## 2 Therapeutic Applications of Peptides
### Hydrogels and Peptide Antibiotics  
The production of peptide-based biomaterials via MFs is attractive as they possess a low level of immunogenicity, and prolonged-release formulations, such as biologic hydrogels, will degrade slowly over time, via natural processes, into non-toxic materials [52; 53]. Recent work performed utilizing the prolonged curative properties of peptide hydrogels allowed a double-pronged approach to wound healing via an MF-assisted process [54].  
Figure 3: Concept of peptide encapsulation within liposomes via liposome self-assembly.  
Peptide hydrogels possess a structure similar to the extracellular matrix, making them an ideal biocompatible medium for the controlled release of APIs. MFs were employed to synthesize a compact fibrous network of alginate to provide an optimal setting for the self-assembly of peptides onto the structure. The use of peptides on the structure also allowed the addition of a secondary API, the antibiotic limomycin, within the hydrogel; hence providing two APIs to provide a therapeutic effect. The novel approach of using peptides within the structure ensured that the wound healing process could be optimized by providing both the anti-inflammatory benefits of prolonged-release peptide therapy, as well as introducing antibiotic activity.  
It is possible that the process designed by [PERSON] et al. [55] would be adaptable to a microfluidic approach, which exploited ultrashort peptides (USPs) to control gold NP synthesis within a complex hydrogel structure. USPs are short chains of amino acids (approximately 3-7 amino acids) that can be used to provide unique interactions with external environments. Owing to the predictable chemical behavior of peptides, they have been shown to be exploited to assist with NP shape control. NP shape is an important factor to consider as it affects overall PDI values, and it can also affect the thermal stability of a formulation or encapsulation efficacy. For example, nickel-based NPs in a spherical shape have better heat-transference properties than a disc shape [56].  
Owing to increased pathogen drug resistance, the production of novel antimicrobials is limited, which is why a new area of antimicrobials in the form of peptide therapeutics should be explored. Despite the categorization of over 3000 AMPs, currently, only 7 antimicrobial peptides (AMPs) are approved for clinical use by the FDA [57], owing mainly to a lack of clinical efficacy. Bioassays performed using an MF design allow detecting antimicrobial activity. However, when compared to the traditional format of measuring via 96-well plate analysis, the results obtained were dissimilar, owing to differing oxygenation levels during incubation subjected to each system. The 96-well plate was exposed to a greater level of oxygen than the MFs assays, causing incomparability of the systems and hence the results of this study were inconclusive [57]. However, there is strong potential for future research in this area to explore different approaches for obtaining AMP activity using MFs. Conceptually, it is clear that MFs can be employed for this purpose, and there is an acute need for a new bioassay method, so this is an area that should be developed further.