Polymethacrylate Coated Electrospun PHB Fibers as a Functionalized Platform for Bio-Diagnostics: Confirmation Analysis on the Presence of Immobilized IgG Antibodies against Dengue Virus.

In this article, a combination of far field electrospinning (FFES) and free-radical polymerization has been used to create a unique platform for protein immobilization via the physical attachment of biomolecules to the surface of the fiber mats. The large specific surface area of the fibers with its tailored chemistry provides a desirable platform for effective analyte-surface interaction. The detailed analysis of protein immobilization on a newly developed bio-receptive surface plays a vital role to gauge its advantages in bio-diagnostic applications. We relied on scanning electron microscopy (SEM), diameter range analysis, and X-ray photoelectron spectroscopy (XPS), along with thermal gravimetric analysis (TGA), water-in-air contact angle analysis (WCA), Fourier transform infrared spectroscopy (FTIR), and atomic force microscopy (AFM) to study our developed platforms and to provide valuable information regarding the presence of biomolecular entities on the surface. Detailed analyses of the fiber mats before and after antibody immobilization have shown obvious changes on the surface of the bioreceptive surface including: (i) an additional peak corresponding to the presence of an antibody in TGA analysis; (ii) extra FTIR peaks corresponding to the presence of antibodies on the coated fiber platforms; and (iii) a clear alteration in surface roughness recorded by AFM analysis. Confirmation analyses on protein immobilization are of great importance as they underlay substantial grounds for various biosensing applications.

Three-dimensional carbon interdigitated electrode arrays for redox-amplification.

Three-dimensional (3D) carbon interdigitated electrode arrays (IDEAs) were fabricated using inexpensive, conventional, UV photolithography of SU-8 with modified exposure and post exposure bake settings followed by pyrolysis in an inert environment. The sensor performance was investigated as a function of both the IDEA digit width/gap ratio and digit height under flow and no flow conditions. We demonstrated a gradual increase in redox amplification with an increase in the IDEA digit width/gap ratio. The highest amplification of 37 was obtained for a width/gap ratio of 1.58 and for an electrode height of 1.1 µm. Redox amplification also increases significantly with an increase in the IDEA height, from a factor of 9 at a 0.22 µm digit height to a factor of 37 at a 1.1 µm height. The effect of potential sweep rates on redox amplification was also investigated. As the sweep rate was decreased from 50 mV/s to 5 mV/s, the collection efficiency increased from 0.92 to 0.97, whereas the amplification increased from 7 to 25. Under flow conditions, the amplification decreases substantially as the cycling of the redox species is impeded by convection, resulting in a drop in collection efficiency. The highest amplification of 37 dropped to 4 for the same electrode at a flow rate of 500 nL/s. Under flow, redox amplification increased with an increase in the IDEA height.

A roadmap to high-speed polymerase chain reaction (PCR): COVID-19 as a technology accelerator.

The limit of detection (LOD), speed, and cost of crucial COVID-19 diagnostic tools, including lateral flow assays (LFA), enzyme-linked immunosorbent assays (ELISA), and polymerase chain reactions (PCR), have all improved because of the financial and governmental support for the epidemic. The most notable improvement in overall efficiency among them has been seen with PCR. Its significance for human health increased during the COVID-19 pandemic, when it emerged as the commonly used approach for identifying the virus. However, because of problems with speed, complexity, and expense, PCR deployment in point-of-care settings continues to be difficult. Microfluidic platforms offer a promising solution by enabling the development of smaller, more affordable, and faster PCR systems. In this review, we delve into the engineering challenges associated with the advancement of high-speed microfluidic PCR equipment. We introduce criteria that facilitate the evaluation and comparison of factors such as speed, LOD, cycling efficiency, and multiplexing capacity, considering sample volume, fluidics, PCR reactor geometry and materials, as well as heating/cooling methods. We also provide a comprehensive list of commercially available PCR devices and conclude with projections and a discussion regarding the current obstacles that need to be addressed in order to progress further in this field.

Doxorubicin Conjugated γ-Globulin Functionalised Gold Nanoparticles: A pH-Responsive Bioinspired Nanoconjugate Approach for Advanced Chemotherapeutics.

