Preparation and characterization of N-heterocyclic chitosan derivative based gels for biomedical applications

The novel N-heterocyclic chitosan aerogel derivatives were prepared by reacting 79% deacetylated chitosan separately with 4-pyridinecarboxaldehyde and 2,6-pyridinedicarboxaldehyde followed by subsequent solvent exchange into acetone, filteration and lyophilization. The identity of the Schiff bases was confirmed by UV–vis absorption spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The N-heterocyclic chitosan derivatives were evaluated by X-ray diffraction (XRD), thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), rheological studies and biological activity. Overall, the N-heterocyclic chitosan derivative based gels open new perspectives in biomedical applications.     

Green synthesis of zinc oxide nanoparticles using Anoectochilus elatus,and their biomedical applications

Zinc and its derivatives requirement increased to enhance human immunity against the different pandemics, including covid-19. Green synthesis is an emerging field of research. Zinc oxide (ZnO) nanoparticles have been prepared from Anoectochilus elatus and characterized using absorption, vibrational and electron microscope analysis. They were carried for antibacterial, inflammatory control tendency, and potential antioxidant activities. The brine shrimp lethal assay tested the biologically derived nanomaterial toxicity and the lethal concentration (LC₅₀) is 599.79 µg/ml. The inhibition against the important disease-causing pathogens was measured against four-gram negative, gram-positive bacteria and two fungus pathogens. The nanomaterial exposed inhibition zone for gram-positive bacteria between 17 mm and 25 mm. The inhibition zone against gram-negative bacteria exists between 19 mm and 24 mm. The anti-inflammatory activity was assessed by inhibition of protein denaturation and protease inhibitory activity using nanomaterial. The antioxidant activity was examined using four assays for the therapeutic activities. The average size range of 60–80 nm nanoparticles has prepared and exposed the good biological activity between 50 µg/ml and 100 µg/ml. The comparative results of anti-inflammatory and antioxidant assay results with standards such as Aspirin and vitamin C exposed that two to three times higher concentrations are required for the fifty percent of inhibitions. The prepared low-cost nanoparticle has exhibited excellent biological activity without any side effects and may enhance immunity.     

Thermal microdevices for biological and biomedical applications

Temperature strongly influences the form and function of biologically important macromolecules and cells. Advances in microfabrication technology have enabled highly localized and accurate temperature control and manipulation, allowing the investigation of thermal effects on biological microsystems. This paper reviews progress in this field, with emphasis on techniques and microdevices with biomedical applications. Recent advances in the study of thermal effects on cellular behavior, enabled by MEMS-based structures are reported. These studies focus on investigating thermal interactions between the cell and its microenvironment. Thermal-based tools for concentration and purification of biologically important macromolecules like DNA and proteins are summarized. These tools address common issues in protein/DNA research, like concentration, separation and purification of samples. With the increasing research focus on the integration of biomedicine with engineering technologies and the several incentives of miniaturization, MEMS-based devices are likely to become increasingly prevalent in biology and medicine. Thermal engineering is expected to continue to play an important role in the improvement of current microdevices and the development of new ones.     

Dioximes: Synthesis and biomedical applications

The selective properties of dioxime compounds were discovered and outlined in the beginning of 20th century by Tschugaeff [L.Z. Tschugaeff, Z. Anorg. Allgem. Chem. 46 (1905) 144]. Dioximes have special properties as analytical reagents for transition metals. Dioximes complexation properties with metals were carried out by many investigations and these complexations showed a wide range of applications such as antimicrobial and theranostic agents. This review will provide general synthetic methods of oximes especially dioximes and brief overview on the applications of dioximes (applications of their metal complexes).     

Anticancer activities of an antimicrobial peptide derivative of Ixosin-B amide

In nature, antimicrobial peptides (AMPs) represent the first line of defense against infection by pathogens; thus, they are generally good candidates for the development of antimicrobial agents. Recently, we reported two potent antimicrobial peptides, KWLRRVWRWWR-amide (MAP-04-03) and KRLRRVWRRWR-amide (MAP-04-04), which were derived from a fragment of Ixosin-B-amide (KSDVRRWRSRY). Since some cationic AMPs exhibited cytotoxic activity against cancer cells, in the current study, we further investigated the anticancer activity of these potent antimicrobial peptides by antiproliferative assays and wound-healing assays, and the effect of peptide on the cytoskeleton alteration and cell morphology were analyzed by confocal microscopy. Results indicated that MAP-04-03 not only exhibited inhibitory effects on the proliferation (IC₅₀ = 61.5 μM) and on the cell migration of MCF-7 breast cancer cells (at a concentration of 5 μM), but also affected the cytoskeleton at the concentration of 25 μM. These results demonstrated that MAP-04-03 can serve as a lead peptide analog for developing potent anticancer agents.     

