COVID-19: A Call for Physical Scientists and Engineers.

The COVID-19 pandemic is one of those global challenges that transcends territorial, political, ideological, religious, cultural, and certainly academic boundaries. Public health and healthcare workers are at the frontline, working to contain and to mitigate the spread of this disease. Although intervening biological and immunological responses against viral infection may seem far from the physical sciences and engineering that typically work with inanimate objects, there actually is much that can-and should-be done to help in this global crisis. In this Perspective, we convert the basics of infectious respiratory diseases and viruses into physical sciences and engineering intuitions, and through this exercise, we present examples of questions, hypotheses, and research needs identified based on clinicians' experiences. We hope researchers in the physical sciences and engineering will proactively study these challenges, develop new hypotheses, define new research areas, and work with biological researchers, healthcare, and public health professionals to create user-centered solutions and to inform the general public, so that we can better address the many challenges associated with the transmission and spread of infectious respiratory diseases.

Facile fabrication of P(OVNG-co-NVCL) thermoresponsive double-hydrophilic glycopolymer nanofibers for sustained drug release.

The thermoresponsive double-hydrophilic glycopolymer (DHG), Poly (6-O-vinyl-nonanedioyl-D-galactose-co-N-vinylcaprolactam) (P(OVNG-co-NVCL)) was synthesized via a chemo-enzymatic process and a free radical copolymerization and the resulting nanofibers were fabricated using an electrospinning process. The desired lower critical solution temperature (LCST) between 32 and 40 °C of the DHG polymers was achieved by adjusting the molar fraction of galactose monomer in the copolymers during the synthesis. The thermoresponsive DHG polymers were found to have good cytocompatibility with Hela cells as determined by the MTT assay, and special recognition of the protein peanut agglutinin (PNA). The drug release properties of these newly designed thermoresponsive DHG P(OVNG-co-NVCL) nanofibers are temperature regulated, can target specific proteins and have the potential application in the field of sustained drug release.

High-Yield Spreading of Water-Miscible Solvents on Water for Langmuir-Blodgett Assembly.

Langmuir-Blodgett (LB) assembly is a classical molecular thin-film processing technique, in which the material is spread onto water surface from a volatile, water-immiscible solvent to create floating monolayers that can be later transferred to solid substrates. LB has also been applied to prepare colloidal thin films with an unparalleled level of microstructural control and thickness, which has enabled the discovery of many exciting collective properties of nanoparticles and the construction of bulk nanostructured materials. To maximize the benefits of LB assembly, the nanoparticles should be well dispersed in both the spreading solvent and on water. This is quite challenging since colloids usually need contrasting surface properties in order to be stable in the water-hating organic solvents and on water surface. In addition, many organic and polymeric nanostructures dissolve in those organic solvents and cannot be processed directly. Using water-liking spreading solvents can avoid this dilemma. However, spreading of water-miscible solvents on water surface is fundamentally challenging due to extensive mixing, which results in significant material loss. Here we report a conceptually simple strategy and a general technique that allows nearly exclusive spreading of such solvents on water surface using electrospray. Since the volume of these aerosolized droplets is reduced by many orders of magnitude, they are readily depleted during the initial spreading step before any significant mixing could occur. The new strategy drastically reduces the burden of material processing prior to assembly and broadens the scope of LB assembly to previously hard-to-process materials. It also avoids the use of toxic volatile organic spreading solvents, improves the reproducibility, and can be readily automated, making LB assembly a more robust tool for colloidal assembly and thin-film fabrication.

Electrospun polyvinyl alcohol/carbon dioxide modified polyethyleneimine composite nanofiber scaffolds.

