Design and syntheses of highly potent teixobactin analogues against Staphylococcus aureus, Methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococci (VRE) in vitro and in vivo

The cyclic depsipeptide, teixobactin kills a number of Gram positive bacteria including Methicillin-resistant Staphylococcus aureus (MRSA) and Mycobacterium tuberculosis without detectable resistance. To date, teixobactin is the only molecule in its class which has shown in vivo antibacterial efficacy. There have been no in vivo evaluation studies on teixobactin analogues. In this work, we have designed and synthesized 10 new in vivo ready teixobactin analogues. These analogues showed highly potent antibacterial activity against Staphylococcus aureus, MRSA, and vancomycin-resistant Enterococci (VRE) in vitro. One analogue, D-Arg4-Leu10-teixobactin 2 was found to be non-cytotoxic in vitro and in vivo. Most importantly, in a mice model of S. aureus keratitis, topical instillation of peptide 2 decreased the bacterial bioburden (>99.0% reduction) and corneal edema significantly when compared to untreated cornea. Collectively, our results establish the excellent therapeutic potential of teixobactin analogue in attenuating bacterial infections and the associated severities

Hybrid Derivative of Cathelicidin and Human Beta Defensin-2 Against Gram-Positive Bacteria: A Novel Approach for the Treatment of Bacterial Keratitis

Bacterial keratitis (BK) is a major cause of corneal blindness globally. This study aimed to develop a novel class of antimicrobial therapy, based on human-derived hybrid host defense peptides (HyHDPs), for treating BK. HyHDPs were rationally designed through combination of functional amino acids in parent HDPs, including LL-37 and human beta-defensin (HBD)-1 to -3. Minimal inhibitory concentrations (MICs) and time-kill kinetics assay were performed to determine the concentration- and time-dependent antimicrobial activity and cytotoxicity was evaluated against human corneal epithelial cells and erythrocytes. In vivo safety and efficacy of the most promising peptide was examined in the corneal wound healing and Staphylococcus aureus (ATCC SA29213) keratitis murine models, respectively. A second-generation HyHDP (CaD23), based on rational hybridization of the middle residues of LL-37 and C-terminal of HBD-2, was developed and was shown to demonstrate good efficacy against methicillin-sensitive and methicillin-resistant S. aureus [MIC = 12.5–25.0 μg/ml (5.2–10.4 μM)] and S. epidermidis [MIC = 12.5 μg/ml (5.2 μM)], and moderate efficacy against P. aeruginosa [MIC = 25-50 μg/ml (10.4–20.8 μM)]. CaD23 (at 25 μg/ml or 2× MIC) killed all the bacteria within 30 min, which was 8 times faster than amikacin (25 μg/ml or 20× MIC). After 10 consecutive passages, S. aureus (ATCC SA29213) did not develop any antimicrobial resistance (AMR) against CaD23 whereas it developed significant AMR (i.e. a 32-fold increase in MIC) against amikacin, a commonly used treatment for BK. Pre-clinical murine studies showed that CaD23 (0.5 mg/ml) achieved a median reduction of S. aureus bioburden by 94% (or 1.2 log10 CFU/ml) while not impeding corneal epithelial wound healing. In conclusion, rational hybridization of human-derived HDPs has led to generation of a potentially efficacious and safe topical antimicrobial agent for treating Gram-positive BK, with no/minimal risk of developing AMR

Nature-inspired antimicrobial nanofibers for infection control

There is a growing demand for durable advanced wound dressings for the management of persistent infections after deep burn injuries. In my thesis, we have designed antibiotic free durable prototype wound dressings by taking advantage of strong interfacial interactions between gelatin (Gel) and epsilon-poly-L-lysine (εPL) and their bio-inspired polydopamine (pDA) crosslinking using ammonium carbonate diffusion method (εPL_Gel_pDA). The εPL_Gel_pDA dressings displayed broad spectrum antimicrobial properties against Gram-positive, Gram-negative and yeast strains. The dressing’s material revealed excellent biocompatibility and cell proliferative properties for both human dermal fibroblasts (hDFs) and immortalized human keratinocytes (HaCaT). In vivo wound healing properties of the dressings were examined in both un-infected, Staphylococcus aureus and Pseudomonas aeruginosa colonized partial- thickness burns of porcine model. In the uninfected burn injury model, the εPL_Gel_pDA mats displayed higher wound closure compared to commercially available silver-based dressings. In the infected burns, εPL_Gel_pDA mats leads to increased wound closure, helps in significant reduction in the bacterial bioburden (>4 log 10 reduction), higher keratinization and faster re-epithelialization when compared to placebo and Aquacel®Ag. Overall, this thesis identified the combined utility of bio- inspired crosslinker, biocompatible antiseptic polymer and εPL_Gel_pDA nanofibers as advanced prototype wound dressings and established its superiority over commercial silver-based dressings. These prototype wound dressings that we developed are beneficial in reducing bacterial colonization and infection, decreasing the dressing change frequency and thus reducing the related pain and nursing cost, helps in absorbing excess exudates and maintaining the wound bed moist. This is a potentially valuable approach for treating life-threatening burn injuries and burn-related infections.Doctor of Philosoph

Ocular Delivery of Predatory Bacteria with Cryomicroneedles Against Eye Infection

