K. Santhosh Kumar

A robust, melting class bulk superhydrophobic material with heat-healing and self-cleaning properties

Superhydrophobic (SH) materials are essential for a myriad of applications such as anti-icing and self-cleaning due to their extreme water repellency. A single, robust material simultaneously possessing melt-coatability, bulk water repellency, self-cleanability, self-healability, self-refreshability, and adhesiveness has been remaining an elusive goal. We demonstrate a unique class of melt-processable, bulk SH coating by grafting long alkyl chains on silica nanoparticle surface by a facile one-step method. The well-defined nanomaterial shows SH property in the bulk and is found to heal macro-cracks on gentle heating. It retains wettability characteristics even after abrading with a sand paper. The surface regenerates SH features (due to reversible self-assembly of nano structures) quickly at ambient temperature even after cyclic water impalement, boiling water treatment and multiple finger rubbing tests. It exhibits self-cleaning properties on both fresh and cut surfaces. This kind of coating, hitherto undisclosed, is expected to be a breakthrough in the field of melt-processable SH coatings.

Novel antibacterial peptides from the skin secretion of the Indian bicoloured frog Clinotarsus curtipes.

HPLC elution profile and MALDI TOF MS analysis of electro-stimulated skin secretion of the Indian Ranid frog Clinotarsus curtipes of the Western Ghats confirmed the presence of multiple peptides. Peptides eluted out of the C18 column at higher hydrophobic solvent region showed antibacterial activity against diverse bacterial strains, including the clinical isolates of V. cholerae and methicillin resistant Staphylococcus aureus (MRSA). Peptidomic analysis of the most potent chromatographic effluent fraction identified five novel peptide amides having sequence homology with brevinin family. These peptides are named as brevinin1CTcu1 (B1CTcu1) to brevinin1CTcu5 (B1CTcu5). Peptide B1CTcu1 is non-haemolytic while the others are haemolytic in nature but all elicited potential antibacterial activity. B1CTcu5 is a twenty-one residue peptide amide having proline hinge region in the middle and the typical C-terminal intramolecular disulfide-bridged hepta peptide domain (Rana box) that is present in most of the brevinin peptides. Analysis of their killing kinetics with E. coli and S. aureus and the ability to induce membrane depolarization proved that these are two independent events. These novel multifunctional peptides play an important role to protect C. curtipes from invading pathogenic microorganisms present in the environment.

Endemic Indirana Frogs of the Western Ghats Biodiversity Hotspot

Frogs of the genus Indirana belong to the endemic family Ranixalidae and are found exclusively in the Western Ghats biodiversity hotspot. Since taxonomy, biology and distribution of these frogs are still poorly understood, we conducted a comprehensive literature review of what is known on the taxonomy, morphology, life history characteristics and breeding biology of these species. Furthermore, we collected information on the geographical locations mentioned in the literature, and combined this with information from our own field surveys in order to generate detailed distribution maps for each species. Apart from serving as a useful resource for future research and conservation efforts, this review also highlights the areas where future research efforts should be focussed.

Structure-Activity Relationship and Mode of Action of a Frog Secreted Antibacterial Peptide B1CTcu5 Using Synthetically and Modularly Modified or Deleted (SMMD) Peptides

All life forms are equipped with rapidly acting, evolutionally conserved components of an innate immune defense system that consists of a group of unique and diverse molecules known as host defense peptides (HDPs). A Systematic and Modular Modification and Deletion (SMMD) approach was followed to analyse the structural requirement of B1CTcu5, a brevinin antibacterial peptide amide identified from the skin secretion of frog Clinotarsus curtipes, India, to show antibacterial activity and to explore the active core region. Seventeen SMMD-B1CTcu5 analogs were designed and synthesised by C and N-terminal amino acid substitution or deletion. Enhancement in cationicity by N-terminal Lys/Arg substitution or hydrophobicity by Trp substitution produced no drastic change in bactericidal nature against selected bacterial strains except S. aureus. But the sequential removal of N-terminal amino acids had a negative effect on bactericidal potency. Analog B1CTcu5-LIAG obtained by the removal of four N-terminal amino acids displayed bactericidal effect comparable to, or in excess of, the parent peptide with reduced hemolytic character. Its higher activity was well correlated with the improved inner membrane permeabilisation capacity. This region may act as the active core of B1CTcu5. Presence of C-terminal disulphide bond was not a necessary condition to display antibacterial activity but helped to promote hemolytic nature. Removal of the C-terminal rana box region drastically reduced antibacterial and hemolytic activity of the peptide, showing that this region is important for membrane targeting. The bactericidal potency of the D-peptide (DB1CTcu5) helped to rule out the stereospecific interaction with the bacterial membrane. Our data suggests that both the C and N-terminal regions are necessary for bactericidal activity, even though the active core region is located near the N-terminal of B1CTcu5. A judicious modification at the N-terminal region may produce a short SMMD analog with enhanced bactericidal activity and low toxicity against eukaryotic cells.

