Anti-proliferative, -migratory and -clonogenic effects of long-lasting nitric oxide release in HepG2 cells.

Nitric oxide (NO) holds promise as a cytotoxic agent against tumors, but its gaseous nature and short half-life hinder direct administration to tumor tissues. Herein, we present novel 6,9-disubstituted purine derivatives designed to ensure sustained NO release, followed by study of their significant anti-proliferative, anti-migratory, and anti-clonogenic effects on HepG2 cell lines, highlighting NO release as a potent effector for treating hepatocellular carcinoma.

Peptide Dendrimer-Based Antibacterial Agents: Synthesis and Applications.

Pathogenic bacteria cause the deaths of millions of people every year. With the development of antibiotics, hundreds and thousands of people's lives have been saved. Nevertheless, bacteria can develop resistance to antibiotics, rendering them insensitive to antibiotics over time. Peptides containing specific amino acids can be used as antibacterial agents; however, they can be easily degraded by proteases in vivo. To address these issues, branched peptide dendrimers are now being considered as good antibacterial agents due to their high efficacy, resistance to protease degradation, and low cytotoxicity. The ease with which peptide dendrimers can be synthesized and modified makes them accessible for use in various biological and nonbiological fields. That is, peptide dendrimers hold a promising future as antibacterial agents with prolonged efficacy without bacterial resistance development. Their in vivo stability and multivalence allow them to effectively target multi-drug-resistant strains and prevent biofilm formation. Thus, it is interesting to have an overview of the development and applications of peptide dendrimers in antibacterial research, including the possibility of employing machine learning approaches for the design of AMPs and dendrimers. This review summarizes the synthesis and applications of peptide dendrimers as antibacterial agents. The challenges and perspectives of using peptide dendrimers as the antibacterial agents are also discussed.

Targeting multidrug resistant Staphylococcus aureus with cationic chlorpromazine-peptide conjugates.

Antimicrobial resistance is a serious public health risk. Its severity is fueled on an unprecedented scale, necessitating the demand for novel antimicrobial scaffolds aimed at novel targets. Herein, we present cationic chlorpromazine peptide conjugates that are rationally intended to targetmultidrug-resistant (MDR) bacteria. The most potent compound, CPWL, of all the conjugates evaluated, showed promising antibacterial activity against clinical, MDR S. aureus, with no cytotoxicity. The molecular docking experiments confirmed that CPWL possessed a very high affinity for S. aureus enoyl reductase (saFabI). Furthermore, CPWL antibacterial action against saFabI was further corroborated by MD simulation studies. Thus, our findings highlight cationic chlorpromazine as a promising scaffold for the development of saFabI inhibitors to target severe staphylococcal infections.

Anionic diketopiperazine induces osteogenic differentiation and supports osteogenesis in a 3D cryogel microenvironment.

Bioactive molecules that enhance or induce osteogenic potential of bone precursor cells have shown vital roles in bone tissue engineering. Herein, we report the design and synthesis of a novel diketopiperazine (DT) that induces osteoblastic differentiation of pre-osteoblasts and bone-marrow-derived stem cells in vitro and enhances the osteogenic potential of cryogel matrix. Such functional diketopiperazines can serve as potential scaffolds for bone healing and regeneration.

Spin coating mediated morphology modulation in self assembly of peptides.

