Advancing the Diagnosis of Periprosthetic Joint Infections: Integrated Microfluidic Platform for Alpha-Defensins-Specific Aptamer Selection and Its Analytical Applications

Periprosthetic joint infections (PJIs) pose a significant challenge in orthopedic surgery, particularly total joint arthroplasty (TJA), due to the potential for implant failure and increased patient morbidity. Early and accurate detection of PJIs is crucial for timely intervention and better patient prognosis. Herein, we successfully screened a high-affinity aptamer targeting alpha-defensin complex human neutrophil protein 1-3 (HNP 1-3; potential PJI biomarkers in synovial fluid [SF]) for the first time using systematic evolution of ligands by exponential enrichment (SELEX) on an integrated microfluidic platform. The compact microfluidic device enabled efficient screening, with each round completed within <2 h, comprising five rounds of positive selection, two rounds of negative selection, and one round of competitive selection. A novel one-aptamer-one-antibody assay was further developed from the optimal aptamer screened, and it could accurately quantify HNP 1-3 in SF within 3 h with only ∼50 μL of SF. The assay demonstrated strong binding affinity and specificity for the target protein in SF. Thirteen PJI SF samples were accurately diagnosed and the assay was accurate over a wide dynamic range (0.32-100 mg/L). This study has showcased a rapid and accurate diagnostic tool for PJI detection, which should see widespread use in the clinic, holding promise for potential analytical applications in orthopedic surgery and improving patient care.

A self-driven, microfluidic, integrated-circuit biosensing chip for detecting four cardiovascular disease biomarkers

Cardiovascular diseases (CVDs) claimed the lives of nearly 21 million people worldwide in 2021, accounting for 30% of global deaths. However, one in five CVD patients is unaware that they have the disease, emphasizing the need for accurate biomarker monitoring. Herein we developed an integrated microfluidic system (IMS) for rapid quantification of four CVD biomarkers, including N-terminal pro B-type natriuretic peptide (NT-proBNP), fibrinogen, cardiac troponin I (cTnI), and C-reactive protein (CRP)- via aptamer-coated interdigitated electrodes (IDE) with integrated circuits (IC) and a self-driven IMS for sample treatment. The device was composed of plasma filtration, metering, and fluidic delay modules, and the former could extract 45% of plasma from a 20-μL blood sample; the metering module could quantify 5 μL of plasma within 90 s. Subsequently, the plasma was transported to a detection chamber, where IC-based IDE sensors made measurements within 5 min. The entire 15-min process allowed us to evaluate biomarkers across a wide dynamic range: NT-proBNP (0.1-10,000 pg/mL), fibrinogen (50-1,000 mg/dL), cTnI (0.1-10,000 pg/mL), and CRP (0.5-9 mg/L). Given that spiked blood samples were measured with reasonable accuracy (>80%), the IMS could see utility in CVD risk assessment and personalized medicine.

Nanoscale sorting of extracellular vesicles via optically-induced dielectrophoresis on an integrated microfluidic system

We reported a microfluidic system for sorting of extracellular vesicles (EVs), which can house DNAs, RNAs, lipids, proteins, and metabolites that are important in intercellular communication. Their presence within bodily fluids has demonstrated potential in both clinical diagnostic and therapeutic applications. Furthermore, EVs exhibit distinct subtypes categorized by their sizes, each endowed with unique biophysical properties. Despite several existing techniques for EV isolation and purification, diminished purity and prolonged processing times still hamper clinical utility; comprehensive capture of EVs remains an ongoing pursuit. To address these challenges, we devised an innovative method for automated sorting of nano-scale EVs employing optically-induced dielectrophoresis on an integrated microfluidic chip. With this approach, EVs of three distinct size categories (small: 100-150 nm, medium-sized: 150-225 nm, and large: 225-350 nm) could be isolated at a purity of 86%. This new method has substantial potential in expediting EV research and diagnostics.

An integrated microfluidic system for automatic detection of cholangiocarcinoma cells from bile

Cholangiocarcinoma (CCA) is an aggressive cancer that originates from the epithelial cells lining the bile ducts. Due to its location deep within the body and nonspecific symptoms in the early stages, it is often diagnosed at the advanced stage, thus leading to worse prognosis. Circulating tumor cells within liquid biopsies (i.e. blood) have been considered as promising biomarkers for CCA diagnosis, though current methods for profiling them are not satisfactory in terms of sensitivity and specificity. Herein we developed a new cancer cell probing and immuno-tracking assay known as "CAPTURE", which was performed on an integrated microfluidic system (IMS) to automate CCA diagnosis from bile with a sample amount of only 1 mL. The assay utilized magnetic beads surface-coated with two affinity reagents, a nucleic acid aptamer (HN16) and a glycosaminoglycan (SCH 45-mix), for capturing cancer cells in bile; the "gold standard" anti-epithelial cell adhesion molecule was used as a comparison. In a single-blind test of 54 CCA-positive (+) and 102 CCA-negative (-) clinical samples, sensitivities and specificities of 96 and 80%, respectively, were documented with the CAPTURE assay on-bench. An IMS composed of a centrifugal module for sample pretreatment and a CAPTURE module for cell capture and staining was integrated with a new "vertical integration module" for detecting cancer cells from bile without human intervention. Furthermore, a novel micro-tier structure within the centrifugal module was designed to block passage of gallbladder stones with diameters >1 mm, thereby preventing their interference during the subsequent CAPTURE assay. Improved sensitivity and specificity (100 & 83%, respectively) by using three affinity reagents were achieved on the IMS when using 26 clinical bile samples, confirming its clinical bio-applicability for CCA diagnosis. This approach could be therefore used for early-stage CCA diagnostics, ideally enabling effective treatment, as well as reducing potential for relapse.

A paper-based aptamer-sandwich assay for detection of HNP 1 as a biomarker for periprosthetic joint infections on an integrated microfluidic platform

BACKGROUND

Total joint arthroplasty (TJA) has significantly improved the quality of life for millions suffering from end-stage arthritis. However, periprosthetic joint infections (PJI) remain a serious complication, necessitating extensive interventions and prolonged antimicrobial treatments. The aging population is expected to lead to a rise in TJA cases, subsequently increasing the incidence of PJI, particularly in the elderly who face higher mortality rates. Current diagnostic methods for suspected PJI, such as radiographs and biochemical markers like CRP and ESR, exhibit limited sensitivity. Therefore, there is a critical need for a specific synovial fluid biomarker assay to enhance PJI diagnosis using specific SF-based assay.

