Quantitative MALDI-MS and Imaging of Fungicide Pyrimethanil in Strawberries with 2-Nitrophloroglucinol as an Effective Matrix

This work explores the use of 2-nitrophloroglucinol (2-NPG) as a matrix for quantitative analysis of the fungicide Pyrimethanil (PYM) in strawberries using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) and imaging. 2-NPG was selected for PYM analysis for optimum sensitivity and precision compared to common matrices α-cyano-4-hydroxylcinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB). PYM-sprayed strawberries were frozen 0, 1, 3, and 4 days after treatment and sectioned for MALDI imaging. The remaining part of each strawberry was processed using quick easy cheap effective rugged and safe (QuEChERS) extraction and analyzed by MALDI-MS and ultraperformance liquid chromatography multireaction-monitoring (UPLC-MRM). MALDI-MS showed comparable performance to UPLC-MRM in calibration, LOD/LOQ, matrix effect, and recovery, with the benefit of fast analysis. The MALDI imaging results demonstrated that PYM progressively penetrated the interior of the strawberry over time and the PYM concentration on tissue measured by MALDI imaging correlated linearly with MALDI-MS and UPLC-MRM measurements and accounts for 79% MALDI-MS and 85% UPLC-MRM values on average. Additionally, quartz crystal microbalance (QCM) was introduced as a new approach to determine strawberry tissue mass per area for MALDI imaging absolute quantitation with sensitive, direct, and localized measurements. This work demonstrates the first example of absolute quantitative MALDI imaging of pesticides in a heterogeneous plant tissue. The novel use of the 2-NPG matrix in quantitative MALDI-MS and imaging could be applied to other analytes, and the new QCM tissue mass per area method is potentially useful for quantitative MALDI imaging of heterogeneous tissues in general.

Delivery of gene editing therapeutics

For the past decades, gene editing demonstrated the potential to attenuate each of the root causes of genetic, infectious, immune, cancerous, and degenerative disorders. More recently, Clustered Regularly Interspaced Short Palindromic Repeats-CRISPR-associated protein 9 (CRISPR-Cas9) editing proved effective for editing genomic, cancerous, or microbial DNA to limit disease onset or spread. However, the strategies to deliver CRISPR-Cas9 cargos and elicit protective immune responses requires safe delivery to disease targeted cells and tissues. While viral vector-based systems and viral particles demonstrate high efficiency and stable transgene expression, each are limited in their packaging capacities and secondary untoward immune responses. In contrast, the nonviral vector lipid nanoparticles were successfully used for as vaccine and therapeutic deliverables. Herein, we highlight each available gene delivery systems for treating and preventing a broad range of infectious, inflammatory, genetic, and degenerative diseases. STATEMENT OF SIGNIFICANCE: CRISPR-Cas9 gene editing for disease treatment and prevention is an emerging field that can change the outcome of many chronic debilitating disorders.

Crystallographic and thermodynamic evidence of negative cooperativity of flavin and tryptophan binding in the flavin-dependent halogenases AbeH and BorH

The flavin-dependent halogenase AbeH produces 5-chlorotryptophan in the biosynthetic pathway of the chlorinated bisindole alkaloid BE-54017. We report that in vitro, AbeH (assisted by the flavin reductase AbeF) can chlorinate and brominate tryptophan as well as other indole derivatives and substrates with phenyl and quinoline groups. We solved the X-ray crystal structures of AbeH alone and complexed with FAD, as well as crystal structures of the tryptophan-6-halogenase BorH alone, in complex with 6-chlorotryptophan, and in complex with FAD and tryptophan. Partitioning of FAD and tryptophan into different chains of BorH and failure to incorporate tryptophan into AbeH/FAD crystals suggested that flavin and tryptophan binding are negatively coupled in both proteins. ITC and fluorescence quenching experiments confirmed the ability of both AbeH and BorH to form binary complexes with FAD or tryptophan and the inability of tryptophan to bind to AbeH/FAD or BorH/FAD complexes. FAD could not bind to BorH/tryptophan complexes, but FAD appears to displace tryptophan from AbeH/tryptophan complexes in an endothermic entropically-driven process.