A novel biocompatible polyvinyl alcohol/carbon dioxide modified polyethyleneimine (PVA/PEI-CO2) composite nanofiber was fabricated by a green and facile protocol, which reduces the cytotoxicity of PEI through the surface modification of the PEI with CO2. The (13)C NMR spectrum, elemental analysis, and TGA show that CO2 has been incorporated in the PEI surface resulting in a relatively stable structure. The resulting PVA/PEI-CO2 composite nanofibers have been characterized by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), contact angle, and scanning electron microscopy (SEM). The results show that the average diameters of the nanofibers range from 265 ± 53 nm to 423 ± 80 nm. The cytotoxicity of PVA/PEI-CO2 composite nanofibers was assessed by cytotoxicity evaluation using the growth and cell proliferation of normal mice Schwann cells. SEM and the MTT assay demonstrated the promotion of cell growth and proliferation on the PVA/PEI-CO2 composite scaffold. It suggests that PEI-CO2 can have tremendous potential applications in biological material research.

A novel self-assembling peptide with UV-responsive properties.

A novel heptapeptide comprising Ile-Gln-Ser-Pro-His-Phe-Phe (IQSPHFF) identified and found to undergo self-assembly into microparticles in solution. To understand the effects of ultraviolet (UV) irradiation on the self-assembly process, IQSPHFF solutions were exposed to the UV light of 365 nm at room temperature. This exposure was found to have a profound effect on the morphology of the self-assembled aggregates, converting the microparticles to nanorod shapes. Circular dichroism and FTIR studies indicated distinct structural differences in the arrangements of the peptide moieties before and after UV irradiation. However, Mass spectrum analysis and high performance liquid chromatography of the peptide molecules before and after UV irradiation demonstrated that the chemical structure of IQSPHFF was not changed. UV-visible spectroscopy and fluorescence spectroscopy studies showed that the absorption peak both increased after UV irradiation. Overall, our data show that the heptapeptide with UV-responsive properties.

Fabrication and aggregation of thermoresponsive glucose-functionalized double hydrophilic copolymers.

Novel double-hydrophilic thermosensitive statistical glycopolymers, poly(N-isopropylacrylamide-co-6-O-vinyladipoyl-D-glucose), were fabricated using a chemoenzymatic process and free radical copolymerization. The structures of the glycopolymers were confirmed by (1)H and (13)C NMR, and their molar mass distributions determined by gel permeation chromatography. UV-vis spectroscopy data showed that the polymers exhibited reproducible temperature-responsive behavior. The self-assembly and critical aggregation concentration was verified by fluorescence spectroscopy with pyrene acting as a hydrophobic probe. Measurements by laser light scattering and transmission electron microscopy revealed that the glycopolymers were able to self-assemble into aggregates with varying particle sizes and morphologies in aqueous solutions.

Metal chelate affinity precipitation: purification of BSA using poly(N-vinylcaprolactam-co-methacrylic acid) copolymers.

This investigation involves the metal chelate affinity precipitation of bovine serum albumin (BSA) using a copper ion loaded thermo-sensitive copolymer. The copolymer of N-vinylcaprolactam with methacrylic acid PNVCL-co-MAA was synthesized by free radical polymerization in aqueous solution, and Cu(II) ions were attached to provide affinity properties for BSA. A maximum loading of 48.1mg Cu(2+) per gram of polymer was attained. The influence of pH, temperature, BSA and NaCl concentrations on BSA precipitation and of pH, ethylenediaminetetraacetic acid (EDTA) and NaCl concentrations on elution were systematically probed. The optimum conditions for BSA precipitation occurred when pH, temperature and BSA concentration were 6.0, 10°C and 1.0 mg/ml, respectively and the most favorable elution conditions were at pH 4.0, with 0.2M NaCl and 0.06 M EDTA. The maximum amounts of BSA precipitation and elution were 37.5 and 33.7 mg BSA/g polymer, respectively. It proved possible to perform multiple precipitation/elution cycles with a minimal loss of polymer efficacy. The results show that PNVCL-co-MAA is a suitable matrix for the purification of target proteins from unfractionated materials.

Optimization of adsorption conditions of BSA on thermosensitive magnetic composite particles using response surface methodology.