RESULTS

This study introduces a novel microfluidic chip with a paper-based aptamer-sandwich assay for the quantitative detection of HNP 1, a crucial PJI biomarker, in synovial fluid. The assay leverages the advantages of aptamers over antibodies, demonstrating high selectivity and affinity for target molecules. The integration of a nitrocellulose (NC) membrane onto the microfluidic platform represents a significant advancement, reducing background signals and simplifying the assay procedure without intricate procedure and pre-treatment. The NC membrane-based microfluidic device offers rapid, cost-effective, and highly sensitive detection of HNP 1, with a limit of detection of 0.5 mg L-1. The microfluidic device demonstrates exceptional performance, detecting up to four clinical samples in approximately 42 min on a single chip with 100 % accuracy, as confirmed by analysis of 12 clinical samples and comparison with "gold-standard". Moreover, the assay exhibits a wide dynamic range of 0.5-100 mg L-1, underscoring its potential as a powerful tool for PJI diagnosis in clinical settings.

SIGNIFICANCE

This work introduces a paper-based microfluidic system tailored for rapid HNP 1 detection using synovial fluid near joint region (and not serum via blood) for better diagnosis. The innovative paper-based aptamer-sandwich assay yields results within 42-min. Significantly, it boasts a wide dynamic range, detecting levels from an impressive 0.5 mg L-1, crucial in the 2.6 mg L-1 threshold region. This heightened sensitivity and expansive detection capability establish our assay as a leader in PJI diagnostics, promising unmatched precision and efficiency in clinical applications.

Highly-specific aptamer targeting SARS-CoV-2 S1 protein screened on an automatic integrated microfluidic system for COVID-19 diagnosis

Variants of the severe acute respiratory syndrome coronavirus (SARS-CoV-2) have evolved such that it may be challenging for diagnosis and clinical treatment of the pandemic coronavirus disease-19 (COVID-19). Compared with developed SARS-CoV-2 diagnostic tools recently, aptamers may exhibit some advantages, including high specificity/affinity, longer shelf life (vs. antibodies), and could be easily prepared. Herein an integrated microfluidic system was developed to automatically carry out one novel screening process based on the systematic evolution of ligands by exponential enrichment (SELEX) for screening aptamers specific with SARS-CoV-2. The new screening process started with five rounds of positive selection (with the S1 protein of SARS-CoV-2). In addition, including non-target viruses (influenza A and B), human respiratory tract-related cancer cells (adenocarcinoma human alveolar basal epithelial cells and dysplastic oral keratinocytes), and upper respiratory tract-related infectious bacteria (including methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae), and human saliva were involved to increase the specificity of the screened aptamer during the negative selection. Totally, all 10 rounds could be completed within 20 h. The dissociation constant of the selected aptamer was determined to be 63.0 nM with S1 protein. Limits of detection for Wuhan and Omicron clinical strains were found to be satisfactory for clinical applications (i.e. 4.80 × 10¹ and 1.95 × 10² copies/mL, respectively). Moreover, the developed aptamer was verified to be capable of capturing inactivated SARS-CoV-2 viruses, eight SARS-CoV-2 pseudo-viruses, and clinical isolates of SARS-CoV-2 viruses. For high-variable emerging viruses, this developed integrated microfluidic system can be used to rapidly select highly-specific aptamers based on the novel SELEX methods to deal with infectious diseases in the future.

Automatic Detection of Two Synovial Fluid Periprosthetic Joint Infection Biomarkers on an Integrated Microfluidic System

Post-arthroplasty periprosthetic joint infection (PJI) is a serious ailment that can be difficult to diagnose. Herein, we developed a novel integrated microfluidic system (IMS) capable of detecting two common PJI biomarkers, alpha defensin human neutrophil peptide 1 (HNP-1) and C-reactive protein (CRP), from synovial fluid (SF). A magnetic bead-based one-aptamer-one-antibody assay was carried out automatically within 45 min on a single chip for simultaneous detection of both biomarkers at concentration ranges of 0.01-50 (HNP-1) and 1-100 (CRP) mg/L. It is the first report for utilizing these two biomarkers as targets to establish the new one-aptamer-one-antibody assay to detect PJI on-chip, and the aptamers demonstrated high specificity to their SF targets. As 20 clinical samples were correctly diagnosed with our IMS (verified by a common gold standard kit), it could serve as a promising tool for PJI diagnostics.

An aptamer-based sandwich assay for detection of alpha-defensin human neutrophil protein 1 on a microfluidic platform

The diagnosis of periprosthetic joint infection (PJI) remains a labor-intensive and challenging issue, with life-threatening complications associated with misdiagnoses. Superior diagnostic approaches are therefore urgently needed, and synovial biomarkers are gaining substantial attention in this capacity. A new aptamer-based sandwich assay was developed where the aptamer probes specific to one such biomarker, alpha-defensin human neutrophil protein 1 (HNP 1), was integrated herein into a new microfluidic platform. The magnetic beads coated with the primary aptamer probe were able to bind the target protein with high affinity and high specificity in synovial fluid and a fluorescent-labelled secondary aptamer were further used to quantify HNP 1 in a sandwich approach. Up to four clinical samples with low volume (∼50 μL each) in a much faster assay including detection within <60 min with 100% accuracy (with totally 13 clinical samples without the need of sample pretreatment) through the use of the aptamer-based sandwich assay were automatically detected on a single chip. The wide dynamic range of this compact device, 0.5-100 mg/L, highlights its utility for future PJI diagnostics in the clinic.

Electromagnetically-driven integrated microfluidic platform using reverse transcription loop-mediated isothermal amplification for detection of severe acute respiratory syndrome coronavirus 2

Rapid, sensitive and accurate diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is of great need for effective quarantining and treatment. Real-time reverse-transcription polymerase chain reaction requiring thermocyling has been commonly used for diagnosis of SARS-CoV-2 though it may take two to 4 h before lengthy sample pretreatment process and require bulky apparatus and well-trained personnel. Since multiple reverse transcription loop-mediated isothermal amplification (multiple RT-LAMP) process without thermocycling is sensitive, specific and fast, an electromagnetically-driven microfluidic chip (EMC) was developed herein to lyse SARS-CoV-2 viruses, extract their RNAs, and perform qualitative analysis of three marker genes by on-chip multiple RT-LAMP in an automatic format within 82 min at a limit of detection of only ∼5000 copies per reaction (i.e. 200 virus/ μL). This compact EMC may be especially promising for SARS-CoV-2 diagnostics in resource-limited countries.

