An integrated multifunctional platform based on biotin-doped conducting polymer nanowires for cell capture, release, and electrochemical sensing

Macromolecule-Nanoparticle-Based Hybrid Materials for Biosensor Applications

Biosensors function as sophisticated devices, converting biochemical reactions into electrical signals. Contemporary emphasis on developing biosensor devices with refined sensitivity and selectivity is critical due to their extensive functional capabilities. However, a significant challenge lies in the binding affinity of biosensors to biomolecules, requiring adept conversion and amplification of interactions into various signal modalities like electrical, optical, gravimetric, and electrochemical outputs. Overcoming challenges associated with sensitivity, detection limits, response time, reproducibility, and stability is essential for efficient biosensor creation. The central aspect of the fabrication of any biosensor is focused towards forming an effective interface between the analyte electrode which significantly influences the overall biosensor quality. Polymers and macromolecular systems are favored for their distinct properties and versatile applications. Enhancing the properties and conductivity of these systems can be achieved through incorporating nanoparticles or carbonaceous moieties. Hybrid composite materials, possessing a unique combination of attributes like advanced sensitivity, selectivity, thermal stability, mechanical flexibility, biocompatibility, and tunable electrical properties, emerge as promising candidates for biosensor applications. In addition, this approach enhances the electrochemical response, signal amplification, and stability of fabricated biosensors, contributing to their effectiveness. This review predominantly explores recent advancements in utilizing macrocyclic and macromolecular conjugated systems, such as phthalocyanines, porphyrins, polymers, etc. and their hybrids, with a specific focus on signal amplification in biosensors. It comprehensively covers synthetic strategies, properties, working mechanisms, and the potential of these systems for detecting biomolecules like glucose, hydrogen peroxide, uric acid, ascorbic acid, dopamine, cholesterol, amino acids, and cancer cells. Furthermore, this review delves into the progress made, elucidating the mechanisms responsible for signal amplification. The Conclusion addresses the challenges and future directions of macromolecule-based hybrids in biosensor applications, providing a concise overview of this evolving field. The narrative emphasizes the importance of biosensor technology advancement, illustrating the role of smart design and material enhancement in improving performance across various domains.

Polymerization within Nanoporous Anodized Alumina Oxide Templates (AAO): A Critical Survey

In the last few years, the polymerization of monomers within the nanocavities of porous materials has been thoroughly studied and developed, allowing for the synthesis of polymers with tailored morphologies, chemical architectures and functionalities. This is thus a subject of paramount scientific and technological relevance, which, however, has not previously been analyzed from a general perspective. The present overview reports the state of the art on polymerization reactions in spatial confinement within porous materials, focusing on the use of anodized aluminum oxide (AAO) templates. It includes the description of the AAO templates used as nanoreactors. The polymerization reactions are categorized based on the polymerization mechanism. Amongst others, this includes electrochemical polymerization, free radical polymerization, step polymerization and atom transfer radical polymerization (ATRP). For each polymerization mechanism, a further subdivision is made based on the nature of the monomer used. Other aspects of "in situ" polymerization reactions in restricted AAO geometries include: conversion monitoring, kinetic studies, modeling and polymer characterization. In addition to the description of the polymerization process itself, the use of polymer materials derived from polymerization in AAO templates in nanotechnology applications, is also highlighted. Finally, the review is concluded with a general discussion outlining the challenges that remain in the field.

Conducting Polymers as Versatile Tools for the Electrochemical Detection of Cancer Biomarkers

The detection of cancer biomarkers has recently become an established method for the early diagnosis of cancer. The sensitive analysis of specific biomarkers can also be clinically applied for the determination of response to treatment and monitoring of disease progression. Because of the ultra-low concentration of cancer biomarkers in body fluids, diagnostic tools need to be highly sensitive and specific. Conducting polymers (CPs) are particularly known to exhibit numerous features that enable them to serve as excellent materials for the immobilization of biomolecules and the facilitation of electron transfer. Their large surface area, porosity, and the presence of functional groups provide CPs with binding sites suitable for capturing biomarkers, in addition to their sensitive and easy detection. The aim of this review is to present a comprehensive summary of the available electrochemical biosensors based on CPs and their composites for the ultrasensitive detection of selected cancer biomarkers. We have categorized the study based on different types of targeted biomarkers such as DNAs, miRNAs, proteins, enzymes, neurotransmitters and whole cancer cells. The sensitivity of their detection is enhanced by the presence of CPs, providing a limit of detection as low as 0.5 fM (for miRNA) and 10 cells (for the detection of cancer cells). The methods of multiplex biomarker detection and cell capture are indicated as the most promising category, since they furnish more accurate and reliable results. Ultimately, we discuss the available CP-based electrochemical sensors and promising approaches for facilitating cancer diagnosis and treatment.

