Design and Manufacturing of a Disposable, Cyclo-Olefin Copolymer, Microfluidic Device for a Biosensor †

Nucleotide detection mechanism and comparison based on low-dimensional materials: A review

The recent pandemic has led to the fabrication of new nucleic acid sensors that can detect infinitesimal limits immediately and effectively. Therefore, various techniques have been demonstrated using low-dimensional materials that exhibit ultrahigh detection and accuracy. Numerous detection approaches have been reported, and new methods for impulse sensing are being explored. All ongoing research converges at one unique point, that is, an impetus: the enhanced limit of detection of sensors. There are several reviews on the detection of viruses and other proteins related to disease control point of care; however, to the best of our knowledge, none summarizes the various nucleotide sensors and describes their limits of detection and mechanisms. To understand the far-reaching impact of this discipline, we briefly discussed conventional and nanomaterial-based sensors, and then proposed the feature prospects of these devices. Two types of sensing mechanisms were further divided into their sub-branches: polymerase chain reaction and photospectrometric-based sensors. The nanomaterial-based sensor was further subdivided into optical and electrical sensors. The optical sensors included fluorescence (FL), surface plasmon resonance (SPR), colorimetric, and surface-enhanced Raman scattering (SERS), while electrical sensors included electrochemical luminescence (ECL), microfluidic chip, and field-effect transistor (FET). A synopsis of sensing materials, mechanisms, detection limits, and ranges has been provided. The sensing mechanism and materials used were discussed for each category in terms of length, collectively forming a fusing platform to highlight the ultrahigh detection technique of nucleotide sensors. We discussed potential trends in improving the fabrication of nucleotide nanosensors based on low-dimensional materials. In this area, particular aspects, including sensitivity, detection mechanism, stability, and challenges, were addressed. The optimization of the sensing performance and selection of the best sensor were concluded. Recent trends in the atomic-scale simulation of the development of Deoxyribonucleic acid (DNA) sensors using 2D materials were highlighted. A critical overview of the challenges and opportunities of deoxyribonucleic acid sensors was explored, and progress made in deoxyribonucleic acid detection over the past decade with a family of deoxyribonucleic acid sensors was described. Areas in which further research is needed were included in the future scope.

Current and Future Trends for Polymer Micro/Nanoprocessing in Industrial Applications

Polymers are widely used in optical devices, electronic devices, energy-harvesting/storage devices, and sensors, owing to their low weight, excellent flexibility, and simple fabrication process. With advancements in micro/nanoprocessing techniques and more demanding application requirements, it is becoming necessary to realize high-resolution fabrication of polymers to prepare miniaturized devices. This is particularly because conventional processing technologies suffer from high thermal stress and strong adhesion/friction, which can irreversibly damage the micro/nanostructures of miniaturized devices. In addition, although the use of advanced fabrication methods to prepare high-resolution micro/nanostructures is explored, these methods are limited to laboratory research or small-batch production. This review focuses on the micro/nanoprocessing of polymeric materials and devices with high spatial precision and replication accuracy for industrial applications. Specifically, the current state-of-the-art techniques and future trends for micro/nanomolding, high-energy beam processing, and micro/nanomachining are discussed. Moreover, an overview of the fabrication and applications of various polymer-based elements and devices such as microlenses, biosensors, and transistors is provided. These techniques are expected to be widely applied for multiscale and multimaterial processing as well as for multifunction integration in next-generation integrated devices, such as photoelectric, smart, and biodegradable devices.

Role of Polymers in Microfluidic Devices

Polymers are sustainable and renewable materials that are in high demand due to their excellent properties. Natural and synthetic polymers with high flexibility, good biocompatibility, good degradation rate, and stiffness are widely used for various applications, such as tissue engineering, drug delivery, and microfluidic chip fabrication. Indeed, recent advances in microfluidic technology allow the fabrication of polymeric matrix to construct microfluidic scaffolds for tissue engineering and to set up a well-controlled microenvironment for manipulating fluids and particles. In this review, polymers as materials for the fabrication of microfluidic chips have been highlighted. Successful models exploiting polymers in microfluidic devices to generate uniform particles as drug vehicles or artificial cells have been also discussed. Additionally, using polymers as bioink for 3D printing or as a matrix to functionalize the sensing surface in microfluidic devices has also been mentioned. The rapid progress made in the combination of polymers and microfluidics presents a low-cost, reproducible, and scalable approach for a promising future in the manufacturing of biomimetic scaffolds for tissue engineering.

