## 1 Introduction  
Peptide-based molecules fall into two distinct classes. The first class consist of peptides, which are short chains of amino acids (AAs), generally considered to be 2-50 AAs in length [1, 2, 3], that depending on their chemical composition, can perform a wide variety of functions, both for diagnostic and therapeutic purposes. With 22 well-known proteinogenic AAs [4] and many more nonproteinogenic AAs, the variability of peptide composition is extremely vast. Proteinogenic AAs are essential for normal human function, regulating metabolism, growth and repair, among other processes [5]; however, they can also be exploited for their medicinal qualities. Over 700 naturally occurring peptides have been identified in nature [6], with much more able to be synthesized artificially, providing a huge library of molecules with potentially life-sustaining effects. Common peptide-based medicines, such as adalimumab (TNF inhibitor) and insulin, are used daily by millions of people for an extensive range of conditions, namely [PERSON]'s disease, diabetes mellitus, and rheumatoid arthritis, among others. The second class of peptide-based molecules consists of proteins, generally >50 AAs and can have complex secondary structures. This class includes enzymes and antibodies. Peptide therapeutics are some of the most valuable medicines available [6]; however, their formulations are far from optimized. All peptide medicines must be delivered parenterally [7], often intravenously, due to the degradative process that occurs upon oral administration, which, despite being less convenient for the patient, still allows the delivery of life-saving medicines. Peptide drugs frequently possess high selectivity and potency while sustaining an agreeable safety profile, for example, novel antimicrobial peptides [8; 9] and chemotherapeutic agents [10]. Their chemical nature often makes their metabolism predictable [11], which is very useful for administration, distribution, metabolism, and excretion (ADME) calculations; however, frequently, the unmodified peptide will have a very unfavorable ADME profile. For this reason, administrative formulation methods like nanoencapsulation, pegylation and peptide-implant reservoirs must be exploited to allow optimized delivery of the peptides. Due to the unique nature of proteins, their diagnostic attributes are also prevalent in many areas of healthcare, including imaging agents for pregnancy tests. Target specificity is one of the major attributes that peptide-based molecules possess, as their individual AA composition extends peptides to be prime candidates for diagnostic techniques, such as antibody isolation, radiotherapeutic imaging and enzyme detection [12]. Peptide-based molecules are already established for diagnostic purposes; however, due to recent nanotechnological advances, a new generation of peptide-based diagnostics could be on the horizon. Peptides have a broad scope of utility, owing to their unique and adaptable pharmacokinetic (PK) and pharmacodynamic (PD) properties, making them ideal candidates for theranostic applications. Depending upon the chemical composition of a peptide chain, attributes, such as amphiphilicity or a high volume of distribution (Vd), may be demonstrated [13]. Knowledge of PK and PD allows analysis of a molecule's potential toxicological profile. Peptide-based products on the market, such as insulin glargine and denosumab, are tested rigorously to establish in-depth safety profiles to prevent harm upon use. Depending upon the peptide's formulation, e.g., nanoencapsulation or pegylation, the toxicology profiles will vary. For example, toxicology profiles relating to nano-encapsulated peptides are speculated to possess lower toxicity than the unmodified peptide [14], while pegylated molecules are compared to their un-pegylated counterparts are more toxicologically similar [15].