Chemical and biochemical analysis on lab-on-a-chip devices fabricated using three-dimensional printing

Design and preparation of an electromechanical implant prototype for an on-demand drug delivery

INTRODUCTION

A bio-implant is a drug-delivery system that is implanted in the human body for a period of more than 30 days. Electromechanical systems are one type of bio-implant that has recently been introduced as a new generation of targeted drug delivery methods. The overarching goal of utilizing these systems is to integrate electrical and mechanical features in order to benefit from the numerous applications of these two systems when used together. The current study aimed to design a prototype of an electromechanical system using Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS), and MultiJet Fusion (MJF) techniques for drug delivery that can release a specific drug dosage in the patient's body by connecting to a sensor or under the control of a signal sent by the physician.

METHODS

Initially, the implant chambers were created in the form of a hollow cylinder, closed at one end, using three different types of 3D printers: FDM, SLS, and MJF. Each implant was then filled with a model drug (pentoxifylline) and sealed with a thin gold membrane. To achieve the lowest voltage required to melt the gold membrane, an electric circuit with controllable DC voltage generator was designed. Finally, the mechanical resistance, drug release rate, and surface morphology of the designed implants were evaluated.

RESULTS

The MJF 3D printer, overally, had higher printing precision and repeatability than other printers; however, the implants printed by the FDM 3D printer were more accurate than other techniques (P value < 0.001), similar to the dimensions of the designed file. The mechanical resistance of the implants was also evaluated, and the polylactic acid implants printed by FDM had the highest value of Young's modulus in both the standard samples and the designed implants. During the 3-month drug leakage study, FDM 3D printed implant had a greater ability to store the desired drug load (P value < 0.001), Furthermore, the SEM micrographs revealed that the polylactic acid implants printed by FDM had minimal porosity in their structure and the layers were well adhered together. The gold membrane with a middle diameter of 2 mm required the lowest voltage of 6 V. As a result, the final electrical circuit was designed with smaller dimensions in order to achieve the voltage required to melt the gold membrane.

CONCLUSION

Due to the lack of drug leakage and other mechanical studies, the electromechanical implant produced by the FDM 3D printer was chosen as the optimal electromechanical implant in this study. Along with the designed small circuit, this implant can release a drug dosage in the patient's body at the physician's demand.

Interconnectable 3D-printed sample processing modules for portable mycotoxin screening of intact wheat

BACKGROUND

The increasing demand for food and feed products is stretching the capacity of the food value chain to its limits. A key step for ensuring food safety is checking for mycotoxin contamination of wheat. However, this analysis is typically performed by rather complex and expensive chromatographic methods, such as liquid chromatography-tandem mass spectrometry (LC-MS/MS). These costly methods require extensive sample preparation that is not easily carried out at different points along the food supply chain. To overcome such challenges in sample processing, an inexpensive and portable sample preparation device was needed, that required low skill, for rapid sample-to-result mycotoxin screening.

RESULTS

We describe 3D-printed and interconnectable modules for simple, integrated and on-site sample preparation, including grinding of wheat kernels, and solvent-based extraction. We characterized these 3D-printed modules for mycotoxin screening and benchmarked them against a laboratory mill using commercial lateral flow device(s) (LFD) and in-house validated LC-MS/MS analysis. Different integrated sieve configurations were compared based on grinding efficiency, and we selected a sieve size of 2 mm allowing grinding of 10 g of wheat within 5 min. Moreover, 10 first time-users were able to operate the grinder module with minimal instructions. Screening for deoxynivalenol (DON) in naturally contaminated samples at the regulatory/legal limit (1.25 mg kg-1) was demonstrated using the developed 3D-printed prototype. The whole process only takes 15 min, from sample preparation to screening result. The results showed a clear correlation (R2 = 0.96) between the LFD and LC-MS/MS.

SIGNIFICANCE

Our findings demonstrate the potential of 3D-printed sample handling equipment as a valuable extension of existing analytical procedures, facilitating the on-site implementation of rapid methods for the determination of mycotoxins in grains. The presented prototype is inexpensive with material costs of 2.5€, relies on biodegradable 3D printing filament and can be produced with consumer-grade printers, making the prototype readily available. As a future perspective, the modular character of our developed tool kit will allow for adaptation to other hard food commodities beyond the determination of DON in wheat.