Antibacterial and Antibiofilm Potential of Microbial Polysaccharide Overlaid Zinc Oxide Nanoparticles and Selenium Nanowire

Here, we report on the synthesis of zinc oxide nanoparticles (ZnO NPs) and selenium nanowires (Se NWs) using microbial exopolysaccharides (EPS) as a mediator and then examine their antibacterial and ecotoxicity effects in vitro and in vivo, respectively. At 100 µg/mL, EPS, EPS-ZnO NPs, and EPS-Se NWs all exhibited potent in vitro antibacterial properties, drastically inhibiting the development of aquatic Gram(-) pathogens. In addition, antibiofilm studies using a microscope revealed that EPS, EPS-ZnO NPs, and EPS-Se NWs at 75 µg/mL prevented biofilm development. Furthermore, the in vivo toxicity was carried out via Danio rerio embryos and Ceriodaphnia cornuta. Danio rerio embryos were determined at different time intervals (6 hpf, 12 hpf, 24 hpf and 48 hpf). The maximum survival rate (100%) was obtained in a control group. Correspondingly, EPS, EPS-ZnO NPs and EPS-Se NWs treated embryos showed a considerable survival rate with 93.3%, 86.7% and 77.2%, respectively, at 100 µg/mL for 48 hpf. The total mortality of C. cornuta was seen at 100 µg/mL, with 56.7% in EPS, 60.0% in EPS-ZnO NPs, and 70.0% in EPS-Se NWs. For C. cornuta, the LC50 values for EPS, EPS-ZnO NPs, and EPS-Se NWs were 90.32, 81.99, and 62.99 µg/mL, respectively. Under a microscope, morphological alterations in C. cornuta were analyzed. After 24 h, an amount of dark substance was seen in the guts of C. cornuta exposed to 100 µg/mL, but in the control group, all of the living C. cornuta were swimming as usual. Our results show that EPS and EPS-ZnO NPs were less harmful than EPS-Se NWs, and that they were successfully employed to shield freshwater crustaceans from the toxins in aquatic environments.

Conducting Polymer-Coated Carbon Cloth Captures and Releases Extracellular Vesicles by a Rapid and Controlled Redox Process

Electrochemical techniques offer great opportunities for the capture of chemical and biological entities from complex mixtures and their subsequent release into clean buffers for analysis. Such methods are clean, robust, rapid, and compatible with a wide range of biological fluids. Here, we designed an electrochemically addressable system, based on a conducting terpolymer [P(EDOT-co-EDOTSAc-co-EDOTEG)] coated onto a carbon cloth substrate, to selectively capture and release biological entities using a simple electrochemical redox process. The conducting terpolymer composition was optimized and the terpolymer-coated carbon cloth was extensively characterized using electrochemical analysis, Raman and Fourier transform-infrared spectroscopy, water contact angle analysis, and scanning electron microscopy. The conductive terpolymer possesses a derivative of EDOT with an acetylthiomethyl moiety (EDOTSAc), which is converted into a "free" thiol that then undergoes reversible oxidation/reduction cycles at +1.0 V and -0.8 V (vs Ag/AgCl), respectively. That redox process enables electrochemical capture and on-demand release. We first demonstrated the successful electrochemical capture/release of a fluorescently labeled IgG antibody. The same capture/release procedure was then applied to release extracellular vesicles (EVs), originating from both MCF7 and SKBR3 breast cancer cell line bioreactors. EVs were captured using the substrate-conjugated HER2 antibody which was purified from commercially available trastuzumab. Capture and release of breast cancer EVs using a trastuzumab-derived HER2 antibody has not been reported before (to the best of our knowledge). A rapid (2 min) release at a low potential (-0.8 V) achieved a high release efficiency (>70%) of the captured, HER2+ve, SKBR3 EVs. The developed system and the electrochemical method are efficient and straightforward and have vast potential for the isolation and concentration of various biological targets from large volumes of biological and other (e.g., environmental) samples.

Oxide nanowire microfluidics addressing previously-unattainable analytical methods for biomolecules towards liquid biopsy

Nanowire microfluidics using a combination of self-assembly and nanofabrication technologies is expected to be applied to various fields due to its unique properties. We have been working on the fabrication of nanowire microfluidic devices and the development of analytical methods for biomolecules using the unique phenomena generated by the devices. The results of our research are not just limited to the development of nanospace control with "targeted dimensions" in "targeted arrangements" with "targeted materials/surfaces" in "targeted spatial locations/structures" in microfluidic channels, but also cover a wide range of analytical methods for biomolecules (extraction, separation/isolation, and detection) that are impossible to achieve with conventional technologies. Specifically, we are working on the extraction technology "the cancer-related microRNA extraction method in urine," the separation technology "the ultrafast and non-equilibrium separation method for biomolecules," and the detection technology "the highly sensitive electrical measurement method." These research studies are not just limited to the development of biomolecule analysis technology using nanotechnology, but are also opening up a new academic field in analytical chemistry that may lead to the discovery of new pretreatment, separation, and detection principles.

