New generation mixed matrix membrane for CO2 separation: Transition from binary to quaternary mixed matrix membrane.

Contemporary advances in material development associated with membrane gas separation refer to the cost-effective fabrication of high-performance, defect-free mixed matrix membranes (MMMs). For clean energy production, natural gas purification, and CO2 capture from flue gas systems, constituting a functional integration of polymer matrix and inorganic filler materials find huge applications. The broad domain of research and development of MMMs focused on the selection of appropriate materials, inexpensive membrane fabrication, and comparative study with other gas separation membranes for real-world applications. This study addressed a comprehensive review of the advanced MMMs wrapping various facets of membrane material selection; polymer and filler particle morphology and compatibility between the phases and the relevance of several fillers in the assembly of MMMs are analyzed. Further, the research on binary MMMs, their problems, and solutions to overcome these challenges have also been discussed. Finally, the future directions and scope of work on quaternary MMM are scrutinized in the article.

Cyclic di-peptide in situ inhibited protein-aggregation.

An increasing number of neurodegenerative diseases seem to be associated with protein misfolding that often leads to misfolded protein aggregates with a ß-sheet conformation and accumulation in the brain which directly contributes to or modulates the associated pathology. Protein aggregation diseases like Huntington's disease results from the deposition of aggregated huntingtin proteins within the nucleus, transmissible prion encephalopathies occur due to extracellular deposition of pathogenic prion proteins whereas Alzheimer's disease from the accumulation of both extracellular ß-amyloid and intracellular hyperphosphorylated tau protein aggregates. In the generalized purpose, we have taken the core sequence of amyloid-ß (responsible for its aggregation) as the aggregating peptide (AP). Among the various emerging therapeutic approaches against aggregation-related degenerative diseases such as diminishing the monomeric precursor protein, inhibiting aggregation, or blocking aggregation-induced cellular toxicity pathways, we focussed on the strategy based on the inhibition of protein aggregation using rationally designed peptide inhibitors comprising both the recognition and ß-breaking component in the sequence. The "O â†’ N acyl migration" concept was used to form cyclic peptide in situ for the generation of a bent unit which may act as disruption moiety for the inhibition process. The kinetics of aggregation was characterized by various biophysical tools (ThT-assay, TEM, CD, and FTIR). Results implied that the designed inhibitor peptides (IP) might be valuable to inhibit all the related aggregated peptides.

Mixed Matrix Membranes for Carbon Capture and Sequestration: Challenges and Scope.

Carbon dioxide (CO2) is a major greenhouse gas responsible for the increase in global temperature, making carbon capture and sequestration (CCS) crucial for controlling global warming. Traditional CCS methods such as absorption, adsorption, and cryogenic distillation are energy-intensive and expensive. In recent years, researchers have focused on CCS using membranes, specifically solution-diffusion, glassy, and polymeric membranes, due to their favorable properties for CCS applications. However, existing polymeric membranes have limitations in terms of permeability and selectivity trade-off, despite efforts to modify their structure. Mixed matrix membranes (MMMs) offer advantages in terms of energy usage, cost, and operation for CCS, as they can overcome the limitations of polymeric membranes by incorporating inorganic fillers, such as graphene oxide, zeolite, silica, carbon nanotubes, and metal-organic frameworks. MMMs have shown superior gas separation performance compared to polymeric membranes. However, challenges with MMMs include interfacial defects between the polymeric and inorganic phases, as well as agglomeration with increasing filler content, which can decrease selectivity. Additionally, there is a need for renewable and naturally occurring polymeric materials for the industrial-scale production of MMMs for CCS applications, which poses fabrication and reproducibility challenges. Therefore, this research focuses on different methodologies for carbon capture and sequestration techniques, discusses their merits and demerits, and elaborates on the most efficient method. Factors to consider in developing MMMs for gas separation, such as matrix and filler properties, and their synergistic effect are also explained in this Review.

Enhanced production of biosurfactant by Bacillus subtilis RSL2 in semicontinuous bioreactor utilizing molasses as a sole substrate.

