Mechanistic understanding on the uptake of micro-nano plastics by plants and its phytoremediation.

Contaminated soil is one of today's most difficult environmental issues, posing serious hazards to human health and the environment. Contaminants, particularly micro-nano plastics, have become more prevalent around the world, eventually ending up in the soil. Numerous studies have been conducted to investigate the interactions of micro-nano plastics in plants and agroecosystems. However, viable remediation of micro-nano plastics in soil remains limited. In this review, a powerful in situ soil remediation technology known as phytoremediation is emphasized for addressing micro-nano-plastic contamination in soil and plants. It is based on the synergistic effects of plants and the microorganisms that live in their rhizosphere. As a result, the purpose of this review is to investigate the mechanism of micro-nano plastic (MNP) uptake by plants as well as the limitations of existing MNP removal methods. Different phytoremediation options for removing micro-nano plastics from soil are also described. Phytoremediation improvements (endophytic-bacteria, hyperaccumulator species, omics investigations, and CRISPR-Cas9) have been proposed to enhance MNP degradation in agroecosystems. Finally, the limitations and future prospects of phytoremediation strategies have been highlighted in order to provide a better understanding for effective MNP decontamination from soil.

Bioinspired synthesis of bioactive glass nanocomposites for hyaluronic acid delivery to bone and skin.

In this study, we present nanocomposites of bioactive glass (BG) and hyaluronic acid (HA) (nano-BGHA) for effective delivery of HA to skin and bone. The synthesis of the nanocomposites has been carried out through the bio-inspired method, which is a modification of the traditional Stober's synthesis as it avoids using ethanol, ammonia, synthetic surfactants, or high-temperature calcination. This environmentally friendly, bio-inspired route allowed the synthesis of mesoporous nanocomposites with an average hydrodynamic radius of ∼190 nm and an average net surface charge of ∼-21 mV. Most nanocomposites are amorphous and bioactive in nature with over 70 % cellular viability for skin and bone cell lines even at high concentrations, along with high cellular uptake (90-100 %). Furthermore, the nanocomposites could penetrate skin cells in a transwell set-up and artificial human skin membrane (StratM®), thus depicting an attractive strategy for the delivery of HA to the skin. The purpose of the study is to develop nanocomposites of HA and BG that can have potential applications in non-invasive treatments that require the delivery of high molecular weight HA such as in the case of osteoarthritis, sports injury treatments, eye drops, wound healing, and some anticancer treatments, if further investigated. The presence of BG further enhances the range to bone-related applications. Additionally, the nanocomposites can have potential cosmeceutical applications where HA is abundantly used, for instance in moisturizers, dermal fillers, shampoos, anti-wrinkle creams, etc.

Insights into microbial diversity on plastisphere by multi-omics.

Plastic pollution is a major concern in marine environment as it takes many years to degrade and is one of the greatest threats to marine life. Plastic surface, referred to as plastisphere, provides habitat for growth and proliferation of various microorganisms. The discovery of these microbes is necessary to identify significant genes, enzymes and bioactive compounds that could help in bioremediation and other commercial applications. Conventional culture techniques have been successful in identifying few microbes from these habitats, leaving majority of them yet to be explored. As such, to recognize the vivid genetic diversity of microbes residing in plastisphere, their structure and corresponding ecological roles within the ecosystem, an emerging technique, called metagenomics has been explored. The technique is expected to provide hitherto unknown information on microbes from the plastisphere. Metagenomics along with next generation sequencing provides comprehensive knowledge on microbes residing in plastisphere that identifies novel microbes for plastic bioremediation, bioactive compounds and other potential benefits. The following review summarizes the efficiency of metagenomics and next generation sequencing technology over conventionally used methods for culturing microbes. It attempts to illustrate the workflow mechanism of metagenomics to elucidate diverse microbial profiles. Further, importance of integrated multi-omics techniques has been highlighted in discovering microbial ecology residing on plastisphere for wider applications.

Bioactivity reinforced surface patch bound collagen-pectin hydrogel.