Thermosensitive core-shell magnetic composite particles with a magnetic silica core and a rich poly (N-vinylcaprolactam) (PNVCL) shell layer were developed for studying the adsorption of bovine serum albumin (BSA) in a batch system. Various analytical and spectroscopic techniques including SEM, FT-IR, VSM and DSC were used to characterize the adsorbents prepared in this study. The combined effects of operating parameters such as initial temperature, pH and initial BSA concentration on the adsorption were analyzed using response surface methodology. The optimum conditions were 40°C, pH 4.68, and initial BSA concentration 2.0 mg/mL. Desorption experiments were conducted by altering the system temperature where a high recovery rate of protein was obtained. The separation process developed here indicates that the dual-responsive smart adsorbent could be an ideal candidate for the separation of protein.

Kinetic evaluation of aminoethylisothiourea on mushroom tyrosinase activity.

This study demonstrates that aminoethylisothiourea (AET), a potent inhibitor of inducible nitric oxide synthase, is an irreversible competitive inhibitor of mushroom tyrosinase by chelation to the active site of tyrosinase when L-3,4-dihydroxyphenylalanine was assayed spectrophotometrically. The spectrophotometric recordings of the inhibition of tyrosinase by AET were characterized by the presence of a lag period prior to the attainment of an inhibited steady-state rate. The lag period corresponded to the time in which AET was reacting with the enzymatically generated o-quinone. Increasing AET concentrations provoked longer lag periods as well as a concomitant decrease in the tyrosinase activity. Both lag period and steady-state rate were dependent on AET, substrate, and tyrosinase concentrations. The inhibition of diphenolase activity of tyrosinase by AET showed positive kinetic cooperativity which arose from the protection of both substrate and o-quinone against inhibition by AET. The UV-visible spectrum of a mixture of tyrosinase and AET exhibited a characteristic shoulder peak ascribed to the chelation of AET to the active site of tyrosinase. Moreover, the presence of copper ions only partially prevented but not reverted mushroom tyrosinase inhibition when CuSO(4) was added to the assay medium on tyrosinase activity.

Adsorption mechanism of Cu2+ from aqueous solution by chitosan-coated magnetic nanoparticles modified with alpha-ketoglutaric acid.

In order to better understand the adsorption mechanism of chitosan-coated magnetic nanoparticles modified with alpha-ketoglutaric acid (alpha-KA-CCMNPs), the removal of Cu(2+) by alpha-KA-CCMNPs from aqueous solution was investigated in a batch system at 18, 35 and 50 degrees C. Different experimental approaches were applied to show mechanistic aspects, such as adsorption isotherms, kinetics and thermodynamics studies. Adsorption equilibrium studies showed that Cu(2+) adsorption followed Langmuir model. The kinetics of the interactions was best described by pseudo-second-order mechanism. The thermodynamic parameters (DeltaG degrees, DeltaH degrees and DeltaS degrees) analysis predicted that the adsorption process was strongly dependent on temperature of medium, and spontaneous and endothermic process. The XPS combined with FT-IR spectra revealed that N atom of -NH- group and O atom of carboxyl group in alpha-KA-CCMNPs coordinated with Cu(2+). Experimental results from this study provide data that would be required if this heavy metal adsorption system was to be "scaled up" for industrial application.

In vitro effect of ozagrel on mushroom tyrosinase.

This investigation, in vitro, shows that ozagrel, an antithrombotic drug, inhibited both monophenolase and diphenolase activities of mushroom tyrosinase when L: -tyrosine and L: -DOPA were assayed spectrophotometrically, respectively. The IC(50) values, for monophenolase and diphenolase activities, were 1.35 and 3.45 mM, respectively. Ozagrel was estimated to be a reversible mixed-type inhibitor of diphenolase activity with the constants (K (S1), K (S2), K (i1), and K (i2)) determined to be 2.21, 3.89, 0.454, and 0.799 mM, repectively. Increasing ozagrel concentrations provoked longer lag periods as well as a concomitant decrease in the monophenolase activity. Inhibition experiment demonstrated that ozagrel bound the enzyme at a site distincted from the substrate active site, but it bound to either E (Enzyme) or ES (Enzyme-Substrate) complex.