pH regulated lactose inspired fabrication of zinc oxide nanoparticles for insulin sensing by LSPR absorption

Nanostructured metal oxide particles with diversified morphologies are in high demand in nanotechnology. The particle size, shape, and overall geometry mainly depend on the fabrication method. This study reports synthesis of zinc oxide nanoparticles (ZnO NPs) from zinc nitrate hexahydrate [Zn(NO3)2.6H2O] precursor in aqueous media at 65 °C by using lactose from cow milk as a reducing agent and regulating pH from 6 to 10. UV-visible absorption gave maximum absorbance (λmax) at 371-375 nm in ethanol for localized surface plasmon resonance (LSPR), FTIR exhibited bands at ca. 439-481 cm-1 for stretching mode Zn-O bonds, and XRD peaks at 2 θ values at 31.8, 34.45, and 36.28° confirmed the fabricated ZnO NPs. The XRD spectra also indicated that the ZnO crystallite (20-30 nm) has a hexagonal wurtzite structure. The average particle sizes measured by DLS were ca. 50-837 nm, and SEM microphotographs demonstrated the morphology of ZnO NPs with a hexagonal, rod-shaped, or spike-like structure. The ZnO NPs were used to investigate the LSPR absorption at various concentrations of insulin, ranging from 2.5 μM to 50 μM. The ZnO NPs fabricated at pH 7 and 10 showed better insulin sensing performance with high precision. The synthesis approach of ZnO NPs with variable morphologies would play a significant function in biomedical science especially real time monitoring of glucose for efficient management of diabetes.

Scanning Electrochemical Microscopy for Chemical Imaging and Understanding Redox Activities of Battery Materials

Improving the charge storage capacity and lifetime and charging/discharging efficiency of battery systems is essential for large-scale applications such as long-term grid storage and long-range automobiles. While there have been substantial improvements over the past decades, further fundamental research would help provide insights into improving the cost effectiveness of such systems. For example, it is critical to understand the redox activities of cathode and anode electrode materials and stability and the formation mechanism and roles of the solid-electrolyte interface (SEI) that forms at the electrode surface upon an external potential bias. The SEI plays a critical role in preventing electrolyte decay while still allowing charges to flow through the system while serving as a charge transfer barrier. While surface analytical techniques such as X-ray photoelectron (XPS), X-ray diffraction (XRD), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and atomic force microscopy (AFM) provide invaluable information on anode chemical composition, crystalline structure, and morphology, they are often performed ex situ, which can induce changes to the SEI layer after it is removed from the electrolyte. While there have been efforts to combine these techniques using pseudo-in situ approaches via vacuum-compatible devices and inert atmosphere chambers connected to glove boxes, there is still a need for true in situ techniques to obtain results with improved accuracy and precision. Scanning electrochemical microscopy (SECM) is an in situ scanning probe technique that can be combined with optical spectroscopy techniques such as Raman and photoluminescence spectroscopy methods to gain insights into the electronic changes of a material as a function of applied bias. This Review will highlight the potential of SECM and recent reports on combining spectroscopic measurements with SECM to gain insights into the SEI layer formation and redox activities of other battery electrode materials. These insights provide invaluable information for improving the performance of charge storage devices.

Development of a porous layer-by-layer microsphere with branched aliphatic hydrocarbon porogens

Porous polymer microspheres are employed in biotherapeutics, tissue engineering, and regenerative medicine. Porosity dictates cargo carriage and release that are aligned with the polymer physicochemical properties. These include material tuning, biodegradation, and cargo encapsulation. How uniformity of pore size affects therapeutic delivery remains an area of active investigation. Herein, we characterize six branched aliphatic hydrocarbon-based porogen(s) produced to create pores in single and multilayered microspheres. The porogens are composed of biocompatible polycaprolactone, poly(lactic-co-glycolic acid), and polylactic acid polymers within porous multilayered microspheres. These serve as controlled effective drug and vaccine delivery platforms.

