PEG wound dressing fabricated by direct-writing melt electrospinning. SEM images of composite fiber mats with 90:10 PCL/PEG ratio and different geometric structures: Square-shape grid with the spacing of 0.6 and 0.8 mm, triangles and rhombuses. All fiber mat images are of the same magnification. Test of bacteria (_Escherichia coli_ and _Staphylococcus aureus_) inhibition zone of fiber mats loaded with ciprofloxacin. Copyright 2018 John Wiley & Sons [116]. One of the most recent studies on melt electrospun drug delivery systems is by [PERSON] et al. [136]. They prepared a black plaster/PEG nanocomposite to promote the in vitro release of water insoluble drugs found in black plasters. The matrix of the black plaster plays the role of the drug carrier and contains a paste of vegetable oil and Red Dan, the main component of which is Pb3O4. Several water-insoluble drugs are found in the paste; one example is Sanguis Draconis (SD) or Dragon's Blood. SD is a resin obtained from the rattan palm _Daemonorops draco_ that is used in traditional medicine to prevent osteoporosis [137]. Since drug absorption by skin is not effective, PEG was added to improve the efficiency as the common drug carrier that it is for solid dispersions [138; 139]. It was proven in the results that when PEG conformed 85% of the fiber composition, the dissolution rate of SD higher than in traditional black plaster. Moreover, the fibers showed uniform diameter with higher porosity and specific surface area, and presented an excellent degradation of the nanocomposite under physiological conditions [136].