Ultrashort Self-Assembling Peptide Hydrogel for the Treatment of Fungal Infections

Abstract

Abstract:The threat of antimicrobial resistance to society is compounded by a relative lack of new clinically effective licensed therapies reaching patients over the past three decades. This has been particularly problematic within antifungal drug development, leading to a rise in fungal infection rates and associated mortality. This paper highlights the potential of an ultrashort peptide, (naphthalene-2-ly)-acetyl-diphenylalanine-dilysine-OH (NapFFKK-OH), encompassing hydrogel-forming and antifungal properties within a single peptide motif, thus overcoming formulation (e.g., solubility, drug loading) issues associated with many currently employed highly hydrophobic antifungals. A range of fungal susceptibility (colony counts) and cell cytotoxicity (MTS cell viability, LIVE/DEAD staining ® with fluorescent microscopy, haemolysis) assays were employed. Scanning electron microscopy confirmed the nanofibrous architecture of our self-assembling peptide, existing as a hydrogel at concentrations of 1% w/v and above. Broad-spectrum activity was demonstrated against a range of fungi clinically relevant to infection (Aspergillus niger, Candida glabrata, Candida albicans, Candida parapsilosis and Candida dubliniensis) with greater than 4 log 10 CFU/mL reduction at concentrations of 0.5% w/v and above. We hypothesise antifungal activity is due to targeting of anionic components present within fungal cell membranes resulting in membrane disruption and cell lysis. NapFFKK-OH demonstrated reduced toxicity against mammalian cells (NCTC 929, suggesting increased selectivity for fungal cells. However, further studies relating to safety for systemic administration is required, given the challenges toxicity has presented in the wider context of antimicrobial peptide drug development. Overall this study highlights the promise of NapFFKK-OH hydrogels, particularly as a topical formulation for the treatment of fungal infections relating to the skin and eyes, or as a hydrogel coating for the prevention of biomaterial related infection.

Antifungal Peptides as Therapeutic Agents

“…Examples include the synthetic killer peptide (KP) and the ultrashort peptide NapFFKK-OH, which, at certain pHs and concentration conditions, undergo a selfassembly process. The results are hydrogel-like aggregates that could slowly release the peptides in physiological conditions, as well as reducing the proteolytic susceptibility and increasing the storage stability of the active compound (Magliani et al, 2011;Albadr et al, 2018). Future clinical studies of these hydrogels and other delivery technologies will determine their safety and efficiency.…”

Ultrashort Peptide Hydrogels Display Antimicrobial Activity and Enhance Angiogenic Growth Factor Release by Dental Pulp Stem/Stromal Cells

“…NapFF ε K ε K-OH was synthesised on a manual nitrogen bubbler apparatus using the 9-fluorenylmethoxucarbonyl (Fmoc) solid phase peptide synthesis chemistry as previously outlined [ 16 ]. Hydrogel formulation was achieved by a pH triggered method as previously described [ 16 , 25 ] and outlined in further detail in Table 1 . Depending on the peptide concentration required (0.5%–2%; measured as % weight/volume ( w / v )), the required amount of peptide was dissolved in an appropriate volume of deionised water (dH 2 O) and titrated with 1 M sodium hydroxide (NaOH) to pH 8.5 and 0.5 M hydrochloric acid (HCl) to pH 7.…”

Unravelling the antimicrobial activity of peptide hydrogel systems: current and future perspectives

“…Although studied less frequently, their benefit within antifungal applications has also been postulated. 42,43 …”