10.1002/advs.202102327Advanced Science821210232

Nucleic acid peptide nanogels for the treatment of bacterial keratitis

Cage-shaped nucleic acid nanocarriers are promising molecular scaffolds for the organization of polypeptides. However, there is an unmet need for facile loading strategies that truly emulate nature's host–guest systems to drive encapsulation of antimicrobial peptides (AMPs) without loss of biological activity. Herein, we develop DNA nanogels with rapid in situ loading of L12 peptide during the thermal annealing process. By leveraging the binding affinity of L12 to the polyanionic core, we successfully confine the AMPs within the DNA nanogel. We report that the thermostability of L12 in parallel with the high encapsulation efficiency, low toxicity and sustained drug release of the pre-loaded L12 nanogels can be translated into significant antimicrobial activity. Using an S. aureus model of infectious bacterial keratitis, we observe fast resolution of clinical symptoms and significant reduction of bacterial bioburden. Collectively, this study paves the way for the development of DNA nanocarriers for caging AMPs with immense significance to address the rise of resistance

Biomimetic aligned nanofibrous dressings containing cell-selective polymer enhance diabetic wound regeneration

Diabetic ulcers remain a significant challenge in wound care due to loss of epithelial cell migration. Aligned nanofibrous scaffolds mimicking the skin's extracellular matrix (ECM) are promising candidates for diabetic wound healing. In this study, a composition of poly(ε-caprolactone), gelatin, and dopamine-containing varying amounts of ε-polylysine (ε-PL) was electrospun to prepare aligned nanofiber wound dressings (ANFDs). We then investigated the morphological, physicochemical, mechanical, and biological properties of fabricated ANDFs. The presence of ε-PL confers bactericidal properties while promoting epithelial and fibroblast adhesion, proliferation, and migration, confirming its cell selectivity. The clinical importance of the ANFDs was then demonstrated in a mice model of full-thickness diabetic wounds. The results confirm that ANFD treatment resulted in a higher rate of wound closure in the linear range of wound closure than wounds treated with silver dressings. Taken together, these results suggest the potential of antimicrobial ANFDs for the treatment of diabetic wounds

Propranolol Ameliorates the Antifungal Activity of Azoles in Invasive Candidiasis

The effectiveness of current antifungal therapies is hampered by the emergence of drug resistance strains, highlighting an urgent need for new alternatives such as adjuvant antifungal treatments. This study aims to examine the synergism between propranolol and antifungal drugs, based on the premise that propranolol is known to inhibit fungal hyphae. In vitro studies demonstrate that propranolol potentiates the antifungal activity of azoles and that the effect is more pronounced for propranolol–itraconazole combination. Using an in vivo murine systemic candidemia model, we show that propranolol–itraconazole combination treatment resulted in a lower rate of body weight loss, decreased kidney fungal bioburden and renal inflammation when compared to propranolol and azole treatment alone or untreated control. Altogether, our findings suggest that propranolol increases the efficacy of azoles against C. albicans, offering a new therapeutic strategy against invasive fungal infections

Antifungal properties of lecithin- and terbinafine-loaded electrospun poly(ε-caprolactone) nanofibres

Topical skin and nail fungal infections form the most numerous and widespread among superficial mycoses. Drug eluting electrospun nanofibres have been shown to have immense potential for the topical delivery of antimicrobials. In this article, we investigated the efficacy of lecithin-loaded electrospun polycaprolactone (PCL) fibers containing terbinafine hydrochloride (terbinafine) for applications in superficial mycoses. Electron microscopy studies indicated that addition of lecithin and terbinafine decreased the average diameter of PCL nanofibers, increase in mechanical properties and wettability of the fibre mats. PCL mats containing lecithin and terbinafine displayed pronounced blue photoluminescence and did not affect cell adhesion and biocompatibility for primary human dermal fibroblasts. The drug loaded mats maintained the antifungal efficacy against moulds as well as dermatophytic fungus. Using an ex vivo porcine skin infection model, we showed that the drug-eluting mats resulted in >5 log reduction in the viability of T. mentagrophytes.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore)NMRC (Natl Medical Research Council, S’pore)Accepted versio

Wound healing properties of magnesium mineralized antimicrobial nanofibre dressings containing chondroitin sulphate-a comparison between blend and core-shell nanofibres

The development of antimicrobial nanofibre dressings that can protect the injured tissues from commensal pathogens while promoting tissue regeneration finds enormous potential in plastic and reconstructive surgery practices. To achieve this goal, we investigated the effect of chondroitin sulphate on the morphology, mechanical properties, wettability and biocompatibility of polydopamine crosslinked electrospun gelatin nanofibres containing mineralized magnesium. To extend the durability of dressings, we prepared composite dressings containing polycaprolactone (PCL) and gelatin as blend or core-shell nanofibres. Nanofibre blends presented greater tensile strength and stretchability, while core-shell nanofibres displayed superior photoluminescent properties. In a porcine model of cutaneous burn injury, both the blend and core-shell nanofibre dressings displayed improved re-epithelialization, wound closure and clinical outcome in comparison to untreated burns. Histology of the biopsied tissues indicated smooth regeneration and collagen organization of the burns treated with core-shell nanostructures than untreated burns. This study compared the physico-chemical and biological properties of composite nanofibres that are capable of accelerating burn wound healing and possess antimicrobial properties, highlighting their potential as wound dressings and skin substitutes.</p

Hybrid derivative of cathelicidin and human beta defensin-2 against Gram-positive bacteria: A novel approach for the treatment of bacterial keratitis

10.1038/s41598-021-97821-3SCIENTIFIC REPORTS11