Antibacterial Activity and Cytotoxicity Screening of Acyldepsipeptide-1 Analogues Conjugated to Silver/Indium/Sulphide Quantum Dots.

The continuous rise in bacterial infections and antibiotic resistance is the driving force behind the search for new antibacterial agents with novel modes of action. Antimicrobial peptides (AMPs) have recently gained attention as promising antibiotic agents with the potential to treat drug-resistant infections. Several AMPs have shown a lower propensity towards developing resistance compared to conventional antibiotics. However, these peptides, especially acyldepsipeptides (ADEPs) present with unfavorable pharmacokinetic properties, such as high toxicity and low bioavailability. Different ways to improve these peptides to be drug-like molecules have been explored, and these include using biocompatible nano-carriers. ADEP1 analogues (SC005-8) conjugated to gelatin-capped Silver/Indium/Sulfide (AgInS2) quantum dots (QDs) improved the antibacterial activity against Gram-negative (Escherichia coli and Pseudomonas aeruginosa), and Gram-positive (Bacillus subtilis, Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus) bacteria. The ADEP1 analogues exhibited minimum inhibition concentrations (MIC) between 63 and 500 µM, and minimum bactericidal concentrations (MBC) values between 125 and 750 µM. The AgInS2-ADEP1 analogue conjugates showed enhanced antibacterial activity as evident from the MIC and MBC values, i.e., 1.6-25 µM and 6.3-100 µM, respectively. The AgInS2-ADEP1 analogue conjugates were non-toxic against HEK-293 cells at concentrations that showed antibacterial activity. The findings reported herein could be helpful in the development of antibacterial treatment strategies.

Review: Structure-Activity Relationship of Antimicrobial Peptoids.

Due to their broad-spectrum activity against Gram-negative and Gram-positive bacteria, natural antimicrobial peptides (AMPs) and their synthetic analogs have emerged as prospective therapies for treating illnesses brought on by multi-drug resistant pathogens. To overcome the limitations of AMPs, such as protease degradation, oligo-N-substituted glycines (peptoids) are a promising alternative. Despite having the same backbone atom sequence as natural peptides, peptoid structures are more stable because, unlike AMP, their functional side chains are attached to the backbone nitrogen (N)-atom rather than the alpha carbon atom. As a result, peptoid structures are less susceptible to proteolysis and enzymatic degradation. The advantages of AMPs, such as hydrophobicity, cationic character, and amphipathicity, are mimicked by peptoids. Furthermore, structure-activity relationship studies (SAR) have shown that tuning the structure of peptoids is a crucial step in developing effective antimicrobials.

Biopolymer-Based Wound Dressings with Biochemical Cues for Cell-Instructive Wound Repair.

Regenerative medicine is an active research sphere that focuses on the repair, regeneration, and replacement of damaged tissues and organs. A plethora of innovative wound dressings and skin substitutes have been developed to treat cutaneous wounds and are aimed at reducing the length or need for a hospital stay. The inception of biomaterials with the ability to interact with cells and direct them toward desired lineages has brought about innovative designs in wound healing and tissue engineering. This cellular engagement is achieved by cell cues that can be biochemical or biophysical in nature. In effect, these cues seep into innate repair pathways, cause downstream cell behaviours and, ultimately, lead to advantageous healing. This review will focus on biomolecules with encoded biomimetic, instructive prompts that elicit desired cellular domino effects to achieve advanced wound repair. The wound healing dressings covered in this review are based on functionalized biopolymeric materials. While both biophysical and biochemical cues are vital for advanced wound healing applications, focus will be placed on biochemical cues and in vivo or clinical trial applications. The biochemical cues aforementioned will include peptide therapy, collagen matrices, cell-based therapy, decellularized matrices, platelet-rich plasma, and biometals.

Acyldepsipeptide Analogues: A Future Generation Antibiotics for Tuberculosis Treatment.

Acyldepsipeptides (ADEPs) are a new class of emerging antimicrobial peptides (AMPs), which are currently explored for treatment of pathogenic infections, including tuberculosis (TB). These cyclic hydrophobic peptides have a unique bacterial target to the conventional anti-TB drugs, and present a therapeutic window to overcome Mycobacterium Tuberculosis (M. tb) drug resistance. ADEPs exerts their antibacterial activity on M. tb strains through activation of the protein homeostatic regulatory protease, the caseinolytic protease (ClpP1P2). ClpP1P2 is normally regulated and activated by the ClpP-ATPases to degrade misfolded and toxic peptides and/or short proteins. ADEPs bind and dysregulate all the homeostatic capabilities of ClpP1P2 while inducing non-selective proteolysis. The uncontrolled proteolysis leads to M. tb cell death within the host. ADEPs analogues that have been tested possess cytotoxicity and poor pharmacokinetic and pharmacodynamic properties. However, these can be improved by drug design techniques. Moreover, the use of nanomaterial in conjunction with ADEPs would yield effective synergistic effect. This new mode of action has potential to combat and eradicate the extensive multi-drug resistance (MDR) problem that is currently faced by the public health pertaining bacterial infections, especially TB.