Developing successful nanomedicine hinges on regulating nanoparticle surface interactions within biological systems, particularly in intravenous nanotherapeutics. We harnessed the surface interactions of gold nanoparticles (AuNPs) with serum proteins, incorporating a γ-globulin (γG) hard surface corona and chemically conjugating Doxorubicin to create an innovative hybrid anticancer nanobioconjugate, Dox-γG-AuNPs. γG (with an isoelectric point of ~7.2) enhances cellular uptake and exhibits pH-sensitive behaviour, favouring targeted cancer cell drug delivery. In cell line studies, Dox-γG-AuNPs demonstrated a 10-fold higher cytotoxic potency compared to equivalent doxorubicin concentrations, with drug release favoured at pH 5.5 due to the γ-globulin corona's inherent pH sensitivity. This bioinspired approach presents a novel strategy for designing hybrid anticancer therapeutics. Our study also explored the intricacies of the p53-mediated ROS pathway's role in regulating cell fate, including apoptosis and necrosis, in response to these treatments. The pathway's delicate balance of ROS emerged as a critical determinant, warranting further investigation to elucidate its mechanisms and implications. Overall, leveraging the robust γ-globulin protein corona on AuNPs enhances biostability in harsh serum conditions, augments anticancer potential within pH-sensitive environments, and opens promising avenues for bioinspired drug delivery and the design of novel anticancer hybrids with precise targeting capabilities.

Rational PCR Reactor Design in Microfluidics.

Limit of detection (LOD), speed, and cost for some of the most important diagnostic tools, i.e., lateral flow assays (LFA), enzyme-linked immunosorbent assays (ELISA), and polymerase chain reaction (PCR), all benefited from both the financial and regulatory support brought about by the pandemic. From those three, PCR has gained the most in overall performance. However, implementing PCR in point of care (POC) settings remains challenging because of its stringent requirements for a low LOD, multiplexing, accuracy, selectivity, robustness, and cost. Moreover, from a clinical point of view, it has become very desirable to attain an overall sample-to-answer time (t) of 10 min or less. Based on those POC requirements, we introduce three parameters to guide the design towards the next generation of PCR reactors: the overall sample-to-answer time (t); lambda (λ), a measure that sets the minimum number of copies required per reactor volume; and gamma (γ), the system's thermal efficiency. These three parameters control the necessary sample volume, the number of reactors that are feasible (for multiplexing), the type of fluidics, the PCR reactor shape, the thermal conductivity, the diffusivity of the materials used, and the type of heating and cooling systems employed. Then, as an illustration, we carry out a numerical simulation of temperature changes in a PCR device, discuss the leading commercial and RT-qPCR contenders under development, and suggest approaches to achieve the PCR reactor for RT-qPCR of the future.

Nitrogen-functionalized graphene quantum dot incorporated GelMA microgels as fluorescent 3D-tissue Constructs.

Biopolymer microgels present many opportunities in biomedicine and tissue engineering. To understand their in vivo behavior in therapeutic interventions, long-term monitoring is critical, which is usually achieved by incorporating fluorescent materials within the hydrogel matrix. Current research is limited due to issues concerning the biocompatibility and instability of the conventional fluorescent species, which also tend to adversely affect the bio-functionality of the hydrogels. Here, we introduce a microfluidic-based approach to generate nitrogen-functionalized graphene quantum dot (NGQD) incorporated gelatin methacryloyl (GelMA) hydrogel microspheres, capable of long-term monitoring while preserving or enhancing the other favorable features of 3D cell encapsulation. A multilayer droplet-based microfluidic device was designed and fabricated to make monodisperse NGQD-loaded GelMA hydrogel microspheres encapsulating skeletal muscle cells (C2C12). Control over the sizes of microspheres could be achieved by tuning the flow rates in the microfluidic device. Skeletal muscle cells encapsulated in these microgels exhibited high cell viability from day 1 (82.9 ± 6.50%) to day 10 (92.1 ± 3.90%). The NGQD-loaded GelMA microgels encapsulating the cells demonstrated higher metabolic activity compared to the GelMA microgels. Presence of sarcomeric α-actin was verified by immunofluorescence staining on day 10. A fluorescence signal was observed from the NGQD-loaded microgels during the entire period of the study. The investigation reveals the advantages of integrating NGQDs in microgels for non-invasive imaging and monitoring of cell-laden microspheres and presents new opportunities for future therapeutic applications.