An integrated microfluidic platform featuring real-time reverse transcription loop-mediated isothermal amplification for detection of COVID-19

An integrated microfluidic platform (IMP) utilizing real-time reverse-transcription loop-mediated isothermal amplification (RT-LAMP) was developed here for detection and quantification of three genes of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; i.e., coronavirus diseases 2019 (COVID-19)): RNA-dependent RNA polymerase, the envelope gene, and the nucleocapsid gene for molecular diagnosis. The IMP comprised a microfluidic chip, a temperature control module, a fluidic control module that collectively carried out viral lysis, RNA extraction, RT-LAMP, and the real-time detection within 90 min in an automatic format. A limit of detection of 5 × 10³ copies/reaction for each gene was determined with three samples including synthesized RNAs, inactive viruses, and RNAs extracted from clinical samples; this compact platform could be a useful tool for COVID-19 diagnostics.

An integrated microfluidic platform featuring real-time reverse transcription loop-mediated isothermal amplification for detection of COVID-19

An integrated microfluidic platform (IMP) utilizing real-time reverse-transcription loop-mediated isothermal amplification (RT-LAMP) was developed here for detection and quantification of three genes of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; i.e., coronavirus diseases 2019 (COVID-19)): RNA-dependent RNA polymerase, the envelope gene, and the nucleocapsid gene for molecular diagnosis. The IMP comprised a microfluidic chip, a temperature control module, a fluidic control module that collectively carried out viral lysis, RNA extraction, RT-LAMP, and the real-time detection within 90 min in an automatic format. A limit of detection of 5 × 10³ copies/reaction for each gene was determined with three samples including synthesized RNAs, inactive viruses, and RNAs extracted from clinical samples; this compact platform could be a useful tool for COVID-19 diagnostics.

Integrated Microfluidic System for Cell-Free DNA Extraction from Plasma for Mutant Gene Detection and Quantification

Ovarian cancer (OvCa) is among the most severe gynecologic cancers, yet individuals may be asymptomatic during its early stages. Routine, early screening for genetic abnormalities associated with OvCa could improve prognoses, and this can be achieved by detecting mutant genes in cell-free DNA (cfDNA). Herein, we developed an integrated microfluidic chip (IMC) that could extract cfDNA from plasma and automatically detect and quantify mutations in the OvCa biomarker BRCA1. The cfDNA extraction module relied on a vortex-type micromixer to mix cfDNA with magnetic beads surface-coated with cfDNA probes and could isolate 76% of molecules from a 200 μL plasma sample in 45 min. The cfDNA quantification module, which comprised a micropump that evenly distributed 4.5 μL of purified cfDNA into the on-chip, allele-specific quantitative polymerase chain reaction (qPCR) zones, was capable of quantifying mutant genes within 90 min. By automating the cfDNA extraction and qPCR processes, this IMC could be used for clinical screening for OvCa-associated mutations.

Aptamer selection against alpha-defensin human neutrophil peptide 1 on an integrated microfluidic system for diagnosis of periprosthetic joint infections

Periprosthetic joint infections (PJIs) arising from joint arthroplasty are dreadful, yet difficult to diagnose in subtle cases. Definite diagnosis requires microbiological culture to confirm the causative pathogens. However, up to 40% of culture-negative PJI needs other surrogate biomarkers such as human neutrophil peptide 1 (HNP 1) to improve diagnostic accuracy or gauge therapeutic responses. To devise a diagnostic method, systematic evolution of ligands by exponential enrichment (SELEX) (five rounds) was used to screen PJI biomarkers on a compact (20 × 20 × 35 cm), integrated microfluidic system equipped with two separate Peltier devices and one magnetic control module where an aptamer with high affinity and specificity for HNP 1, which has been used as one of the synovial fluid (SF) biomarkers for detecting PJI, was identified for the first time. Two rounds of negative selection (with immunoglobulin G & human serum album) on-chip followed by one round of unique "competitive selection" with SF extracted from PJI patients validated the specificity of the HNP 1 aptamer. The dissociation constant was measured to be 19 nM. The applicability of SF HNP 1 levels for diagnosing PJI was then verified by a new aptamer-based enzyme-linked immunosorbent assay (ELISA)-like assay. It is envisioned that this new aptamer and the associated assay could be used in future clinical applications.

Isolation and quantification of extracellular vesicle-encapsulated microRNA on an integrated microfluidic platform

Ovarian cancer (OvCa) is the most fatal among gynecological cancers and affects many women worldwide. Since OvCa is prone to metastasis, which significantly increases chances of death, biomarkers for early-stage OvCa are greatly needed. This study develops an integrated microfluidic platform for isolating and quantifying one of the OvCa blood biomarkers. As a demonstration, microRNA-21 (miRNA-21), which is one of the important biomarkers for cancers, was isolated and measured in this study. Extracellular vesicles (EVs) in blood were first captured and isolated by anti-CD63-coated magnetic beads. Then, EV-encapsulated miRNA-21 was isolated by complementary DNA-coated magnetic beads, and finally the isolated miRNA-21 was quantified by digital polymerase chain reaction (digital PCR, dPCR). The integrated chip featured a sample treatment module and a miRNA quantification module that automated the entire process, and the limit of detection (LOD) was 11 copies per mL. The inaccuracy of the miRNA quantification module (i.e. dPCR) was found to be <12%. Additionally, spiked samples and clinical samples were used to test the performance of the developed platform. It is envisioned that the developed system can serve as a valuable and promising tool for OvCa biomarker measurements.

An integrated microfluidic platform for detection of ovarian clear cell carcinoma mRNA biomarker FXYD2

In this work we developed an integrated microfluidic system for automatically detecting the ovarian clear cell carcinoma (OCCC) biomarker FXYD2. Dealing with ascites from ovarian cancer patients, capture of cancer cells, isolation of messenger RNA, and quantitative reverse-transcription polymerase chain reaction were integrated into a single microfluidic chip and carried out on-chip automatically. OCCC is a subtype of ovarian cancer with a high mortality risk, and a high FXYD2 gene expression level was shown to be closely associated with OCCC. The lowest limit of quantification using a benchtop protocol of this system could be as low as 100 copies per sample. By normalizing the expression to a housekeeping gene, GAPDH, a simple cycle threshold ratio index could distinguish high FXYD2 expression cells from the low-expression ones. This developed platform may therefore facilitate future OCCC diagnosis and/or prognosis.

