An ultrasensitive streptavidin-functionalized carbon nanotubes platform for chemiluminescent immunoassay

Ultrasound-Based Micro-/Nanosystems for Biomedical Applications

Due to the intrinsic non-invasive nature, cost-effectiveness, high safety, and real-time capabilities, besides diagnostic imaging, ultrasound as a typical mechanical wave has been extensively developed as a physical tool for versatile biomedical applications. Especially, the prosperity of nanotechnology and nanomedicine invigorates the landscape of ultrasound-based medicine. The unprecedented surge in research enthusiasm and dedicated efforts have led to a mass of multifunctional micro-/nanosystems being applied in ultrasound biomedicine, facilitating precise diagnosis, effective treatment, and personalized theranostics. The effective deployment of versatile ultrasound-based micro-/nanosystems in biomedical applications is rooted in a profound understanding of the relationship among composition, structure, property, bioactivity, application, and performance. In this comprehensive review, we elaborate on the general principles regarding the design, synthesis, functionalization, and optimization of ultrasound-based micro-/nanosystems for abundant biomedical applications. In particular, recent advancements in ultrasound-based micro-/nanosystems for diagnostic imaging are meticulously summarized. Furthermore, we systematically elucidate state-of-the-art studies concerning recent progress in ultrasound-based micro-/nanosystems for therapeutic applications targeting various pathological abnormalities including cancer, bacterial infection, brain diseases, cardiovascular diseases, and metabolic diseases. Finally, we conclude and provide an outlook on this research field with an in-depth discussion of the challenges faced and future developments for further extensive clinical translation and application.

Electrochemiluminescent resonance energy transfer between amino-modified g-C3N4/Bi2MoO6 composite and carboxyl CoS2 nanoboxes for sensitive detection of alpha fetoprotein

This work demonstrates an effective quenching electrochemiluminescent (ECL) immunosensor based on resonance energy transfer for the sensitive detection of alpha fetoprotein (AFP). In this strategy, graphitic carbon nitride (g-C3N4) was coupled with bismuth molybdenum oxide (Bi2MoO6) to form a g-C3N4/Bi2MoO6 nanocomposite as a novel type of ECL immunosensor. The as-synthesized amino-modified g-C3N4/Bi2MoO6 nanocomposite presents strong and stable cathodic ECL activity compared to pristine g-C3N4. One plausible reason is that the synergistic effect between the g-C3N4 and Bi2MoO6 could facilitate charge transfer process and thereby enhancing the separation efficiency of electron-hole pairs. The other functional part of the immunosensor, carboxyl CoS2 nanoboxes with a broad absorption range, was rationally designed and introduced. The evidence that the absorption spectra of carboxyl CoS2 NBs overlap with ECL spectra of g-C3N4/Bi2MoO6 nanocomposite holds accountable for exceptionally weakened ECL signal. This sandwich-type immunosensor was setup based on quenching mechanism concerning amino-modified g-C3N4/Bi2MoO6 as an ECL donor and carboxyl CoS2 NBs as an ECL accepter. The strategy was optimized to achieve a convincible and sensitive detection goal for AFP with a wide quantifiable range of 0.5 pg/mL-10 ng/mL whilst a sufficiently low detection limit of 0.04 pg/mL (S/N = 3). This immunosensor shows great potential for real sample analysis with reasonable recoveries ranging from 95.5 to 99.0 %, demonstrating its high precision for AFP determination.

A biogenesis construction of CuO@MWCNT via Chenopodium album extract: an effective electrocatalyst for synaptic plasticity neurodegenerative drug pollutant detection

Clioquinol (CLQ) is one of the most toxic halogenated neurodegenerative drugs, and its synaptic plasticity effect directly affects human health and the environment. Cupric oxide (CuO) is an ideal electrocatalyst owing to its earth-abundance, non-toxic nature, and cost-effectiveness. Since phenolate oxygen and pyridine nitrogen in CLQ act as an electron donor and pave the way for detection with Cu2+ ions in the CuO. Designing the architecture of CuO with a multi-walled carbon nanotube (MWCNT) is a sensible strategy to improve the electrochemical activity of the developed sensor. Inspired by the bio-synthesis and green processing, we have demonstrated the in-situ synthesis of CuO nanosphere-decorated MWCNT by Chenopodium album leaf extract through a sonochemical approach and explored its electrochemical sensing performance toward CLQ. The physical comprehensive characterization of prepared nanocomposite was investigated by various microscopic and spectroscopic techniques. For comparison studies, the CuO nanosphere was prepared by the same preparation process without MWCNT. Based on the physical characterization outcomes, the morphological nature of CuO was observed to be a sphere-like structure, which was decorated on the MWCNT with an average crystallite size of 16 nm (± 1 nm). Based on the electrochemical studies, the fabricated nanocomposite exhibits a wider linear range of 0.025-1375 μM, with a minimum detection limit of 4.59 nM L-1 toward CLQ. The viability examination on the biological matrix obtained considerable spike recoveries.

Expanding the scope of chemiluminescence in bioanalysis with functional nanomaterials

Nanomaterial-enabled chemiluminescence (CL) detection has become a growing area of interest in recent years. We review the development of nanomaterial-based CL detection strategies and their applications in bioanalysis. Much progress has been achieved in the past decade, but most attempts still remain in the proof-of-concept stage. This review highlights recent advances in nanomaterials in CL detection and organizes them into three groups based on their role in detection: as a sensing platform, as a signal probe, and applications in homogeneous systems. Furthermore, we have discussed the critical challenges we are facing and future prospects of this field.