An AI-based approach for detecting cells and microbial byproducts in low volume scanning electron microscope images of biofilms

Microbially induced corrosion (MIC) of metal surfaces caused by biofilms has wide-ranging consequences. Analysis of biofilm images to understand the distribution of morphological components in images such as microbial cells, MIC byproducts, and metal surfaces non-occluded by cells can provide insights into assessing the performance of coatings and developing new strategies for corrosion prevention. We present an automated approach based on self-supervised deep learning methods to analyze Scanning Electron Microscope (SEM) images and detect cells and MIC byproducts. The proposed approach develops models that can successfully detect cells, MIC byproducts, and non-occluded surface areas in SEM images with a high degree of accuracy using a low volume of data while requiring minimal expert manual effort for annotating images. We develop deep learning network pipelines involving both contrastive (Barlow Twins) and non-contrastive (MoCoV2) self-learning methods and generate models to classify image patches containing three labels—cells, MIC byproducts, and non-occluded surface areas. Our experimental results based on a dataset containing seven grayscale SEM images show that both Barlow Twin and MoCoV2 models outperform the state-of-the-art supervised learning models achieving prediction accuracy increases of approximately 8 and 6%, respectively. The self-supervised pipelines achieved this superior performance by requiring experts to annotate only ~10% of the input data. We also conducted a qualitative assessment of the proposed approach using experts and validated the classification outputs generated by the self-supervised models. This is perhaps the first attempt toward the application of self-supervised learning to classify biofilm image components and our results show that self-supervised learning methods are highly effective for this task while minimizing the expert annotation effort.

Raw natural rubber latex-based bio-adhesive for the production of particleboard: formulation and optimization of process parameters

In this study, bio-adhesives from natural rubber latex (NRL) were combined with starch and formic acid to fabricate jute stick-based particleboards (JSPs). Different blends of NRL, starch, and formic acid, i.e., 6 : 1 : 1, 2 : 1 : 1, and 2 : 3 : 3, were used to produce particleboards using a pressing temperature of 180 °C and applied pressure of 5 MPa using a 5 min pressing time. The particleboards were tested for physical, mechanical, and thermal properties according to ANSI standards. Based on initial screening, the best formula (NRL/starch/formic acid of 2 : 3 : 3) was used to optimize the temperature and pressing time for the highest board performance. The highest density, tensile strength, modulus of elasticity, and modulus of rupture were 830 g cm⁻³, 10.51, 2380, and 20.05 N mm⁻², respectively. Thermo-gravimetric analysis indicated that thermal decomposition of samples primarily occurred in a temperature range of 265 to 399 °C, indicating good thermal performance. The measured physical and mechanical properties of the produced JSPs fulfilled the production standards. However, fulfilling the water absorption and thickness swelling criteria was a challenge. The results indicate that NRL is a promising alternative binder when blended with starch and formic acid.

In this study, bio-adhesives from natural rubber latex (NRL) were combined with starch and formic acid to fabricate jute stick-based particleboards (JSPs).

Green synthesis of iron oxide nanoparticle using Carica papaya leaf extract: application for photocatalytic degradation of remazol yellow RR dye and antibacterial activity