Polyacrylonitrile fibers efficiently loaded with tamoxifen citrate using wet-spinning from co-dissolving solution.

Tamoxifen citrate (TAM)-loaded polyacrylonitrile (PAN) fibers were prepared using an improved wet-spinning technique. TAM was used as a model drug to evaluate the potential application of the loaded fiber system for drug delivery. PAN was first homogeneously dissolved in the N,N-dimethylacetamide (DMAc) solution containing TAM and then the co-dissolving solution was solidified to prepare the fibers using a wet-spinning method. Chemical, morphological and mechanical property characterizations were carried out, as well as the studies of the drug release properties. TAM was successfully encapsulated into a monofilament fiber, and this system was stable in terms of high loading capacity and effectiveness in release. The diameter of drug-loaded fiber was in the range of 40-60 microm. The best values of the tensile strength at 2.968 cN/dtex and breaking elongation at 14.9% of drug-loaded fibers were obtained when the drug loading content was 23.1 wt.%. These characteristics were suitable for the weaving process. The in vitro release experiment indicated that constant drug release from the fiber was observed for a long duration of time. Kinetic studies demonstrated that the system followed the Higuchi kinetics. These findings demonstrate that controlled release of drugs from PAN fibers could be potentially useful in drug delivery systems.

Comparison: adsorption of papain using immobilized dye ligands on affinity membranes.

Novel membranes that involve the immobilization of Reactive Red 120 or Reactive Brown 10 as dye ligands were prepared. These were used in the purification of papain from papaya powder extracts. Papain adsorption capacities for the Red 120 and Brown 10 membranes were 143.6 mg/g and 107.3mg/g, respectively. The effectiveness of adsorption was demonstrated by Freundlich isotherm proficiency. The enzyme was eluted from the respective dye membranes using 1.0M NaCl at pH 6.0 and yields of over 80% were found for the Red 120-CS (chitosan)-nylon membrane whereas only a 50% recovery was possible using the Brown 10-CS-nylon membranes. It is concluded that Red 120-CS-nylon membranes could play an active role in the separation and purification of papain from crude extracts. This system has the potential to be developed for the commercial isolation of the protein.

Optimization of adsorption conditions of papain on dye affinity membrane using response surface methodology.

The adsorption of papain on Reactive Blue 4 dye-ligand affinity membrane was investigated in a batch system. The combined effects of operating parameters such as initial pH, temperature, and initial papain concentration on the adsorption were analyzed using response surface methodology. The optimum adsorption conditions were determined as initial pH 7.05, temperature 39 degrees C, and initial papain concentration 11.0mg/ml. At optimum conditions, the adsorption capacity of dye-ligand affinity membrane for papain was found to be 27.85 mg/g after 120 min adsorption. The papain was purified 34.6-fold in a single step determined by fast protein liquid chromatography. More than 85% of the adsorbed papain was desorbed using 1.0M NaCl at pH 9.0 as the elution agent. The purification process showed that the dye-ligand immobilized composite membrane gave good separation of papain from aqueous solution.

Microencapsulation of tamoxifen: application to cotton fabric.

Tamoxifen microcapsules and drug loaded medicated fabrics were investigated. The microcapsules were prepared using a complex coacervation procedure involving gelatin B and acacia gum. The morphology, particle size, drug loading capacity and in vitro release characteristics of the drug microcapsules were optimized for coating tamoxifen microcapsules onto the cotton fabrics. Infrared (IR) spectra and SEM were used to characterize the medicated fabrics and air permeability and laundering testing were undertaken to determine the efficiency and effectiveness of the system. Results showed that optimum condition for the microcapsules was at drug/polymer ratio 1:4, polymer concentration 3%, and rate of stirring 1000 rpm. In vitro release assays demonstrated that the tamoxifen was liberated over 10h after an initial bust rate period. SEM images illustrated that the tamoxifen microcapsules were spherical in shape and were also tightly fixed on to the cotton fabrics fast. These observations demonstrate that we have designed and fabricated a medicated system that potentially could be applied within a transdermal drug delivery system and so act in a system for the treatment of breast cancer.