Recent Advances on Cell Culture Platforms for In Vitro Drug Screening and Cell Therapies: From Conventional to Microfluidic Strategies

The clinical translations of drugs and nanomedicines depend on coherent pharmaceutical research based on biologically accurate screening approaches. Since establishing the 2D in vitro cell culture method, the scientific community has improved cell-based drug screening assays and models. Those advances result in more informative biochemical assays and the development of 3D multicellular models to describe the biological complexity better and enhance the simulation of the in vivo microenvironment. Despite the overall dominance of conventional 2D and 3D cell macroscopic culture methods, they present physicochemical and operational challenges that impair the scale-up of drug screening by not allowing a high parallelization, multidrug combination, and high-throughput screening. Their combination and complementarity with microfluidic platforms enable the development of microfluidics-based cell culture platforms with unequivocal advantages in drug screening and cell therapies. Thus, this review presents an updated and consolidated view of cell culture miniaturization's physical, chemical, and operational considerations in the pharmaceutical research scenario. It clarifies advances in the field using gradient-based microfluidics, droplet-based microfluidics, printed-based microfluidics, digital-based microfluidics, SlipChip, and paper-based microfluidics. Finally, it presents a comparative analysis of the performance of cell-based methods in life research and development to achieve increased precision in the drug screening process.

Radioactive isotope separation with 3D-printed flow-based device

Radioactive isotope (RI) metals are a new type of tracer for positron emission tomography generated from the target metal by proton irradiation using a cyclotron. The generated metal RIs need to be separated from the target metal rapidly and effectively. In the present study, we developed a 3D-printed flow device to separate metal RIs from target metals. The separation was performed with selective formation of ethylenediaminetetraacetic acid (EDTA) complex based on the difference in formation constants. The RI metal selectively formed a EDTA complex, thus changing its ionic charge in solution. The solution was then introduced into a cation exchange column for selective adsorption of the target metal. The solution with added chelator and controlled pH was introduced into the developed system and automatically separated metal RI from target metals within 14 min. The separation method was applied to separate RI ⁶⁷Ga from target metal Zn using a mixture of 107 pg L^{-1 67}Ga in 250 mg L^-1 Zn²⁺. The recoveries of ⁶⁷Ga and Zn were 97% and 100%, respectively. Furthermore, an ultraviolet (UV) radiation reactor was integrated into the system to decompose the EDTA complex and recover the Ga³⁺ ion. Ga³⁺ recovery by UV radiation was effective, 87%. The developed system was also successfully applied to the separation of Zr and Y. Therefore, the method and system can be applied to separate other metal RIs from target metals.

Analytical Chemistry: Tasks, Resolutions and Future Standpoints of the Quantitative Analyses of Environmental Complex Sample Matrices

Currently, the challenges that analytical chemistry has to face are ever greater and more complex both from the point of view of the selectivity of analytical methods and their sensitivity. This is especially true in quantitative analysis, where various methods must include the development and validation of new materials, strategies, and procedures to meet the growing need for rapid, sensitive, selective, and green methods. In this context, given the International Guidelines, which over time, are updated and which set up increasingly stringent “limits”, constant innovation is required both in the pre-treatment procedures and in the instrumental configurations to obtain reliable, accurate, and reproducible information. In addition, the environmental field certainly represents the greatest challenge, as analytes are often present at trace and ultra-trace levels. These samples containing analytes at ultra-low concentration levels, therefore, require very labor-intensive sample preparation procedures and involve the high consumption of organic solvents that may not be considered “green”. In the literature, in recent years, there has been a strong development of increasingly high-performing sample preparation techniques, often “solvent-free”, as well as the development of hyphenated instrumental configurations that allow for reaching previously unimaginable levels of sensitivity. This review aims to provide an update of the most recent developments currently in use in sample pre-treatment and instrument configurations in the environmental field, also evaluating the role and future developments of analytical chemistry in light of upcoming challenges and new goals yet to be achieved.

Current and future trends of additive manufacturing for chemistry applications: a review

Three-dimensional (3-D) printing, also known as additive manufacturing, refers to a method used to generate a physical object by joining materials in a layer-by-layer process from a three-dimensional virtual model. 3-D printing technology has been traditionally employed in rapid prototyping, engineering, and industrial design. More recently, new applications continue to emerge; this is because of its exceptional advantage and flexibility over the traditional manufacturing process. Unlike other conventional manufacturing methods, which are fundamentally subtractive, 3-D printing is additive and, therefore, produces less waste. This review comprehensively summarises the application of additive manufacturing technologies in chemistry, chemical synthesis, and catalysis with particular attention to the production of general laboratory hardware, analytical facilities, reaction devices, and catalytically active substances. It also focuses on new and upcoming applications such as digital chemical synthesis, automation, and robotics in a synthetic environment. While discussing the contribution of this research area in the last decade, the current, future, and economic opportunities of additive manufacturing in chemical research and material development were fully covered.