Controlled continuous patterning of polymeric nanofibers on three-dimensional substrates using low-voltage near-field electrospinning.

We report on a continuous method for controlled electrospinning of polymeric nanofibers on two-dimensional (2D) and three dimensional (3D) substrates using low voltage near-field electrospinning (LV NFES). The method overcomes some of the drawbacks in more conventional near-field electrospinning by using a superelastic polymer ink formulation. The viscoelastic nature of our polymer ink enables continuous electrospinning at a very low voltage of 200 V, almost an order of magnitude lower than conventional NFES, thereby reducing bending instabilities and increasing control of the resulting polymer jet. In one application, polymeric nanofibers are freely suspended between microstructures of 3D carbon on Si substrates to illustrate wiring together 3D components in any desired pattern.

Electrified lab on disc systems: A comprehensive review on electrokinetic applications.

Many advanced microfluidic Lab-on-disc (LOD) devices require an on-board power supply for powering active components. LODs with an on-board electrical power supply are called electrified-LODs (eLODs) and are the subject of the present review. This survey comprises two main parts. First, we discuss the different means of delivering electrical energy to a spinning disc including slip-ring, wireless power transmission, and on-board power supply. In the second part, we focus on utilizing electrical power on eLODs for three electrokinetic microfluidic processes: electrophoresis, electroosmotic flow, and dielectrophoresis. Electrokinetic phenomena enable propulsion, separation, and manipulation of different fluids and various types of microparticles/cells. We summarize the theoretical and experimental results for all three electrokinetic phenomena enacted on centrifugal platforms. While extensive numerical modeling and experimental research are available for electrokinetics on stationary platforms, there is a noticeable lack of development in this area when executed on rotating platforms. The review concludes by comparing the strengths and weaknesses of different electrokinetic techniques implemented on centrifugal platforms, and additionally, the most promising applications of electrokinetic-assisted eLOD devices are singled out.

A novel approach to dielectrophoresis using carbon electrodes.

Carbon-electrode dielectrophoresis (carbon-DEP) is demonstrated here as an alternative to more traditional DEP techniques. Carbon-DEP combines advantages of metal-electrode and insulator-based DEP by using low-cost fabrication techniques and low voltages for particle manipulation. The use of 3-D electrodes is proved to yield significant advantages over the use of traditional planar electrodes. This paper details the fabrication of dense arrays of tall high aspect ratio carbon electrodes on a transparent fused-silica substrate. The shrinkage of the SU-8 structures during carbonization is characterized and a design tool for future devices is provided. Applications of carbon electrodes in DEP are then detailed and include particle positioning, high-throughput filtering and cell focusing using positive-DEP. Manipulated cells include Saccharomyces cerevisiae and Drosophila melanogaster. The advantages and disadvantages of carbon-DEP are discussed at the end of this work.

Distinct Roles of Tensile and Compressive Stresses in Graphitizing and Properties of Carbon Nanofibers.

It is generally accepted that inducing molecular alignment in a polymer precursor via mechanical stresses influences its graphitization during pyrolysis. However, our understanding of how variations of the imposed mechanics can influence pyrolytic carbon microstructure and functionality is inadequate. Developing such insight is consequential for different aspects of carbon MEMS manufacturing and applicability, as pyrolytic carbons are the main building blocks of MEMS devices. Herein, we study the outcomes of contrasting routes of stress-induced graphitization by providing a comparative analysis of the effects of compressive stress versus standard tensile treatment of PAN-based carbon precursors. The results of different materials characterizations (including scanning electron microscopy, Raman and X-ray photoelectron spectroscopies, as well as high-resolution transmission electron microscopy) reveal that while subjecting precursor molecules to both types of mechanical stresses will induce graphitization in the resulting pyrolytic carbon, this effect is more pronounced in the case of compressive stress. We also evaluated the mechanical behavior of three carbon types, namely compression-induced (CIPC), tension-induced (TIPC), and untreated pyrolytic carbon (PC) by Dynamic Mechanical Analysis (DMA) of carbon samples in their as-synthesized mat format. Using DMA, the elastic modulus, ultimate tensile strength, and ductility of CIPC and TIPC films are determined and compared with untreated pyrolytic carbon. Both stress-induced carbons exhibit enhanced stiffness and strength properties over untreated carbons. The compression-induced films reveal remarkably larger mechanical enhancement with the elastic modulus 26 times higher and tensile strength 2.85 times higher for CIPC compared to untreated pyrolytic carbon. However, these improvements come at the expense of lowered ductility for compression-treated carbon, while tension-treated carbon does not show any loss of ductility. The results provided by this report point to the ways that the carbon MEMS industry can improve and revise the current standard strategies for manufacturing and implementing carbon-based micro-devices.