Microarray detection method for pathogen genes by on-chip signal amplification using terminal deoxynucleotidyl transferase

A microarray detection method based on on-chip signal amplification using terminal deoxynucleotidyl transferase (TdT) was developed to visualize pathogenic genes. Cyclic olefin copolymer (COC) substrate for microarrays was treated with oxygen plasma to induce hydrophilic surface properties. The capture probe DNA was immobilized on the COC surface by UV irradiation. The 3ʹ end of the capture probe DNA immobilized on the COC surface was modified with a phosphate group to provide resistance against the TdT reaction. Therefore, the TdT reaction was triggered only when the capture probe DNA acquired the target gene, and biotin-11-deoxyuridine triphosphate (b-dUTP) was continuously added to the 3ʹ end of the target gene. Thereafter, streptavidin-conjugated gold nanoparticles (s-AuNPs) tagged the poly uridine tails by the biotin–streptavidin interaction. The visual signal was amplified by silver enhancement in the presence of the s-AuNPs. The usefulness of this detection method was confirmed by analyzing four pathogens and allowing their visual identification.

Rolling Circle Amplification-based Copper Nanoparticle Synthesis on Cyclic Olefin Copolymer Substrate and Its Application in Aptasensor

This study aimed to develop a label-free fluorescent aptasensor for the detection of diazinon (DZN) on a cyclic olefin copolymer (COC) substrate. The aptasensor design was based on rolling circle amplification (RCA) technology and the use of self-assembled copper nanoparticles (CuNPs). A dual-function (DF) probe, capable of binding to circular DNA and an aptamer, was designed and immobilized on a COC-bottom 96-well plate. An aptamer was used for selective recognition of DZN, and the specific site of the aptamer that strongly reacted with DZN was successfully identified using circular dichroism (CD) analysis. In presence of DZN, the aptamer and DZN formed a strong complex, thus providing an opportunity for hybridization of the DF probe and circular DNA, thereby initiating an RCA reaction. Repetitive poly thymine (T) sequence with a length of 30-mer, generated in the RCA reaction, served as a template for the synthesis of fluorescent copper nanoparticles, emitting an orange fluorescence signal (at approximately 620 nm) proportional to the amount of RCA product, within 10 min under UV irradiation. The CuNP fluorescence was imaged and quantified using an image analysis software. A linear correlation of the fluorescence signal was confirmed in the DZN concentration range of 0.1–3 ppm, with a detection limit of 0.15 ppm. Adoption of a label-free detection method, utilizing RCA and fluorescent CuNPs on COC substrates, reduced the need for complex equipment and requirements for DZN analysis, thereby representing a simple and rapid sensing method circumventing the limitations of current complex and labor-intensive methods.

PCR-assisted impedimetric biosensor for colibactin-encoding pks genomic island detection in E. coli samples

A fast PCR-assisted impedimetric biosensor was developed for the selective detection of the clbN gene from the polyketide synthase (pks) genomic island in real Escherichia coli samples. This genomic island is responsible for the production of colibactin, a harmful genotoxin that has been associated with colorectal cancer. The experimental protocol consisted of immobilizing the designated forward primer onto an Au electrode surface to create the sensing probe, followed by PCR temperature cycling in blank, positive, and negative DNA controls. Target DNA identification was possible by monitoring changes in the system’s charge transfer resistance values (R_ct) before and after PCR treatment through electrochemical impedance spectroscopy (EIS) analysis. Custom-made, flexible gold electrodes were fabricated using chemical etching optical lithography. A PCR cycle study determined the optimum conditions to be at 6 cycles providing fast results while maintaining a good sensitivity. EIS data for the DNA recognition process demonstrated the successful distinction between target interaction resulting in an increase in resistance to charge transfer (R_ct) percentage change of 176% for the positive DNA control vs. 21% and 20% for the negative and non-DNA-containing controls, respectively. Results showed effective fabrication of a fast, PCR-based electrochemical biosensor for the detection of pks genomic island with a calculated limit of detection of 17 ng/μL.