Sites For Immobilization Research Articles

An ultrasensitive electrochemical anti-lysozyme aptasensor with biorecognition surface based on aptamer/amino-rGO/ionic liquid/amino-mesosilica nanoparticles

In this work, a novel method based on aptamers is proposed for electrochemical measurement of lysozyme. To this end, screen-printed carbon electrode (SPCE) was modified with a nanocomposite made from amino-reduced graphene oxide (Amino-rGO) synthesized from natural graphite powder, an ionic liquid (IL), and amino-mesosilica nanoparticles (Amino-MSNs). The composition of the nanocomposite (Amino-rGO/IL/Amino-MSNs) results in high thermal and chemical stability, conductivity, surface-to-volume ratio, cost efficiency, biocompatibility, and great bioelectrocatalysis characteristics. Presence of numerous amino groups, as well as remaining oxygen defects in rGO, provides a suitable site for immobilization of aptamers. Furthermore, use of this nanocomposite leads to considerable enhancement of the electrochemical signal and improved method sensitivity. Covalent coupling of aptamer’s amino groups with that of the nanocomposite using glutaraldehyde (GLA) as a linker helps immobilize amino-linked lysozyme aptamers (Anti-Lys aptamers) on nanocomposite. The modified electrode was characterized using electrochemical methods such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The immobilized aptamer selectively adsorbs lysozyme (Lys) on the electrode interface, leading to increased Charge Transfer Resistance (RCT) in EIS and decrease in the DPV peak currents which are used as analytical signals. Two separate calibration curves were drawn using the data acquired from EIS and DPV. The prepared anti-Lys aptasensor has two very low LODs equal to 2.1 and 4.2 fmol L−1 with wide detection ranges of 10 fmol L−1 to 200 nmol L−1, and 20 fmol L−1 to 50 nmol L−1 for EIS and DPV calibration curves, respectively. The SPCE/Amino-rGO/IL/Amino-MSNs/APT also showed high reproducibility, specificity, sensitivity, and rapid response to Lys which has various applications in fields of bioengineering and biomedicine.

Development of a facile and low-cost chitosan-modified carbon cloth for efficient self-pumping enzymatic biofuel cells

Enzymatic biofuel cell (EBC) attracts much attention recently in fuel cell community because of its unique feature to enable the enzyme as a catalyst, rather than precious metal, to oxidize the fuel. However, the embedment of carbon nanotubes, commonly used in the anodic electrode of EBC to electrically wire the enzyme, suffers from their complicated synthetic procedure and fragile assembly. In this regard, we demonstrate a facile and low-cost route to achieve a desired immobilization of the glucose oxidase on a robust, flexible conducive carbon cloth. Our result indicates that the EBC using chitosan-modified carbon cloth via tripolyphosphate as anodic electrode exhibits a better performance than that via Nafion, leading to a 53% improvement of area power density. Such an enhancement can be attributed to the formation of the open porous structure on chitosan-modified carbon cloth, beneficial for the immobilization sites of the glucose oxidase and thereby facilitating more electron transfer in glucose oxidation reaction. The self-pumping EBC, driven by a capillary force of micro-fluidic channel plate, delivers an efficient area and volume power density of 0.549 mWcm−2 and 114.52 mWcm−3, respectively, enabling to open an alternative to the lightweight and portable applications.

Bifunctional S, N-Codoped carbon dots-based novel electrochemiluminescent bioassay for ultrasensitive detection of atrazine using activated mesoporous biocarbon as enzyme nanocarriers