Controlling the morphology and nanostructure of self-assembled peptide molecules is of fundamental importance to chemistry and material science due to their bioactivity in both in vivo and in vitro settings, ability to act as templates for conjugating bio-recognition elements, hybrid supramolecular assembly, possible detection and treatment of diseases and so on. In this article, we show that spin coating, a widely utilized method for obtaining ultra-thin polymer films, has been utilised to modulate the self-assembly of peptide molecules, which has traditionally been achieved by chemical functionalisation of the molecules. With the specific example of diphenylalanine-based peptide molecules, we show that a variety of self-assembled architectures such as long fibrils, short fibrils, globules, nanodots, and so on, spanning over large areas can be obtained by simultaneously varying the spinning speed (RPM) and the solution concentration (Cp) during spin coating. We correlate the variation in morphology to a transition from spin dewetting at very low Cp (or high RPM) to the formation of continuous films at high Cp (or low RPM) during the initial stage of spin coating. We further show the generality of the approach by achieving distinct self-assembled morphologies with diphenylalanine analogues with different C-terminal and N-terminal groups by modulation of spin coating parameters, though the exact morphology obtained under identical coating conditions depends on the chemical nature of the peptide molecules. The work opens up a new possible route for creating complex peptide assemblies on demand by simultaneous control of molecular functionalisation and spin coating parameters vis - a - vis the applied centrifugal force.

Blended polar/nonpolar peptide conjugate interferes with human insulin amyloid-mediated cytotoxicity.

Insulin, a peptide hormone and a key regulator of blood glucose level, is routinely administered to type-I diabetic patients to achieve the required glycemic control. Insulin aggregation and ensuing amyloidosis has been observed at repeated insulin injection sites and in injectable formulations. The latter occurs due to insulin agglomeration during shipping and storage. Such insulin amyloid leads to enhanced immunogenicity and allow potential attachment to cell membranes leading to cell permeability and apoptosis. Small molecule inhibitors provide useful interruption of this process and inhibit protein misfolding as well as amyloid formation. In this context, we report the propensity of a palmitoylated peptide conjugate to inhibit insulin aggregation and amyloid-mediated cytotoxicity, via designed interference with polypeptide interfacial interactions.

A colored hydrophobic peptide film based on self-assembled two-fold topology.

Structural colors are abundant in nature and bear advantages over pigment-based colors, such as higher durability, brilliance and often physical hydrophobicity, thus underlying their vast potential for technological applications. Recently, biomimetics of complex natural topologies resulting in such effects has been extensively studied, requiring advanced processing and fabrication techniques. Yet, artificial topologies combining structural coloration and hydrophobicity have not been reported. Herein, we present the bottom-up fabrication of short self-assembling peptides as surface covering films, resulting in an easily achievable multilevel morphology of primary structures in a foam-like enclosure, producing structural colors and hydrophobicity. We demonstrate simple techniques allowing controlled coloration of different surfaces while maintaining an >100° water contact angle (WCA). The new artificial topology is much simpler than the natural counterparts and is not limited to a specific peptide, thus allowing the design of modular materials with unparalleled multifunctionalities and potential for further tuning and modifications.

A naphthalimide-based peptide conjugate for concurrent imaging and apoptosis induction in cancer cells by utilizing endogenous hydrogen sulfide.

The excessive production of endogenous hydrogen sulfide (H2S) in cancer cells leads to enhanced tumor growth and metastasis. On the other hand, decreased endogenous H2S suppresses tumor growth. The reported approaches for inhibiting tumor growth are selective silencing of the tumor-promoting genes and pharmacological inhibition of these proteins. To enhance the antitumor efficacy of frontline chemotherapeutic agents, herein, we synthesized a highly sensitive endogenous H2S responsive fluorescent probe, i.e., a hydrogen sulfide-sensing naphthalimide-based peptide conjugate (HSNPc), which showed selective inhibition of proliferation of cancer cells due to apoptosis induction. Furthermore, HSNPc suppressed the glycolytic reserve, a critical energy source for the proliferation of cancer cells. HSNPc also decreased the Young's modulus of HeLa cells compared to the control cells, which demonstrated a direct relation between cell apoptosis and cell stiffness. Taken together, we demonstrated the dual function of detection and killing of cancer cells by HSNPc that can be likened to a theranostic role.

Bioinspired adenine-dopamine immobilized polymer hydrogel adhesives for tissue engineering.