Relationship between amino acid ratios and decline in estimated glomerular filtration rate in diabetic and non-diabetic patients in South Africa.

BACKGROUND: Diabetic kidney disease is a major complication resulting from type 1 and type 2 diabetes. Currently, the microalbuminuria test is used to monitor renal function; however, it does not detect albumin until progressive loss of renal function has occurred. OBJECTIVE: This study analysed the relationship between changes in amino acid ratios and estimated glomerular filtration rate (eGFR) decline in diabetic and non-diabetic patients. METHODS: Urine samples were collected from participants between February 2019 to April 2019 and analysed from November 2020 to January 2021. Diabetic (glycated haemoglobin > 6.4%) and non-diabetic patients (glycated haemoglobin ≤ 6.4%) from Chris Hani Baragwanath Hospital, South Africa, were further categorised based on the degree of renal function predicted by the eGFRs. Amino acids were quantified using tandem mass spectrometry to determine the concentrations and ratios of tyrosine/phenylalanine, ornithine/arginine, arginine/citrulline and citrulline/ornithine at different stages of the chronic kidney disease. RESULTS: Among diabetic patients, the tyrosine/phenylalanine ratio showed a statistically significant increase (p = 0.04) as the eGFR declined from stage 1 to stage 4; the ornithine/arginine ratio showed a strong negative correlation with eGFR. The citrulline/ornithine ratio differed between the diabetic and non-diabetic patients in stage 1 of chronic kidney disease. CONCLUSION: Amino acid ratios (ornithine/arginine and tyrosine/phenylalanine) are affected by the progression of diabetes and can be correlated to renal function. The citrulline/ornithine ratios differ between the studied groups in stage 1 of the disease and may be utilised to predict the onset of chronic kidney disease.

Enhanced brain penetration of pretomanid by intranasal administration of an oil-in-water nanoemulsion.

AIM: To enhance the drug delivery to the brain with an oil-in-water nanoemulsion of pretomanid via intranasal (IN) administration. MATERIALS & METHODS: The study involved 70 male Sprague-Dawley rats (160-180 g) that received either 20 mg/kg body weight (b.w.) a nanoemulsion or a 20 mg/kg b.w. of pretomanid in solution via the IN route. The drug was quantified by liquid chromatography-tandem mass spectrometry to investigate whole tissue-drug concentrations, and mass spectrometric imaging to visualize drug localization in the brain. RESULTS: Nanoemulsion delivery concentrations of pretomanid in the brain reached peak concentrations (Cmax) of 12,062.3 ng/g that is significantly higher than the required therapeutic level. The mass spectrometric imaging analysis clearly showed a time dependent and uniform distribution in the brain. CONCLUSION: The results of this study show that IN delivery of oil-in-water nanoemulsion may be very promising for targeting anatomical tuberculosis reservoirs, such as the brain.

Synthesis of novel 1,2,4-thiadiazinane 1,1-dioxides via three component SuFEx type reaction.

Herein, we report the preparation of 1,2,4-thiadiazinane 1,1-dioxides from reaction of ß-aminoethane sulfonamides with dichloromethane, dibromomethane and formaldehyde as methylene donors. The ß-aminoethane sulfonamides were obtained through sequential Michael addition of amines to α,ß-unsaturated ethenesulfonyl fluorides followed by further DBU mediated sulfur(vi) fluoride exchange (SuFEx) reaction with amines at the S-F bond.

Synthesis, 2D-NMR and molecular modelling studies of pentacycloundecane lactam-peptides and peptoids as potential HIV-1 wild type C-SA protease inhibitors.

In this study, eight non-natural peptides and peptoids incorporating the pentacycloundecane (PCU) lactam were designed and synthesized as potential inhibitors of the wild type C-SA HIV-protease. Five of these inhibitors gave IC(50) values ranging from 0.5 up to 0.75 µM against the resistance-prone wild type C-South African HIV-protease. NMR EASY-ROESY studies enabled us to describe the secondary structure of three of these compounds in solution. The 3D structures of the selected cage peptides were also modelled in solution using QM/MM/MD simulations. Satisfactory agreement between the NMR observations and the low energy calculated structures exists. Only one of these inhibitors (11 peptoid), which showed the best IC(50)(0.5 µM), exhibited a definable 3-D structure in solution. Autodock4 and AutodockVina were used to model the potential interaction between these inhibitors and the HIV-PR. It appears that the docking results are too crude to be correlated with the relative narrow range of experimental IC(50) values (0.5-10 µM). The PCU-peptides and peptoides were several orders less toxic (145 µM for 11 and 102 µM for 11 peptoid) to human MT-4 cells than lopinavir (0.025 µM). This is the first example of a polycyclic cage framework to be employed as an HIV-PR transition state analogue inhibitor and can potentially be utilized for other diseases related proteases. [Figure: see text].

Synthesis, screening and computational investigation of pentacycloundecane-peptoids as potent CSA-HIV PR inhibitors.