The growth-associated metabolites are produced during the exponential phase; however, this phase terminates due to substrate depletion or product inhibition. In the present study, a semicontinuous mode with a fill-and-draw strategy was applied to extend the exponential phase of the biosurfactant production to overcome the product inhibition and in turn, enhance the yield. Bioreactor studies were performed in batch mode, followed by the semicontinuous operation. A potential biosurfactant producer Bacillus subtilis RSL2 was used in this study at the previously optimized conditions of pH 6.6, temperature 41 °C and 5% (w/v) of molasses. A better mass transfer was achieved in the bioreactor as compared to the shake flask study. In the batch bioreactor study, 90% of sugar was utilized with simultaneous 13.7 g L-1 of biosurfactant production. The sugar utilization was further improved to > 98% in the case of semicontinuous operation employing a fill-and-draw strategy. The exponential phase got extended up to 18 days and a total of 13 L of media was fed in the semicontinuous operation of 21 days as compared to 1.5 L of working volume in the batch reactor. The biosurfactant yield was enhanced by 1.5 folds and was found to be 0.97 g g-1. The produced biosurfactant was identified as a lipopeptide. The interfacial properties of the biosurfactant along with colloidal and thermal stability have been investigated. The critical micelle concentration of the produced biosurfactant was 70 mg L-1. The present study highlighted the efficient utilization of molasses for the production of biosurfactant, an alternative metabolite, in a semicontinuous mode of bioreactor.

Synthesis of highly fluorescent, amine-functionalized carbon dots from biotin-modified chitosan and silk-fibroin blend for target-specific delivery of antitumor agents.

Carbon dots (CDs) have been a promising theranostic tool with high biocompatibility and a tailorable fluorescence profile. Herein, we report the synthesis of highly fluorescent amine-functionalized CDs from low molecular weight chitosan (LMWC) and silk-fibroin (SF) blends. The synthesized CDs were quasi-spherical in shape with a size of 3 ± 1.5 nm. A significant increase in fluorescent intensity and quantum yield was achieved upon increasing the SF content due to nitrogen doping. For inducing target specificity to cancer cells, biotin was covalently conjugated to the CDs, and the conjugation was determined by FTIR spectroscopy. The conjugate was further loaded with 5-fluorouracil (5-FU) as a model anti-cancer drug. The MTT assay showed increased cytotoxicity of the conjugated CDs in cancer cells compared to normal cells. The live-cell imaging in MCF-7 cell lines showed bright blue-colored fluorescence and increased internalization of the conjugated CDs than the non-conjugate ones due to receptor-mediated endocytosis.

Breaker peptides against amyloid-ß aggregation: a potential therapeutic strategy for Alzheimer's disease.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, for which blocking the early steps of extracellular misfolded amyloid-ß (Aß) aggregation is a promising therapeutic approach. However, the pathological features of AD progression include the accumulation of intracellular tau protein, membrane-catalyzed cell death and the abnormal deposition of Aß. Here, we focus on anti-amyloid breaker peptides derived from the Aß sequence and non-Aß-based peptides containing both natural and modified amino acids. Critical aspects of the breaker peptides include N-methylation, conformational restriction through cyclization, incorporation of unnatural amino acid, fluorinated molecules, polymeric nanoparticles and PEGylation. This review confers a general idea of such breaker peptides with in vitro and in vivo studies, which may advance our understanding of AD pathology and develop an effective treatment strategy against AD.

Enhanced melanoidin removal by amine-modified Phyllanthus emblica leaf powder.

Melanoidins are classified as hazardous colouring and polluting biopolymers, which are generated in very large amounts in molasses-based distillery effluent. In this study, melanoidin was removed through adsorption using amine surface-modified Phyllanthus emblica leaf powder (PELP) as a low-cost natural adsorbent. The amine-modified adsorbents were prepared by forming self-assembled monolayers (SAMs). The pzc of melanoidin and anime-modified PELP were found to be 6.9 and 3.8, respectively. RSM-CCD was used to optimize the environmental conditions considering adsorbent doses (0.2-2 % w/v), pH (3-11) and temperature (25-55 °C). A complete decolourization of melanoidin (98.50 ± 1 %) was observed at the optimized conditions (44.0 °C, pH = 5.93 and dose = 1.34 % w/v) along with 93.4 ± 0.2 % of COD reduction. The surface modification enhanced the maximum adsorption capacity to 616.2 mg g-1 i.e. 2.5 folds. The modified adsorbent also resulted in colour removal and COD reduction as 91 ± 3 and 84 ± 2 %, respectively from a real spentwash sample.

Synthesis of functionalized silk-coated chitosan-gold nanoparticles and microparticles for target-directed delivery of antitumor agents.

Chemically modified biopolymers derived nanomaterials have shown great potential in drug delivery and live-cell imaging. We have developed two materials, doxorubicin-loaded chitosan-gold nanoparticles and beads, both embedded with functionalized silk fibroin. Nanoparticles with size 8 ± 3 nm were synthesized using chitosan as reducing and stabilizing agent. Beads with 900-1000 µm size were formulated by the ionic gelation technique. Both the materials were coated with functionalized silk fibroin for targeted and sustained drug release properties. The coated materials showed retarded drug release compared to the uncoated ones. The cytotoxicity was assessed in HeLa cell lines, which demonstrated a maximum dose-dependent decrease in cell viability for the cells treated with folate conjugated silk fibroin coated nanoparticles. The live-cell imaging of the nanoparticles unveiled the increased cellular uptake of the coated materials by seven folds than the uncoated ones. Thus, functionalized silk coated materials can be effective drug delivery tools for targeted and sustained drug release.