A highly selective and stable cationic polyelectrolyte encapsulated black phosphorene based impedimetric immunosensor for Interleukin-6 biomarker detection

Due to the insufficiency of binding sites for the immobilized recognition biomolecules on the immunosensing platform, cancer detection becomes challenging. Whereas, the degradation of black phosphorene (BP) in the presence of the environmental factors becomes a concerning issue for use in electrochemical sensing. In this study, BP is successfully encapsulated by polyallylamine (PAMI) to increase its stability as well as to enhance its electrochemical performance. The successful encapsulation of BP is ensured through X-ray Photoelectron spectroscopy and Raman spectroscopy, whereas the stability of black phosphorus is ensured by Zeta potential measurements and cyclic voltammetry tests. The developed BP-PAMI composite showed high stability in the ambient environment and exhibited improved electrochemical performances. The impedimetric immunosensor was developed on a BP-PAMI modified laser burned graphene (LBG) to detect interleukin-6 biomarkers using electrochemical impedance spectroscopy (EIS). Under the optimized parameters, the fabricated immunosensor demonstrated a wide linear range of 0.003-75 ng/mL, limit of detection (LOD) of 1 pg/mL. Based on the experimental analysis, the developed sensing strategy can be employed as an easy, disposable, cost-effective and highly selective point-of-care cancer detection. In addition, the developed technique can be applied broadly for detecting other biomarkers after treating with suitable biomolecules.

Natural Fish Trap-Like Nanocage for Label-Free Capture of Circulating Tumor Cells

Nanomaterials have achieved several breakthroughs in the capture of circulating tumor cells (CTCs) over the past decades. However, artificial fabrication of label-free nanomaterials used for high-efficiency CTC capture is still a challenge. Through billions of years of evolution and natural selection, various complicated and precise hierarchical structures are developed. Here, a novel fish trap-like "nanocage" structure derived from the natural Chrysanthemum pollen is reported and a nanocage-featured film for the label-free capture of CTCs and CTC clusters is constructed. The nanocage-featured film effectively captures 92% rare cancer cells with a broad spectrum of cancer types, due to the synergistic effect of nanocage-CTC filopodia matching, high contact area, and strong adhesion force between the cancer cells and the nanocage. Furthermore, the nanocage-featured film successfully detects CTCs and CTC clusters in 2 or 4 mL blood taken from 21 cancer patients (stages I-IV) suffering from various types of cancers. This novel, abundant, and economical fish trap-like "nanocage" may provide new perspectives for the application of natural nanomaterials in clinical CTC capture and analysis.

A novel anticoagulant affinity membrane for enhanced hemocompatibility and bilirubin removal

Affinity membrane is widely employed to promote specific adsorption of toxins and reduce the blood purification therapeutic time. However, it suffers from insufficient toxin binding and low hemocompatibility. Herein, a novel anticoagulant affinity membrane (AAM) was developed to clear bilirubin from human blood in a pore-flow-through way. Firstly, a nylon net membrane with a regularly arranged pore as the matrix was coated with poly(pyrrole-3-carboxylic acid) via chemical vapor deposition (CVD) method. Then, poly(L-arginine) (PLA) as a highly specific ligand of bilirubin, was immobilized onto the surface of the composited membrane after the modification of heparin. Owing to the 3-dimensional molecular architecture of PLA, up to 86.1 % of bilirubin was efficiently cleared. Besides, the AAM exhibited effective anticoagulant activity in the measurement of clotting time, with suppressed thrombus formation, low hemolysis ratio, minimized platelet and leukocyte adhesion, and excellent biosafety. Therefore, the AAM has enormous potential in blood purification therapy for enhancing hemocompatibility and bilirubin removal.

Development and Clinical Prospects of Techniques to Separate Circulating Tumor Cells from Peripheral Blood

Detection of circulating tumor cells (CTC) is an important liquid biopsy technique that has advanced considerably in recent years. To further advance the development of technology for curing cancer, several CTC technologies have been proposed by various research groups. Despite their potential role in early cancer diagnosis and prognosis, CTC methods are currently used for research purposes only, and very few methods have been accepted for clinical applications because of difficulties, including CTC heterogeneity, CTC separation from the blood, and a lack of thorough clinical validation. Although current CTC technologies have not been truly implemented, they possess high potential as future clinical diagnostic techniques for individualized cancer. Here, we review current developments in CTC separation technology. We also explore new CTC detection methods based on telomerase and nanomaterials, such as in vivo flow cytometry. In addition, we discuss the difficulties that must be overcome before CTC can be applied in clinical settings.

Facile Preparation of WO3-x Dots with Remarkably Low Toxicity and Uncompromised Activity as Co-reactants for Clinical Diagnosis by Electrochemiluminescence

The exceptional nature of WO_3-x dots has inspired widespread interest, but it is still a significant challenge to synthesize high-quality WO_3-x dots without using unstable reactants, expensive equipment, and complex synthetic processes. Herein, the synthesis of ligand-free WO_3-x dots is reported that are highly dispersible and rich in oxygen vacancies by a simple but straightforward exfoliation of bulk WS₂ and a mild follow-up chemical conversion. Surprisingly, the WO_3-x dots emerged as co-reactants for the electrochemiluminescence (ECL) of Ru(bpy)₃ ²⁺ with a comparable ECL efficiency to the well-known Ru(bpy)₃ ²⁺ /tripropylamine (TPrA) system. Moreover, compared to TPrA, whose toxicity remains a critical issue of concern, the WO_3-x dots were ca. 300-fold less toxic. The potency of WO_3-x dots was further explored in the detection of circulating tumor cells (CTCs) with the most competitive limit of detection so far.