How 3D printing can boost advances in analytical and bioanalytical chemistry

3D printing fabrication methods have received lately an enormous attention by the scientific community. Laboratories and research groups working on analytical chemistry applications, among others, have advantageously adopted 3D printing to fabricate a wide range of tools, from common laboratory hardware to fluidic systems, sample treatment platforms, sensing structures, and complete fully functional analytical devices. This technology is becoming more affordable over time and therefore preferred over the commonly used fabrication processes like hot embossing, soft lithography, injection molding and micromilling. However, to better exploit 3D printing fabrication methods, it is important to fully understand their benefits and limitations which are also directly associated to the properties of the materials used for printing. Costs, printing resolution, chemical and biological compatibility of the materials, design complexity, robustness of the printed object, and integration with commercially available systems represent important aspects to be weighted in relation to the intended task. In this review, a useful introductory summary of the most commonly used 3D printing systems and mechanisms is provided before the description of the most recent trends of the use of 3D printing for analytical and bioanalytical chemistry. Concluding remarks will be also given together with a brief discussion of possible future directions.

Review of 3D-Printed functionalized devices for chemical and biochemical analysis

Recent developments in three-dimensional printing (3DP) have attracted the attention of analytical scientists interested in fabricating 3D devices having promising geometric functions to achieve desirable analytical performance. To break through the barrier of limited availability of 3DP materials and to extend the chemical reactivity and functionalities of devices manufactured using conventional 3DP, new approaches are being developed for the functionalization of 3D-printed devices for chemical and biochemical analysis. This Review discusses recent advances in the chemical functionalization schemes used in the main 3DP technologies, including (i) post-printing modification and surface immobilization of reactive substances on printed materials, (ii) pre-printing incorporation of reactive substances into raw printing materials, and (iii) combinations of both strategies, and their effects on the selectivity and/or sensitivity of related analytical methods. In addition, the state of the art of 3D-printed functionalized analytical devices for enzymatic derivatization and sensing, electrochemical sensing, and sample pretreatment applications are also reviewed, highlighting the importance of introducing new functional and functionalized materials to facilitate future 3DP-enabled manufacturing of multifunctional analytical devices.

Point-of-care diagnostics for infectious diseases: From methods to devices

The current widespread of COVID-19 all over the world, which is caused by SARS-CoV-2 virus, has again emphasized the importance of development of point-of-care (POC) diagnostics for timely prevention and control of the pandemic. Compared with labor- and time-consuming traditional diagnostic methods, POC diagnostics exhibit several advantages such as faster diagnostic speed, better sensitivity and specificity, lower cost, higher efficiency and ability of on-site detection. To achieve POC diagnostics, developing POC detection methods and correlated POC devices is the key and should be given top priority. The fast development of microfluidics, micro electro-mechanical systems (MEMS) technology, nanotechnology and materials science, have benefited the production of a series of portable, miniaturized, low cost and highly integrated POC devices for POC diagnostics of various infectious diseases. In this review, various POC detection methods for the diagnosis of infectious diseases, including electrochemical biosensors, fluorescence biosensors, surface-enhanced Raman scattering (SERS)-based biosensors, colorimetric biosensors, chemiluminiscence biosensors, surface plasmon resonance (SPR)-based biosensors, and magnetic biosensors, were first summarized. Then, recent progresses in the development of POC devices including lab-on-a-chip (LOC) devices, lab-on-a-disc (LOAD) devices, microfluidic paper-based analytical devices (μPADs), lateral flow devices, miniaturized PCR devices, and isothermal nucleic acid amplification (INAA) devices, were systematically discussed. Finally, the challenges and future perspectives for the design and development of POC detection methods and correlated devices were presented. The ultimate goal of this review is to provide new insights and directions for the future development of POC diagnostics for the management of infectious diseases and contribute to the prevention and control of infectious pandemics like COVID-19.

Can 3D Printing Bring Droplet Microfluidics to Every Lab?-A Systematic Review

In recent years, additive manufacturing has steadily gained attention in both research and industry. Applications range from prototyping to small-scale production, with 3D printing offering reduced logistics overheads, better design flexibility and ease of use compared with traditional fabrication methods. In addition, printer and material costs have also decreased rapidly. These advantages make 3D printing attractive for application in microfluidic chip fabrication. However, 3D printing microfluidics is still a new area. Is the technology mature enough to print complex microchannel geometries, such as droplet microfluidics? Can 3D-printed droplet microfluidic chips be used in biological or chemical applications? Is 3D printing mature enough to be used in every research lab? These are the questions we will seek answers to in our systematic review. We will analyze (1) the key performance metrics of 3D-printed droplet microfluidics and (2) existing biological or chemical application areas. In addition, we evaluate (3) the potential of large-scale application of 3D printing microfluidics. Finally, (4) we discuss how 3D printing and digital design automation could trivialize microfluidic chip fabrication in the long term. Based on our analysis, we can conclude that today, 3D printers could already be used in every research lab. Printing droplet microfluidics is also a possibility, albeit with some challenges discussed in this review.