A novel and ultrasensitive electrochemiluminescent (ECL) bioassay has been developed for the detection of atrazine (ATZ), whereby bifunctional S, N-codoped carbon dots (S, N-CDs) and activated mesoporous bicarbons (BCs) have been innovatively integrated to synergistically amplify the ECL signal. When endogenous dissolved O2 is used as a coreactant, its sluggish reduction hinders the enhancement of ECL intensity of the luminophore, thus restricting its further application in bioanalysis. Here, bifunctional S, N-CDs severe as not only the ECL luminophore but the coreaction accelerator of dissolved O2 to generate more intermediates to boost the coreaction without using any other coreactant and coreaction accelerator. The as-formed nanoarchitectures of BCs possess enlarged surface area as the nanocarriers. They could provide adequate active sites for immobilization of tyrosinase (Tyr), which greatly prompts the ECL bioassay applications. Such a smart integration of bifunctional S, N-CDs, activated mesoporous BCs and the enzyme inhibition reaction achieves a unique and attractive high-performance signal-on ECL bioassay, realizing ultrasensitive detection of ATZ. Under the optimal condition, this bioassay exhibits two linear ranges, from 0.0001 to 0.01 μg L−1 and 0.01–20 μg L−1 with a detection limit of 0.08 ng L−1 at signal to noise ratio of 3. The as-fabricated assay is sensitive and economical, opening a new way for the enhancement of ECL signal output and a versatile strategy for ultrasensitive ECL bioanalysis.

A Highly Accurate Pixel-Based FRAP Model Based on Spectral-Domain Numerical Methods

We introduce a new, to our knowledge, numerical model based on spectral methods for analysis of fluorescence recovery after photobleaching data. The model covers pure diffusion and diffusion and binding (reaction-diffusion) with immobile binding sites, as well as arbitrary bleach region shapes. Fitting of the model is supported using both conventional recovery-curve-based estimation and pixel-based estimation, in which all individual pixels in the data are utilized. The model explicitly accounts for multiple bleach frames, diffusion (and binding) during bleaching, and bleaching during imaging. To our knowledge, no other fluorescence recovery after photobleaching framework incorporates all these model features and estimation methods. We thoroughly validate the model by comparison to stochastic simulations of particle dynamics and find it to be highly accurate. We perform simulation studies to compare recovery-curve-based estimation and pixel-based estimation in realistic settings and show that pixel-based estimation is the better method for parameter estimation as well as for distinguishing pure diffusion from diffusion and binding. We show that accounting for multiple bleach frames is important and that the effect of neglecting this is qualitatively different for the two estimation methods. We perform a simple experimental validation showing that pixel-based estimation provides better agreement with literature values than recovery-curve-based estimation and that accounting for multiple bleach frames improves the result. Further, the software developed in this work is freely available online.

Site-specific immobilization of lysozyme upon affinity chromatography resin by forecasting lysine activity and controlling pH and epoxy group density

Here, a site-specific immobilization strategy for lysozyme was discussed. First, we calculated the surface micro-environment of lysozyme as a model protein and forecasted the nucleophilic attack activity order of six lysine residues within lysozyme, namely, K96> K97 and K33>K1, K13, and K116. Second, lysozyme was immobilized on agarose resin (epoxy group density 22.34 μmol/g) and incubated at pH 9.5 for 12 h. We then compared the peptide maps of free and immobilized lysozyme and established a quantitative detection method for immobilization sites. Third, we studied the effect of immobilization conditions such as epoxy group density and pH upon immobilization sites. When lysozyme was immobilized upon resin with a high epoxy group density (22.34 μmol/g) at pH 9.5 for 12 h, multiple lysozyme immobilization sites were found, including K33, K96 and K97; when lysozyme was immobilized upon resin with a low epoxy group density (11.36 μmol/g) at pH 9.5 for 12 h, only one lysozyme immobilization site was found, K96. The pH also had an effect upon immobilization sites. When immobilization was performed at pH≥10.5 with low epoxy group density resin (11.36 μmol/g) for 12 h, the immobilization sites included at least K33, K96 and K97; when immobilization was performed at pH 9.5 with other conditions remaining unchanged, the only lysozyme immobilization site found was at K96. These experimental results were highly consistent with the forecasted results, revealing some regularities of immobilization site control for lysozyme upon affinity chromatography resin.