A multiplexed nanoliter array-based microfluidic platform for quick, automatic antimicrobial susceptibility testing

Antimicrobial resistance stemming from indiscriminate usage of antibiotics has emerged as a global healthcare issue with substantial economic implications. The inefficacy of commonly used antibiotics combined with superfluous consumption has worsened the issue. Rapid antimicrobial susceptibility testing (AST) to antibiotics can be advantageous in thwarting bacterial infections. Therefore, this study developed a simple nanoliter array-based microfluidic platform for performing rapid AST, which can handle and manipulate liquids both in nanoliter and microliter volumes. The platform consisted of two microfluidic devices, one for performing AST and another for diluting antibiotics and these two were suitably integrated. The microfluidic device used for generating microarrays for AST experiments is single-layered (no air layer) and has no active microvalves and air hole, which makes the device easy to fabricate and use. The loading process ensures uniform distribution of bacteria and relies on displacing the air from microarrays through porous polydimethylsiloxane membranes. Furthermore, the chip for dilution consisted of active microfluidic components, and could prepare and test seven different concentrations of antibiotics, which make the platform multiplexed and be capable of evaluating minimum inhibitory concentrations (MICs), a clinically relevant parameter. MIC determination requires less number of bacteria (∼2000) and hence shortens the pre-culture step, i.e. bacteria culture in blood and urine. This automated system demonstrated AST and evaluated MICs using Escherichia coli and two antibiotics, including ampicillin and streptomycin, and the results were ascertained using a gold standard method. It only took 8-9 h to perform AST, which is substantially less compared to a conventional process and hence is of high clinical utility.

Isolation and recovery of extracellular vesicles using optically-induced dielectrophoresis on an integrated microfluidic platform

Cell-released, membrane-encapsulated extracellular vesicles (EVs) serve as a means of intercellular communication by delivering bioactive cargos including proteins, nucleic acids and lipids. EVs have been widely used for a variety of biomedical applications such as biomarkers for disease diagnosis and drug delivery vehicles for therapy. Herein, this study reports a novel method for label-free, contact-free isolation and recovery of EVs via optically-induced dielectrophoresis (ODEP) on a pneumatically-driven microfluidic platform with minimal human intervention. At an optimal driving frequency of 20 kHz and a voltage of 20 Vpp, an ODEP force from a 75 μm moving light beam was characterized to be 23.5-97.7 fN in 0.2 M sucrose solution. Furthermore, rapid enrichment of EVs with a small volume of only 27 pL in 32 s achieved an increase of 272-fold by dynamically shrinking circular light patterns. Moreover, EVs could be automatically isolated and recovered within 25 min, while achieving a releasing efficiency of 99.8% and a recovery rate of 52.2% by using an integrated microfluidics-based optically-induced EV isolation (OIEV) platform. Given the capacity of label-free, contact-free EV isolation, and automatic, easy-releasing EV recovery, this integrated OIEV platform provides a unique approach for EV-based disease diagnosis and drug delivery applications.

An automated and portable antimicrobial susceptibility testing system for urinary tract infections

Urinary tract infections (UTIs) are bacterial infections that 1) commonly affect females, 2) can pose high risks to impair kidney function, 3) are often treated with broad-spectrum antibiotics, and 4) are associated with high recurrence rates due to the evolution of drug-resistant strains. To choose the appropriate antibiotic, the minimum inhibitory concentration (MIC) among a panel of antibiotics should be determined before administration to avoid inadequate dosing or use of wrong antibiotics. To meet with the unmet needs, we developed a bead-based method for bacterial preconcentration with capture rates ranging from 20-50% and then automatically performed on-chip AST on an automated device which was composed of a pneumatic control module, a temperature control module and a chip image processing module. The developed portable system was capable of automatically conducting AST and MIC measurements using urine samples (via image analysis) in only 4.5-9 h and tested on four common UTIs bacterial strains. This compact system may therefore be promising for point-of-care personalized medicine in the near future.

Optimization of aptamer selection on an automated microfluidic system with cancer tissues

Cancer is among the world's most deadly inflictions, and early diagnosis is critical. Aptamers have shown utility as cancer probes since they can be screened rapidly in vitro against cancer tissues using systematic evolution of ligands by exponential enrichment (SELEX) process. However, bench-top SELEX procedures are relatively labor-intensive and time-consuming; ideally, they could instead be carried out on microfluidic devices, yet this requires optimization of buffer and reaction conditions. Herein an integrated microfluidic system (IMS) was established to automatically carry out the optimization of aptamer selection. A "formulation chip" was developed that could mix salt solutions at differing final concentrations, and the resulting optimal binding buffer was transferred to another "optimization-SELEX chip" for the following tissue-SELEX. Two aptamers were successfully screened; one of which, H-45, exhibited high specificity and affinity towards ovarian cancer tissue samples, suggesting that this IMS might be a promising device for screening of cancer associated aptamers for cancer diagnosis.

An integrated microfluidic system for early detection of sepsis-inducing bacteria

Since early diagnosis of sepsis may assist clinicians in initiating timely, effective, and prognosis-improving antibiotic therapy, we developed an integrated microfluidic chip (IMC) for rapid isolation of both Gram-positive and Gram-negative bacteria from blood. The device comprised a membrane-based filtration module (90 min operating time), a bacteria-capturing module using a micro-mixer containing magnetic beads coated with "flexible neck" regions of mannose-binding lectin proteins for bacteria capture (20 min), and a miniature polymerase chain reaction (PCR) module for bacteria identification (90 min via TaqMan® probe technology). The filter separated all white blood cells and 99.5% of red blood cells from bacteria, which were captured at rates approaching 85%. The PCR assay's limit of detection was 5 colony-forming units (CFU) per reaction, and the entire process was completed in only 4 h. Since this is far less than that for culture-based approaches, this IMC may serve as a promising device for detection of sepsis.

An aptamer interacting with heat shock protein 70 shows therapeutic effects and prognostic ability in serous ovarian cancer

Ovarian cancer (OvCa) is the most lethal gynecologic malignancy owing to its high chemoresistance and late diagnosis, which lead to a poor prognosis. Hence, developing new therapeutic modalities is important for OvCa patient treatment. Our previous results indicated that a novel aptamer, Tx-01, can specifically recognize serous carcinoma cells and tissues. Here, we aim to clarify the clinical role and possible molecular mechanisms of Tx-01 in OvCa. Immunostaining and statistical analysis were performed to detect the interaction of Tx-01 and heat shock protein 70/Notch1 intracellular domain (HSP70/NICD) in OvCa. The in vitro and in vivo experiments were carried out to demonstrate the potential mechanisms of Tx-01. Results show that Tx-01 reduced serous OvCa OVCAR3 cell migration and invasion and inhibited HSP70 nuclear translocation by interrupting the intracellular HSP70/NICD interaction. Furthermore, Tx-01 suppressed serous-type OVCAR3 cell tumor growth in vivo. Tx-01 acts as a prognostic factor through its interaction with membrane-bound HSP70 (mHSP70 that locates on the cell surface without direct interaction to NICD) on ascitic circulating tumor cells (CTCs) and is reported to be involved in natural killer (NK) cell recognition and activation. Our data demonstrated that Tx-01 interacted with HSP70 and showed therapeutic and prognostic effects in serous OvCa. Tx-01 might be a potential inhibitor for use in serous OvCa treatment.