Low-cost and open-source strategies for chemical separations

In recent years, a trend toward utilizing open access resources for laboratory research has begun. Open-source design strategies for scientific hardware rely upon the use of widely available parts, especially those that can be directly printed using additive manufacturing techniques and electronic components that can be connected to low-cost microcontrollers. Open-source software eliminates the need for expensive commercial licenses and provides the opportunity to design programs for specific needs. In this review, the impact of the "open-source movement" within the field of chemical separations is described, primarily through a comprehensive look at research in this area over the past five years. Topics that are covered include general laboratory equipment, sample preparation techniques, separations-based analysis, detection strategies, electronic system control, and software for data processing. Remaining hurdles and possible opportunities for further adoption of open-source approaches in the context of these separations-related topics are also discussed.

Design and Assembly of a Thin-Plate Mechatronic Atomizer by 3D Printing

Microfluidic structures and devices have been studied over decades for the transport of liquid through internal channels using versatile microfabrication schemes such as surface and bulk micromachining technologies. One challenge in consideration of the device design involves the breakthrough of microfluidic reservoir and channels being substantially limited in two-dimensional (2D) geometry. However, recent progress of the emerging 3D printing technologies has showed great potential to overcome this problem in a simple manner. This paper comprehensively reports an additive manufacturing of polylactic acid (PLA) layers to significantly improve the complexity in the formation of the 3D microfluidic structures as compared to conventional micro-manufacturing techniques. Moreover, a handheld mechatronic device with a small height of ~10 mm, assembled with a thin planar atomizer and a micro controller, was produced and demonstrated for generation of droplets (~6 μm in diameter). Both the analytical and experimental results indicated that the grids of channel microstructures were simply varied by different line widths (300–500 μm) and spacing (250–400 μm) 3D printed within the device, thereby providing the design capability for capillary flow. In this regard, a variety of complex micro devices fabricated via computer-aided design (CAD) and the 3D printing method could be applied for more applications than ever, such as microfluidic delivery of biomedical materials and health care devices of a small size.

How chemical engineers can contribute to fight the COVID-19

The SARS-CoV-2 virus, promoter of COVID-19, already infected millions of people around the world, resulting in thousands of fatal victims. Facing this unprecedented crisis in human history, several research groups, industrial companies and governments have been spending efforts to develop vaccines and medications. People from distinct knowledge fields are doing their part in order to overcome this crisis. Chemical Engineers are also contributing in the development of actions to control the SARS-CoV-2 virus. However, many chemical engineers still do not know how to use the knowledge acquired from Chemical Engineering school to collaborate in the fight against the COVID-19. In this context, the present paper aims to discuss several knowledge fields within the Chemical Engineering and correlated areas successfully applied to create innovative and effective solutions in the fight against the COVID-19.

Microextraction approaches for bioanalytical applications: An overview

Biological samples are usually complex matrices due to the presence of proteins, salts and a variety of organic compounds with chemical properties similar to those of the target analytes. Therefore, sample preparation is often mandatory in order to isolate the analytes from troublesome matrices before instrumental analysis. Because the number of samples in drug development, doping analysis, forensic science, toxicological analysis, and preclinical and clinical assays is steadily increasing, novel high throughput sample preparation approaches are calling for. The key factors in this development are the miniaturization and the automation of the sample preparation approaches so as to cope with most of the twelve principles of green chemistry. In this review, recent trends in sample preparation and novel strategies will be discussed in detail with particular focus on sorptive and liquid-phase microextraction in bioanalysis. The actual applicability of selective sorbents is also considered. Additionally, the role of 3D printing in microextraction for bioanalytical methods will be pinpointed.

Integration of a 3D-printed read-out platform with a quantum dot-based immunoassay for detection of the avian influenza A (H7N9) virus

Outbreaks and potential epidemics of the highly pathogenic avian influenza virus pose serious threats to human health and the global economy. As such, its timely and accurate detection is critically important. In the present study, positive hybridoma cells (6B3) were obtained, which were used to secrete high-titer avian influenza virus (AIV) H7N9 monoclonal antibodies (H7N9 mAb). Based on these mAbs, quantum dot-based lateral flow immunochromatographic strips (QD-LFICS) were developed for AIV H7N9 detection. Under optimized conditions, results from a commercial fluorescent strip reader indicated that the limit of detection of QD-LFICS was 0.0268 HAU. To achieve rapid on-site testing, a mini 3D-printed read-out platform was fabricated to allow observation of QD-LFICS by the naked eye. More importantly, QD-LFICS were found to be practical and specific for the detection of actual samples compared with a real-time polymerase chain reaction.