A polydopamine patterned perfluoropolymer-based substrate for protein microarray applications

In this work, we developed a new composite substrate for protein microarrays, which was based on a perfluorinated surface presenting the polydopamine (PDA) microspots array. Conventional protein microarray substrates often suffer from the high background noise and inconsistent signal quantification due to the nonspecific protein binding and non-uniform microspots morphology. The composite substrate in this work addressed these issues by taking advantages of the properties of the perfluorinated surface and PDA. The hydrophobic and oleophobic perfluorinated surface possessed good protein antifouling property with minimal nonspecific protein adsorption, while the PDA microspots provided the immobilization sites for the antibodies to anchor onto the surface to build the protein microarray. We fabricated the composite substrate by photolithography and optimized the protein microarray performance by tuning the surface roughness of the PDA microspots. To illustrate the applications of the composite substrate in protein microarray technology, we performed the immunoassay-based detection of cytokines.

Surface-functionalization of isotactic polypropylene via dip-coating with a methacrylate-based terpolymer containing perfluoroalkyl groups and poly(ethylene glycol)

Isotactic polypropylene (PP) is one of the most popular plastics. However, the remarkably low surface energy of PP prevents the surface functionalization of PP. We studied the surface functionalization of PP by dip-coating with a maleic anhydride-grafted chlorinated polypropylene (MPO)/methacrylate-based terpolymer mixture. A methacrylate-based terpolymer (PMFP) was synthesized, which contained perfluoroalkyl (Rf)-conjugated monomers and poly(ethylene glycol)-conjugated monomers. Tape-peeling tests revealed that MPO successfully immobilized PMFP on a PP surface, although PMFP was less adhesive to PP. X-ray photoelectron spectroscopy (XPS), contact angle, and protein adsorption measurements revealed that the Rf groups and PEG chains in PMFP were segregated to the outermost surface of the dip-coated layer. The surface segregation of these moieties produced a low-fouling surface on the PP substrate. In addition, we synthesized a terpolymer that contained Rf groups and PEG chains with carboxy groups at their termini (PMFB) and used it to dip-coat a PP substrate. The surface segregation of side chains in PMFB induced the presentation of carboxy groups at the outermost surface, which were used as reactive sites for enzyme immobilization. We studied the surface functionalization of PP by dip-coating with a maleic anhydride-grafted chlorinated polypropylene (MPO) /methacrylate-based terpolymer mixture. A methacrylate-based terpolymer (PMFP) was synthesized, which contained perfluoroalkyl (Rf)-conjugated monomers and poly(ethylene glycol)-conjugated monomers. We found that the presence of MPO aided the adhesion of the terpolymer to the PP surface and that the coated PP surface exhibited low protein-fouling properties. In addition, the dip-coating of a terpolymer containing reactive groups (–COOH) with MPO caused the reactive groups to be presented at an outermost surface.

Investigating the Effect of Two-Point Surface Attachment on Enzyme Stability and Activity.

Immobilization on solid supports provides an effective way to improve enzyme stability and simplify downstream processing for biotechnological applications, which has been widely used in research and in applications. However, surface immobilization may disrupt enzyme structure due to interactions between the enzyme and the supporting substrate, leading to a loss of the enzyme catalytic efficiency and stability. Here, we use a model enzyme, nitroreductase (NfsB), to demonstrate that engineered variants with two strategically positioned surface-tethering sites exhibit improved enzyme stability when covalently immobilized onto a surface. Tethering sites were designed based on molecular dynamics (MD) simulations, and enzyme variants containing cysteinyl residues at these positions were expressed, purified, and immobilized on maleimide-terminated self-assembled monolayer (SAM) surfaces. Sum frequency generation (SFG) vibrational spectroscopy and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy were used to deduce the NfsB enzyme orientations, which were found to be consistent with those predicted from the MD simulations. Thermal stability analyses demonstrated that NfsB variants immobilized through two tethering sites exhibited generally improved thermal stability compared with enzymes tethered at only one position. For example, NfsB enzyme chemically immobilized via positions 423 and 111 exhibits at least 60% stability increase compared to chemically immobilized NfsB mutant via a single site. This research develops a generally applicable and systematic approach using a combination of simulation and experimental methods to rationally select protein immobilization sites for the optimization of surface-immobilized enzyme activity and stability.