Rapid antimicrobial susceptibility tests on an integrated microfluidic device for precision medicine of antibiotics

This study reports an integrated microfluidic device that was capable of executing rapid antimicrobial susceptibility tests with one, two, or even three antibiotics against two clinically isolated multi-drug-resistant bacteria strains (including carbapenem-resistant Escherichia coli and methicillin-resistant Staphylococcus aureus). Bacteria were automatically mixed for 10 min with serially diluted antibiotics with a novel, membrane-type micromixer consisting of two circular micropumps, and the minimum inhibitory concentrations (MIC) were then determined via simple colorimetric reactions in only 4.5-6 h using only 3 μL of bacteria sample of each reaction (as opposed to 24 h and 50 μL, respectively, with the conventional broth micro-dilution method). In addition to determining MICs of antibiotics (ceftazidime, gentamicin, meropenem, vancomycin and linezolid), interaction effects across antibiotics combinations (gentamicin/meropenem or ceftazidime/gentamicin/meropenem) at different dosages were explored. The efficacy of polypharmacy showed additivity when gentamicin or ceftazidime/gentamicin were combined with meropenem to treat carbapenem-resistant Escherichia coli. This represents the first time that the perplexing clinical decision to choose multiple antibiotics for combination therapy against drug resistant bacteria can be realized on an integrated microfluidic device within 6 h.

Detection and isolation of free cancer cells from ascites and peritoneal lavages using optically induced electrokinetics (OEK)

Detection of free gastric cancer cells in peritoneal lavages and ascites plays a vital role in gastric cancer. However, due to the low content of cancer cells in patients' peritoneal lavages, traditional detection methods lack sensitivity and cannot satisfy clinical demand. In this study, we used an optically induced electrokinetics (OEK) microfluidic method for label-free separation and characterization of patient gastric cancer cells. This method showed high effectiveness and sensitivity. We successfully separated cancer cells from a simulated peritoneal lavage mixture of gastric cancer cell lines and peritoneal lavage cells in a ratio of 1:1000. We further separated gastric cancer cells from six patients' ascites with purity up to 71%. In addition, we measured the cell membrane capacitances, which may be used as a biomarker for gastric cancer cells. Thus, our method can be used to effectively and rapidly detect peritoneal metastasis and to acquire cellular electrical information.

Dual aptamer assay for detection of Acinetobacter baumannii on an electromagnetically-driven microfluidic platform

Rapid detection of Acinetobacter baumannii (AB) is critical for limiting healthcare-associated infections and providing the best treatment for infected individuals. Herein an integrated microfluidic device for AB diagnosis utilizing a new dual aptamer assay was developed for point-of-care (POC) applications; magnetic beads coated with AB-specific aptamers were used to capture bacteria, and quantum dots (QD) bound to a second aptamer were utilized to quantify the amount of bacteria with a light-emitting diode (LED)-induced fluorescence module integrated into the device. Within a rapid detection of 30 min, a limit of detection of only 100 colony-forming units (CFU)/reaction was obtained, and all necessary microfluidic devices were actuated by a combination of permanent magnets and electromagnets. The pumping rate of the micropump was 270 μL/min at only 10 V, which is amenable for POC applications with lower power consumption, and only 10 μL of sample and reagents were required. Given these attributes, an automatic POC device was demonstrated which could perform a dual aptamer assay to diagnose AB by using electromagnetically-driven microfluidic system. This system provides a rapid, sensitive, low power and reagents consumption and fully automated for AB detection by using a dual aptamer assay. It will allow rapid clinical diagnosis of AB in the near future.

An integrated microfluidic system for rapid, automatic and high-throughput staining of clinical tissue samples for diagnosis of ovarian cancer

Accurate cancer diagnostic methods are of urgent need. Since traditional immunohistochemistry (IHC)-based approaches, while reliable, are labor-intensive and require well-trained technicians, we developed an integrated microfluidic platform capable of labeling ovarian cancer biomarkers (i.e. aptamer) within formalin-fixed, paraffin embedded tissues via molecular probes. Both aptamer-based 1) fluorescent staining and 2) IHC staining of clinical tissue samples could be automated in the microfluidic system in only 2-3 h (40-50% faster than conventional approaches) with <0.5 mL of reagents, signifying that this device could serve as a promising diagnostic tool for ovarian cancer.

Screening of multiple hemoprotein-specific aptamers and their applications for the binding, quantification, and extraction of hemoproteins in a microfluidic system

The blood hemoproteins, albumin, γ-globulin, and fibrinogen, serve as biomarkers for a variety of human diseases, including kidney and hepatorenal syndromes. Therefore, there is a need to quickly and accurately measure their concentrations in blood. Herein, nucleic acid aptamers demonstrating high affinity and specificity toward these hemoproteins were selected via systematic evolution of ligands by exponential enrichment, and their ability to capture their protein targets was assessed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by a tetramethyl benzidine assay. The limits of detection for the hemoproteins were all around 10-3 μM, and dissociation constant values of 131, 639, and 29nM were obtained; capture rates were measured to be 66%, 71%, and 61%, which is likely to be suitable for clinical diagnostics. Furthermore, a multi-layer microfluidic disk system featuring hemoprotein-specific aptamers for depleting hemoproteins was demonstrated. It could be a promising approach to use aptamers to replace conventional antibodies.

Two-step magnetic bead-based (2MBB) techniques for immunocapture of extracellular vesicles and quantification of microRNAs for cardiovascular diseases: A pilot study

Extracellular vesicles (EVs) have attracted increasing attention because of their potential roles in various biological processes and medical applications. However, isolation of EVs is technically challenging mainly due to their small and heterogeneous size and contaminants that are often co-isolated. We have thus designed a two-step magnetic bead-based (2MBB) method for isolation a subset of EVs as well as their microRNAs from samples of a limited amount. The process involves utilizing magnetic beads coated with capture molecules that recognize EV surface markers, such as CD63. Captured EVs could be eluted from beads or lyzed directly for subsequent analysis. In this study, we used a second set of magnetic beads coated with complementary oligonucleotides to isolate EV-associated microRNAs (EV-miRNAs). The efficiencies of 2MBB processes were assessed by reverse transcription-polymerase chain reaction (RT-PCR) with spiked-in exogenous cel-miR-238 molecules. Experimental results demonstrated the high efficiency in EV enrichment (74 ± 7%, n = 4) and miRNA extraction (91 ± 4%, n = 4). Transmission electron micrographs (TEM) and nanoparticle tracking analysis (NTA) show that captured EVs enriched by 2MBB method could be released and achieved a higher purity than the differential ultracentrifugation (DUC) method (p < 0.001, n = 3). As a pilot study, EV-miR126-3p and total circulating cell-free miR126-3p (cf-miR126-3p) in eight clinical plasma samples were measured and compared with the level of protein markers. Compared to cf-miR126-3p, a significant increase in correlations between EV-miR126-3p and cardiac troponin I (cTnI) and N-terminal propeptide of B-type natriuretic peptide (NT-proBNP) was detected. Furthermore, EV-miR126-3p levels in plasma samples from healthy volunteers (n = 18) and high-risk cardiovascular disease (CVD) patients (n = 10) were significantly different (p = 0.006), suggesting EV-miR126 may be a potential biomarker for cardiovascular diseases. 2MBB technique is easy, versatile, and provides an efficient means for enriching EVs and EV-associated nucleic acid molecules.

