Platform For Immobilization Research Articles

Multilayered Mesoporous Composite Nanostructures for Highly Sensitive Label-Free Quantification of Cardiac Troponin-I.

Cardiac troponin-I (cTnI) is a well-known biomarker for the diagnosis and control of acute myocardial infarction in clinical practice. To improve the accuracy and reliability of cTnI electrochemical immunosensors, we propose a multilayer nanostructure consisting of Fe3O4-COOH labeled anti-cTnI monoclonal antibody (Fe3O4-COOH-Ab1) and anti-cTnI polyclonal antibody (Ab2) conjugated on Au-Ag nanoparticles (NPs) decorated on a metal–organic framework (Au-Ag@ZIF-67-Ab2). In this design, Fe3O4-COOH was used for separation of cTnI in specimens and signal amplification, hierarchical porous ZIF-67 extremely enhanced the specific surface area, and Au-Ag NPs synergically promoted the conductivity and sensitivity. They were additionally employed as an immobilization platform to enhance antibody loading. Electron microscopy images indicated that Ag-Au NPs with an average diameter of 1.9 ± 0.5 nm were uniformly decorated on plate-like ZIF-67 particles (with average size of 690 nm) without any agglomeration. Several electrochemical assays were implemented to precisely evaluate the immunosensor performance. The square wave voltammetry technique exhibited the best performance with a sensitivity of 0.98 mA mL cm−2 ng−1 and a detection limit of 0.047 pg mL−1 in the linear range of 0.04 to 8 ng mL−1.

Electrochemical detection of human epidermal growth factor receptor 2 using an aptamer on cobalt phthalocyanines – Cerium oxide nanoparticle conjugate

The role of the biointerface design towards the development of an impedimetric biosensor for the electrochemical detection of human epidermal growth factor receptor 2 (HER2) is investigated. Two novel cobalt phthalocyanines: cobalt tetraphenyl acetic acid phthalocyanine and cobalt tetraphenyl propionic acid phthalocyanine are compared as signal amplifiers and immobilization platforms of the HB5 aptamer towards the electrochemical detection of HER2. In addition, the phthalocyanines are coupled with the metal based cerium oxide nanoparticles. The efficiency of each electrode modification step and the performance of the constructed aptasensors were assessed by impedance spectroscopy. The aptasensors showed very low limit of detection values (all less than 0.2 ng/mL) with high sensitivity and stability. Furthermore, the aptasensors showed very good performance even in human serum samples. Considering these results, the aptasensors demonstrate great potential for improved monitoring of human epidermal growth factor receptor 2 levels for the management of breast cancers.

Nb4C3Tx (MXene)/Au/DNA Aptasensor for the Ultraselective Electrochemical Detection of Lead in Water Samples

AbstractAn electrochemical aptasensor was designed for the ultraselective and sensitive detection of Pb2+ by using lead‐specific binding DNA oligonucleotide as the molecular recognition element on Au nanoparticles/Nb4C3Tx MXene (Au@Nb4C3Tx) modified electrode. The Au@Nb4C3Tx is conjugated with thiol‐modified lead‐binding DNA through the Au−S bond. The DNA−Au@Nb4C3Tx modified glassy carbon electrode exhibited ultrahigh selectivity and enhanced response towards the detection of Pb2+ with a detection limit of 4 nM and linear range of 10 nM to 5 μM. This work has proved the possibility of using Nb4C3Tx as a robust immobilization platform for DNA oligonucleotides towards different environmental sensing and biomedical applications.

Development of rapid CO2 utilizing microbial ecosystem onto the novel & porous FPUF@nZVI@TAC@ASP hybrid for green coal desulphurization