On-Board Cone Beam Computed Tomography as Radiation Therapy Simulation for Emergent Cases

To investigate dosimetric clinical appropriateness of on-board kV cone beam computed tomography patient simulation (CBCT-Sim) for palliative treatment plans at a remote satellite clinic having no conventional computed tomographic simulation (CT-Sim) when travel isn't a viable option. Our current approach is a separation calculation using two opposing fields on a water phantom. A CBCT of the patient would improve the plan by utilizing the patient's actual geometry and we expect to see dose points in the CBCT-Sim plan image set less than 3% different than a conventional CT, and the separation calculation to be within 5% of the conventional CT-Sim plan. Patients treated for the four most likely emergent or immobile disease sites (brain, thoracic spine, lumbar spine, and pelvis) with an original CT-Sim and at least one CBCT during course of treatment were investigated retrospectively. Three brain patients, three T-spine, three L-spine, and two pelvis patients were used. The patients’ images were copied into a new, anonymous patient. A new CT-density curve was created in the treatment planning software for the CBCT based on CT-density phantom data. A standard plan for each given site was planned on the original CT image set, then copied on both a heterogenous and homogenous CBCT image set. The homogenous CBCT image was density overridden to water. A rectangular water phantom was also created for a separation calculation plan, which is our standard practice for these cases. For the brain cases, the CT and heterogenous CBCT plans were both contoured with critical structures. For all cases, seven to eleven points of interest in all directions (isocenter, and fractional separation distances in 3-dimentional space) were used to compare both CBCT-Sim plans and the separation calculation to the standard CT plan. For all cases, the average dose difference per case compared to the standard CT-Sim plan was less than 3% for either CBCT-Sim plan and less than 4% for the separation calculation plan; however, the separation calculations showed large deviations, up to 7.2%, while the CBCTs showed a maximum of 4.8%. Between all cases, the average dose difference was lowest compared to CT-Sim plans for the heterogenous CBCT plan with 1.2±0.7%, while the homogenous CBCT plan difference was 1.4±0.7% and the separation calculation was 1.7±1.1%. The most dosimetric benefit for the heterogenous CBCT-Sim plans was seen for the brain plans, followed by the T-spine plans, with negligible benefit for pelvis and L-spine plans. Dosimetric accuracy is improved with a CBCT-Sim compared to our standard separation-based plan, due to the use of actual patient geometry and density.

A novel DNA based bioassay toward ultrasensitive detection of Brucella using gold nanoparticles supported histidine: A new platform for the assay of bacteria in the cultured and human biofluids with and without polymerase chain reactions (PCR)

Brucella organisms, which are small aerobic intracellular coccobacilli, localize in the reproductive organs of host animals, causing abortions and sterility. In this work, we used a novel method to preparation of excellent genosensor on the surface of low-toxic substrate (gold nanoparticles) supported histidine prepared by fully electrodeposition method. The results of the present work show that the nano-Au-Hist provide suitable active sites for the DNA probe immobilization. The fabricated DNA genosensor employs cyclic voltammetry (CV), and square wave voltammetry (SWV) techniques for monitoring the behavior of the redox probe. To survey the morphological pattern and surface structural characterizations, the Field Emission-Scanning Electron Microscopy (FE-SEM) has been applied. In summary, the gold nanoparticles supported by histidine was checked for immobilization of a Brucella-specific probe and detection of hybridization with a variety of sequences with a high sensitivity. The high sensitivity would be related to more favorable conformation and deflection angle of the probe for an efficient hybridization, higher surface concentration of the probe, and/or enhanced diffusion regime. These lead to better display of the entangled target sequences arising from the nanobiotechnology. The proposed genosensor showed a perfect distinction between complementary, non-complementary and mismatched DNA sequences. The engineered genosensor for detection of the complementary/non-complementary sequences were assayed. The fabricated genosensor was evaluated for the assay of the bacteria in the cultured and human samples with and without polymerase chain reactions (PCR). The genosensor could detect the complementary sequence in linear concentration range of 1 × 10−1 to 1 × 10−10 μM, and a low limit of quantification 0.1 pM.