Unleashing the potential of cell membrane-based nanoparticles for COVID-19 treatment and vaccination.

Introduction: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a particular coronavirus strain responsible for the coronavirus disease 2019 (COVID-19), accounting for more than 3.1 million deaths worldwide. Several health-related strategies have been successfully developed to contain the rapidly-spreading virus across the globe, toward reduction of both disease burden and infection rates. Particularly, attention has been focused on either the development of novel drugs and vaccines, or by adapting already-existing drugs for COVID-19 treatment, mobilizing huge efforts to block disease progression and to overcome the shortage of effective measures available at this point.Areas covered: This perspective covers the breakthrough of multifunctional biomimetic cell membrane-based nanoparticles as next-generation nanosystems for cutting-edge COVID-19 therapeutics and vaccination, specifically cell membrane-derived nanovesicles and cell membrane-coated nanoparticles, both tailorable cell membrane-based nanosystems enriched with the surface repertoire of native cell membranes, toward maximized biointerfacing, immune evasion, cell targeting and cell-mimicking properties.Expert opinion: Nano-based approaches have received widespread interest regarding enhanced antigen delivery, prolonged blood circulation half-life and controlled release of drugs. Cell membrane-based nanoparticles comprise interesting antiviral multifunctional nanoplatforms for blocking SARS-CoV-2 binding to host cells, reducing inflammation through cytokine neutralization and improving drug delivery toward COVID-19 treatment.

Rapid Lipid Content Screening in Neochloris oleoabundans Utilizing Carbon-Based Dielectrophoresis.

In this study, we carried out a heterogeneous cytoplasmic lipid content screening of Neochloris oleoabundans microalgae by dielectrophoresis (DEP), using castellated glassy carbon microelectrodes in a PDMS microchannel. For this purpose, microalgae were cultured in nitrogen-replete (N+) and nitrogen-deplete (N-) suspensions to promote low and high cytoplasmic lipid production in cells, respectively. Experiments were carried out over a wide frequency window (100 kHz-30 MHz) at a fixed amplitude of 7 VPP. The results showed a statistically significant difference between the dielectrophoretic behavior of N+ and N- cells at low frequencies (100-800 kHz), whereas a weak response was observed for mid- and high frequencies (1-30 MHz). Additionally, a finite element analysis using a 3D model was conducted to determine the dielectrophoretic trapping zones across the electrode gaps. These results suggest that low-cost glassy carbon is a reliable material for microalgae classification-between low and high cytoplasmic lipid content-through DEP, providing a fast and straightforward mechanism.

The integration of 3D carbon-electrode dielectrophoresis on a CD-like centrifugal microfluidic platform.

We introduce the integration of a novel dielectrophoresis (DEP)-assisted filter with a compact disk (CD)-based centrifugal platform. Carbon-electrode dielectrophoresis (carbon-DEP) refers to the use of carbon electrodes to induce DEP. In this work, 3D carbon electrodes are fabricated using the C-MEMS technique and are used to implement a DEP-enabled active filter to trap particles of interest. Compared to traditional planar metal electrodes, 3D carbon electrodes allow for superior filtering efficiency. The system includes mounting modular 3D carbon-DEP chips on an electrically interfaced rotating disk. This allows simple centrifugal pumping to replace the large footprint syringe pump approaches commonly used in DEP systems. The advantages of the CD setup include not only a reduced footprint, but also complexity and cost reduction by eliminating expensive precision pumps and fluidic interconnects. To demonstrate the viability of this system we quantified the filter efficiency in the DEP trapping of yeast cells from a mix of latex and yeast cells. Results demonstrate selective filtering at flow rates up to 35 microl min(-1). The impact of electrode height, DEP chip misalignment and particle sedimentation on filter efficiency and the advantages this system represents are analyzed. The ultimate goal is to obtain an automated platform for bioparticle sorting with application in different fields such as point-of-care diagnostics and cell-based therapies.