Silver nanostructures prepared via novel green approach as an effective platform for biological and environmental applications

Silver nanoparticles play a significant role in biomedical sciences due to their unique properties allowing for their use as an effective sensing and remediation platform Herein, the green synthesis of silver nanostructures (Ag NSs), prepared via aqueous extract of waste Brassica oleracea leaves in the presence of silver nitrate solution (10^-4 M), is reported. The Ag NSs are fully characterized and their efficacy with respect to 4-nitrophenol reduction, glucose sensing, and microbes is determined. Visually, the color of silver nitrate containing solution altered from colorless to yellowish, then reddish grey, confirming the formation of Ag NSs. HRTEM and SEAD studies revealed the Ag NSs to have different morphologies (triangular, rod-shaped, hexagonal, etc., within a size range of 20–40 nm) with face-centered cubic (fcc) crystal structure. The Ag NSs possess high efficacy for nitrophenol reduction (<11 min and degradation efficiency of 98.2%), glucose sensing (LOD: 5.83 µM), and antimicrobial activity (E. coli and B. subtilis with clearance zones of 18.3 and 14 mm, respectively). Thus, the current study alludes towards the development of a cost-effective, sustainable, and efficient three-in-one platform for biomedical and environmental applications.     

Screening and identification of novel isolate Streptomyces sp., NLKPB45 from Nellore costal region for its biomedical applications

Actinobacteria, which are the prolific producers of antibiotics and significant suppliers to the pharmaceutical industry, can produce a wide variety of bioactive metabolites. An actinomycete strain designated NLKPB45 was isolated from mangrove soils samples of Nellore coastal regions Andhra Pradesh and assessed for antibiotic production and activity against pathogenic bacteria. From a total of 9 mangrove soil samples, 143 acinomycetes were isolated. Among the isolated them 6 actinomycetes strains showed potential antibacterial activity against at two tested pathogens gram positive and gram negative bacteria E. coli and S. aureus. The potent strain NLKPB45 was identified by 16S gene isolation and sequencing to the Streptomyces genus. The ethyl acetate extracts also as shown excellent antimicrobial activity against Salmonella sp., staphylococcus aureus, E. coli, and B. subtilus were detected in both the supernatant extract samples from fermentations of culture NLKPB45. The anticancer activity of extracts in the HeLa with IC₅₀ value of 37.1924 μg/ml, MCF-7 IC₅₀ value of 40.9177 μg/ml and HT 29 IC₅₀ value of 43.3758 μg/ml.     

Physicochemical and bioactivity of cross-linked chitosan–PVA film for food packaging applications

This work aimed to develop a novel antimicrobial coating based on chitosan and PVA to evaluate its effect on minimally processed tomato by means of microbiological analyses. In this report an antimicrobial film was prepared by blending chitosan (CS) and poly(vinyl alcohol) (PVA) with glutaraldehyde as the cross-linker. The miscibility and morphology of the film were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The thermal property of the chitosan–PVA film was examined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The microbiological screening has demonstrated the antimicrobial activity of the film against food pathogenic bacteria viz. Escherichia coli, Staphylococcus aureus, and Bacillus subtilis. The obtained results indicate the film may be a promising material for food packaging applications.     

The novel economical synthesis and antimicrobial activity of a trithiocarbonate derivative

The compound diethyl 2,2′-(thiocarbonyl-bis(sulfanediyl))-diacetate 4 belongs to the trithiocarbonate class containing a trithiocarbonate function group flanked by ethyl acetate. In this procedure, a novel economic synthesis route to obtain compound 4 is described. This compound proved to possess broad-spectrum antimicrobial activity both in vitro and in vivo, and could be used as a lead compound. It is worth mentioning that this compound has been patented [No. US 9,988,348 B1; date of patent: June 5, 2018].     

Effect of crosslinking in chitosan/aloe vera-based membranes for biomedical applications

The positive interaction between polysaccharides with active phytochemicals found in medicinal plants may represent a strategy to create active wound dressing materials useful for skin repair. In the present work, blended membranes composed of chitosan (Cht) and aloe vera gel were prepared through the solvent casting, and were crosslinked with genipin to improve their properties. Topography, swelling, wettability, mechanical properties and in vitro cellular response of the membranes were investigated. With the incorporation of aloe vera gel into chitosan solution, the developed chitosan/aloe-based membranes displayed increased roughness and wettability; while the genipin crosslinking promoted the formation of stiffer membranes in comparison to those of the non-modified membranes. Moreover, in vitro cell culture studies evidenced that the L929 cells have high cell viability, confirmed by MTS test and calcein-AM staining. The findings suggested that both blend compositions and crosslinking affected the physico-chemical properties and cellular behavior of the developed membranes.     