• Coal desulphurization with high CO 2 consumption by bacteria on a hybrid was studied. • FPUF@nZVI@TAC@ASP offered immobilization platform to grow desulphurization bacteria. • nZVI coating enhanced coal desulphurization by breaking C-S bond & iron recycling. • S (43.3), Fe (20), NH 4 (0.08), NO 3 (0.05), PO 4 (0.01) kg/m 3 /day removal witnessed. • 4500 ppm of CO 2 was consumed to remove 1 kg sulphur, makes this study impactful. Self-capturing carbon dioxide (CO 2 ) from the polluted atmosphere and consuming it into the coal reactor for cheap coal desulphurization is an ideal solution to smog and global warming. Herein, a novel engineered microbial ecosystem was developed over zero-valent iron (nZVI) decorated functional polyurethane (FPUF) biocarrier for coal bio-desulphurization coupled with rapid utilization of CO 2 . FPUF was structured with nZVI for quenching sulphur, iron, and nitrogen species from coal, and present them to TAC/ASP microbes for rapid degradation. Self-assembled and rapid CO 2 utilizing microbial ecosystem (FPUF@nZVI@TAC@ASP) was shortly emerged as rapid coal treatment device as it removed CO 2 (54 kg/m 3 /day), sulphur (43.3 kg/m 3 /day), iron (20 kg/m 3 /day), NH 4 + (0.08 kg/m 3 /day), NO 3 – (0.05 kg/m 3 /day), and PO 4 3- (0.01 kg/m 3 /day). Super-high CO 2 fixation along with high sulphur removal rate (43.3 kg/m 3 /day) also yielded 400 mol/h/g protein. That further provided ample supply of HCO 3 – , S 2 O 3 2- and SO 4 2- species to microbes, which ultimately resulted in highly dense microbial ecosystem (14 g/L/h). Highest coal treatment efficiency (90%) was recorded, at sulphur/CO 2 ratio of 20 and 14-h residence time, which was 30 times better performance than previously reported studies. Practical and commercialized application of developed process (tested in 5-liter coal-reactor), was found very impressive, as treatment of 1 kg coal produced 180 g of sulphur and mitigated 4500 ppm of CO 2. The developed process has potential direct industrial application for coal, crude oil, petroleum, flue gas and natural gas desulphurization. This study opens a new gateway for the investigation and design of more innovative desulphurization and CO 2 mitigation researches.

Fabrication of alkoxysilane substituted polymer-modified disposable biosensing platform: Towards sperm protein 17 sensing as a new cancer biomarker

SP17 is a mammalian protein found in the testis and spermatozoa that have been identified as a tumor-associated antigen in a range of human cancers. A unique method for fabricating the first ultrasensitive, selective, and label-free immunosensor for the detection of SP17, a new cancer biomarker in complicated serum samples, is presented in this paper. This immunosensor was also the first biosensor built using a disposable ITO sheet modified with an aminosilane known as APTMS as an immobilization platform for fabricating the SP17 biosensor. The immobilization of chemical and biological species onto the electrode surface was cross-verified by various analytical and morphological techniques. Stepwise modifications done on the immunoelectrodes were also studied using electrochemical techniques. Selective interaction between anti-SP17 and SP17 with varying concentrations (100–5000 pg mL−1) was measured with the DPV technique. The immunosensor exhibited low LOD and LOQ of 70.07 and 233.57 pg mL−1, respectively, with a sensitivity of 0.013 μA mL pg−1 cm−2. The fabricated immunosensor performance was analyzed by quantifying the SP17 concentrations in patient serum samples. The data obtained from the developed immunosensor demonstrated excellent reproducibility, repeatability, and selectivity among various interferants, including cancer biomarkers. Further, the observed results have been validated via ELISA, which showed good agreement with the electrochemical results. This could establish a new platform for detecting other cancer biomarkers and can be employed for clinical diagnostics applications.

Amorphous metal-organic frameworks on PtCu hydrogels: Enzyme immobilization platform with boosted activity and stability for sensitive biosensing

Cell-free enzymatic catalysis (CFEC) is emerging biotechnology that simulates biological transformations without living cells. However, the high cost of separation and preparation of the enzyme has hindered the practical application of the CFEC. Enzyme immobilization technologies using solid supports to stabilize enzymes have been regarded as an efficient strategy to address this issue. Nevertheless, the activity and stability of the immobilized enzymes are still crucial challenges for working in vitro. Herein, an enzyme immobilization platform is developed by using PtCu hydrogels coated with amorphous metallic-organic frameworks (MOFs) as multifunctional carriers to encapsulate horseradish peroxidase (HRP). Specifically, PtCu hydrogels acting as a "reservoir of metal ions" can interact with the immobilized enzyme and facilitate electron transfer, leading to the boosted enzyme catalytic performances. Furthermore, amorphous MOFs on the surface of PtCu hydrogels serve as an "armor" to protect the internal enzymes from various perturbation environments. The resultant enzyme immobilization platform (PtCu@HRP@ZIF-8) not only shows an approximately 2.4-fold enhanced activity compared with free enzyme but also exhibits improved stability against harsh conditions. The PtCu@HRP@ZIF-8-based biosensor is constructed for sensitive sensing of organophosphorus pesticides (OPs). The proposed biosensor exhibits a favorable linear relationship with the concentration of paraoxon-ethyl from 6 to 800 ng/mL, with a low detection limit of 1.8 ng/mL. This work reveals the promising potential of our proposed enzyme immobilization platform in practical applications.