Synthesis of iron oxide nanoparticles by the recently developed green approach is extremely promising because of its non-toxicity and environmentally friendly behavior. In this study, nano scaled iron oxide particles (α-Fe₂O₃) were synthesized from hexahydrate ferric chloride (FeCl₃.6H₂O) with the addition of papaya (Carica papaya) leaf extract under atmospheric conditions. The synthesis of iron oxide nanoparticles was confirmed by systematic characterization using FTIR, XRD, FESEM, EDX and TGA studies. The removal efficiency of remazol yellow RR dye with the synthesized iron oxide nanoparticles as a photocatalyst was determined along with emphasizing on the parameters of catalyst dosage, initial dye concentration and pH. Increasing the dose of iron oxide nanoparticles enhanced the decolorization of the dyes and a maximum 76.6% dye degradation was occurred at pH 2 after 6 h at a catalyst dose of 0.8 g/L. Unit removal capacity of the photocatalyst was found to be 340 mg/g at dye concentration of 70 ppm and at a catalyst dose of 0.4 g/L. The synthesized nanoparticles showed moderate antibacterial activity against Klebsiella spp., E.Coli, Pseudomonas spp., S.aureus bacterial strains. Although the cytotoxic effect of nanoparticles against Hela, BHK-21 and Vero cell line was found to be toxic at maximum doses but it can be considered for tumor cell damage because it showed excellent activity against the Hela and BHK-21 cell lines.

Is nuclear viscosity dependent on temperature?

Nuclear viscosity is an indispensable ingredient of the nuclear fission collective dynamical models. It governs the exchange of energy between the collective variables and the thermal bath. Its dependence on the shape and temperature is a matter of controversy. By using systems of intermediate fissility we have demonstrated in a recent study that the viscosity parameters is larger for compact shapes, and decreases for larger deformations of the fissioning system, at variance with the conclusions of the statistical model modified to include empirically viscosity and time scales. In this contribution we propose an experimental scenario to highlight the possible dependence of the viscosity from the temperature.

Switchable Bioelectrocatalysis Controlled by Dual Stimuli-Responsive Polymeric Interface

The engineering of bionanointerfaces using stimuli-responsive polymers offers a new dimension in the design of novel bioelectronic interfaces. The integration of electrode surfaces with stimuli-responsive molecular cues provides a direct control and ability to switch and tune physical and chemical properties of bioelectronic interfaces in various biodevices. Here, we report a dual-responsive biointerface employing a positively responding dual-switchable polymer, poly(NIPAAm-co-DEAEMA)-b-HEAAm, to control and regulate enzyme-based bioelectrocatalysis. The design interface exhibits reversible activation-deactivation of bioelectrocatalytic reactions in response to change in temperature and in pH, which allows manipulation of biomolecular interactions to produce on/off switchable conditions. Using electrochemical measurements, we demonstrate that interfacial bioelectrochemical properties can be tuned over a modest range of temperature (i.e., 20-60 °C) and pH (i.e., pH 4-8) of the medium. The resulting dual-switchable interface may have important implications not only for the design of responsive biocatalysis and on-demand operation of biosensors, but also as an aid to elucidating electron-transport pathways and mechanisms in living organisms by mimicking the dynamic properties of complex biological environments and processes.

Studies on Bacterial Proteins Corona Interaction with Saponin Imprinted ZnO Nanohoneycombs and Their Toxic Responses

Molecular imprinting generates robust, efficient, and highly mesoporous surfaces for biointeractions. Mechanistic interfacial interaction between the surface of core substrate and protein corona is crucial to understand the substantial microbial toxic responses at a nanoscale. In this study, we have focused on the mechanistic interactions between synthesized saponin imprinted zinc oxide nanohoneycombs (SIZnO NHs), average size 80-125 nm, surface area 20.27 m(2)/g, average pore density 0.23 pore/nm and number-average pore size 3.74 nm and proteins corona of bacteria. The produced SIZnO NHs as potential antifungal and antibacterial agents have been studied on Sclerotium rolfsii (S. rolfsii), Pythium debarynum (P. debarynum) and Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), respectively. SIZnO NHs exhibited the highest antibacterial (∼50%) and antifungal (∼40%) activity against Gram-negative bacteria (E. coli) and fungus (P. debarynum), respectively at concentration of 0.1 mol. Scanning electron spectroscopy (SEM) observation showed that the ZnO NHs ruptured the cell wall of bacteria and internalized into the cell. The molecular docking studies were carried out using binding proteins present in the gram negative bacteria (lipopolysaccharide and lipocalin Blc) and gram positive bacteria (Staphylococcal Protein A, SpA). It was envisaged that the proteins present in the bacterial cell wall were found to interact and adsorb on the surface of SIZnO NHs thereby blocking the active sites of the proteins used for cell wall synthesis. The binding affinity and interaction energies were higher in the case of binding proteins present in gram negative bacteria as compared to that of gram positive bacteria. In addition, a kinetic mathematical model (KMM) was developed in MATLAB to predict the internalization in the bacterial cellular uptake of the ZnO NHs for better understanding of their controlled toxicity. The results obtained from KMM exhibited a good agreement with the experimental data. Exploration of mechanistic interactions, as well as the formation of bioconjugate of proteins and ZnO NHs would play a key role to interpret more complex biological systems in nature.