In this report, we discuss the design of a novel collagen/pectin (CP) hybrid composite hydrogel (CPBG) containing in-situ mineralized bioactive glass (BG) particles to simulate an integrative 3D cell environment. Systematic analysis of the CP sol revealed collagen and pectin molecules interacted regardless of both possessing similar net negative charge through the mechanism of surface patch binding interaction. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) confirmed this associative interaction which resulted in the formation of a hybrid crosslinked network with the BG nanoparticles acting as pseudo crosslink junctions. Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDAX) and Transmission Electron Microscopy (TEM) results confirmed uniform mineralization of BG particles, and their synergetic interaction with the network. The in-vitro bioactivity tests on CPBG indicated the formation of bone-like hydroxyapatite (Ca10(PO4)6(OH)2) microcrystals on its surface after interaction with simulated body fluid. This hydrogel was loaded with a model antifungal drug amphotericin-B (AmB) and tested against Candida albicans. The AmB release kinetics from the hydrogel followed the Fickian mechanism and showed direct proportionality to gel swelling behavior. Rheological analysis revealed the viscoelastic compatibility of CPBG for the mechanical load bearing applications. Cell viability tests indicated appreciable compatibility of the hydrogel against U2OS and HaCaT cell lines. FDA/PI on the hydrogel portrayed preferential U2OS cell adhesion on hydrophobic hydroxyapatite layer compared to hydrophilic surfaces, thereby promising the regeneration of both soft and hard tissues.

Microbial remediation of micro-nano plastics: Current knowledge and future trends.

An alarming rise of micro-nano plastics (MNPs) in environment is currently causing the biggest threat to biotic and abiotic components around the globe. These pollutants, apart from being formed through fragmentation of larger plastic pieces and are also manufactured for commercial usage. MNPs enter agro-ecosystem, wildlife, and human body through the food chain, ingestion or through inhalation, causing blockage in the blood-brain barrier, lower fertility, and behavioural abnormalities among other problems. Hence, it becomes essential to develop novel procedures for remediation of MNPs. Among the numerous existing methods, microbial remediation promises to degrade/recover MNPs via a green route. Since microbial remediation processes mostly depend upon biotic and abiotic factors such as (temperature, pH, oxidative stress, etc.), it becomes easy to influence changes in the plastic pollutants. Hence, with the help of recent technologies, a complete degradation/removal of MNPs can be expected by utilizing the respective carbon content as energy sources for growth of microorganisms. In this review, considering the urgent environmental need, the impact of micro-nano plastics on ecosystem along with its corresponding degradation mechanisms has been brought out. Also, importance of the various recent research approaches in MNPs remediation is highlighted. Finally, the role of enzyme and membrane technology, nanoparticle technology, and metagenomics in remediation of MNPs are discussed for the first time in detail to bring out a novel remedy for the environment.

ZnO Nanoparticles Modified with an Amphipathic Peptide Show Improved Photoprotection in Skin.

ZnO nanoparticles of different sizes were functionalized with an amphipathic peptide, and its effect on nanoparticle stabilization and UV photoprotective activity was studied in this article. The peptide-modified nanoparticles exhibited lower aggregation, significant reduction in Zn2+ leaching in vitro and even inside the cells for smaller particle sizes, reduced photocatalytic activity, and reduced cellular toxicity under UV-B treated conditions. In addition, the peptide-modified 60 nm ZnO nanoparticles showed lower genotoxicity, lower oxidative stress induction levels, less DNA damage responses, and less immunogenic potential than the bare counterparts in the presence of UV-B rays. They localized more in the stratum corneum and epidermis ex vivo, indicating better retention in epidermis, and demonstrated improved UV-B protection and/or skin integrity in SKH-1 mice in vivo compared to unmodified nanoparticles and commercial UV-protective agents tested. To our knowledge, this is the first report on the application of peptide-modified ZnO nanoparticles for improved photoprotection.

Role of cellulose functionality in bio-inspired synthesis of nano bioactive glass.