Removal of Cu2+ from aqueous solution by chitosan-coated magnetic nanoparticles modified with alpha-ketoglutaric acid.

Chitosan-coated magnetic nanoparticles (CCMNPs), modified with a biodegradable and eco-friendly biologic reagent, alpha-ketoglutaric acid (alpha-KA), was used as a magnetic nanoadsorbent to remove toxic Cu(2+) ions from aqueous solution. The prepared magnetic nanoadsorbents were characterized by FTIR, TEM, VSM, XRD, and EDS. Factors influencing the adsorption of Cu(2+), e.g., initial metal concentration, initial pH, contact time and adsorbent concentration were investigated. TEM images show that the dimension of multidispersed circular particles is about 30 nm and no marked aggregation occurs. VSM patterns indicate superparamagnetic properties of magnetic nanoadsorbents. EDS pictures confirm the presence of the Cu(2+) on the surface of magnetic nanoadsorbents. Equilibrium studies show that Cu(2+) adsorption data follow Langmuir model. The maximum adsorption capacity (q(max)) for Cu(2+) ions was estimated to be 96.15 mg/g, which was higher than that of pure CCMNPs. The desorption data show no significant desorption hysteresis occurred. In addition, the high stability and recovery capacity of the chitosan-coated magnetic nanoparticles modified with alpha-ketoglutaric acid (alpha-KA-CCMNPs) suggest that these novel magnetic nanoadsorbents have potential applications for removing Cu(2+) from wastewater.

Removal of Cu2+ from aqueous solution by adsorption onto a novel activated nylon-based membrane.

A novel activated nylon-based membrane was prepared and applied as an adsorbent for the removal of Cu2+ from aqueous solutions. It involved three stages: (i) deposition of a chitosan layer that functionalized the nylon membrane, (ii) cross-linking with epichlorohydrin to stabilize the polymer layer and enabling grafting, and (iii) iminodiacetic acid grafting. SEM and EDX techniques were used to characterize the composition of the membranes. Dynamic adsorption experiments on membranes were carried out at various pH values, contact times, adsorption dosages and initial metal concentrations to determine optimum membrane adsorption properties. The adsorption isotherm relating to Cu2+ fitted the Langmuir equation and an adsorption equilibrium constant and adsorption capacity of 2.345x10(-3)mg/ml and 10.794mg/g were determined, respectively. The experimental data was analyzed using two adsorption kinetic models, pseudo-first-order and pseudo-second-order with the latter system providing the best fit. Finally complete regeneration of the activated nylon membrane was possible using 100mmol/l Na2EDTA.

Adsorption of papain with Cibacron Blue F3GA carrying chitosan-coated nylon affinity membranes.

Covalent coupling of chitosan (CS) to activated nylon membrane was performed after the reaction of the microporous nylon membrane with formaldehyde. Non-specific adsorption on the CS-coated nylon membrane decreased greatly, compared with plain nylon membrane. The dye Cibacron Blue F3GA (CB F3GA) as a ligand was then covalently immobilized on the CS-coated membranes. Physical properties of the composite membrane and its applications in affinity membrane chromatography were examined. The contents of CS and CB F3GA-attached membranes were 89.6 mg/g nylon membrane and 146.1 micromol/g nylon membrane, respectively. These CB F3GA-attached composite membranes were used in the papain adsorption studies. Higher papain adsorption capacity, up to 235.3mg/g affinity membrane, was obtained. The adsorption isotherm fitted the Freundlich model well. Significant amount of the adsorbed papain (about 94.3%) was eluted by 1.0M NaSCN at pH 9.0. Experiments on regeneration and dynamic adsorption were also performed. It appears that CB F3GA-CS nylon membranes can be applied for papain separation without causing any denaturation.