Effect of Graphene vs. Reduced Graphene Oxide in Gold Nanoparticles for Optical Biosensors-A Comparative Study.

Aiming to develop a nanoparticle-based optical biosensor using gold nanoparticles (AuNPs) synthesized using green methods and supported by carbon-based nanomaterials, we studied the role of carbon derivatives in promoting AuNPs localized surface plasmon resonance (LSPR), as well as their morphology, dispersion, and stability. Carbon derivatives are expected to work as immobilization platforms for AuNPs, improving their analytical performance. Gold nanoparticles (AuNPs) were prepared using an eco-friendly approach in a single step by reduction of HAuCl4·3H2O using phytochemicals (from tea) which act as both reducing and capping agents. UV–Vis spectroscopy, transmission electron microscopy (TEM), zeta potential (ζ-potential), and X-ray photoelectron spectroscopy (XPS) were used to characterize the AuNPs and nanocomposites. The addition of reduced graphene oxide (rGO) resulted in greater dispersion of AuNPs on the rGO surface compared with carbon-based nanomaterials used as a support. Differences in morphology due to the nature of the carbon support were observed and are discussed here. AuNPs/rGO seem to be the most promising candidates for the development of LSPR biosensors among the three composites we studied (AuNPs/G, AuNPs/GO, and AuNPs/rGO). Simulations based on the Mie scattering theory have been used to outline the effect of the phytochemicals on LSPR, showing that when the presence of the residuals is limited to the formation of a thin capping layer, the quality of the plasmonic resonance is not affected. A further discussion of the application framework is presented.

Antioxidant-biocompatible and stable catalase-based gelatin\u2013alginate hydrogel scaffold with thermal wound healing capability: immobilization and delivery approach

Hydrogel-based matrix prepared using biopolymers is a new frontier of emerging platforms for enzyme immobilization for biomedical applications. Catalase (CAT) delivery can be effective in inhibiting reactive oxygen species (ROS)-mediated prolongation of the wound healing process. In this study, to improve CAT stability for effective application, gelatin(Gel)–alginate (Alg) biocompatible hydrogel (Gel–Alg), as immobilization support, was prepared using calcium chloride as an ionic cross-linker. High entrapment efficiency of 92% was obtained with 2% Gel and 1.5% Alg. Hydrogel immobilized CAT (CAT–Gel–Alg) showed a wide range of pH from 4 to 9 and temperature stability between 20 to 60 °C, compared to free CAT. CAT–Gel–Alg kinetic parameters revealed an increased Km (24.15 mM) and a decreased Vmax (1.39 µmol H2O2/mg protein min) × 104. CAT–Gel–Alg retained 52% of its original activity after 20 consecutive catalytic runs and displayed improved thermal stability with a higher t1/2 value (half-life of 100.43 vs. 46 min). In addition, 85% of the initial activity was maintained after 8 weeks’ storage at 4 °C. At 24 h after thermal injury, a statistically significant difference in lesion sizes between the treated group and the control group was reported. Finally, our findings suggest that the superior CAT–Gel–Alg stability and reusability are resonant features for efficient biomedical applications, and ROS scavenging by CAT in the post-burn phase offers protection for local treatment of burned tissues with encouraging wound healing kinetics.