Expanding Application of Immobilized Candida Antarctica Lipase B: A Green Enzyme Catalyst for Knoevenagel Condensation Reaction

We propose a green synthesis of benzopyran compound based on immobilized lipase. Firstly, by using a combined electrospun membrane and biocompatible chitosan, we show that the chitosan-functionalized electrospun PMA-co-PAA fibrous membrane can provide effective anchoring sites for immobilization of the Candida antarctica lipase B (CALB), and a maximum loading amount of CALB (152 mg/g) can be achieved. Then, the resulting membrane displays enhanced stability in catalyzing Knoevenagel condensation reaction of salicylaldehyde with active methylene compound in mixed aqueousorganic media. The catalytic activity and stability of the CALB on chitosan-modified fiber is better than its non-immobilized counterpart. Furthermore, this immobilize CALB catalyst still retained about 45 % of the initial activity after 5 cycles, which potentially had implications for the design of “green” enzyme catalyst for sustainable organic synthesis.

Immobilization and characterization of PLGA nanoparticles on polyethylene terephthalate cardiovascular grafts for local drug therapy of associated graft complications

The cardiovascular graft associated complications limit the long-term patency of the graft and restrict the patient's life quality. In the present study, PLGA nanoparticles were covalently immobilized onto the woven form of crimped polyethylene terephthalate (PET, Dacron®) cardiovascular graft to treat the early thrombosis, inflammation, or bacterial infection via local delivery of therapeutic agents. PET surface was firstly functionalized to produce reactive amino groups used as anchor sites for covalent immobilization of PLGA nanoparticles by end-point technique. The functionalized surface characterized by electro kinetic analyzer showed marked negative surface potential values up to −41 mV at high pH value indicating the presence of amino groups on PET surface. The scanning electron microscopy observations of nano-coated PET showed topographic architecture of homogenously distributed monolayer of PLGA nanoparticles on the PET surfaces. Profoundly, the immobilized nanoparticles manifested stability under blood flow-mimetic conditions for 24 h. The cytotoxicity and biocompatibility of the nano-coated PET in mouse L929 fibroblasts revealed adequate biocompatibility in terms of the cellular adhesion and growth pattern without remarkable cytotoxicity.

CRITERIA FOR IMPACT ASSESSMENT OF THE ROADS OF I AND II ORDER ON PROTECTED NATURAL AND CULTURAL AREAS

This paper is a presentation of a part of the elaborate developed for PE Roads of Serbia entitled ‘Impacts of the roads of I and II order on protected natural and cultural sites’. The paper focuses on methodological aspects and criteria for the assessment of vulnerability degree of protected areas and immobile cultural sites, influenced by negative impacts caused by the roads of I and II order. Negative impacts from traffic activities on natural protected areas and cultural heritage were assessed as singular and cumulative with the purpose of determination of critical hotspots which would require special attention by PE Roads of Serbia, institution in charge of the maintenance of road infrastructure, in the sense of application of adequate technical and organizational measures for protection. Scope of the elaborate was whole territory of the Republic of Serbia, meaning all protected natural areas and cultural sites which could theoretically be affected by the roads of I and II order. For the purpose of the elaborate, the authors developed a matrix for the assessment of vulnerability degree from the available elements. Based on the matrix for the assessment of vulnerability degree and obtained results, the intensity of the impact of the roads was divided into four categories: insignificant, small, moderate and high.

Increase in IgG-binding Capacity of Recombinant Protein a Immobilized on Heterofunctional Amino and Epoxy Agarose