Anti-Escherichia coli Functionalized Silver-Doped Carbon Nanofibers for Capture of E. coli in Microfluidic Systems

Silver-doped carbon nanofibers (SDCNF) are used as the base material for the selective capture of Escherichia coli in microfluidic systems. Fibers were spun in a glovebox with dry atmosphere maintained by forced dry air pumped through the closed environment. This affected the evaporation rate of the solvent during the electrospinning process and the distribution of silver particles within the fiber. Antibodies are immobilized on the surface of the silver-doped polyacrylonitrile (PAN) based carbon nanofibers via a three-step process. The negatively charged silver particles present on the surface of the nanofibers provide suitable sites for positively charged biotinylated poly-(L)-lysine-graft-poly-ethylene-glycol (PLL-g-PEG biotin) conjugate attachment. Streptavidin and a biotinylated anti-E. coli antibody were then added to create anti-E. coli surface functionalized (AESF) nanofibers. Functionalized fibers were able to immobilize up to 130 times the amount of E. coli on the fiber surface compared to neat silver doped fibers. Confocal images show E. coli remains immobilized on fiber mat surface after extensive rinsing showing the bacteria is not simply a result of non-specific binding. To demonstrate selectivity and functionalization with both gram negative and gram-positive antibodies, anti-Staphylococcus aureus surface functionalized (ASSF) nanofibers were also prepared. Experiments with AESF performed with Staphylococcus aureus (S. aureus) and ASSF with E. coli show negligible binding to the fiber surface showing the selectivity of the functionalized membranes. This surface functionalization can be done with a variety of antibodies for tunable selective pathogen capture.

Conducting Polymer-Based Composite Materials for Therapeutic Implantations: From Advanced Drug Delivery System to Minimally Invasive Electronics

Conducting polymer-based composites have recently becoming popular in both academic research and industrial practices due to their high conductivity, ease of process, and tunable electrical properties. The multifunctional conducting polymer-based composites demonstrated great application potential for in vivo therapeutics and implantable electronics, including drug delivery, neural interfacing, and minimally invasive electronics. In this review article, the state-of-the-art conducting polymer-based composites in the mentioned biological fields are discussed and summarized. The recent progress on the synthesis, structure, properties, and application of the conducting polymer-based composites is presented, aimed at revealing the structure-property relationship and the corresponding functional applications of the conducting polymer-based composites. Furthermore, key issues and challenges regarding the implantation performance of these composites are highlighted in this paper.

Nanostructured Substrates for Detection and Characterization of Circulating Rare Cells: From Materials Research to Clinical Applications

Circulating rare cells in the blood are of great significance for both materials research and clinical applications. For example, circulating tumor cells (CTCs) have been demonstrated as useful biomarkers for "liquid biopsy" of the tumor. Circulating fetal nucleated cells (CFNCs) have shown potential in noninvasive prenatal diagnostics. However, it is technically challenging to detect and isolate circulating rare cells due to their extremely low abundance compared to hematologic cells. Nanostructured substrates offer a unique solution to address these challenges by providing local topographic interactions to strengthen cell adhesion and large surface areas for grafting capture agents, resulting in improved cell capture efficiency, purity, sensitivity, and reproducibility. In addition, rare-cell retrieval strategies, including stimulus-responsiveness and additive reagent-triggered release on different nanostructured substrates, allow for on-demand retrieval of the captured CTCs/CFNCs with high cell viability and molecular integrity. Several nanostructured substrate-enabled CTC/CFNC assays are observed maturing from enumeration and subclassification to molecular analyses. These can one day become powerful tools in disease diagnosis, prognostic prediction, and dynamic monitoring of therapeutic response-paving the way for personalized medical care.

Sensing of circulating cancer biomarkers with metal nanoparticles

The analysis of circulating cancer biomarkers, including cell-free and circulating tumor DNA, circulating tumor cells, microRNA and exosomes, holds promise in revolutionizing cancer diagnosis and prognosis using body fluid analysis, also known as liquid biopsy. To enable clinical application of these biomarkers, new analytical tools capable of detecting them in very low concentrations in complex sample matrixes are needed. Metal nanoparticles have emerged as extraordinary analytical scaffolds because of their unique optoelectronic properties and ease of functionalization. Hence, multiple analytical techniques have been developed based on these nanoparticles and their plasmonic properties. The aim of this review is to summarize and discuss the present development on the use of metal nanoparticles for the analysis of circulating cancer biomarkers. We examine how metal nanoparticles can be used as (1) analytical transducers in various sensing principles, such as aggregation induced colorimetric assays, plasmon resonance energy transfer, surface enhanced Raman spectroscopy, and refractive index sensing, and (2) signal amplification elements in surface plasmon resonance spectroscopy and electrochemical detection. We critically discuss the clinical relevance of each category of circulating biomarkers, followed by a thorough analysis of how these nanoparticle-based designs have overcome some of the main challenges that gold standard analytical techniques currently face, and what new directions the field may take in the future.