On-line separation of bacterial cells by carbon-electrode dielectrophoresis.

Dielectrophoresis (DEP) represents a powerful approach to manipulate and study living cells. Hitherto, several approaches have used 2-D DEP chips. With the aim to increase sample volume, in this study we used a 3-D carbon-electrode DEP chip to trap and release bacterial cells. A continuous flow was used to plug an Escherichia coli cell suspension first, to retain cells by positive DEP, and thereafter to recover them by washing with peptone water washing solution. This approach allows one not only to analyze DEP behavior of living cells within the chip, but also to further recover fractions containing DEP-trapped cells. Bacterial concentration and flow rate appeared as critical parameters influencing the separation capacity of the chip. Evidence is presented demonstrating that the setup developed in this study can be used to separate different types of bacterial cells.

Droplet and Particle Generation on Centrifugal Microfluidic Platforms: A Review.

The use of multiphase flows in microfluidics to carry dispersed phase material (droplets, particles, bubbles, or fibers) has many applications. In this review paper, we focus on such flows on centrifugal microfluidic platforms and present different methods of dispersed phase material generation. These methods are classified into three specific categories, i.e., step emulsification, crossflow, and dispenser nozzle. Previous works on these topics are discussed and related parameters and specifications, including the size, material, production rate, and rotational speed are explicitly mentioned. In addition, the associated theories and important dimensionless numbers are presented. Finally, we discuss the commercialization of these devices and show a comparison to unveil the pros and cons of the different methods so that researchers can select the centrifugal droplet/particle generation method which better suits their needs.

Sub-10 nm nanogap fabrication on suspended glassy carbon nanofibers.

Glassy carbon nanofibers (GCNFs) are considered promising candidates for the fabrication of nanosensors for biosensing applications. Importantly, in part due to their great stability, carbon electrodes with sub-10 nm nanogaps represent an attractive platform for probing the electrical characteristics of molecules. The fabrication of sub-10 nm nanogap electrodes in these GCNFs, which is achieved by electrically stimulating the fibers until they break, was previously found to require fibers shorter than 2 µm; however, this process is generally hampered by the limitations inherent to photolithographic methods. In this work, to obtain nanogaps on the order of 10 nm without the need for sub-2 µm GCNFs, we employed a fabrication strategy in which the fibers were gradually thinned down by continuously monitoring the changes in the electrical resistance of the fiber and adjusting the applied voltage accordingly. To further reduce the nanogap size, we studied the mechanism behind the thinning and eventual breakdown of the suspended GCNFs by controlling the environmental conditions and pressure during the experiment. Following this approach, which includes performing the experiments in a high-vacuum chamber after a series of carbon dioxide (CO2) purging cycles, nanogaps on the order of 10 nm were produced in suspended GCNFs 52 µm in length, much longer than the ~2 µm GCNFs needed to produce such small gaps without the procedure employed in this work. Furthermore, the electrodes showed no apparent change in their shape or nanogap width after being stored at room temperature for approximately 6 months.

Mathematical modeling and computational analysis of centrifugal microfluidic platforms: a review.

Centrifugal microfluidic platforms or lab-on-discs (LODs) have evolved into a popular technology for automating chemical and biological assays. LODs today enable scientists to implement and integrate different operational units, including fluid mixing, droplet generation, cell-sorting, gene amplification, analyte detection, and so forth. For an efficient design and cost-effective implementation of any microfluidic device, including LODs, theoretical analysis and considerations should play a more important role than they currently do. The theoretical analysis we will show is especially essential to the investigation of detailed phenomena at the small length scales and high-speed typical for LODs where a wide range of forces may be involved. Previous LOD review papers presented mostly experimental results with theory as an afterthought. Hence, a review paper focused on the theoretical aspects, and associated computational studies of LOD devices is an urgent need. In the present review paper, all previous computational studies on LOD devices are categorized as single-phase flows, two-phase flows, network simulation, and solids. For each of these categories, the governing equations and important formulas are presented and explained. Moreover, a handy scaling analysis is introduced to aid scientists when comparing different competing forces in LOD devices. We hope that by surveying and contrasting various theoretical LOD studies, we shed some light on existing controversies and reveal where additional theoretical work is needed.