Abstract P3-19-03: Preliminary results of a feasibility study assessing radiation response with MRI/CT directed preoperative accelerated partial breast irradiation in the prone position for hormone responsive early stage breast cancer

Abstract BACKGROUND: Accelerated partial breast irradiation (APBI) has emerged as an alternative to whole breast irradiation (WBI) following lumpectomy for select patients. However, the challenges to post-operative APBI include targeting inaccuracy and the inability to measure tumor response to radiation. We hypothesized that preoperative APBI (pAPBI) could reliably target the tumor using MRI-guidance that is acquired prone in combination with our established prone breast radiation delivery. We developed methodology for prone CT simulation to establish radiation position, MRI acquisition in treatment position, registration of MRI-CT data for treatment planning, and treatment delivery with daily cone-beam CT using the same immobilization platform. This study aimed to assess the reproducibility, toxicity and local control associated with MRI/CT-directed prone pAPBI. METHODS: This was a prospective, single arm study enrolling patients >50 yo with clinical (c) Stage IA ER+/PR+/HER2- breast cancer intending lumpectomy. Axillary US and MRI imaging to confirm clinical node negative disease was required. A planning CT in the prone position was followed by MRI using the same prone immobilization platform. Rigid registration of MRI-CT data was used for radiation planning. pAPBI of 3850 cGy was delivered in 10 fractions BID with the same prone immobilization technique. Another MRI was obtained 4 weeks post-APBI to assess tumor response. The intensity, kinetics and volume of the lesion on MRI was quantitatively assessed and an experienced reader evaluated MRI volume and kinetic changes in the tumor post-APBI. Lumpectomy was performed 4-6 weeks after APBI. Simon 2 stage design required assessment after accrual of 19 patients for assessment of feasibility. RESULTS: Nineteen cStage IA ER+/PR+/HER2- breast cancer patients with a median age of 65 (range 51-78) were enrolled on the study, completed APBI, lumpectomy, and adjuvant AI. Median follow up was 3.4 years. Mean clinical tumor size was 1.1 cm ± 0.4 and mean path tumor size was 0.94 cm ± 0.6. There was complete pathologic response in 10.5% (n=2) and an additional 36.8% (n=7) were downstaged from clinical stage (measured by mammogram/US) to pathologic stage, resulting in a total response of 47.4% (n=9). Six (31.6%) patients had stable disease after APBI. Four (21.0%) were upstaged from clinical stage to pathological stage. Tumor response detected by MRI significantly correlated with tumor response based on clinical to pathologic stage (p=0.03). Cosmesis was rated as excellent/good in 89.5% (n=17) patients post-APBI. Cosmesis worsened to fair in 2 patients post-APBI, one of which required adjuvant WBI after focal triple negative breast cancer was detected on pathology. Three patients had positive macrometastatic lymph nodes on final pathology despite clinically negative nodes on imaging. One in-breast recurrence outside the RT field was detected by MRI at 14 months, resulting in a locoregional recurrence rate of 5.4% at 3.4 years. Another patient developed metastases at 20 months. CONCLUSIONS: Using the same prone platform, all patients successfully underwent CT simulation, MRI acquisition, and completed pAPBI. Nearly half of enrolled patients had a measurable tumor response to pAPBI based on MRI and pathologic response, confirming the accuracy and reproducibility of defining tumor targets with our MRI/CT-directed pAPBI approach. While this methodology for prone pAPBI resulted in good cosmesis and local control and remains a promising approach for select patients, the challenge of excluding patients with subclinical lymph node positive disease remains. Correlative studies will determine whether Ki-67 and OncotypeDx pre- and post-APBI can help predict response to pAPBI. Citation Format: Sasha Beyer, Tamara Smith, Ashley Sekhon, Jose Bazan, Sachin Jhawar, Erin Healy, Lai Wei, Vedat Yildiz, Mohamed Mohamed, Michael Knopp, Julia White. Preliminary results of a feasibility study assessing radiation response with MRI/CT directed preoperative accelerated partial breast irradiation in the prone position for hormone responsive early stage breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-19-03.

Printable Graphene Oxide Nanocomposites as Versatile Platforms for Immobilization of Functional Biomolecules

AbstractA series of novel nanocomposites containing graphene oxide (GO) suitable for stereolithography is presented. Different loads of GO are tested, identifying that these materials can be printed with concentrations up to 2.5 wt% GO, presenting improved mechanical properties for concentrations below 1.0 wt% GO. In this range, the nanocomposites exhibit higher strength and toughness when compared to the pristine resin. Microscopic analyses of the material demonstrate that this can be correlated with the good compatibility of GO with the resin, which favors its homogeneous dispersion in the form of flexible nanoplates. After manufacturing, the availability of GO to participate in surface modification reactions with chitosan (CHI) and an alkaline phosphatase (ALP) is evaluated. CHI and ALP are well‐known to act as biological cues in biorecognition processes, evidencing that these nanocomposites are suitable as platforms for selective immobilization of functional biomolecules.