Protein an affinity materials were widely used in purification of monoclonal antibodies and treatment of autoantibody-associated diseases. Due to the low binding capacity of protein A affinity materials compared to other ion exchange materials, protein A affinity materials are often discussed to be the bottleneck among current purification processes and diseases treatment. In this study, the heterofunctional amino and epoxy agarose was used to immobilize the recombinant protein A (rSpA). The immobilization courses of rSpA and the effect of pH and ionic strength and amino density of the heterofunctional supports on the coupling efficiencies of rSpA were investigated. The optimum conditions for rSpA immobilized on the heterofuntional supports were determined as pH 8.0, the ionic strength of 5 mM borate buffer, and the amino density of 15 μmol g-1. Moreover, the 3D structure of B domain from protein A was analyzed by PyMol software and the web-based program MemBrain. The most likely immobilization sites of B domain were located at the Lys-49 and Lys-50, exposing the IgG-binding pocket to the medium. After immobilization, the remaining epoxy groups were blocked with the ethanolamine to obtain the rSpA affinity materials with different ligand density for antibody adsorption from the human plasma. The static and dynamic IgG-binding capacities were determined to be 42 and 32 mg g-1, respectively. The high IgG-binding capacities could be attributed to the oriented attachment of rSpA on the heterofunctional supports, and these results demonstrate that the heterofunctional amino and epoxy agarose is very promising to permit the oriented covalent attachment of rSpA, and that way to prepare affinity materials with high binding capacity.

Transcriptomic analyses uncover emerging roles of mucins, lysosome/secretory addressing and detoxification pathways in insect midguts.

The study of insect midgut features has been made possible by the recent availability of transcriptome datasets. These data uncovered the preferential expression of mucus-forming mucins at midgut regions that require protection (e.g. the acidic middle midgut of Musca domestica) or at sites of enzyme immobilization, particularly around the peritrophic membrane of Spodoptera frugiperda. Coleoptera lysosomal peptidases are directed to midgut lumen when over-expressed and targeted to lysosomes by a mechanism other than the mannose 6-phosphate-dependent pathway. We show that this second trend is likely conserved across Annelida, Mollusca, Nematoda, and Arthropoda. Furthermore, midgut transcriptomes of distantly related species reveal a general overexpression of xenobiotic detoxification pathways. In addition to attenuating toxicity of plant-derived compounds and insecticides, we also discuss a role for these detoxification pathways in regulating host-microbiota interactions by metabolizing bacterial secondary metabolites.

Fe3O4@PAM@NTA-Ni2+ Magnetic Composite Nanoparticles for Highly Specific Separation of His-tagged Proteins

A facile approach has been developed to synthesize Fe3O4@PAM (polyacrylamide) nanoparticles (NPs) with carboxyl groups on the surfaces by copolymerization with acrylamide and acrylic acid in Fe3O4 NPs aqueous suspension. Nitrilotriacetic acid (NTA) was conjugated to the magnetic NPs via well-known carboniimide chemistry using EDC and NHS. The Ni2+ ions loaded on the surface of NPs provide abundant docking sites for immobilization of His-tagged green fluorescent proteins (His-tagged GFP). The high magnetic property of Fe3O4@PAM@NTA-Ni2+ allows an easy separation of the NPs from solution under an external magnetic field, with high His-tagged protein binding capacity (42 μg protein/mg of NPs). The NPs can be recycled for at least four times without significant loss of binding capacity to proteins. These materials show great potential to separate His-tagged protein with low-cost purification at industrial scale.

Harnessing the power of microbial nanowires.

SummaryThe reduction of iron oxide minerals and uranium in model metal reducers in the genus Geobacter is mediated by conductive pili composed primarily of a structurally divergent pilin peptide that is otherwise recognized, processed and assembled in the inner membrane by a conserved Type IVa pilus apparatus. Electronic coupling among the peptides is promoted upon assembly, allowing the discharge of respiratory electrons at rates that greatly exceed the rates of cellular respiration. Harnessing the unique properties of these conductive appendages and their peptide building blocks in metal bioremediation will require understanding of how the pilins assemble to form a protein nanowire with specialized sites for metal immobilization. Also important are insights into how cells assemble the pili to make an electroactive matrix and grow on electrodes as biofilms that harvest electrical currents from the oxidation of waste organic substrates. Genetic engineering shows promise to modulate the properties of the peptide building blocks, protein nanowires and current‐harvesting biofilms for various applications. This minireview discusses what is known about the pilus material properties and reactions they catalyse and how this information can be harnessed in nanotechnology, bioremediation and bioenergy applications.

Highly Sensitive and Reusable Membraneless Field-Effect Transistor (FET)-Type Tungsten Diselenide (WSe2) Biosensors.