Microfluidic Inverted Flow of Ternary Water/Hydrophilic/Hydrophobic Organic Solvent Solution in a Y-Type Microchannel and a Proposal of the Response Microfluidic Analysis through the Experiment

Two solutions that are individually fed at the same flow rate into two separate microchannels of a microchip, combine to form a single channel (a Y-type microchannel). This flow is either parallel for immiscible solutions or initially parallel, but then becomes homogeneous through diffusion, for miscible solutions. However, a new type of microfluidic behavior in a Y-type microchannel that was neither parallel nor homogeneous flow has been observed using, for example, water/acetonitrile (3:4.5, v/v) and acetonitrile/ethyl acetate (3.5:4, v/v) mixed solutions. Each mixed solution was marked with distinctive dyes and delivered at the same flow rate into a Y-type microchannel under laminar flow conditions. In the single channel, the two phases were initially observed to flow in parallel, but then apparently swapped to flow on the opposite wall while retaining parallel flow with a slight change in the components of the two phases. We have named this type of laminar flow "microfluidic inverted flow" for ternary water/hydrophilic/hydrophobic organic solvent mixed solutions. The inverted flow of a ternary water/acetonitrile/ethyl acetate system was examined in detail under various flow conditions. We also proposed a concept of response microfluidic analysis based on such microfluidic inverted flow.

Low cost 3D microfluidic chips for multiplex protein detection based on photonic crystal beads

Point-of-care testing (POCT) devices used in multiplex bioassays are in great demand for clinical, environmental and biomedical applications. Photonic crystal beads (PCBs), as structural color self-coding carriers, can be integrated with microfluidic chips to realize convenient and highly sensitive biomarker detection. Here we developed a three dimensional (3D) microfluidic chip based on PCBs, which is low cost and easy to manufacture for mass production and application. The chip was fabricated with polyethylene terephthalate, polymethyl methacrylate sheets, a Ni square mesh grid and transparent double-sided tape. In practice, the target molecules could be captured by PCBs immobilized with probes in a flow-through manner. It was found that the as-proposed chip needed less washing and its background was effectively reduced in comparison with a flow-over chip. Besides, the limit of detection (LOD) of anti-human alpha fetoprotein (AFP) was calculated to be 18.92 ng mL^-1, which could meet the need of clinical detection of AFP. Furthermore, the chip demonstrated the feasibility of simultaneous detection of human immunoglobulin G, carcinoembryonic antigen and AFP, which suggests that it has a broad application prospect in multiplex bioassays.

Flexible Electronics Based on Micro/Nanostructured Paper

Over the past several years, a new surge of interest in paper electronics has arisen due to the numerous merits of simple micro/nanostructured substrates. Herein, the latest advances and principal issues in the design and fabrication of paper-based flexible electronics are highlighted. Following an introduction of the fascinating properties of paper matrixes, the construction of paper substrates from diverse functional materials for flexible electronics and their underlying principles are described. Then, notable progress related to the development of versatile electronic devices is discussed. Finally, future opportunities and the remaining challenges are examined. It is envisioned that more design concepts, working principles, and advanced papermaking techniques will be developed in the near future for the advanced functionalization of paper, paving the way for the mass production and commercial applications of flexible paper-based electronic devices.

3D-printed miniaturized fluidic tools in chemistry and biology

3D printing (3DP), an additive manufacturing (AM) approach allowing for rapid prototyping and decentralized fabrication on-demand, has become a common method for creating parts or whole devices. The wide scope of the AM extends from organized sectors of construction, ornament, medical, and R&D industries to individual explorers attributed to the low cost, high quality printers along with revolutionary tools and polymers. While progress is being made but big manufacturing challenges are still there. Considering the quickly shifting narrative towards miniaturized analytical systems (MAS) we focus on the development/rapid prototyping and manufacturing of MAS with 3DP, and application dependent challenges in engineering designs and choice of the polymeric materials and provide an exhaustive background to the applications of 3DP in biology and chemistry. This will allow readers to perceive the most important features of AM in creating (i) various individual and modular components, and (ii) complete integrated tools.