In-situ side-chain peptide cyclization as a breaker strategy against the amyloid aggregating peptide.

Accumulation and deposition of misfolded amyloid ß (Aß) peptide outside the nerve cells are one of the major causes of Alzheimer's disease (AD). To date, one of the promising therapeutic strategies for AD is to block the early steps associated with the aggregation of Aß peptide. We have developed synthetic breaker peptides derived from the original Aß sequences that undergo self-cyclization in situ. We have focussed and replaced Val-18 (of Aß) by side-chain modified glutamic acid (Glu-OBn) to generate adequate turn through in-situ peptide cyclization to disrupt the ß-sheet structure of Aß. The disruption of amyloid fibril formation and the mechanism of the 'inhibition of aggregation' were studied by various biophysical methods, such as ThT-assay, TEM, Congo-red birefringence study. CD and FTIR spectroscopy were used to characterize the conformational change during the aggregation process. Results suggest that designed breaker peptides may be useful to inhibit and disrupt not only Aß peptide but related peptides that undergo aggregation.

Fabrication of nanoparticles from a synthesized peptide amphiphile as a versatile therapeutic cargo for high antiproliferative activity in tumor cells.

Nanoparticles with encapsulated small molecules have attained vital importance in anticancer research. Peptide-based nanoparticles show their versatility in drug delivery due to their excellent biocompatibility and nontoxic nature. We demonstrate here the design and fabrication of peptide-based nanoparticles as dual-therapeutic cargo for the controlled release of hydrophilic 5-Fluorouracil (5Fu) and hydrophobic camptothecin (CPT), simultaneously. The covalent conjugation of 5Fu with the peptide, through a stimuli-responsive linker, provided better control over the release of 5Fu and dramatically reduced the possibility of leaching of the small molecule. As anticipated, the peptide-5Fu nanoparticles were efficient to encapsulate a second chemotherapeutic molecule CPT in its hydrophobic region. The stimuli-responsive release of 5Fu was carefully monitored by HPLC, NMR, and UV-visible spectroscopy. On the other hand, the release of the hydrophobic drug CPT from the nanoparticles was determined to be in a diffusion-controlled fashion. Assessment of performance in human cervical HeLa cell lines demonstrated the peptide-drug nanoparticles to be highly nontoxic. Whereas, the simultaneous release of the two antitumor agents, in a controlled manner, resulting in rapid antiproliferation of the tumor cells.

Folding and stability of recombinant azoreductase enzyme from Chromobacterium violaceum.

Azoreductase from Chromobacterium violaceum was characterized biophysically using experimental and computational tools. The in-silico docking and cross-linking experiments using glutaraldehyde suggest dimeric nature of the enzyme. The enzyme structure was modelled and also studied using circular dichroism (CD) spectroscopy which suggests 40% α- helix, 30% ß- sheet and 30% random coils. In the modelled structure of the azoreductase, the cofactor flavin mononucleotide (FMN) binding energy was -3.8 kJ/mol. The binding of FMN affects the azoreductase-cofactor complex stability. The stability-folding studies indicate that the cofactor, FMN is required for folding, stability and activity. Overall, the data provides interesting insight into stability and biophysical parameters of the azoreductase protein.

Biochemical characterization of a stable azoreductase enzyme from Chromobacterium violaceum: Application in industrial effluent dye degradation.

The presence of dye, including azo functional group (NN) containing dyes, in industrial waste water is one of the major causes of water pollution. This report showcases the functional role of azoreductase from Chromobacterium violaceum (MTCC No: 2656) as a valuable enzyme for degradation of azo dyes. The enzyme was cloned, expressed, purified and biochemically characterized and further tested for degradation efficiency of azo group containing dyes like methyl red, amaranth and methyl orange. The degraded azo dye products (metabolites) resulted by the action of azoreductase enzyme had reduced toxicity on fibroblast cell lines (L929) as compared to raw and intact dye. Further, good stability of the enzyme makes it more suitable for various applications related to the degradation and decolourisation of effluent dyes.

Development of a photoresponsive chitosan conjugated prodrug nano-carrier for controlled delivery of antitumor drug 5-fluorouracil.