Polymeric Nanowires for Diagnostic Applications

Polymer nanowire-related research has shown considerable progress over the last decade. The wide variety of materials and the multitude of well-established chemical modifications have made polymer nanowires interesting as a functional part of a diagnostic biosensing device. This review provides an overview of relevant publications addressing the needs for a nanowire-based sensor for biomolecules. Working our way towards the detection methods itself, we review different nanowire fabrication methods and materials. Especially for an electrical signal read-out, the nanowire should persist in a single-wire configuration with well-defined positioning. Thus, the possibility of the alignment of nanowires is discussed. While some fabrication methods immanently yield an aligned single wire, other methods result in disordered structures and have to be manipulated into the desired configuration.

Microbial exopolymer-capped selenium nanowires - Towards new antibacterial, antibiofilm and arbovirus vector larvicides?

Arboviral diseases and microbial pathogens resistant to commercially available drugs are on the rise. Herein, a facile microbial-based approach was developed to synthesize selenium nanowires (Se NWs) using microbial exopolymer (MEP) extracted from the Bacillus licheniformis (probiotic bacteria). MEP-Se NWs were characterized using UV-Visible, XRD, FTIR, HR-TEM, FE-SEM and EDX. An UV-Visible peak was detected at 330 nm while XRD spectrum data pointed out the crystalline nature of MEP-Se NWs. FTIR spectrum revealed functional groups with strong absorption peaks in the range 3898.52-477.97 cm^-1. FE-SEM and HR-TEM revealed that the obtained structures were nanowires of 10-30 nm diameter. Se presence was confirmed by EDX analysis. MEP-Se NWs at 100 μg/ml highly suppressed the growth of both Gram ^(-) and Gram ⁽⁺⁾ bacteria. Further, microscopic analysis evidenced that 75 μg/ml MEP-Se NWs suppressed biofilm formation. Hemolytic assays showed that MEP-Se NWs were moderately cytotoxic. In addition, LC₅₀ values lower than 10 μg/ml were estimated testing MEP-Se NWs on both Aedes aegypti and Culex quinquefasciatus 3rd instar larvae. Morphological and histological techniques were used to elucidate on the damages triggered in mosquito tissues, with special reference to midgut, post-exposure to MEP-Se NWs. Therefore, based on our findings, MEP-Se NWs can be considered for entomological and biomedical applications, with special reference to the management of biofilm forming microbial pathogens and arbovirus mosquito vectors.

Crustin-capped selenium nanowires against microbial pathogens and Japanese encephalitis mosquito vectors - Insights on their toxicity and internalization

Herein, we reported a method to synthesize selenium nanowires (Cr-SeNWs) relying to purified cysteine-rich antimicrobial peptide crustin in presence of ascorbic acid. Cr-SeNWs were characterized by UV-vis, XRD, FTIR and Raman spectroscopy, as well as SEM, HR-TEM and EDAX. The UV-vis spectroscopy peak was noted at 350 nm. XRD showed the crystalline nature of Cr-SeNWs through diffraction peaks observed 2θ at 12° and 28° corresponding to (020), and (241) lattice planes, respectively. HR-TEM results shed light on the size of Cr-SeNWs, ranging from 17 to 47 nm. Raman spectroscopy and EDAX analysis of Cr-SeNWs showed presence of 57% selenium element. Furthermore, Cr-SeNWs showed higher antimicrobial activity on Gram-positive bacteria (Staphylococcus aureus, Enterococcus faecalis) over Gram-negative ones (Pseudomonas aeruginosa, Escherichia coli). The zone of inhibition was larger on S. aureus (50 μg/ml = 4.0 mm, 75 μg/ml = 7.2 mm) and E. faecalis (50 μg/ml = 3.1 mm, 75 μg/ml = 5.1 mm), over P. aeruginosa (50 μg/ml = 2.1 mm, 75 μg/ml = 4.8 mm), E. coli (50 μg/ml = 1.3 mm, 75 μg/ml = 4.3 mm) bacteria. The antibiofilm activity of Cr-SeNWs was also investigated and biofilm reduction was observed at 75 μg/ml. In addition, Cr-SeNWs were highly effective as larvicides against Zika virus and Japanese encephalitis mosquito vectors, i.e., Culex quinquefasciatus and Culex tritaeniorhynchus, with LC₅₀ values of 4.15 and 4.85 mg/l, respectively. The nanowire toxicity and internalization was investigated through confocal laser scanning microscopy and histological studies. To investigate the potential of Cr-SeNWs for real-world applications, we also evaluated Cr-SeNWs in hemolytic assays, showing no cytotoxicity till 5 mg/ml. Besides, higher antioxidant activity at the concentration at 100 μg/ml was noted, if compared with purified crustin. The strong antioxidant potential of this nanomaterial can be helpful to boost the shelf-life potential of Cr-SeNWs-based pesticides and antimicrobials.