In search of abundant cheaper natural polymer for bio-inspired bioactive glass nanoparticles synthesis, cellulose and its derivatives have been considered as a template. Different templates explored in the present studies are pure cellulose, methyl cellulose and amine grafted cellulose. To the best of our knowledge, for the first time of the considered templates, pure cellulose and amine grafted cellulose results in in situ nano particulate composite formation while interestingly methyl cellulose proves to be an excellent sacrificial template for the synthesis of uniform bioglass nanoparticles of diameter in the range of 55nm. Further, viscoelastic measurements were carried out using dynamic mechanical analyzer. Herein, an attempt has been made to establish structure-mechanical relationship based on the templates. Moreover, in vitro bioactivity is also observed to be affected by the nature of the template molecule used for the synthesis of bioactive glass.

Non-invasive Oil-Based Method to Increase Topical Delivery of Nucleic Acids to Skin.

Topical delivery of nucleic acids to skin has huge prospects in developing therapeutic interventions for cutaneous disorders. In spite of initial success, clinical translation is vastly impeded by the constraints of bioavailability as well as stability in metabolically active environment of skin. Various physical and chemical methods used to overcome these limitations involve invasive procedures or compounds that compromise skin integrity. Hence, there is an increasing demand for developing safe skin penetration enhancers for efficient nucleic acid delivery to skin. Here, we demonstrate that pretreatment of skin with silicone oil can increase the transfection efficiency of non-covalently associated peptide-plasmid DNA nanocomplexes in skin ex vivo and in vivo. The method does not compromise skin integrity, as indicated by microscopic evaluation of cellular differentiation, tissue architecture, enzyme activity assessment, dye penetration tests using Franz assay, and cytotoxicity and immunogenicity analyses. Stability of nanocomplexes is not hampered on pretreatment, thereby avoiding nuclease-mediated degradation. The mechanistic insights through Fourier transform infrared (FTIR) spectroscopy reveal some alterations in the skin hydration status owing to possible occlusion effects of the enhancer. Overall, we describe a topical, non-invasive, efficient, and safe method that can be used to increase the penetration and delivery of plasmid DNA to skin for possible therapeutic applications.

Efficient Cellular Entry of (r-x-r)-Type Carbamate-Plasmid DNA Complexes and Its Implication for Noninvasive Topical DNA Delivery to Skin.

Arginine-rich cell penetrating peptides are powerful tools for in vitro as well as in vivo delivery of a wide plethora of biomolecules. However, presence of consecutive arginine residues leads to enhanced amenability for proteolytic degradation as well as steric hindrances for membrane interactions which compromise its bioavailability. In order to overcome these limitations we previously reported a safe and stable octaarginine based oligomer, i.e., (r-x-r)4-carbamate, where the backbone amide linkages were replaced by carbamate linkages and 6-aminohexanoic acid based spacer moieties were incorporated for better flexibility, hydrophobicity, optimal spacing of guanidinium groups, and protection against proteolytic cleavage; resulting in improved transfection efficiency over its amide counterpart. In the present work we have investigated the mechanism behind this enhanced transfection efficiency and, based on our observations, demonstrate how the synergistic effect of rationalized oligomer designing, complex characteristics, and cell type contributes to overall effective intracellular delivery. Our results indicate that the (r-x-r)4-carbamate-plasmid DNA complexes primarily utilize lipid raft dependent pathway of cellular entry more than other pathways, and this possibly facilitates their increased entry in the lipid raft rich milieu of skin cells. We also emphasize the utility of oligomer (r-x-r)4-carbamate as an efficient carrier for topical delivery of nucleic acids in skin tissue. This carrier can be utilized for safe, efficient, and noninvasive delivery of therapeutically relevant macromolecular hydrophilic cargo like nucleic acids to skin.

Non-invasive topical delivery of plasmid DNA to the skin using a peptide carrier.