A structure-free digital microfluidic platform for detection of influenza a virus by using magnetic beads and electromagnetic forces

H1N1, a subtype of influenza A virus, has emerged as a global threat in the past decades. Due to its highly infectious nature, an accurate and rapid detection assay is urgently required. Therefore, this study presents a new type of digital microfluidic platform for H1N1 virus detection by utilizing a one-aptamer/two-antibodies assay on magnetic beads. The droplets containing magnetic beads were driven by electromagnetic forces on a structure-free, super-hydrophobic surface to automate the entire assay within 40 min. With different levels of hydrophobic modification, the droplets could be easily controlled and positioned without any assisted microstructure. The tunable electromagnetic forces could be adjusted for three kinds of operating modes for the manipulations of beads and droplets, including movement of droplets containing magnetic beads, mixing of two droplets and beads extraction out of droplets. When compared with previous studies, the manipulations of droplets and magnetic particles in this study are more flexible as they can be easily adjusted by fine-tuning the magnetic flux density. Furthermore, the magnetic beads also served as three-dimensional substrates for the new enzyme-linked immunosorbent assay (ELISA)-like assay. The magnetic beads were conjugated with aptamers, which have high specificity towards H1N1 viruses such that they could be specifically captured and detected. The horseradish peroxidase-conjugated secondary antibody was then used to activate tyramide-tetramethylrhodamine (TTMR) such that fluorescent signals could be amplified. With this approach, the limit of detection was experimentally found to be 0.032 hemagglutination units/reaction, which is sensitive enough for clinical diagnostics. This kind of digital microfluidic platform with the ELISA-like assay could effectively reduce the consumption of samples and reagents such that the volume of all droplets including the H1N1 sample, antibodies, TTMR and wash buffers was only 20 μL. This is the first time that a digital microfluidic platform was demonstrated such that the entire diagnostic process for influenza A H1N1 viruses could be performed by using electromagnetic forces, which could be promising for rapid and accurate diagnosis of influenza.

Optimization of an enzyme linked DNA aptamer assay for cardiac troponin I detection: synchronous multiple sample analysis on an integrated microfluidic platform

In this study, an enzyme linked DNA aptamer based assay was optimized for human cardiac troponin I (cTnI) detection which is a prominent biomarker for acute myocardial infarction (AMI), on an integrated microfluidic platform. This platform allowed for the multiplex detection of six samples (5 μL per sample), and only 30 min were required for detection. First, cTnI-specific aptamers were surface-coated on magnetic beads. Bead-captured proteins were allowed to bind to a primary cTnI antibody and then to a secondary antibody labelled with horseradish peroxidase. Finally, chemiluminescence intensities were detected for quantification of cTnI. Purified proteins, serum from AMI patients and unknown serum samples were used to test the efficacy of the on-chip system. The limit of detection was measured to be only 12 ng L-1, and off-target effects from other proteins were minimal. This sensitive, cTnI-specific aptamer-based assay could consequently be used for reliable diagnosis of AMI.

A sample-to-answer, portable platform for rapid detection of pathogens with a smartphone interface

Emerging and re-emerging infectious diseases pose global threats to human health. Although several conventional diagnostic methods have been widely adopted in the clinic, the long turn-around times of "gold standard" culture-based techniques, as well as the limited sensitivity of lateral-flow strip assays, thwart medical progress. In this study, a smartphone-controlled, automated, and portable system was developed for rapid molecular diagnosis of pathogens (including viruses and bacteria) via the use of a colorimetric loop-mediated isothermal amplification (LAMP) approach on a passive, self-driven microfluidic device. The system was capable of 1) purifying viral or bacterial samples with specific affinity reagents that had been pre-conjugated to magnetic beads, 2) lysing pathogens at low temperatures, 3) executing isothermal nucleic acid amplification, and 4) quantifying the results of colorimetric assays for detection of pathogens with an integrated color sensor. The entire, 40 min analytical process was automatically performed with a novel punching-press mechanism that could be controlled and monitored by a smartphone. As a proof of concept, the influenza A (H1N1) virus and methicillin-resistant Staphylococcus aureus bacteria were used to characterize and optimize the device, and the limits of detection were experimentally found to be 3.2 × 10^-3 hemagglutinating units (HAU) per reaction and 30 colony-forming units (CFU) per reaction, respectively; both such values represent high enough sensitivity for clinical adoption. Moreover, the colorimetric assay could be both qualitative and quantitative for detection of pathogens. This is the first instance of an easy-to-use, automated, and portable system for accurate and sensitive molecular diagnosis of either viruses or bacteria, and it is envisioned that this smartphone-controlled apparatus may serve as a platform for clinical, point-of-care pathogen detection, particularly in resource-limited settings.

An integrated microfluidic system for on-chip enrichment and quantification of circulating extracellular vesicles from whole blood

Circulating extracellular vesicles (EVs), which can contain a wide variety of molecules such as proteins, messenger ribonucleic acids (mRNAs), micro ribonucleic acids (miRNAs) and deoxyribonucleic acids (DNAs) from cells or tissues of origin, have attracted great interest given their potential to serve as biomarkers that can be harvested in body fluids (i.e., relatively non-invasive). Since enrichment and detection of circulating EVs from whole blood have proven challenging, we report herein a fully integrated microfluidic system combining a membrane-based filtration module (i.e. pneumatically-driven microfluidic devices) and a magnetic-bead based immunoassay capable of automating blood treatment, EV enrichment, and EV quantification directly from human whole blood. Three functional modules were implemented; the first, a stirring-enhanced filtration module for separating plasma from blood cells, was characterized by a plasma recovery rate of 65%, a filtrate flow rate of 22 μL min^-1, and a vesicle recovery rate of 94% within only 8 min (using 500 μL of blood). The second module, a magnetic bead-based EV enrichment device for immunocapture of circulating EVs from plasma, was characterized by a capture rate of 45%. The final module performed an on-chip enzyme-linked immunosorbent assay for plasma EV quantification in plasma. Given the automated capacity of this system, it could show promise in circulating EV research and clinical point-of-care applications.