"On-Off-On" Photoelectrochemical/Visual Lab-on-Paper Sensing via Signal Amplification of CdS Quantum Dots@Leaf-Shape ZnO and Quenching of Au-Modified Prism-Anchored Octahedral CeO2 Nanoparticles

An effective "on-off-on" photoelectrochemical (PEC)/visual sensing system based on cleaning-switchable lab-on-paper device was designed to achieve ultrasensitive detection of analytes. The first amplified "signal-on" PEC state was gained by CdS quantum dots sensitized leaf-shape ZnO (CdS QDs/leaf-shape ZnO) structure, which was assembled on reduced graphene oxide (rGO) modified paper electrode. Then Au-modified prism-anchored octahedral CeO₂ nanoparticles (Au@PO-CeO₂ NPs), as an efficient signal quencher, were immobilized on the CdS QDs/leaf-shape ZnO with the assistance of DNA hybridization, resulting in a noticeable photocurrent response decrement with the "signal-off" PEC state. With the addition of analytes, the quencher Au@PO-CeO₂ NPs were immediately released from the sensing surface and robust PEC response was recovered to the signal-on state again. Meanwhile, the disengaged quencher in electrolyte solution flowed to the colorimetric detection area of lab-on-paper device and catalyzed oxidation of the chromogenic substrate 3,3',5,5'-tetramethylbenzidine in the presence of H₂O₂ to form the colored product, making the analytes detection more convincing with the visual discrimination. Under optimal conditions, the proposed PEC/visual lab-on-paper device possessed the detection limits toward adenosine and potassium ion as low as 0.15 and 0.06 nM, respectively. With ingenious design of actuating conversion process between hydrophilicity and hydrophobicity by slipping paper tab to solve cleaning issue in the assay procedures, the cleaning-switchable lab-on-paper device was constructed for high-performance biosensing applications. It provides an unambiguous simplicity and portable operation for exploring high reliability and sensitivity of novel point-of-care diagnostic tool with dual-signal readout.

One-step three-dimensional printing of enzyme/substrate-incorporated devices for glucose testing

To substantially simplify the fabrication of analytical devices for rapid screening tests, in this study we employed multi-material fused deposition modeling-type three-dimensional printing (3DP) and two functionalized thermoplastic filaments-acrylonitrile butadiene styrene (ABS) incorporating peroxidase-mimicking iron oxide (Fe₃O₄) nanoparticles and polyvinyl alcohol (PVA) infiltrated with the chromogenic substrate o-phenylenediamine (OPD)-for the one-step manufacture of enzyme/substrate-incorporated multi-well plates. Upon contact with samples, these fabricated devices (i) released the chromogenic substrate OPD into the solution, (ii) efficiently catalyzed the oxidation of OPD mediated by the peroxidase substrate H₂O₂, (iii) enabled assays of those substances availably oxidized by their specific oxidases to generate H₂O₂, and (iv) facilitated colorimetric observation by the naked eye or through absorbance measurements after loading into a microplate reader. With glucose oxidase immobilized in each well, samples appropriately diluted could be directly loaded for derivatizing and analyzing glucose without adding any other reagents. After assay optimization, the limits of detection reached as low as 2.8 μM for H₂O₂ and 5.0 μM for glucose; the method's applicability was illustrated in terms of determining glucose concentrations in urine, serum, and plasma samples. These 3D-printed peroxidase mimic/chromogenic substrate-incorporated multi-well plates appear to be highly suitable for rapid and high-throughput screening of glucose in clinical samples. We demonstrate that adequate functionalization of raw materials for 3DP can contribute to the development of novel multifunctional devices with many potential practical applications.

Highly integrated autonomous lab-on-a-chip device for on-line and in situ determination of environmental chemical parameters

The successful integration of sample pretreatment stages, sensors, actuators and electronics in microfluidic devices enables the attainment of complete micro total analysis systems, also known as lab-on-a-chip devices. In this work, we present a novel monolithic autonomous microanalyzer that integrates microfluidics, electronics, a highly sensitive photometric detection system and a sample pretreatment stage consisting on an embedded microcolumn, all in the same device, for on-line determination of relevant environmental parameters. The microcolumn can be filled/emptied with any resin or powder substrate whenever required, paving the way for its application to several analytical processes: separation, pre-concentration or ionic-exchange. To promote its autonomous operation, avoiding issues caused by bubbles in photometric detection systems, an efficient monolithic bubble removal structure was also integrated. To demonstrate its feasibility, the microanalyzer was successfully used to determine nitrate and nitrite in continuous flow conditions, providing real time and continuous information.

From functional structure to packaging: full-printing fabrication of a microfluidic chip

This paper presents a concept of a full-printing methodology aiming at convenient and fast fabrication of microfluidic devices. For the first time, we achieved a microfluidic biochemical sensor with all functional structures fabricated by inkjet printing, including electrodes, immobilized enzymes, microfluidic components and packaging. With the cost-effective and rapid process, this method provides the possibility of quick model validation of a novel lab-on-chip system. In this study, a three-electrode electrochemical system was integrated successfully with glucose oxidase immobilization gel and sealed in an ice channel, forming a disposable microfluidic sensor for glucose detection. This fully-printed chip was characterized and showed good sensitivity and a linear section at a low-level concentration of glucose (0-10 mM). With the aid of automatic equipment, the fully-printed sensor can be massively produced with low cost.