Topical delivery to skin is an essential step in non-invasive application of nucleic acid therapeutics for cutaneous disorders. The barrier posed by different layers of the skin - stratum corneum on top followed by the viable epidermis below - makes it extremely challenging for large hydrophilic molecules like nucleic acids to efficiently enter the uncompromised skin. We report an amphipathic peptide Mgpe9 (CRRLRHLRHHYRRRWHRFRC) that can penetrate the uncompromised skin, enter skin cells and deliver plasmid DNA efficiently as nanocomplexes in vitro and in vivo without any additional physical or chemical interventions prevalent currently. We observe efficient gene expression up to the highly proliferating basal layer of the skin without observable adverse reactions or toxic effects after delivery of reporter plasmids. The entry mechanism of nanocomplexes possibly involves reversible modulation of junction proteins accompanied by transient changes in skin structure. This peptide holds potential to be used as an efficient transporter of therapeutic nucleic acids to the skin.

Tailored smart bioactive glass nanoassembly for dual antibiotic in vitro sustained release against osteomyelitis.

The effect of cetyltrimethylammonium bromide (CTAB) concentration as a sacrificial template on tunable mesostructure textured bioactive glass nanoparticles has been explored and characterized. For the 10 mM CTAB concentration templated sample, smart bioactive glass nanoassembly (nBGA) has been tailored for dual antibiotic sustained release against osteomyelitis disease. The loading of two different drugs on the bioglass has been controlled through a thin chitosan sheath. To our knowledge, for the first time synergistic co-drug delivery of two antibiotics, namely sodium ampicillin and gentamicin sulfate, through bioglass nanoassembly, along with bone regeneration has been considered. Sustained co-release kinetics of dual anti-biotic drugs at different time points was evaluated. In addition to this, the in situ loss in bacterial viability with time of the dual drug loaded bioglass nanoassembly has been quantified against two different mono- and co-bacterial cultures by live/dead BacLight bacterial viability kit. Additionally, osteoblast like osteosarcoma cells proliferation on the dual drug loaded bioglass nanoassembly surface has been quantified in the presence and absence of bacterial challenge. This study provides a new insight into the application of bioactive glass as an efficient co-drug delivery vehicle for osteomyelitis.

Fluorescence and Förster resonance energy transfer investigations on DNA oligonucleotide and PAMAM dendrimer packing interactions in dendriplexes.

Considering the importance of short oligonucleotide packing in dendriplex-mediated gene delivery, a direct insight into the 14-mer oligonucleotide and dendrimer interactions using fluorescence and FRET techniques is the focus of this study. Fluorometric titrations of various fluorophore-tagged oligonucleotides with the first three PAMAM dendrimer generations showed a decrease in the fluorescence intensity with two break points, namely Z and Z, for each titration. The first break point for each dendrimer was identical to the neutralization point observed by basic biophysical studies for the corresponding dendrimer generations. Additionally, FRET studies on dual tagged oligonucleotide (DFT) molecules revealed a third break point at the charge ratio (Z) where there was the highest fluorescence energy transfer from the donor to the acceptor fluorophores. Altogether, dendriplex formation was considered to take place via three steps with an increase in the dendrimer concentration, where initially there was monomeric complexation at the neutralization point (Z) followed by loosely held molecular aggregation of the dendrimer (Z). In the final step, dendrimer molecular aggregates were held tightly together for the closest possible packing of the oligonucleotide molecules onto their surface. The effective molecular packing is identified by the highest FRET intensity for the dendrimer of generation 2 at a charge ratio of 0.34 (Z±).

Bio-inspired synthesis of microporous bioactive glass-ceramic using CT-DNA as a template.

We report, for the first time, bio-inspired synthesis of a bioactive glass-ceramic with superior textural properties in atmospheric conditions using CT-DNA as template. The phase composition, structure, morphology, and textural properties of the bioactive glass sample were evaluated with various analytical techniques before and after in vitro tests. The BET surface area analysis of the obtained glass-ceramic sample reveals that it possesses a high surface area with a range of (micro- to meso-) pore sizes. The TEM analysis of the glass-ceramic phase indicates that the amorphous phase consists of spherical particles, whereas the crystalline phase is found to have needle-like shape. In the glass-ceramic, we find a new type of crystalline phase (Na0.11Ca0.89)(P0.11Si0.89)O3, which is different from the earlier observation on 45S5® glass-ceramic sample. The accelerated in vitro bioactivity of the glass-ceramic is evidenced based on the hydroxyl carbonate apatite (HCA) layer formation on the glass-ceramic surface after immersing the bioglass sample in simulated body fluid (SBF), by FTIR, SEM and EDX analysis. Additionally, the ion release kinetics of the bioglass sample in SBF is followed by ICP-AES with simultaneous pH measurements. The in vitro cytotoxicity experiments on the glass-ceramic sample using osteosarcoma cells by following the MTT assay method indicate that the sample has good biocompatibility and may serve as an effective biomaterial for bone tissue engineering.