In recent years when the demand for high-performance biosensors has been aroused, a field-effect transistor (FET)-type biosensor (BioFET) has attracted great interest because of its high sensitivity, label-free detection, fast detection speed, and miniaturization. However, the insulating membrane in the conventional BioFET, which is essential in preventing the surface dangling bonds of typical semiconductors from nonspecific bindings, has limited the sensitivity of biosensors. Here, we present a highly sensitive and reusable membraneless BioFET based on a defect-free van der Waals material, tungsten diselenide (WSe2). We intentionally generated a few surface defects that serve as extra binding sites for the bioreceptor immobilization through weak oxygen plasma treatment, consequently magnifying the sensitivity values to 2.87 × 105 A/A for 10 mM glucose. The WSe2 BioFET also maintained its high sensitivity even after several cycles of rinsing and glucose application were repeated.

An ultrasensitive and selective electrochemical aptasensor based on rGO-MWCNTs/Chitosan/carbon quantum dot for the detection of lysozyme

An aptamer-based method is described for the electrochemical determination of lysozyme. A glassy carbon electrode was modified with a nanocomposite composed of reduced graphene oxide (rGO), multi-walled carbon nanotubes (MWCNTs), chitosan (CS), and a synthesized carbon quantum dot (CQD) from CS. The composition of the nanocomposite (rGO-MWCNT/CS/CQD) warrants a high surface-to-volume ratio, high conductivity, high stability, and great electrocatalytic activity. This nanocomposite provides a suitable site for better immobilization of aptamers due to the existence of many amino and carboxyl functional groups, and remaining oxygen-related defects properties in rGO. In addition, this nanocomposite allows considerable enhancement of the electrochemical signal and contributes to improving sensitivity. The amino-linked lysozyme aptamers were immobilized on the nanocomposite through covalent coupling between the amino groups of the aptamer and the amino groups of the nanocomposite using glutaraldehyde (GLA) linker. The modified electrode was characterized by electrochemical methods including differential pulse voltammetry (DPV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). In the presence of lysozyme, the immobilized aptamer selectively caught the target lysozyme on the electrode interface that leads to a decrease in the DPV peak current and an increase in Charge Transfer Resistance (Rct) in EIS as an analytical signal. Using the obtained data from DPV and EIS techniques, two calibration curves were drawn. The anti-lysozyme aptasensor proposed has two very low LODs. These measures are 3.7 and 1.9 fmol L−1 within the wide detection ranges of 20 fmol L−1 to 10 nmol L−1, and 10 fmol L−1 to 100 nmol L−1 for DPV and EIS calibration curves, respectively. The GCE/rGO-MWCNT/CS/CQD showed sensitivity, high reproducibility, specificity and rapid response for lysozyme which can be used in biomedical fields.

Adjustable thermal barrier of cotton fabric by multilayer immobilization of PCM nanocapsules

Poly(diallyldimethylammonium chloride) encapsulated n-octadecane nanocapsules (Cap+) were facilely immobilized on cationized cotton at ambient temperature by stepwise coating with poly-4-styrenesulfonic acid (PSS) binder and Cap+ nanocapsules via layer-by-layer technique. The negative molecules of PSS binder spontaneously attached on the cationized cotton and then acted as negative sites for further immobilization of positively charged Cap+ nanocapsules through electrostatic interaction. The increase of quantity of immobilized Cap+ nanocapsules could be obtained by increasing the number of PSS/Cap+ treatment cycles. The prolonged duration of thermoregulating action was obtained when increasing the quantity of Cap+ immobilized on the cotton fabric, resulting in the adjustable thermal barrier property of cotton fabric. The cotton sample immobilized with 5 cycles of PSS/Cap+ treatment exhibited the highest reduction of surface temperature, i.e. ~ 2.5 °C for longer than 10 min when the surrounding temperature was about 50 °C. In addition, this sample could retain about 77% of original quantity of immobilized Cap+ after 15 washing cycles. The facile polyelectrolyte assisted nanoencapsulation and immobilization of PCM nanocapsules on the cotton fabrics proposed in this study were effectively performed using low concentrations of non-toxic chemicals, in which they might be incorporated into the conventional fabric finishing system.