Nanotechnology for COVID-19: Therapeutics and Vaccine Research.

The current global health threat by the novel coronavirus disease 2019 (COVID-19) requires an urgent deployment of advanced therapeutic options available. The role of nanotechnology is highly relevant to counter this "virus" nano enemy. Nano intervention is discussed in terms of designing effective nanocarriers to counter the conventional limitations of antiviral and biological therapeutics. This strategy directs the safe and effective delivery of available therapeutic options using engineered nanocarriers, blocking the initial interactions of viral spike glycoprotein with host cell surface receptors, and disruption of virion construction. Controlling and eliminating the spread and reoccurrence of this pandemic demands a safe and effective vaccine strategy. Nanocarriers have potential to design risk-free and effective immunization strategies for severe acute respiratory syndrome coronavirus 2 vaccine candidates such as protein constructs and nucleic acids. We discuss recent as well as ongoing nanotechnology-based therapeutic and prophylactic strategies to fight against this pandemic, outlining the key areas for nanoscientists to step in.

A LEGO inspired fiber probe analytical platform for early diagnosis of Dengue fever.

Based on the concept of LEGO toys, a fiber probe analytical platform (FPAP) was developed as a powerful diagnostic tool offering higher sensitivity in detection of infectious agents compared to established methods. Using the form and the function of LEGO toys, this protocol describes a fiber-based, 96-well plate, which suspends a new class of chemically-designed, electrospun fibers within the assay. This clamping strategy allows both sides of the developed fiber mats to interact with biomolecules within the assay thus benefiting from the tailored chemical and physical properties of these fiber-based bioreceptors in attracting the biomolecules to the surface. The fabrication method of FPAP involves one-step electrospinning of the chemically designed fibers, 3D printing of the LEGO-like probing segments, and assembly of the device followed by ELISA procedure. FPAP follows the same principles of operation as that of a conventional enzyme linked immunosorbent assay (ELISA), therefore, it can be run by lab technicians, expert in ELISA. FPAP was used for early diagnosis of Dengue fever and provided an 8-fold higher sensitivity while the limit of detection (LOD) was recorded to be in femto-gram per milliliter range which is significantly low when compared to other existing techniques or conventional assay. This platform allows different types of paper/fiber bio-receptive platforms to be incorporated within the design that promises simultaneous recognition of multiple infectious agents.

Microplasma direct writing for site-selective surface functionalization of carbon microelectrodes.

Carbon micro- and nanoelectrodes fabricated by carbon microelectromechanical systems (carbon MEMS) are increasingly used in various biosensors and supercapacitor applications. Surface modification of as-produced carbon electrodes with oxygen functional groups is sometimes necessary for biofunctionalization or to improve electrochemical properties. However, conventional surface treatment methods have a limited ability for selective targeting of parts of a surface area for surface modification without using complex photoresist masks. Here, we report microplasma direct writing as a simple, low-cost, and low-power technique for site-selective plasma patterning of carbon MEMS electrodes with oxygen functionalities. In microplasma direct writing, a high-voltage source generates a microplasma discharge between a microelectrode tip and a target surface held at atmospheric pressure. In our setup, water vapor acts as an ionic precursor for the carboxylation and hydroxylation of carbon surface atoms. Plasma direct writing increases the oxygen content of an SU-8-derived pyrolytic carbon surface from ~3 to 27% while reducing the carbon-to-oxygen ratio from 35 to 2.75. Specifically, a microplasma treatment increases the number of carbonyl, carboxylic, and hydroxyl functional groups with the largest increase observed for carboxylic functionalities. Furthermore, water microplasma direct writing improves the hydrophilicity and the electrochemical performance of carbon electrodes with a contact-angle change from ~90° to ~20°, a reduction in the anodic peak to cathodic peak separation from 0.5 V to 0.17 V, and a 5-fold increase in specific capacitance from 8.82 mF∙cm-2 to 46.64 mF∙cm-2. The plasma direct-writing technology provides an efficient and easy-to-implement method for the selective surface functionalization of carbon MEMS electrodes for electrochemical and biosensor applications.