Nontoxic adhesive hydrogels are of great importance in tissue engineering. Herein, we report a simple synthesis of a few biocompatible hydrogels from adenine and dopamine immobilized polyacrylic acid (PAA) and alginic acid (Alg) polymers. The adenine-dopamine adduct incorporated hydrogels showed enhanced adhesiveness, transparency and biocompatibility, and induced cell proliferation in 2D and 3D-cell culture models within 24 h. Moreover, blending the modified PAA and Alg polymers (P2P4) further increased the stability and bioactivity of the hydrogel. Such biogels can be developed as smart materials for biomedical applications.

Peptide Nanostructure-Mediated Antibiotic Delivery by Exploiting H2S-Rich Environment in Clinically Relevant Bacterial Cultures.

Stimuli-responsive self-destructing soft structures serve as versatile hosts for the encapsulation of guest molecules. A new paradigm for H2S-responsive structures, based on a modified tripeptide construct, is presented along with microscopy evidence of its time-dependent rupture. As a medicinally interesting application, we employed these commercial antibiotic-loaded soft structures for successful drug release and inhibition of clinically relevant, drug-susceptible, and methicillin-resistant Staphylococcus aureus.

Functional Catechol-Metal Polymers via Interfacial Polymerization for Applications in Water Purification.

Phenols and polyphenols have been used as a scaffold for generating multidimensional molecular architectures via complexation with metal ions. Here, we report the synthesis and characterization of metallopolymer films from three catechol derivatives having different alkyl/aryl substituents via complexation with iron and copper ions at the organic-water interface. Such interfacial polymerization is instantaneous, one step to generate functional materials, and gives good control over the organization of repeating units along the film. The films were transferred to different substrates such as filter paper, cotton, or polyester fabrics. The films are superhydrophobic with a contact angle >160° which can be tuned by regulating the orientation of nonpolar groups at the interface during polymerization. In addition, the fabricated cloth membrane showed excellent oil/water separation efficiency of more than 99% even after 50 cycles. The polymers also showed good dye extraction capacity from aqueous solutions with fast kinetics data. Such metallopolymer networks can serve as a versatile material for applications in catalysis, protective coatings, drug delivery, water filtration membranes, and liquid separations.

Tripeptide-induced modulation of mesenchymal stem cell biomechanics stimulates proliferation and wound healing.

We demonstrate the ability of two tripeptides to promote proliferation and modulate the mechanical properties of human mesenchymal stem cells (hMSCs). Notably, Young's modulus of peptide-treated hMSCs was found to be ∼2 fold higher compared to the control group. These peptides promoted wound healing in hMSCs, without stimulating osteogenic and adipogenic differentiation, thus showing high potential in vascular tissue engineering applications.

Caspase-3 mediated programmed cell death by a gold-stabilised peptide carbene.

The synthesis of novel N-heterocyclic carbene complexes derived from a tripeptide ligand (L), containing non-natural amino acid, thiazolylalanine is described here. The peptide ligand was reacted with suitable precursors to generate gold and mercury carbene complexes. The plausible structures of both complexes were predicted by spectroscopic data and DFT calculations. The binding energy data was also analyzed to predict their stability. The gold carbene complex (1A), showed activity against MCF7 breast cancer cell line due to mitochondrial triggered caspase-3 mediated programmed cell death. Its internalization inside cells could be observed due to autofluorescence. This study affords a methodology for successful generation of peptide carbene complexes for their therapeutic potential.

Controlled release of hydrogen sulfide significantly reduces ROS stress and increases dopamine levels in transgenic C. elegans.

Hydrogen sulfide, an endogenous signalling molecule, is central to several pathophysiological processes in mammalian systems. It scavenges reactive oxygen species and is known to ameliorate dopaminergic neuronal degeneration in neurotoxin-induced Parkinson's disease models. The rapid volatilization of H2S from spontaneously releasing sulfide salts being a challenge, we describe peptide conjugates which exhibit tris(2-carboxyethyl)phosphine mediated "slow and sustained" H2S release. These conjugates reduced hydrogen peroxide-induced oxidative stress and significantly increased dopamine levels in transgenic C. elegans.