Controlled drug delivery offers improved therapeutic efficacy of the drugs while minimizing side effects. Biocompatible polymers and nanomaterials have emerged as effective carriers for the controlled delivery of drugs. We have synthesized a prodrug of 5-fluorouracil (5FU) covalently conjugated to low molecular weight chitosan (LMWC) via a photocleavable linker. The conjugate was designed to be cleaved under 365 nm UV-A radiations, which is regarded as relatively safe for the cells and release 5FU in a dose-dependent manner. The conjugate showed enhanced water solubility compared to LMWC and forms hydrogel and DMSO gel. The conjugate polymer was also fabricated into nanoparticles by ionic gelation technique. The size of the nanoparticles was found to be in the range 70-90 nm, thus should have the ability to penetrate into living cells. In vitro release study of 5FU from the conjugate showed controlled release of the antitumor drug over time. The synthesized nanoparticles and the gel, therefore, could be a good model for controlled release of antitumor drugs.

Quantitative single-nucleotide polymorphism analysis in secondary-structured DNA by affinity capillary electrophoresis using a polyethylene glycol-peptide nucleic acid block copolymer.

To estimate allele frequency of single-nucleotide polymorphisms (SNPs) in pooled DNAs with secondary structures, an affinity capillary electrophoresis was developed using an allele-specific peptide nucleic acid probe modified with polyethylene glycol. This probe disrupted secondary structures of DNA analytes and hybridized to them during electrophoresis. Such DNA-binding capability allowed separation of the folded analytes with a single-base difference within 20 min. The feed ratio of the target allele was evaluated by calculating the peak area ratio. The averaged difference between the feed and observed ratio was 1.5%. This method should be of general applicability to quantitative SNP analyses.

Estimation of binding constants of peptide nucleic acid and secondary-structured DNA by affinity capillary electrophoresis.

An affinity capillary electrophoresis method was developed to determine a binding constant between a peptide nucleic acid (PNA) and a hairpin-structured DNA. A diblock copolymer composed of PNA and polyethylene glycol (PEG) was synthesized as a novel affinity probe. The base sequence of the probe's PNA segment was complementary to a hairpin-structured region of a 60-base single-stranded DNA (ssDNA). Upon applying a voltage, the DNA hairpin migrated slowly compared to a random sequence ssDNA in the presence of the PNA probe. This retardation was induced by strand invasion of the PNA into the DNA hairpin to form a hybridized complex, where the PEG segment received a large amount of hydrodynamic friction during electrophoresis. The binding constant between the PNA probe and the DNA hairpin was easily determined by mobility analysis. This simple method would be potentially beneficial in studying binding behaviors of various artificial nucleotides to natural DNA or RNA.

Direct detection of 8-oxo-deoxyguanosine using UV resonance Raman spectroscopy.

8-oxo-deoxyguanosine (8-oxo-dG) is a major oxidative lesion in DNA and is responsible for mutation and cancer. Current techniques for detecting 8-oxo-dG are indirect methods. Thus, development of new methodologies is needed to directly detect such oxidative lesions. In this article, we have used ultraviolet resonance Raman (UVRR) spectroscopy as a novel analytical technique for the detection of 8-oxo-dG. Here, the UVRR spectrum of 8-oxo-dG was acquired and compared to that of deoxyguanosine (dG) and deoxyadenosine (dA). Data analysis shows a distinct UVRR spectrum of 8-oxo-dG with characteristic peaks. Detection of 8-oxo-dG was easily achieved from a mixture with dG. These results reveal that UVRR spectroscopy shows promise as a direct method for detecting 8-oxo-dG.

RNA is more UV resistant than DNA: the formation of UV-induced DNA lesions is strongly sequence and conformation dependent.

DNA and RNA hairpins, which represent well-folded oligonucleotide structures, were irradiated and the amount of damaged hairpins was directly quantified by using ion-exchange HPLC. The types of photoproducts formed in the hairpins were determined by ESI-HPLC-MS/MS experiments. Irradiation of hairpins with systematically varied sequences and conformations (A versus B) revealed remarkable differences regarding the amount of photolesions formed. UV-damage formation is, therefore, a strongly sequence and conformation dependent process.

Cleavable substrate containing molecular beacons for the quantification of DNA-photolyase activity.

In order to gain deeper insight into the function and interplay of proteins in cells it is essential to develop methods that allow the profiling of protein function in real time, in solution, in cells, and in cell organelles. Here we report the development of a U-type oligonucleotide (molecular beacon) that contains a fluorophore and a quencher at the tips, and in addition a substrate analogue in the loop structure. This substrate analogue induces a hairpin cleavage in response to enzyme action, which is translated into a fluorescence signal. The molecular beacon developed here was used to characterize DNA-photolyase activity. These enzymes represent a challenge for analytical methods because of their low abundance in cells. The molecular beacon made it possible to measure the activity of purified class I and class II photolyases. Photolyase activity was even detectable in crude cell extracts.