Kinetic studies of amino acid-based surfactant binding to DNA.

In this work, the binding kinetics of amino acid-based surfactants, presenting different linkers and head groups, with calf thymus (CT)-DNA was studied using stopped-flow fluorescence spectroscopy. The kinetic studies were carried out as a function of Na(+) concentration and surfactant-to-DNA charge ratio. The surfactant binding on DNA took place in two consecutive steps, for which the corresponding first and second relative rate constants (k(1) and k(2)) were determined. The fast step was attributed to the surfactant binding to DNA and micelle formation in its vicinity, the slower step to DNA condensation and possible rearrangement of the surfactant aggregates. In general, both relative rate constants increase with surfactant concentration and decrease with the ionic strength of the medium. The architecture of the surfactant was found to have a significant impact on the kinetics of the DNA-surfactant complexation. Surfactants with amide linkers showed larger relative rate constants than those with ester linkers. The variation of the relative rate constants with the head groups of the surfactants, alanine and proline, was found to be less obvious, being partially dependent on the surfactant concentration.

An investigation on interaction between 14mer DNA oligonucleotide and CTAB by fluorescence and fluorescence resonance energy transfer studies.

Possible interaction mechanisms between oligonucleotide (DNA) of 14 base pairs with cetyl trimethyl ammonium bromide (CTAB) were postulated based on fluorescence and fluorescence resonance energy transfer (FRET) studies. Detailed FRET investigations were carried out by fluorometric titrations of the surfactant with various oligonucleotide duplexes with 5'-tagged fluorescein (donor) (D(D)), 5'-tagged TAMRA (acceptor) (D(A)) and both (D(DA)). In general, fluorescence spectra of the duplexes (D(D), D(A) and D(DA)) revealed a reduction in the fluorescence intensities of 5'-fluorescein as well as 5'-TAMRA and thereafter an attainment of saturation with increase in the surfactant concentration. The observed changes in the oligonucleotide fluorescence intensities for the duplexes under investigation could be attributed to the microenvironmental changes during the oligonucleotide-CTAB interaction. Considering together, it appeared that the interaction is a three-stage process, wherein the initial addition of surfactant caused neutralization of the 14mer at Z(+/-)(1) = 0.8, which is manifested by a slight reduction in fluorescence intensity. Further, addition of the surfactant molecules sharply reduced the fluorescence intensity of the oligonucleotide depicting oligonucleotide induced self-assembly until the second break point (Z(+/-)(2) = 1.7). From the second break point, a striking resonance energy transfer was observed from donor to acceptor, which revealed shortening of distance between 5' ends of the oligonucleotides that attained a saturation at Z(+/-)(3) = 2.5. Similar three-stage interaction of oligonucleotide with the surfactant has also been observed through fluorometric titrations in the presence of NaCl. However, in the presence of the salt, neutralization of oligonucleotide, surfactant aggregation and FRET occurred at higher charge ratios due to the screening effect of Na+ ions followed by an increase in critical association concentration (CAC) of the surfactant. Overall, investigations probe possible structural changes in the 14mer oligonucleotide-CTAB complex upon increase in the surfactant concentration.

Role of linker groups between hydrophilic and hydrophobic moieties of cationic surfactants on oligonucleotide-surfactant interactions.