Parkinson's Disease: The Emerging Role of Gut Dysbiosis, Antibiotics, Probiotics, and Fecal Microbiota Transplantation.

The role of the microbiome in health and human disease has emerged at the forefront of medicine in the 21st century. Over the last 2 decades evidence has emerged to suggest that inflammation-derived oxidative damage and cytokine induced toxicity may play a significant role in the neuronal damage associated with Parkinson's disease (PD). Presence of pro-inflammatory cytokines and T cell infiltration has been observed in the brain parenchyma of patients with PD. Furthermore, evidence for inflammatory changes has been reported in the enteric nervous system, the vagus nerve branches and glial cells. The presence of α-synuclein deposits in the post-mortem brain biopsy in patients with PD has further substantiated the role of inflammation in PD. It has been suggested that the α-synuclein misfolding might begin in the gut and spread "prion like" via the vagus nerve into lower brainstem and ultimately to the midbrain; this is known as the Braak hypothesis. It is noteworthy that the presence of gastrointestinal symptoms (constipation, dysphagia, and hypersalivation), altered gut microbiota and leaky gut have been observed in PD patients several years prior to the clinical onset of the disease. These clinical observations have been supported by in vitro studies in mice as well, demonstrating the role of genetic (α-synuclein overexpression) and environmental (gut dysbiosis) factors in the pathogenesis of PD. The restoration of the gut microbiome in patients with PD may alter the clinical progression of PD and this alteration can be accomplished by carefully designed studies using customized probiotics and fecal microbiota transplantation.

Coarse-Grained Simulations of Peptide Nanoparticle Formation: Role of Local Structure and Nonbonded Interactions.

Biocompatible nanostructures play an important role in drug delivery and tissue engineering applications. Controlled growth of peptide-based nanoparticles with specific morphology needs an understanding of the role of the sequence and solvation properties. In a previous combined experimental-computational study, we identified factors that govern the formation of well-defined aggregates by self-assembled pentapeptides using single amino acid substitution ( Mishra , N. K. ; Jain , A. ; Peter , C. ; Verma , S. J. Phys. Chem. B 2017 , 121 , 8155 - 8161 ). The atomistic simulation study suggested a subtle interplay between various peptide properties like rigidity/flexibility, hydrogen bonding, partitioning of aromatic residues, and dimerization of peptides that determine the different morphologies, while the overall aggregation propensity was mostly determined by the composition of the methanol/water solvent mixture. The size of the simulated aggregates and the time scales were rather restricted due to the atomistic character of the study. Here, we present an extension to a coarse-grained representation that allows for much larger system sizes and longer time scales. To this end, we have optimized a MARTINI model so that it can deal with a system that relies on local structure formation. We combine information on local behavior from atomistic studies and apply supportive dihedral angles together with local adjustment of the bead types to find the right interplay of solvent and peptides. Finally, to mimic the dimers, an introduction of additional bonds between the monomers was necessary. By adding the modifications stepwise, we were able to disentangle the influences of the various contributions, like the rigidity/flexibility of the peptides, dimer formation, or nonbonded properties of the beads, on the overall aggregation propensity and morphology of the nanoparticles. The obtained models resemble the experimental and atomistic behavior and are able to provide mechanistic insight into peptide nanoparticle formation.

Revisiting the role of the slit-skin smear in the diagnosis of Indian post-kala-azar dermal leishmaniasis.