Herein, we present the first pentacycloundecane (PCU) diol peptoid derived HIV protease inhibitors with IC(50) values ranging from 6.5 to 0.075 µM. Five derivatives were synthesized in an attempt to understand the structure activity relationship of this class of compounds for HIV protease inhibition. NMR spectroscopy (new Efficient Adiabatic Symmetrized Rotating Overhauser Effect Spectroscopy, EASY-ROESY) was employed to determine the predominant conformation of the active compound. In this study docking studies and MD simulations provided insight into the binding theme of this class of peptoid inhibitors to the CSA-HIV PR active site. Conserved and stable hydrogen bonding between the hydroxyl groups of the inhibitors and the active site Asp25/Asp25' residues were observed from the docking and along the MD trajectories.

Pentacycloundecane-diol-based HIV-1 protease inhibitors: biological screening, 2D NMR, and molecular simulation studies.

Novel compounds incorporating a pentacycloundecane (PCU) diol moiety were designed, synthesized, and evaluated as inhibitors of the wild-type C-South African (C-SA) HIV-1 protease. Seven compounds are reported herein, three of which displayed IC(50) values in the 0.5-0.6 µM range. The cytotoxicity of PCU cage peptides toward human MT-4 cells appears to be several orders of magnitude less toxic than the current antiviral medications ritonavir and lopinavir. NMR studies based on the observed through-space (1)H,(1)H distances/contacts in the EASY-ROESY spectra of three of the considered PCU peptide inhibitors enabled us to describe their secondary solution structure. Conserved hydrogen bonding interactions were observed between the hydroxy group of the PCU diol inhibitors and the catalytic triad (Asp25, Ile26, Gly27) of HIV protease in docking and molecular dynamics simulations. The biological significance and possible mode of inhibition by PCU-based HIV protease inhibitors discussed herein facilitates a deeper understanding of this family of inhibitors and their potential application to a vast number of alternative diseases related to proteases.

Synthesis and structural studies of pentacycloundecane-based HIV-1 PR inhibitors: a hybrid 2D NMR and docking/QM/MM/MD approach.

Pentacycloundecane (PCU) lactam-peptide based HIV protease inhibitors were synthesized and nanomolar activity against the resistance-prone wild type C-South African HIV protease is reported. NMR investigations indicated that the activity is related to the chirality of the PCU moiety and its ability to induce conformations of the coupled peptide side chain. EASY-ROESY NMR experiments gave information about the 3D structure of the cage peptides and 3D solution structure could be linked to the experimental IC(50) activity profile of the considered inhibitors. QM/MM/MD simulations of the inhibitors in solution confirmed the NMR observed conformations. Docking experiments and QM/MM/MD simulations of the inhibitor-HIV PR complexes were also performed. These computational results complimented the experimental inhibition activities and enabled us to report a unique binding mode for PCU-based inhibitors at the active site of HIV-protease enzyme. A conserved hydrogen bonding pattern between the norstatine type functional group of the PCU hydroxylactam and active site residues, ASP25/ASP25', was observed in all active compounds. The biological significance and possible mode of inhibition by PCU-based HIV PR inhibitors discussed herein provide us with a deeper understanding of the mode of action of these novel inhibitors. The PCU-peptides are between 6000 and 8500 time less toxic to human MT-4 cells than Lopinavir. This potentially creates new application avenues for these putative inhibitors to be investigated against a vast number of other disease-related proteases.

Pentacycloundecane-based inhibitors of wild-type C-South African HIV-protease.

In this study, we present the first account of pentacycloundecane (PCU) peptide based HIV-protease inhibitors. The inhibitor exhibiting the highest activity made use of a natural HIV-protease substrate peptide sequence, that is, attached to the cage (PCU-EAIS). This compound showed nanomolar IC(50) activity against the resistance-prone wild type C-South African HIV-protease (C-SA) catalytic site via a norstatine type functional group of the PCU hydroxy lactam. NMR was employed to determine a logical correlation between the inhibitory concentration (IC(50)) results and the 3D structure of the corresponding inhibitors in solution. NMR investigations indicated that the activity is related to the chirality of the PCU moiety and its ability to induce conformations of the coupled peptide side chain. The results from docking experiments coincided with the experimental observed activities. These findings open up useful applications for this family of cage peptide inhibitors, considering the vast number of alternative disease related proteases that exist.

Synthesis and NMR assignment of pentacycloundecane precursors of potential pharmaceutical agents.

The synthesis and complete NMR elucidation of eight novel pentacycloundecane (PCU) derivatives are reported. These compounds are precursors in the synthesis of PCU-based anti-tuberculosis (TB) agents and potential human immunodeficiency virus (HIV) protease inhibitors. Two-dimensional (2D) NMR techniques were used to assign the NMR spectra for these compounds. Substitution of the cage molecule at (C-8/11) further complicates the assignment, since some of the substituted alkyl chain groups overlap with the cage proton signals. The side chain heteroatoms also introduce a rare through-space deshielding effect to some of the carbon atoms of the cage skeleton. Ring strain in the rigid cage skeleton appears to induce drastic electronic changes in some parts of the cage framework. This observation is more dramatic for the C-4 methylene group of the cage diols and the cage ethers.