Magnetic casein aggregates as an innovative support platform for laccase immobilization and bioremoval of crystal violet

In this study, casein@CoFe2O4 was fabricated through a green synthesis methodology and applied to immobilize laccase. The constructed casein@CoFe2O4 exhibited porous structures with distinct cavities and suitable magnetic properties. The abundance of aromatic functional groups on the surface renneted casein and possible π-type interaction between laccase and para-κ-casein resulted in a successful immobilization. The biocatalyst retained 50% of its initial activity after 24 reusability cycles, indicating stable immobilization of laccase onto the casein microstructures. The stability of laccase after immobilization was improved by 300% in comparison with the free enzyme, especially in basic pH values. The constructed laccase@casein@CoFe2O4 was then incorporated to remove crystal violet (CV) as an environmentally harmful synthetic tri-phenylmethane dye. The prepared heterogeneous biocatalyst effectively diminished the antimicrobial activity of CV up to 81.3% in 40 min against some bacterial strains, resulting from the formation of more minor toxic metabolites identified by liquid chromatography coupled with mass spectroscopy after degradation procedure. The proposed green and feasible method for the preparation of magnetic casein aggregates has not been previously reported. The incorporation of casein, which acted as a molecular chaperon, resulted in a significant improvement in the enzymatic stability and exhibited appropriate reusability for the constructed biocatalytic system.

Fabrication of Low-Fouling Surfaces on Alkyne-Functionalized Poly-(p-xylylenes) Using Click Chemistry.

A facial, versatile, and universal method that breaks the substrate limits is desirable for antifouling treatment. Thin films of functional poly-p-xylylenes (PPX) that are deposited using chemical vapor deposition (CVD) provide a powerful platform for surface immobilization of molecules. In this study, we prepared an alkyne-functionalized PPX coating on which poly (sulfobetaine methacrylate-co-Az) could be conjugated via click chemistry. We found that the conjugated polymers were very stable and inhibited cell adhesion and protein adsorption effectively. The same conjugation strategy could also be applied to conjugate azide-containing poly (ethylene glycol) and poly (NIPAAm). The results indicate that our method provides a simple and robust tool for fabricating antifouling surfaces on a wide range of substrates using CVD technology of functionalized poly (p-xylylenes) for biosensor, diagnostics, immunoassay, and other biomaterial applications.

Core-shell fibremats comprising a poly(AM/DAAM)/ADH nanofibre core and nylon6 shell layer are an attractive immobilization platform for constructing immobilised enzymes.

Core-shell fibremats, comprising poly(acrylamide)-co-poly(diacetone-acrylamide)/adipic dihydrazide [poly(AM/DAAM)/ADH] core-nanofibres and hydrophobic polymer shell layers, are a new class of platforms for constructing various immobilised enzymes. In this study, to elucidate the impacts of the shell-layer material on fibremat properties and enzymatic activities, we synthesised core-shell fibremats with shell layers comprising nylon6 or acetyl cellulose (AcCel) instead of poly(ε-caprolactone) (PCL), as in our previous study. Transmission and scanning electron microscopy images revealed that the lactase-encapsulated poly(AM/DAAM)/ADH-nylon6 and -AcCel fibremats were both constructed like the poly(AM/DAAM)/ADH-PCL one. Leakage measurements of the beforehand loaded molecules inside the core-nanofibres revealed that both fibremats exhibited efficient permeability for low-molecular-weight molecules and stable retention of enzyme molecules inside the core-nanofibres. Meanwhile, the fibremats' mechanical properties considerably depended on the choice of shell-layer material. The thermal analyses of the lactase-encapsulated fibremats revealed residual water inside the core nanofibres. The core-shell fibremats fabricated with a nylon6 or PCL shell exhibited excellent enzymatic activities (102 and 114%, respectively, compared to that of free lactase), superior to that of the same amount of free enzyme in a buffer. Furthermore, both core-shell fibremats retained over 95% of their initial enzymatic activities, even after they were re-used 10 times.