Microfluidic technologies in cell isolation and analysis for biomedical applications

Efficient platforms for cell isolation and analysis play an important role in applied and fundamental biomedical studies. As cells commonly have a size of around 10 microns, conventional handling approaches at a large scale are still challenged in precise control and efficient recognition of cells for further performance of isolation and analysis. Microfluidic technologies have become more prominent in highly efficient cell isolation for circulating tumor cells (CTCs) detection, single-cell analysis and stem cell separation, since microfabricated devices allow for the spatial and temporal control of complex biochemistries and geometries by matching cell morphology and hydrodynamic traps in a fluidic network, as well as enabling specific recognition with functional biomolecules in the microchannels. In addition, the fabrication of nano-interfaces in the microchannels has been increasingly emerging as a very powerful strategy for enhancing the capability of cell capture by improving cell-interface interactions. In this review, we focus on highlighting recent advances in microfluidic technologies for cell isolation and analysis. We also describe the general biomedical applications of microfluidic cell isolation and analysis, and finally make a prospective for future studies.

Bacterial capture efficiency in fluid bloodstream improved by bendable nanowires

Bacterial infectious diseases, such as sepsis, can lead to impaired function in the lungs, kidneys, and other vital organs. Although established technologies have been designed for the extracorporeal removal of bacteria, a high flow velocity of the true bloodstream might result in low capture efficiency and prevent the realization of their full clinical potential. Here, we develop a dialyzer made by three-dimensional carbon foam pre-grafted with nanowires to isolate bacteria from unprocessed blood. The tip region of polycrystalline nanowires is bent readily to form three-dimensional nanoclaws when dragged by the molecular force of ligand-receptor, because of a decreasing Young’s moduli from the bottom to the tip. The bacterial capture efficiency was improved from ~10% on carbon foam and ~40% on unbendable single-crystalline nanowires/carbon foam to 97% on bendable polycrystalline nanowires/carbon foam in a fluid bloodstream of 10 cm s⁻¹ velocity.

Bacteria and other pathogens entering the blood stream can have serious consequences, which can even lead to death. Here, the authors developed a sieve containing nano-sized claws that capture and hold these intruders, thus aiding their removal from patient’s blood

Manipulating cell fate: dynamic control of cell behaviors on functional platforms

We review the recent advances and new horizons in the dynamic control of cell behaviors on functional platforms and their applications.

Magnetic Nanowire Networks for Dual-Isolation and Detection of Tumor-Associated Circulating Biomarkers

Purpose: Recent developments in genomic and molecular methods have revolutionized the range of utilities of tumor-associated circulating biomarkers in both basic and clinical research. Herein, we present a novel approach for ultrasensitive extraction of cfDNA and CTCs, at high yield and purity, via the formation of magnetic nanowire networks. Materials and Methods: We fabricated and characterized biotinylated cationic polyethylenimine and biotinylated antibody cocktail-conjugated magnetic polypyrrole NWs (PEI/mPpy NW and Ab cocktail/mPpy NW, respectively). We applied these NWs to the extraction of cfDNA and CTC from the blood of 14 patients with lung cancer. We demonstrated reliable detection of EGFR mutations based on digital droplet PCR analysis of cfDNA and CTC DNA from patients with lung cancer. Results: The NW networks confined with a high density of magnetic nanoparticles exhibited superior saturation magnetization, which enabled rapid and high-yield capture whilst avoiding or minimizing damage and loss. The NW networks enabled the co-isolation of CTCs and cfDNA of high quality and sufficient quantities, thus allowing the amplification of rare and low-prevalence cancer-related mutations. Conclusion: The simple, versatile, and highly efficient nanowire network tool allows sensitive and robust assessment of clinical samples.

Fast Preparation of Polydopamine Nanoparticles Catalyzed by Fe2+/H2O2 for Visible Sensitive Smartphone-Enabled Cytosensing

It is highly desired to develop facile methods for fast preparation of polydopamine nanoparticles (PDANS) for intensive promising applications. Considering the system of Fe²⁺/H₂O₂ can generate reactive oxygen species efficiently, which can accelerate the self-oxidative polymerization of dopamine, a new time-saving method has been proposed to prepare PDANS catalyzed by Fe²⁺/H₂O₂. Thereafter, a novel kind of colorimetric nanoprobe for sensitive detection of human breast cancer cells (MDA-MB-231 cell) based on the obtained PDANS-loaded pH indicator molecules (thymolphthalein) has been developed successfully. The loading capacity of PDANS toward thymolphthalein molecules can reach as high as 165.40 mg/g, which will be a great help to enhancing the sensitivity. Following the color change principle of pH indicators, once simply triggered by basic water, the developed cytosensor offers a visible sensitive smartphone-enabled cytosensing of human breast cancer cells. It has been proved that the rational designed cytosensor is favorable to sensitive detection of cancer cells. By the virtue of its easy use, the proposed smartphone-enabled strategy can provide a novel testing approach for point-of-care bioassay beyond cytosensing in remote areas.

Identification and Quantitation of Circulating Tumor Cells

Circulating tumor cells (CTCs) are shed from the primary tumor into the circulatory system and act as seeds that initiate cancer metastasis to distant sites. CTC enumeration has been shown to have a significant prognostic value as a surrogate marker in various cancers. The widespread clinical utility of CTC tests, however, is still limited due to the inherent rarity and heterogeneity of CTCs, which necessitate robust techniques for their efficient enrichment and detection. Significant recent advances have resulted in technologies with the ability to improve yield and purity of CTC enrichment as well as detection sensitivity. Current efforts are largely focused on the translation and standardization of assays to fully realize the clinical utility of CTCs. In this review, we aim to provide a comprehensive overview of CTC enrichment and detection techniques with an emphasis on novel approaches for rapid quantification of CTCs.