Construction and characterization of molecular nonwoven fabrics consisting of cross-linked poly(γ-methyl-L-glutamate)

Molecular nonwoven fabrics in the form of ultrathin layer-by-layer (LbL) helical polymer films with covalent cross-linking were assembled on substrates by an alternate ester-amide exchange reaction between poly(γ-methyl L-glutamate) (PMLG) and cross-linking agent ethylene diamine or 4,4'-diamino azobenzene. The regular growth of helical monolayers without excessive adsorption and the formation of amide bonds were confirmed by ultraviolet-visible (UV-vis) spectrophotometry, quartz crystal microbalance (QCM), ellipsometry, and infrared reflection-absorption spectroscopy (IR-RAS) measurements. Nanostructures with high uniformity and ultrathin films with few defects formed by helical rod segments of PMLG were characterized by atomic force microscopy (AFM) and Kelvin probe force microscopy (KFM).

Mechanical and Electrical Properties: Electrospun Alginate/Carbon Nanotube Composite Nanofiber

Nanofibers of the composite of alginate (Alg) and carbon nanotube (CNT) were prepared using electrospinning method out of aqueous solutions. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), mechanical measurement, and electrical conductivity were done to characterize the Alg/CNT composite nanofibers morphology and properties. The SEM and TEM images show the CNT to be well incorporated along the nanofibers. The study shows that the introduction of CNT results in improvement in tensile strength and electrical conductivity of the Alg matrix. The electrospinning of Alg/CNT composites could potentially supply useful options for the fabrication of biomaterial scaffolds.DOI: http://dx.doi.org/10.3329/dujs.v60i1.10350  Dhaka Univ. J. Sci. 60(1): 125-128 2012 (January)

Stimuli responsive poly(1-[11-acryloylundecyl]-3-methyl-imidazolium bromide): dewetting and nanoparticle condensation phenomena

A stimuli-responsive homopolymer poly(ILBr) is fabricated via a "two-phase" atom transfer radical polymerization (ATRP) process, where ILBr stands for the reactive ionic liquid surfactant, 1-[11-acryloylundecyl]-3-methyl-imidazolium bromide. An extraordinarily wide molecular weight distribution (PDI = 6.0) was obtained by introducing the initiator (4-bromomethyl methyl benzoate) in a heterogeneous two-phase process. The molecular weight distribution of poly(ILBr) was characterized by size-exclusion chromatography (SEC). The resulting homopolymer was found to be surface active and stimuli responsive. Poly(ILBr) films coated on quartz exhibit stimuli-responsive dewetting after ion exchange of Br(-) by PF(6)(-). This dewetting phenomenon can be understood in chain segmental terms as a stimuli-induced structural relaxation and appears to be the first such reported stimuli-responsive polymeric dewetting. Titrating aqueous poly(ILBr) with aqueous bis(2-ethylhexyl)sulfosuccinate induces nanophase separation and results in the condensation of nanoparticles 30-60 nm in diameter.