Immobilization of GOx Enzyme on SiO2-Coated Ni-Co Ferrite Nanocomposites as Magnetic Support and Their Antimicrobial and Photocatalytic Activities.

The present study used a sol–gel auto-combustion approach to make silica (SiO2)-coated Ni–Co ferrite nanocomposites that would be used as a platform for enzyme immobilization. Using glutaraldehyde as a coupling agent, glucose oxidase (GOx) was covalently immobilized on this magnetic substrate. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), and fourier transform infrared spectroscopy (FTIR) was used to determine the structural analysis and morphology of Ni–Co ferrite/SiO2 nanocomposites. FTIR spectra confirmed the binding of GOx to Ni–Co ferrite/SiO2 nanocomposites, with a loading efficiency of around 85%. At alkaline pH and higher temperature, the immobilized GOx enzyme exhibited increased catalytic activity. After 10 times of reuses, it still had 69% catalytic activity. Overall, the immobilized GOx displayed higher operational stability than the free enzyme under severe circumstances and was easily recovered by magnetic separation. With increased doping concentration of the nanocomposites, the photocatalytic activity was assessed using a degradation process in the presence of methylene blue dye under UV light irradiation, which revealed that the surface area of the nanocomposites with increased doping concentration played a significant role in improving photocatalytic activity. The antibacterial activity of Ni–Co ferrite/SiO2 nanocomposites was assessed using the agar well diffusion method against Escherichia coli, a gram-negative bacteria (ATCC 25922). Consequently, it was revealed that doping of Ni2+ and Co2+ in Fe2O4/SiO2 nanocomposites at varied concentrations improved their antibacterial properties.

Thionine functionalized hollow N-doped carbon nanoboxes: As a high-performance substrate for fabrication of label-free electrochemical aptasensor toward ultrasensitive detection of carcinoembryonic antigen

• A novel electrochemical aptasensor based on Thi@N-C n -box/AuNPs nanocomposites was developed for the determination of CEA. • The Thi@N-C n -box/AuNPs nanocomposites were synthesized to improve the sensitivity of aptasensor. • The aptasensor was successfully used for CEA detection in serum sample. During recent years, the combination of aptamer with new nanomaterials has led to significant improvements in the performance of aptamer-based sensors. The hollow N-doped carbon nanoboxes (N-C n -box) have attracted a lot of attention due to their unique physical and chemical properties and also significant intrinsic cavities which are suitable for loading specific chemicals. In this study, a label free electrochemical aptasensor is described, using thionine (Thi), as a signal molecule, gold nanoparticles (AuNPs) and N-C n -box, as signal amplification platform and high-performance substrate for aptamer strings immobilization for the measurement of carcinoembryonic antigen (CEA), as a model molecule. The presence of the target molecule impedes electron transfer which leads to a decrease in the Thi-associated square wave voltammetry (SWV) peak currents. This approach increases the amount of redox probe at the electrode surface and reduces the distance between the redox probe and the electrode surface. Therefore, this strategy exhibited higher sensitivity and wider linearity in the range of 0.1 fM to 30 nM (17 fg mL −1 –5.4 ng mL −1 ) with a LOD of 0.03 fM (5 fg mL −1 ) and also with good selectivity in the presence of different off-target species. This is the first report on the rational design of N-C n -box shelled with Thi for the electrochemical application.

Stretchable silver@CNT-poly(vinyl alcohol) films with efficient electromagnetic shielding prepared by polydopamine functionalization

The design of CNT/polymer composite shields is reduced to resolve the issue of CNTs agglomeration which has been tackled by complex and harsh chemical treatments damaging their electrical conductivity and limiting shielding capability. Herein, CNTs were coated with polydopamine (PDA) by exploiting the in-situ spontaneous polymerization of PDA on organic/inorganic surfaces. The PDA functional layer not only resulted in improved CNT dispersion after 2 h-coating time but also served as a platform for subsequent immobilization of silver nanoparticles by the catechol and nitrogen-containing groups of PDA. The well-dispersed CNT and the incorporation of extra silver particles conductive phase resulted in flexible and highly conductive Ag@PDA@CNT-poly(vinyl alcohol) (PVA) films with significantly improved shielding effectiveness of 42.75 dB with respect to pristine CNTs (21 dB). The size of silver particles controlled by PDA polymerization time, the formation of an efficient conductive network and conduction/interfacial polarization-induced loss mechanisms were reasoned to be responsible for dictating the films shielding performance. Such low-key and green approach could be instrumental to developing other metal/CNT polymer films as next-generation lightweight shields for flexible electronics.