Synthesis and characterization of conductive, biodegradable, elastomeric polyurethanes for biomedical applications

Biodegradable conductive polymers are currently of significant interest in tissue repair and regeneration, drug delivery, and bioelectronics. However, biodegradable materials exhibiting both conductive and elastic properties have rarely been reported to date. To that end, an electrically conductive polyurethane (CPU) was synthesized from polycaprolactone diol, hexadiisocyanate, and aniline trimer and subsequently doped with (1S)-(+)-10-camphorsulfonic acid (CSA). All CPU films showed good elasticity within a 30% strain range. The electrical conductivity of the CPU films, as enhanced with increasing amounts of CSA, ranged from 2.7 ± 0.9 × 10(-10) to 4.4 ± 0.6 × 10(-7) S/cm in a dry state and 4.2 ± 0.5 × 10(-8) to 7.3 ± 1.5 × 10(-5) S/cm in a wet state. The redox peaks of a CPU1.5 film (molar ratio CSA:aniline trimer = 1.5:1) in the cyclic voltammogram confirmed the desired good electroactivity. The doped CPU film exhibited good electrical stability (87% of initial conductivity after 150 hours charge) as measured in a cell culture medium. The degradation rates of CPU films increased with increasing CSA content in both phosphate-buffered solution (PBS) and lipase/PBS solutions. After 7 days of enzymatic degradation, the conductivity of all CSA-doped CPU films had decreased to that of the undoped CPU film. Mouse 3T3 fibroblasts proliferated and spread on all CPU films. This developed biodegradable CPU with good elasticity, electrical stability, and biocompatibility may find potential applications in tissue engineering, smart drug release, and electronics. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2305-2314, 2016.

Efficient Capture and Isolation of Tumor-Related Circulating Cell-Free DNA from Cancer Patients Using Electroactive Conducting Polymer Nanowire Platforms

Circulating cell-free DNA (cfDNA) is currently recognized as a key non-invasive biomarker for cancer diagnosis and progression and therapeutic efficacy monitoring. Because cfDNA has been detected in patients with diverse types of cancers, the use of efficient strategies to isolate cfDNA not only provides valuable insights into tumour biology, but also offers the potential for developing new cancer-specific targets. However, the challenges associated with conventional cfDNA extraction methods prevent their further clinical applications. Here, we developed a nanostructured conductive polymer platform for the efficient capture and release of circulating cfDNA and demonstrated its potential clinical utility using unprocessed plasma samples from patients with breast and lung cancers. Our results confirmed that the platform's enhanced efficiency allows tumor-specific circulating cfDNA to be recovered at high yield and purity.

Nanotechnology for enrichment and detection of circulating tumor cells

Circulating tumor cells (CTCs) are a hallmark of invasive behavior of cancer, responsible for the development of metastasis. Their detection and analysis have significant impacts in cancer biology and clinical practice. However, CTCs are rare events and contain heterogeneous subpopulations, requiring highly sensitive and specific techniques to identify and capture CTCs with high efficiency. Nanotechnology shows strong promises for CTC enrichment and detection owning to the unique structural and functional properties of nanoscale materials. In this review, we discuss the CTC enrichment and detection technologies based on a variety of functional nanosystems and nanostructured substrates, with the goal to highlight the role of nanotechnology in the advancement of basic and clinical CTC research.

Recent Advances in Nanostructured Conducting Polymers: from Synthesis to Practical Applications

Conducting polymers (CPs) have been widely studied to realize advanced technologies in various areas such as chemical and biosensors, catalysts, photovoltaic cells, batteries, supercapacitors, and others. In particular, hybridization of CPs with inorganic species has allowed the production of promising functional materials with improved performance in various applications. Consequently, many important studies on CPs have been carried out over the last decade, and numerous researchers remain attracted to CPs from a technological perspective. In this review, we provide a theoretical classification of fabrication techniques and a brief summary of the most recent developments in synthesis methods. We evaluate the efficacy and benefits of these methods for the preparation of pure CP nanomaterials and nanohybrids, presenting the newest trends from around the world with 205 references, most of which are from the last three years. Furthermore, we also evaluate the effects of various factors on the structures and properties of CP nanomaterials, citing a large variety of publications.