Novel chitin and chitosan nanofibers in biomedical applications

Chitin and its deacetylated derivative, chitosan, are non-toxic, antibacterial, biodegradable and biocompatible biopolymers. Due to these properties, they are widely used for biomedical applications such as tissue engineering scaffolds, drug delivery, wound dressings, separation membranes and antibacterial coatings, stent coatings, and sensors. In the recent years, electrospinning has been found to be a novel technique to produce chitin and chitosan nanofibers. These nanofibers find novel applications in biomedical fields due to their high surface area and porosity. This article reviews the recent reports on the preparation, properties and biomedical applications of chitin and chitosan based nanofibers in detail.     

Synthesis and SAR study of novel anticancer and antimicrobial naphthoquinone amide derivatives

A series of novel naphthoquinone amide derivatives of the bioactive quinones, plumbagin, juglone, menadione and lawsone, with various amino acids were synthesized. The compounds were characterized by ¹H NMR, ¹³C NMR, Mass, IR and elemental analysis. All the compounds were evaluated for their anticancer activity against HeLa and SAS cancer cell lines and 3D-QSAR indicated the presence of electron donating group near sulphur enhanced the activity against HeLa cells. Among the derivatives synthesized, compounds 11f, 10a, 10b and 10g were the most active with IC₅₀ values of 16, 12, 14 and 24.5 μM, respectively. The analogues were also screened for antimicrobial activity against two human bacterial pathogens, the Gram-positive Methicillin resistant Staphylococcus aureus (MRSA) and the Gram-negative Pseudomonas aeruginosa and a human yeast pathogen, Fluconazole resistant Candida albicans (FRCA). Among the synthesized compounds, 8g, 10g and 11g exhibited maximum antibacterial activity towards MRSA and antifungal activity against FRCA in well diffusion method.     

Synthesis of novel sulfonamide analogs containing sulfamerazine/sulfaguanidine and their biological activities

Sulfamerazine and sulfaguanidine are clenched with p-nitrobenzoyl chloride and the products obtained are reduced to Na_xS in ethanol–water. Novel sulfonamides (6a–g and 9a–g) were synthesized by the reaction of these reduced products (4 and 8) with various sulfonyl chlorides (5a–g). The structures of these compounds were characterized using spectroscopic analysis (IR, ¹H-NMR, ¹³C-NMR and HRMS) technique. Antimicrobial activity of sulfonamides (3, 4, 7, 8, 6a–g and 9a–g) was evaluated by the agar diffusion method. These compounds showed antimicrobial activity against tested microorganism strains (Gram-positive bacteria, clinic isolate and yeast and mold). Compounds 9d, 9e, 9a, 6d and 6e showed particularly antimicrobial activity against tested Gram-positive (Bacillus cereus and B. subtilis) and Gram-negative (Enterobacter aerogenes) bacteria.     

Synthesis and antimicrobial activity of the Schiff base from chitosan and citral

Chitosan, a biocompatible, biodegradable, non-toxic polymer, is prepared from chitin, which is the second most naturally occurring biopolymer after cellulose. The Schiff base of chitosan was synthesized by the reaction of chitosan with citral working under high-intensity ultrasound. The effect of the molar ratio of chitosan to citral, reaction time, and temperature on the yield has been investigated. The optimal conditions were a temperature of 50 °C, a molar ratio of chitosan to citral of 1:6, and a reaction time of 10 h. The maximum yield achieved was 86.4% under optimum conditions. The structure of the Schiff base was characterized by FTIR spectroscopy, elemental analysis, and X-ray diffraction studies. The strong peaks at 1648.3 and 1610.6 cm⁻¹ are due to CN and CC stretching vibrations. The results confirmed that amino groups on chitosan reacted with citral to form the Schiff base. The antimicrobial activities of chitosan and Schiff base of chitosan were investigated against Escherichia coil, Staphylococcus aureus, and Aspergillus niger. The results indicate that the antimicrobial activity of the Schiff base increases with an increase in the concentration. It was also found that the antimicrobial activity of the Schiff base was stronger than that of chitosan.     