The interaction between DNA and amino-acid-based surfactants with different linker groups was investigated by gel electrophoresis, ethidium bromide exclusion assays, circular dichroism, and melting temperature determinations. The studies showed that the strength of the interaction between the oligonucleotides and the surfactants is highly dependent on the linker of the surfactant. For ester surfactants, no significant interaction was observed for surfactant-to-DNA charge ratios up to 12. On the other hand, amide surfactants were shown to interact strongly with the oligonucleotides; these surfactants could displace up to 75% of the ethidium bromide molecules bound to the DNA and induced significant changes in the circular dichroism spectra. When comparing the headgroups of the surfactants, it was observed that surfactants with more hydrophobic headgroups (proline vs alanine) interacted more strongly with the DNA, in good agreement with previous studies.

Use of adapted Aspergillus niger in the bioleaching of spent refinery processing catalyst.

Spent refinery processing catalyst is listed as a hazardous waste; the toxicity characteristic leaching procedure (TCLP) extracts of the catalyst are found to contain heavy metals at concentrations exceeding the regulated levels. In the present investigation, Aspergillus niger was adapted to single metal ions Ni, Mo or Al (at 100-2,000 mg/L in steps of 100mg/L) and then to a mixture of Ni, Mo and Al (at a mass ratio of 1:2:6, as approximately present in the spent catalyst). Adaptation experiments with single metals showed that the fungus could tolerate up to 1,000 mg/L Ni, 1,200 mg/L Mo and 2,000 mg/L Al. In the presence of a mixture of these metals, the fungus was able to tolerate up to 100mg/L Ni, 200mg/L Mo and 600 mg/L Al. One-step bioleaching experiments with 1 wt% spent catalyst (of particle size <37 microm) were carried out using un-adapted and various adapted fungal strains. In contrast to the adapted strains, the un-adapted strain showed no growth in the presence of the catalyst. Ni:Mo:Al-adapted strain was the most efficient in the leaching of metals from the catalyst (at 78.5% Ni, 82.3% Mo and 65.2% Al) over 30 days due to its tolerance to the toxic elements at 1 wt%. More importantly, the Ni:Mo:Al-adapted strain was capable of bioleaching up to 3 wt% spent catalyst. The TCLP extracts of the spent catalyst after bioleaching using the Ni:Mo:Al-adapted strain showed the concentrations of Ni and Mo were well within the regulated levels.

Bioleaching of spent refinery processing catalyst using Aspergillus niger with high-yield oxalic acid.

A spent refinery processing catalyst was physically and chemically characterized, and subjected to one-step and two-step bioleaching processes using Aspergillus niger. During bioleaching of the spent catalysts of various particle sizes ("as received", 100-150 microm, <37 microm, and x =2.97 (average) microm) and pulp densities, the biomass dry weight and pH were determined. The corresponding leach liquor was analysed for excreted organic acids along with heavy metal values extracted from the catalyst. Chemical characterization of the spent catalyst confirmed the presence of heavy metal including Al (33.3%), Ni (6.09%) and Mo (13.72%). In general, the presence of the spent catalyst caused a decrease in the biomass yield and an increase in oxalic acid secretion by A. niger. The increase in oxalic acid secretion with a decrease in the catalyst particle size (up to <37 microm) led to corresponding increase in the extraction of metal values. The highest extraction of metal values from the spent catalyst (at 1% w/v pulp density and particle size <37 microm) were found to be 54.5% Al, 58.2% Ni and 82.3% Mo in 60 days of bioleaching. Oxalic acid secretion by A. niger in the presence of the spent catalyst was stimulated using 2-[N-Morpholino]ethanesulfonic acid (MES) buffer (pH 6), which resulted in comparable metal extraction (58% Al, 62.8% Ni and 78.9% Mo) in half the time required by the fungus in the absence of the buffer. Spent medium of A. niger grown in the absence and in the presence of MES buffer were found to leach almost similar amounts of Al and Ni, except Mo for which the spent medium of buffered culture was significantly more effective than the non-buffered culture. Overall, this study shows the possible use of bioleaching for the extraction of metal resources from spent catalysts. It also demonstrated the advantages of buffer-stimulated excretion of organic acids by A. niger in bioleaching of the spent catalyst.