Correction: Bacterial detection and identification from human synovial fluids on an integrated microfluidic system

Correction for 'Bacterial detection and identification from human synovial fluids on an integrated microfluidic system' by Ting-Hang Liu et al., Analyst, 2019, 144, 1210-1222.

An integrated microfluidic system for antimicrobial susceptibility testing with antibiotic combination

Polypharmacy is routinely administered to fight severe infections, though it has led to rampant multi-drug resistance in many bacterial strains. Preferably, antimicrobial susceptibility testing (AST) would be carried out prior to antibiotic prescription, though it is generally thought to be too complex and labor-intensive. In order to assist clinicians with better antibiotic administration for the effective treatment of bacterial infections, an integrated microfluidic system (IMS) capable of automating AST for 1-2 antibiotics against clinical bacterial pathogens was developed herein. Accurate determination of the minimum and fractional inhibitory concentrations of vancomycin, gentamicin, and linezolid were determined by assaying growth of two clinical methicillin-resistant Staphylococcus aureus isolates via a colorimetric assay on-chip. By applying various antibiotic combinations against a single pathogen in multiple chambers, the IMS could identify the optimal drug combination and the minimum effective dosage by evaluating the fractional inhibitory concentration index. This IMS possessed several advantages over conventional methods, including (1) a 50% reduction in bacterial sample and reagent volume (<50 μL per well), (2) less potential for human error due to its automatic nature, (3) faster liquid manipulation time by integrating the microfluidic components rather than labor-intensive process, and (4) straightforward result interpretation via colorimetric change instead of turbidity degree. Personalized medicine for treatment of bacterial infections may therefore be realized using this IMS.

Generating digital drug cocktails via optical manipulation of drug-containing particles and photo-patterning of hydrogels

An integrated microfluidic system combining 1) an optically-induced-dielectrophoresis (ODEP) module for manipulation of drug-containing particles and 2) an ultraviolet (UV) "direct writing" module capable of patterning hydrogels was established herein for automatic formulation of customized digital drug cocktails. Using the ODEP module, the drug-containing particles were assembled by using moving light patterns generated from a digital projector. The hydrogel, poly(ethylene glycol) diacrylate (PEGDA), was used as the medium in the ODEP module such that the assembled drug-containing particles could be UV-cured and consequently encapsulated in "pills" of specific sizes and shapes by using the UV direct writing module. At an optimal ODEP force of 335 pN, which was achieved in a solution of 15% PEGDA in 0.2 M sucrose, it was possible to manipulate and UV-cure the drug-containing particles. Furthermore, with a digital micromirror device inside the UV direct writing module, different UV patterns could be designed and projected, allowing for the digital drug cocktails to be packaged into different shapes in <60 s. As a demonstration, emulsion droplets containing two different anti-cancer drugs were further tested to show the capability of the developed device. This represents an automatic digital drug cocktail formulating device which stands to revolutionize personalized medicine.

Design and Demonstration of Tunable Amplified Sensitivity of AlGaN/GaN High Electron Mobility Transistor (HEMT)-Based Biosensors in Human Serum

We have developed a swift and simplistic protein immunoassay using aptamer functionalized AlGaN/GaN high electron mobility transistors (HEMTs). The unique design of the sensor facilitates protein detection in a physiological salt environment overcoming charge screening effects, without requiring sample preprocessing. This study reports a tunable and amplified sensitivity of solution-gated electric double layer (EDL) HEMT-based biosensors, which demonstrates significantly enhanced sensitivity by designing a smaller gap between the gate electrode and the detection, and by operating at higher gate voltage. Sensitivity is calculated by quantifying NT-proBNP, a clinical biomarker of heart failure, in buffer and untreated human serum samples. The biosensor depicts elevated sensitivity and high selectivity. Furthermore, detailed investigation of the amplified sensitivity in an increased ionic strength environment is conducted, and it is revealed that a high sensitivity of 80.54 mV/decade protein concentration can be achieved, which is much higher than that of previously reported FET biosensors. This sensor technology demonstrates immense potential in developing surface affinity sensors for clinical diagnostics.

Simultaneous detection of multiple NT-proBNP clinical samples utilizing an aptamer-based sandwich assay on an integrated microfluidic system

Although cardiovascular diseases such as heart failure (HF) affect 30 million people globally, the early detection of HF has, until recently, been difficult and prone to misdiagnoses. Monitoring the circulatory levels of a relatively new biomarker, the N-terminal prohormone of a B-type natriuretic peptide, could be used for early risk evaluation of HF. Therefore, we developed a pneumatically-driven, automatic integrated microfluidic platform equipped with micromixers, micropumps, and microvalves for the simultaneous detection of NT-proBNP in up to six clinical samples within 25 min by using a novel aptamer-based sandwich assay, and the limit of detection was only 1.53 pg mL-1; given that the chip is 64% more compact than those developed in our prior works and requires only 5 μL of sample input, it may serve as a promising tool for early diagnosis of HF.

An integrated microfluidic system for rapid detection and multiple subtyping of influenza A viruses by using glycan-coated magnetic beads and RT-PCR

The influenza A (InfA) virus, which poses a significant global public health threat, is routinely classified into "subtypes" based on viral hemagglutinin (HA) and neuraminidase (NA) antigens. Because there are nearly 200 viral subtypes, current diagnostic approaches require multiplexing or array systems to cover various subtypes of HA and NA. A microfluidic chip featuring a HA × NA array was consequently developed herein for diagnosis and subtyping of InfA viruses via the use of glycan-coated magnetic beads followed by reverse transcription (RT) polymerase chain reaction (PCR). Up to 12 InfA subtypes were simultaneously detected in an automated fashion in less than 100 minutes on this microfluidic platform, representing a significant improvement in analysis speed compared to benchtop RT-PCR and chip-based microarray systems. The limits of detection of the RT-PCR assays ranged from 40 to 3000 copy numbers for the different subtypes of InfA viruses, around two orders of magnitude higher than in previous studies using microfluidic technologies. In summary, the array-type microfluidic chip system provides a rapid, sensitive, and fully automated approach for detection and multiple subtyping of InfA.

A microfluidic platform integrated with field-effect transistors for enumeration of circulating tumor cells

Circulating tumor cells (CTCs) are one of the promising cancer biomarkers whose concentrations are measured not only in the initial diagnostic stages, but also as treatment progresses. However, the existing methods for CTC detection are relatively time-consuming and labor-intensive. In this study, a new microfluidic platform integrated with field-effect transistors (FETs) and chambers for the trapping of CTCs was developed. This novel design could not only trap CTCs from whole blood samples, but also enumerate them via FET sensing of CTC-specific aptamer-CTC complexes. The FET output signal was experimentally found to increase with the increasing number of captured CTCs. More importantly, the enumeration of spiked CTCs in blood samples could be achieved in accordance with the signals measured on the FET devices. We therefore believe that this automated system could be a useful tool for enumeration of CTCs.