3D-Printing of Functional Biomedical Microdevices via Light- and Extrusion-Based Approaches

3D-printing is a powerful additive manufacturing tool, one that enables fabrication of biomedical devices and systems that would otherwise be challenging to create with more traditional methods such as machining or molding. Many different classes of 3D-printing technologies exist, most notably extrusion-based and light-based 3D-printers, which are popular in consumer markets, with advantages and limitations for each modality. The focus here is primarily on showcasing the ability of these 3D-printing platforms to create different types of functional biomedical microdevices-their advantages and limitations are covered with respect to other classes of 3D-printing, as well as the past, recent, and future efforts to advance the functional microdevice domain. In particular, the fabrication of micromachines/robotics, drug-delivery devices, biosensors, and microfluidics is addressed. The current challenges associated with 3D-printing of functional microdevices are also addressed, as well as future directions to improve both the printing techniques and the performance of the printed products.

Colorimetric and Electrochemiluminescence Dual-Mode Sensing of Lead Ion Based on Integrated Lab-on-Paper Device

A highly selective two-point separation strategy was designed based on a cross-like all-in-one lab-on-paper analytical device. The stable and cleavable enzyme-coated reduced graphene oxide (rGO)-PdAu probe was fabricated as the signal reporter to enable the visualization and electrochemiluminescence (ECL) dual-mode sensing of Pb²⁺. Concretely, the experimental workflow consists of the following process: (i) fabrication of the lab-on-paper device and growth of Au nanoparticles on ECL detection zone, (ii) immobilization of Pb²⁺-specific DNAzyme, and (iii) hybridization between DNAzyme and rGO-PdAu-glucose oxidase (GOx) labeled oligonucleotide to form the double-stranded DNA. Upon addition of Pb²⁺ into the prepared system, the double-helix structure of the DNA was destroyed, resulting in the release of cleaved rGO-PdAu-GOx probe to visualization bar to promote the effective oxidation and color change of 3,3',5,5'-tetramethylbenzidine. As a consequence, the color change can be recognized by naked eye, meanwhile GOx on an uncleaved signal probe can oxidize glucose along with the H₂O₂ production. As a co-reaction reagent for luminol ECL system, the concentration of H₂O₂ is proportional to the ECL intensity, which constitutes a new mechanism for colorimetric and ECL dual mode to detect Pb²⁺. With the method developed here, the concentration of Pb²⁺ could be easily determined by the naked eye within a linear range from 5 to 2000 nM, as well as by monitoring the decreased ECL intensity of luminol in a linear range of 0.5-2000 nM. This work not only constructs a simple and versatile platform for on-site visible monitoring of Pb²⁺ in tap water and river water but also furnishes a strategy for designing a dual-mode sensing toward different heavy metal ions based on specific DNAzyme in the fields of environmental monitoring-related technologies.

Plasmonic Sensing with 3D Printed Optics

Three-dimensional (3D) printing has undergone an exponential growth in popularity due to its revolutionary and near limitless manufacturing capabilities. Recent trends have seen this technology utilized across a variety of scientific disciplines, including the measurement sciences, but precise fabrication of optical components for high-performance biosensing has not yet been demonstrated. We report here 3D printing of high-quality, custom prisms by stereolithography that enable Kretschmann-configured plasmonic sensing of bacterial toxins. Simple benchtop polishing procedures render a smooth surface that supports propagation of surface plasmon polaritons with a deposited gold layer, which exhibit high bulk refractive index sensitivities and are capable of discriminating trace levels of cholera toxin on a supported lipid membrane interface. Further evidence of the flexibility of this manufacturing technique is demonstrated with printed prisms of varied geometries and in situ monitoring of nanoparticle growth by total internal reflection spectroscopy. This work represents the first example of 3D printed light-guiding sensing platforms and demonstrates the versatility and broad perspective of 3D printing in optical detection.

3D-Printed Microflow Injection Analysis Platform for Online Magnetic Nanoparticle Sorptive Extraction of Antimicrobials in Biological Specimens as a Front End to Liquid Chromatographic Assays