A novel label-free and reusable electrochemical cytosensor for highly sensitive detection and specific collection of CTCs

Circulating tumor cells (CTCs) contain a great deal of information of tumor phenotype. Therefore, highly sensitive detection and specific enrichment of CTCs are of intense interest. Herein, a label-free electrochemical impedance spectroscopy cytosensor with effective surface recognition between specific epithelial cell adhesion molecules (EpCAM) over-expressed on the cell membrane and EpCAM aptamer was developed for the detection of CTCs. After immobilization of 6-mercapto-1-hexanol (MCH) onto the gold electrode, the capture probe can be directionally inserted in MCH interspaces, which can improve the sensitivity of the cytosensor. A wide detection range from 30 to 1×10(6)cellsmL(-1) with a detection limit as low as 10cellsmL(-1) is reached on the condition of acceptable stability and reproducibility. The cytosensor can easily distinguish CTCs from the real blood sample due to the specific combination of EpCAM and EpCAM aptamer. Furthermore, the cytosensor can be reused 8 times and enrich CTCs by Uracil DNA Excision Mix specific cleaving the deoxyuridines (dUs) of the aptamer. The collected CTCs can contribute to further study. Thus, we reported that this cytosensor is a promising technique for the early monitoring and therapy of cancer.

A reusable electrochemical immunosensor fabricated using a temperature-responsive polymer for cancer biomarker proteins

In the present study, we describe a reusable electrochemical immunosensor for the repeated detection of cancer biomarkers using a single platform. The integration of a temperature-responsive polymer on the electrode surface enables easy manipulation of the biological sensing interface (i.e., addition of biotin, streptavidin, and antibody), thus allowing for temperature-induced regeneration and disruption of the interface architecture of the electrode surface. Using our immunosensor, we demonstrate sequential amperometric detection of three tumor markers: CA125, CEA, and PSA. Interestingly, greatly amplified signals are achieved by immersing the immunosensor in a solution of horseradish peroxidase (HRP) and antibody-labeled nanoparticles, resulting in a linear range of 0.0064 to 256 U/mL, 1 pg/mL to 100 ng/mL, and 10 pg/mL to 10 ng/mL with a detection limit of 0.007 U/mL, 0.7 pg/mL, and 0.9 pg/mL for CA125, CEA, and PSA, respectively. By alternating temperature, the immunosensor adsorbs and desorbs the biological elements without damage. Our proposed methodology can be expanded to measure other relevant biological species by repeated detection and thus has enormous potential for industrial and clinical applications.

Capturing Cancer: Emerging Microfluidic Technologies for the Capture and Characterization of Circulating Tumor Cells

Circulating tumor cells (CTCs) escape from primary or metastatic lesions and enter into circulation, carrying significant information of cancer progression and metastasis. Capture of CTCs from the bloodstream and the characterization of these cells hold great significance for the detection, characterization, and monitoring of cancer. Despite the urgent need from clinics, it remains a major challenge to capture and retain these rare cells from human blood with high specificity and yield. Recent exciting advances in micro/nanotechnology, microfluidics, and materials science have enable versatile, robust, and efficient cell isolation and processing through the development of new micro/nanoengineered devices and biomaterials. This review provides a summary of recent progress along this direction, with a focus on emerging methods for CTC capture and processing, and their application in cancer research. Furthermore, classical as well as emerging cellular characterization methods are reviewed to reveal the role of CTCs in cancer progression and metastasis, and hypotheses are proposed in regard to the potential emerging research directions most desired in CTC-related cancer research.

An Innovative Strategy for the Fabrication of Functional Cell Sheets Using an Electroactive Conducting Polymer

Here, we report the development of an electric field-assisted methodology for constructing 3D C2C12 cell sheets with the potential for cell surface modification. In this method, a conducting polymer, polypyrrole (Ppy), is electrodeposited via biotin doping, and then chemical conjugation of biotinylated bone morphogenetic protein 2 (BMP2) is achieved using a biotin-streptavidin cross-linker. Subsequently, C2C12 cells are cultured on BMP2-immobilized Ppy surfaces to induce interactions between cell surface receptors and bound BMP2 ligands. Following these procedures, layers of BMP2-immobilized cells can be easily detached from the Ppy surface by applying an electrical potential. This novel method results in high affinity, ligand-bound cell sheets, which exhibit homogeneous coverage with membrane-bound proteins and signal activation that occurs via maximal receptor accessibility. Using this strategy to engineer the cell surface with desirable ligands results in structures that mimic in vivo tissues; thus, the method reported here has potential applications in regenerative medicine and tissue engineering.

Electroactive polypyrrole nanowire arrays: synergistic effect of cancer treatment by on-demand drug release and photothermal therapy

An electroresponsive drug release system based on polypyrrole (Ppy) nanowires was developed to induce the local delivery of anticancer drug, doxorubicin (DOX), according to the applied electric field. DOX-conjugated Ppy nanowire (NW) (DOX/Ppy NW) array was initially prepared by electrochemical deposition of a mixture of pyrrole monomers and biotin as dopants in the anodic alumina oxide membrane as a sacrificial template. Morphological observation by scanning electron microscopy revealed free-standing and 3D nanotopographical features with large surface area and high density. In addition, we investigated the antitumor efficacy of DOX released from DOX/Ppy NW array in response to the external electric field using two kinds of cancer cell lines, human oral squamous carcinoma cells (KB cells) and human breast cancer cells (MCF7 cells). Meanwhile, strong photothermal effect as a result of a near-infrared absorbing ability of Ppy synergistically maximizes the chemotherapeutic efficacy. Our results suggested that the proposed multifunctional Ppy platform possessing several beneficial features is very promising for many therapeutic applications including cancer.