BACKGROUND: Post kala azar dermal leishmaniasis (PKDL) is a neglected dermatosis that develops as a sequel to kala azar after apparent complete treatment. Being a non life threatening condition, patients often delay treatment thereby maintaining a reservoir of infection. The diagnosis of PKDL rests on the demonstration of the parasite in tissue smears, immune diagnosis by detection of parasite antigen or antibody in blood, or detection and quantitation of parasite DNA in tissue specimens. Sophisticated molecular tests are not only expensive but also need skilled hands and expensive equipment. To be useful, diagnostic methods must be accurate, simple and affordable for the population for which they are intended. AIMS: This study was designed to assess functionality and operational feasibility of slit-skin smear examination. METHODS: Sensitivity and specificity was evaluated by performing slit-skin smear and histo-pathological examination in 46 PKDL patients and the results were compared with the parasite load in both the slit aspirate and tissue biopsy specimens by performing quantitative Real-time PCR (Q-PCR). RESULTS: The slit-skin smear examination was more sensitive than tissue biopsy microscopy. The parasite loads significantly differed among various types of clinical lesions (P < 0.05). The threshold of parasite load for detection by SSS microscopy was 4 parasites/µl in slit aspirate and 60 parasites/µg tissue DNA in tissue biopsy while that for tissue microscopy was 63 parasites/µl and 502 parasites/µg tissue DNA respectively. As detection of Leishmania donovani bodies may be challenging in inexperienced hands, the microscopic structure of these has been detailed along with a comprehensive discussion of pre analytical, analytical and post analytical variables affecting its identification. To facilitate the diagnosis of PKDL, some scenarios have been suggested taking into consideration the clinical, epidemiological, immunological and microscopic aspects. CONCLUSION: Such evidence based medicine helps minimize intuition, systematize clinical experience and provides a diagnostic rationale as sufficient grounds for a clinical decision.

Peptide-Based Scaffold for Nitric Oxide Induced Differentiation of Neuroblastoma Cells.

Nitric oxide is a gaseous messenger involved in neuronal differentiation, development and synaptogenesis, in addition to many other physiological functions. Therefore, it is imperative to maintain an optimal nitric oxide concentration to ensure its biochemical function. A sustained nitric oxide releasing scaffold, which supports neuronal cell differentiation, as determined by morphometric analysis of neurite outgrowth, is described. Moreover, the effect of nitric oxide on the neuroblastoma cell line was also confirmed by immunofluorescent analysis of neuronal nuclear protein (NeuN), specific neuronal marker and neurofilament (NF) protein, which revealed a significant increase in their expression levels, in comparison with undifferentiated cells.

Directed adenine functionalization for creating complex architectures for material and biological applications.

In this feature article, targeted design strategies are outlined for modified adenine nucleobase derivatives in order to construct metal-mediated discrete complexes, ring-expanded purine skeletons, linear and catenated coordination polymers, shape-selective MOFs, and purine-capped nanoparticles, with a wide range of applications from gas and solvent adsorption to bioimaging agents and anticancer metallodrugs. The success of such design strategies could be ascribed to the rich chemistry of purine and pyrimidine derivatives, versatile coordination behavior, ability to bind a host of metal ions, which could be further tuned by the introduction of additional functionalities, and their inherent propensity to hydrogen bond and exhibit π-π interactions. These noncovalent interactions produce stable frameworks and network solids that are useful as advanced materials, and the biocompatibility of these ligand complexes provides an impetus for assessing novel biological applications.

Supramolecular Photoactivatable Anticancer Hydrogels.

A photoactivatable dopamine-conjugated platinum(IV) anticancer complex (Pt-DA) has been incorporated into G-quadruplex G4K+ borate hydrogels by using borate ester linkages (Pt-G4K+B hydrogel). These were characterized by 11B NMR, attenuated total reflection Fourier transform infrared spectroscopy, circular dichroism, scanning electron microscopy and transmission electron microscopy. Microscopy investigations revealed the transformation of an extended fiber assembly into discrete flakes after incorporation of Pt-DA. Pt-DA showed photocytotoxicity against cisplatin-resistant A2780Cis human ovarian cancer cells (IC50 74 µM, blue light) with a photocytotoxic index <2, whereas Pt-G4K+B hydrogels exhibited more potent photocytotoxicity (IC50 3 µM, blue light) with a photocytotoxic index >5. Most notably, Pt-DA and Pt-G4K+B hydrogels show selective phototoxicity for cancer cells versus normal fibroblast cells (MRC5).