In this work, the concept of 3D-printed microflow injection (3D-μFI) embodying a dedicated multifunctional 3D-printed stator onto a rotary microvalve along with a mesofluidic sample preparation platform is proposed for the first time. A transparent 3D-printed stereolithographic mesofluidic chip device accommodating polyaniline (PANI) decorated magnetic nanoparticles (32.5 ± 3.8 mg) is harnessed to in-line sorptive microextraction as a front end to liquid chromatography with peak focusing. As a proof-of-concept application, the 3D-μFI assembly was resorted to matrix cleanup and automatic programmable-flow determination of organic emerging contaminants (4-hydroxybenzoate analogues and triclosan as antimicrobial model analytes) in human saliva and urine samples. By using a sample volume of 1.0 mL with a loading flow rate of 200 μL min^-1, an eluent volume of 120 μL at 80 μL min^-1, and online HPLC injection of 300 μL of the mixture of eluate and Milli-Q water (in a 1:2 ratio) to prevent band broadening effects of the most polar analytes, the limits of detection (3σ criterion) ranged from 1.1 to 4.5 ng mL^-1 for methylparaben (MP), ethylparaben (EP), propylparaben (PrP), phenylparaben (PhP), butylparaben (BP), and triclosan (TCS). Enhancement factors of 16-25 were obtained for the target analytes. Spike recoveries ranged from 84 to 117% for both saliva and urine samples. The online 3D-μFI hyphenated method is synchronized with the chromatographic separation and features a chip lifetime of more than 20 injections with minimal losses of moderately nonpolar compounds on the walls of the mesofluidic device.

Cerium Dioxide-Mediated Signal "On-Off" by Resonance Energy Transfer on a Lab-On-Paper Device for Ultrasensitive Detection of Lead Ions

In this report, a 3D microfluidic lab-on-paper device for ultrasensitive detection of lead cation was designed using phoenix tree fruit-shaped CeO₂ nanoparticles (PFCeO₂ NPs) as the catalyst and 50 nm silver NPs (Ag NPs) as the quencher. First, snowflake-like Ag NPs were grown on the paper working electrode through an in situ growth method and used as a matrix for DNAzymes that were specific for lead ions (Pb²⁺). After the addition of Ag NP-labeled substrate strands, the Ag NPs restrained the electrochemiluminescence (ECL) intensity of luminol greatly through the resonance energy transfer from luminol to Ag NPs. However, under the existence of Pb²⁺, the substrate strands were separated, and then PFCeO₂ NP-labeled signal strands were hybridized with the DNAzymes. The ECL signal was improved greatly under the fast catalytic reaction between PFCeO₂ NPs and H₂O₂, which converted the response from signal off to signal on state, resulting in sensitive detection of Pb²⁺. Under the optimal conditions, the ECL signal response exhibited a good linear relationship with the logarithm of lead cation in a wide linear range of 0.05-2000 nM and an ultralow detection limit of 0.016 nM. Meanwhile, a sensor featured with good specificity, acceptable stability, reproducibility, and low cost provides a promising portable, simple, and effective strategy for Pb²⁺ detection.

Additive Biotech-Chances, challenges, and recent applications of additive manufacturing technologies in biotechnology

The diversity and complexity of biotechnological applications are constantly increasing, with ever expanding ranges of production hosts, cultivation conditions and measurement tasks. Consequently, many analytical and cultivation systems for biotechnology and bioprocess engineering, such as microfluidic devices or bioreactors, are tailor-made to precisely satisfy the requirements of specific measurements or cultivation tasks. Additive manufacturing (AM) technologies offer the possibility of fabricating tailor-made 3D laboratory equipment directly from CAD designs with previously inaccessible levels of freedom in terms of structural complexity. This review discusses the historical background of these technologies, their most promising current implementations and the associated workflows, fabrication processes and material specifications, together with some of the major challenges associated with using AM in biotechnology/bioprocess engineering. To illustrate the great potential of AM, selected examples in microfluidic devices, 3D-bioprinting/biofabrication and bioprocess engineering are highlighted.

Steric paper based ratio-type electrochemical biosensor with hollow-channel for sensitive detection of Zn2

The construction of flexible platform possessing the functions of immobilizing, separating, rinsing, and high-throughput analysis plays a significant role in biological and clinical research. Herein, hollow-channel technique was integrated with lab-on-paper for the simultaneous determination of two different concentrations of Zn²⁺ based on the origami principle, in which microfluidic channels were first patterned on a cellulose paper using commercial solid-state wax printer. Hollow-channels were created by laser cutting method as the role of both injecting ending and reaction tank. After screen printing three electrodes system, the resulting planar paper sheets were then folded into steric structures and functionalized by in-situ synthesized reduced graphene oxide. As a proof-of-concept, such lab-on-paper device was employed in the ratiometric electrochemical monitoring of zinc ion from the environment and HepG2 cells extract, by combining with co-catalysis of porous metal-organic frameworks and hemin/G-quadruplex toward H₂O₂ in the linear range of 0.1-7,000nmol/L. The results indicated that integrating hollow-channel with steric lab-on-paper offered a new methodological approach for the development of metal ions monitoring research. It is believed that it could be useful for various point-of-care related research fields, such as, on-site environmental monitoring, food safety, and disease diagnosis.