Efficient label-free chemiluminescent immunosensor based on dual functional cupric oxide nanorods as peroxidase mimics

Dual-functional cupric oxide nanorods (CuONRs) as peroxidase mimics are proposed for the development of a flow-through, label-free chemiluminescent (CL) immunosensor. Forming the basis of this cost-efficient, label-free immunoassay, CuONRs, synthesized using a simple hydrothermal method, were deposited onto epoxy-activated standard glass slides, followed by immobilization of biotinylated capture antibodies through a streptavidin bridge. The CuONRs possess excellent catalytic activity, along with high stability as a solid support. Antigens could then be introduced to the sensing system, forming large immunocomplexes that prevent CL substrate access to the surface, thereby reducing the CL signal in a concentration dependent fashion. Using carcinoembryonic antigen (CEA) as a model analyte, the proposed label-free immunosensor was able to rapidly determine CEA with a wide linear range of 0.1-60ngmL^-1 and a low detection limit of 0.05ngmL^-1. This nanozyme-based immunosensor is simple, sensitive, cost-efficient, and has the potential to be a very promising platform for fast and efficient biosensing applications.

How to make nanobiosensors: surface modification and characterisation of nanomaterials for biosensing applications

This report aims to provide the audience with a guideline for construction and characterisation of nanobiosensors that are based on widely used affinity probes including antibodies and aptamers.

Smart CuS Nanoparticles as Peroxidase Mimetics for the Design of Novel Label-Free Chemiluminescent Immunoassay

In the present work, a novel label-free chemiluminescent (CL) immunoassay method was designed by employing smart CuS nanoparticles (CuSNPs) as peroxidase mimetics. The CuSNPs were synthesized through a simple coprecipitation method, and showed high catalytic activity and stability. This efficient label-free CL immunoassay could be easily achieved through a simple strategy. First, CuSNPs dispersed in chitosan were modified on the epoxy-functionalized glass slide to form a solid CL signal interface. Streptavidin was then used to functionalize CuSNPs to capture the biotinylated antibody, further producing a sensing interface. After online incubation with antigen molecules, the formed antibody-antigen complex on the biosensing substrate could prevent the diffusion channel of CL substrate toward the signal interface, and restrained the mimic enzyme-catalyzed CL reaction, finally resulting in the decrease of CL signals of the assay system. Compared to the label-based CL immunoassay, the proposed label-free assay mode is more simple, cheap and fast. Using a model analyte alpha-fetoprotein, the label-free CL immunoassay method had a linear range of 0.1-60 ng/mL and a low detection limit of 0.07 ng/mL. Moreover, the peroxidase mimetic-based label-free CL immunoassay system showed good specificity, acceptable repeatability, and good accuracy. The study provided a promising strategy for the development of highly efficient label-free CL immunoassay system.

A sandwich-type electrochemical immunosensor based on the biotin- streptavidin-biotin structure for detection of human immunoglobulin G

A sandwich-type immunosensor is designed and fabricated to detect the human immunoglobulin G (HIgG) using polyaniline and tin dioxide functionalized graphene (GS-SnO2-PAN) as the platform and biotin-functionalized amination magnetic nanoparticles composite (B-Fe3O4@APTES) as the label. GS-SnO2-PAN is used as the sensing agent to capture the primary anti-HIgG (Ab1) and SnO2 reduces the stack of GS. The B-Fe3O4@APTES with a large surface area and excellent biocompatibility captures second antibody (Ab2) efficiently based on the highly selective recognition of streptavidin to biotinylated antibody. The B-Fe3O4@APTES has better electro-catalytic activity in the reduction of hydrogen peroxide (H2O2) and the "biotin-streptavidin-biotin" (B-SA-B) strategy leads to signal amplification. Under optimal conditions, the immunosensor has a wide sensitivity range from 1 pg/L to 10 ng/L and low detection limit of 0.33 pg/L (S/N = 3) for HIgG. The immunosensor has high sensitivity, fast assay rate, as well as good reproducibility, specificity, and stability especially in the quantitative detection of biomolecules in serum samples.

Ru(bpy)3(2+)/nanoporous silver-based electrochemiluminescence immunosensor for alpha fetoprotein enhanced by gold nanoparticles decorated black carbon intercalated reduced graphene oxide

A highly sensitive sandwich-type electrochemiluminescence (ECL) immunosensor was proposed for the quantitative determination of alpha fetoprotein (AFP) using gold nanoparticles decorated black carbon intercalated reduced graphene oxide (Au-rGO@CB) as sensing platform and nanoporous silver (NPS) loaded Ru(bpy)3(2+) as labels. In this work, intercalation of CB inhibited the accumulation of rGO and Au-rGO@CB was firstly used to immobilize primary antibody (Ab1) in ECL system. NPS prepared by the dealloying of binary alloy has high pore volume and surface areas, which was used to load amount of secondary antibodies (Ab2) and Ru(bpy)3(2+), which could greatly enhance the ECL intensity. Under optimal conditions, the designed immunosensor exhibited wider linear range from 0.0001 to 30 ng/mL with a relative lower detection limit of 33 fg/mL for AFP detection. Overall, the designed immunosensor exhibited high sensitivity and selectivity, good repeatability and stability. This proposed method provided a potential application for clinical monitoring of AFP.