Laccase-mediated functionalization of chitosan by caffeic and gallic acids for modulating antioxidant and antimicrobial properties

A new strategy for the functionalization of chitosan with caffeic acid (CA) or gallic acid (GA) using laccase from Trametes versicolor is presented for the first time, yielding a product with modulated antioxidant and antimicrobial properties. UV-vis spectroscopy coupled to HPLC-SEC analysis and cyclic voltammetry kinetic studies showed that laccase catalyzes the oxidation of phenolic acids to electrophilic o-quinones, which undergo new oligomer/polymer-forming structures originated by C-C coupling between the benzene rings and C-O-C coupling involving phenolic side-chains. Furthermore, pH tunable reactions/interactions of the laccases oxidized o-quinones with nucleophilic amino groups of chitosan were determined with FTIR and ¹H NMR spectroscopy's. The highest antioxidant activity was found to be for chitosan modified with phenolic acids at pH 4.5, exhibit also an increased activity against Escherichia coli and Listeria monocytogenes compared to untreated chitosan.     

A novel pH sensitive water soluble fluorescent nanomicellar sensor for potential biomedical applications

Herein we report on the synthesis and sensor activity of a novel pH sensitive probe designed as highly water-soluble fluorescent micelles by grafting of 1,8-naphthalimide–rhodamine bichromophoric FRET system (RNI) to the PMMA block of a well-defined amphiphilic diblock copolymer—poly(methyl methacrylate)–b-poly(methacrylic acid) (PMMA₄₈–b-PMAA₂₇). The RNI-PMMA₄₈–b-PMAA₂₇ adduct is capable of self-assembling into micelles with a hydrophobic PMMA core, containing the anchored fluorescent probe, and a hydrophilic shell composed of PMAA block. Novel fluorescent micelles are able to serve as a highly sensitive pH probe in water and to internalize successfully HeLa and HEK cells. Furthermore, they showed cell specificity and significantly higher photostability than that of a pure organic dye label such as BODIPY. The valuable properties of the newly prepared fluorescent micelles indicate the high potential of the probe for future biological and biomedical applications.     

In vitro evaluation of the biomedical properties of chitosan and quaternized chitosan for dental applications

The aim of this study was to evaluate the potential dental applications of chitosan (CS) and N-[1-hydroxy-3-(trimethylammonium)propyl]chitosan chloride (HTCC). HTCC was prepared by reacting CS with glycidyltrimethylammonium chloride (GTMAC). CS and HTCC were characterized by infrared (FITR) and ¹H NMR spectroscopy. The antibacterial activity of CS and HTCC against oral pathogens, their proliferation activity and effects on the ultrastructure of human periodontal ligament cells (HPDLCs) were investigated. The results indicated that four oral strains were susceptible to CS and HTCC with minimum inhibitory concentrations (MICs) ranging from 0.25 to 2.5 mg/mL. The in vitro 3-(4,5-dimethyl-2-thizolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay determined that CS at 2000, 1000, 100, and 50 μg/mL could stimulate the proliferation of HPDLCs. Instead, HTCC inhibited the proliferation at the same concentrations but accelerated the proliferation of HPDLCs at relatively low concentrations (10, 3, 1.5, 1, and 0.3 μg/mL). Transmission electron microscopy (TEM) observations revealed that the ultra-architecture of HPDLC was seriously destroyed by HTCC treatment at 1000 μg/mL. Taken together, these results contribute information necessary to enhance our understanding of CS and HTCC in the dental field.     

Environmentally benign synthesis and antimicrobial study of novel chalcogenophosphates

We report in this work an environmentally benign zinc mediated synthesis of aryl and benzyl phosphorochalcogenoates in ethanol within a short reaction time. In vitro antimicrobial study along with statistical analysis and seed germination assay were performed. These chalcogenophosphates possess strong antimicrobial activity against the reference strains. The antibacterial activity was determined against four standard strains (Bacilus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa). The antifungal activity was evaluated against one fungal strain Candida albicans.     

Molecular cloning and biological characterization of novel antimicrobial peptides, pilosulin 3 and pilosulin 4, from a species of the Australian ant genus Myrmecia

Venom of an Australian ant species of the Myrmecia pilosula species complex (mss. name Myrmecia banksi Taylor) contains two major allergenic peptides, pilosulin 1 and pilosulin 2. To obtain novel cDNA clones that encode the pilosulin-related bioactive peptides, mRNA of another Myrmecia species was subjected to RT-PCR in which the forward primer corresponds to a nucleotide sequence in the leader sequences of pilosulin 1 and pilosulin 2. As a result, we isolated cDNA clones encoding the novel antimicrobial peptides pilosulin 3 and pilosulin 4. The nucleotide and the amino acid sequences of all four pilosulins have high homology except for the mature peptide coding regions. Synthetic pilosulin 3 and pilosulin 4 peptides displayed antimicrobial activity with histamine-releasing and low hemolytic activities.