Cross-species testing and utility of microsatellite loci in Indirana frogs

BackgroundMicrosatellite loci are widely used in population and conservation genetic studies of amphibians, but the availability of such markers for tropical and subtropical taxa is currently very limited. In order to develop resources for conservation genetic studies in the genus Indirana, we tested amplification success and polymorphism in 62 previously developed microsatellite loci, in eight Indirana species - including new candidate species. Developing genomic resources for this amphibian taxon is particularly important as it is endemic to the Western Ghats biodiversity hotspot, and harbours several endangered species.FindingsThe cross-species amplification success rate varied from 11.3 % to 29.0 % depending on the species, with 29 - 80 % of the amplifying loci being polymorphic. A strong negative correlation between cross-species amplification success (and polymorphism) and genetic distance separating target from source species was observed.ConclusionsOur results provide additional genetic support for the existence of genetically divergent cryptic species within the genus Indirana. The tested markers should be useful for population and conservation genetic studies in this genus, and in particular, for species closely related to the source species, I. beddomii.

pH-responsive superomniphobic nanoparticles as versatile candidates for encapsulating adhesive liquid marbles

Conventional adhesives are rarely used in sophisticated applications such as micro-fluidic devices or ‘operations of bonding from a distance’ due to their permanent wetting characteristics. Liquid marbles offer exceptional switching between non-wetting and wetting on demand. In this contribution, we present a novel approach to encapsulate both hydrophilic (epoxy resin) and hydrophobic (siloxane polymer) liquids via wrapping them with superomniphobic nanoparticles. The free energy for marble formation is lower for a hydrophobic liquid (0.931 × 10−16 J), whereas a hydrophilic liquid registers a higher value of 1.86 × 10−16 J. The mechanical bursting energy for hydrophobic marbles (20 μJ) is lower than that for their hydrophilic counterpart (48.6 μJ). The static friction coefficients of epoxy-based liquid marble are between 0.015 and 0.020 on glass, aluminium and stainless steel substrates. As a highlight, the nanoparticle coating is responsive to pH, and the bursting time of the liquid marbles can be tuned from <1 minute to several hours. It is demonstrated that the adhesive strength of cross-linked epoxy obtained by a liquid marble route is higher than that obtained vis-a-vis a conventional wetting route. The liquid marbles presented in this work can be ruptured by changing the pH, have a lower friction coefficient compared to the bare liquids (more rolling distance, which is highly essential for bonding of an intricate space from a distance) and are useful as dry adhesives.

TM1-IR680 peptide for assessment of surgical margin and lymph node metastasis in murine orthotopic model of oral cancer

Treatment outcome after surgical removal in oral carcinoma is poor due to inadequate methodologies available for marking surgical margins. Even though some methodologies for intraoperative margin assessment are under clinical and preclinical trials for other solid tumours, a promising modality for oral cancer surgery is not developed. Fluorescent-based optical imaging using Near Infrared (NIR) dyes tagged to tumour specific target will be an optimal tool for this purpose. One such target, Gastrin Releasing Peptide Receptor (GRPR) was selected for the study, and its binding peptide, TM1-IR680, was tested for its efficacy for surgical margin prediction in murine orthotopic model of oral cancer, derived from primary samples. Here, for the first time in a preclinical analysis, we show that the size and margin of oral cancer can be predicted, as revealed by 3D-imaging. Interestingly, the peptide was sensitive enough to detect lymph nodes that harboured dispersed tumour cells before colonization, which was impossible to identify by conventional histopathology. We recommend the use of TM1-NIR dyes alone or in combination with other technologies to improve the clinical outcome of oral cancer surgery.

Live detection and purification of cells based on the expression of a histone chaperone, HIRA, using a binding peptide.

Flowcytometry is a reliable method for identification and purification of live cells from a heterogeneous population. Since permeabilized cells cannot be sorted live in a FACS sorter, its application in isolation of functional cells largely depends on antibodies for surface markers. In various fields of biology we find intracellular markers that reveal subpopulations of biological significance. Cell cycle stage specific molecules, metastatic signature molecules, stemness associated proteins etc. are examples of potential markers that could improve the research and therapy enormously. Currently their use is restricted by lack of techniques that allow live detection. Even though a few methods like aptamers, droplet-based microfluidics and smartflares are reported, their application is limited. Here, for the first time we report a simple, cost-effective and efficient method of live sorting of cells based on the expression of an intracellular marker using a fluorophore-tagged binding peptide. The target molecule selected was a histone chaperone, HIRA, the expression of which can predict the fate of differentiating myoblast. Our results confirm that the peptide shows specific interaction with its target; and it can be used to separate cells with differential expression of HIRA. Further, this method offers high purity and viability for the isolated cells.

Engineering chemokines to develop putative anti HIV-1 agents

Background Even though, Highly Active Antiretroviral Therapy (HAART) has resulted in significant reduction in mortality associated with Acquired Immune Deficiency Syndrome (AIDS), the side-effects and difficulties in patient compliance warrants the search for new therapeutic options. One potential strategy is to design chemokine analogues that will prevent the entry of human immunodeficiency virus-1 (HIV-1) into the target cell by competitively blocking its interaction with CC chemokine-5 (CCR5) receptor. The objective of the present study is to design and validate the efficacy of chemokine analogues based on the viral macrophage inflammatory protein-II (vMIP-II) core as putative anti-HIV agents.

Synthesis of a Shark Repellent Peptide Toxin, Pardaxin (16-33) on a Highly Flexible Polymer Support: Clpser

A high swelling resin, CLPSER has been developed and utilized for the solid phase synthesis of Pardaxin, which is an 18-residue peptide. The resin was characterized by gel phase (13)C NMR, IR and SEM. The utility of the new polymer support in polypeptide synthesis was further established by the comparative synthesis of pardaxin with commercially available Merrifield resin. The MALDI TOF MS, amino acid analysis and the HPLC revealed the superior quality of CLPSER.