Impedimetric aptasensor for HER2 biomarker using graphene quantum dots, polypyrrole and cobalt phthalocyanine modified electrodes

A method is presented for the electrochemical detection of the breast cancer biomarker human epidermal growth factor receptor 2 (HER2). A glassy carbon electrode was modified using two techniques known as sequential adsorption and electro-polymerization, and the results are compared. The highly conductive polypyrrole (PPy) is used, in the presence of sulfur/nitrogen doped graphene quantum dots (SNGQDs) and a known cobalt phthalocyanine (CoPc). The different nanomaterials were used as an immobilization platform for the HER2 specific HB5 aptamer via amide linkage. The nanomaterials were arranged in various ways on the glassy carbon electrode, to investigate the effect of the electrode interface on the operational characteristics of a biosensor. The immobilized aptamer selectively recognizes HER2 on the electrode interface, and this leads to an increased charge transfer resistance (Rct) of the electrode when using ferricyanide as the electrochemical probe. The developed immunosensors showed high sensitivity with the best detection limit of 0.00141 ng/mL. The results showed that the method is simple and sensitive enough for the determination of HER2 in serum samples with good reproducibility and accuracy.

Controllable Synthesis of Hollow Microtubular Covalent Organic Frameworks as an Enzyme-Immobilized Platform for Enhancing Catalytic Activity.

Despite great achievement that has been made in the synthesis of covalent organic frameworks (COFs), precise construction of COFs with well-defined nano/microstructures poses a rigorous challenge. Herein, we introduce a simple template-free strategy for controllable synthesis of hollow microtubular COFs. The obtained COFs show a spontaneous morphology transformation from a microfiber to a hollow microtubular structure when the concentrations of catalytic acid are regulated elaborately. Furthermore, the as-prepared COFs exhibit high crystallinity, well-defined hollow tubular morphology, and high surface areas (∼2600 m2/g). Taking the advantages of the unique morphological structure, the hollow microtubular COFs can serve as an ideal host material for enzymes. The resultant biocomposites show high catalytic performance and can be successfully applied to rapid and high-efficiency proteolysis of proteins. This work blazes a trail for controllable synthesis of the hollow microtubular COFs through a template-free process and expands the application of COFs as a promising platform for enzyme immobilization.

A poly (propylene imine) dendrimer – Carbon nanofiber based aptasensor for bisphenol A in water

• An aptasensor route not susceptible to BPA electro-oxidation fouling is developed. • A carbon nanofibre-dendrimer nanocomposite is prepared for aptamer immobilisation. • The aptasensor detected BPA in a sub-nanomolar concentration by EIS and DPV. • BPA was detected in real water sample and the results were validated with GC. We report a poly (propylene imine) dendrimer-carbon nanofiber nanocomposite (CNFs-PPI) immobilisation platform based aptasensor for bisphenol A (BPA). Amino modified aptamers were immobilised on the CNFs-PPI platform on a glassy carbon electrode (GCE) by covalent bonding using glutaraldehyde as a cross-linker. The interfacial changes on the surface of the electrode during the biosensor fabrication and operation were investigated using electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The proposed aptasensor (GCE/CNFs-PPI/NH-Apt) was able to detect BPA in the range of 1–10 nM, with limits of detection of 0.03 and 0.06 nM obtained from DPV and EIS respectively. The biosensor stability was investigated. Furthermore, the biosensor had good selectivity towards the BPA molecule in the presence of interfering species and exhibited repeatability with a relative standard deviation of 3.8% with good stability. Real sample application of the proposed aptasensor in water samples was investigated and recoveries between 91.8% and 100.3% were obtained.

Development of PAMAM dendrimer-modified magnetic chitosan: a novel platform for α-amylase immobilization

Development of PAMAM dendrimer-modified magnetic chitosan: a novel platform for α-amylase immobilization