An automatic integrated microfluidic system for allergy microarray chips

Billions of people suffer from allergies, though in many cases, the source allergen is unknown. If one knows which allergens to avoid, this would result in an improved quality of life. Since a rapid, high-throughput, automatic allergen detection method is of great need, an integrated system combining microfluidic techniques and microarray chips has been developed herein to automate the allergen detection process. The developed microfluidic system could automatically carry out the entire procedure such as reagent incubation, hybridization, transport, and washing without any intermediate step. The microarray chip could be easily detached from the microfluidic chip afterwards, enabling it to be read under a fluorescence scanner. The experimental results indicated that the developed microfluidic system can automatically perform all the incubation processes, including hybridization, reagent transportation, and washing. It is worth noting that active mixing has been applied in the present study which is different from our previous study using micro-channels for passive incubation. Comparable results to a conventional benchtop approach were obtained in ∼30% less time with ∼25% less samples/reagents. Similar results were also demonstrated while detecting immunoglobulin E samples. The developed system could therefore provide a rapid, reliable, and automated approach for detecting allergen-specific antibodies in human serum.

An integrated microfluidic system with field-effect-transistor sensor arrays for detecting multiple cardiovascular biomarkers from clinical samples

Certain blood-borne biomarkers offer a potent methodology for understanding the risk of cardiovascular diseases (CVDs) with clinicians generally advocating the use of multiple biomarkers for proper risk assessment of CVDs. Herein four such CVDs biomarkers- C-reactive protein (CRP), N-terminal pro b-type natriuretic peptide (NT-proBNP), cardiac troponin I (cTnI), and fibrinogen- were rapidly (5 min) analyzed from clinical samples (~ 4 µL) on an integrated microfluidic platform equipped with 1) immobilized highly specific aptamer probes and 2) field-effect transistor (FET)-based sensor arrays. The calibration curve from the FET sensor arrays showed good agreement in the physiological concentration ranges for CRP (0.1-50 mg/L), NT-proBNP (50-10,000 pg/mL), cTnI (1-10,000 pg/mL), and fibrinogen (0.1-5 mg/mL). The developed prototype of this fully automated portable device requires minimal reagent and sample inputs and consequently shows great promise for next-generation point-of-care devices assaying multiple CVDs biomarkers in clinical samples.

Bacterial detection and identification from human synovial fluids on an integrated microfluidic system

An integrated microfluidic system was developed for detecting and identifying four bacteria in human joint fluid with the limit of detection as low as 100 colony forming units (CFUs) per milliliter (or 20 CFUs per reaction).

An automated microfluidic system for selection of aptamer probes against ovarian cancer tissues

Because of the difficulty of treatment in its latest stages, cancer is among the leading causes of death worldwide. Therefore, high-affinity and specificity biomarkers are still in demand for many cancer types, and the utility of aptamers to serve in this regard has been explored recently. Although a process known as "systematic evolution of ligands by exponential enrichment" (SELEX) has been used to generate aptamer-based cancer biomarkers, this approach is complicated, time-consuming, and labor-intensive. An automated microfluidic system was consequently developed herein to screen ovarian cancer-specific aptamers via on-chip SELEX with clinical cancer tissue samples. The integrated microfluidic system consisted of an integrated microfluidic chip, a temperature control module equipped with 12 thermoelectric coolers, and a flow control module for controlling 36 electromagnetic valves such that the entire, tissue-based SELEX process could be fully automated and carried out within 15 h. Highly specific ovarian cancer aptamers with high affinity (dissociation constant of 129 nM) to their cellular targets were screened with this system. Given the comparable specificity to their much more expensive antibody counterparts, these aptamers, when used in conjunction with the developed microfluidic system, may be used to diagnose ovarian cancer in its earliest stages.

Detecting miRNA biomarkers from extracellular vesicles for cardiovascular disease with a microfluidic system

According to World Health Organization reports, cardiovascular diseases (CVDs) are amongst the major causes of death globally and are responsible for over 18 million deaths every year. Traditional detection methods for CVDs include cardiac computerized tomography scans, electrocardiography, and myocardial perfusion imaging scans. Although diagnosis of CVDs through such bio-imaging techniques is common, these methods are relatively costly and cannot detect CVDs in their earliest stages. In contrast, the levels of certain micro RNA (miRNA) biomarkers extracted from extracellular vesicles (EVs) in the bloodstream have been recognized as promising indicators for early CVD detection. However, detection and quantification of miRNA using existing methods are relatively labor-intensive and time-consuming. In this study, a new integrated microfluidic system equipped with highly sensitive field-effect transistors (FETs) was capable of performing EV extraction, EV lysis, target miRNA isolation and miRNA detection within 5 h. The limit of detection was within the physiological range (femtomolar) for two targeted miRNAs, miR-21 and miR-126, meaning that this integrated microfluidic system has the potential to be used as a tool for early detection of CVDs.

An integrated microfluidic platform to perform uninterrupted SELEX cycles to screen affinity reagents specific to cardiovascular biomarkers

As cardiovascular diseases (CVD) are responsible for millions of deaths annually, there is a need for rapid and sensitive diagnosis of CVD at earlier stages. Aptamers generated by systematic evolution of ligands by exponential enrichment (SELEX) processes have been shown to be superior to conventional antibody-based cardiac biomarker detection. However, SELEX is a complicated, lengthy procedure requiring multiple rounds of extraction/amplification and well-trained personnel. To circumvent such issue, we designed an automated, miniaturized SELEX platform for the screening of aptamers towards three protein biomarkers associated with CVDs: N-terminal pro-peptide of B-type natriuretic peptide, human cardiac troponin I, and fibrinogen. The developed microfluidic platform was equipped with microfluidic devices capable of sample transport and mixing along with an on-chip nucleic acid amplification module such that the entire screening process (5 rounds of selection in 8 h.) could be performed consecutively on a single chip while consuming only 35 µL of reagents in each cycle. This system may therefore serve as a promising, sensitive, cost-effective platform for the selection of aptamers specific for CVD biomarkers.

Microfluidic platforms for rapid screening of cancer affinity reagents by using tissue samples

Cancer is the most serious disease worldwide, and ovarian cancer (OvCa) is the second most common type of gynecological cancer. There is consequently an urgent need for early-stage detection of OvCa, which requires affinity reagent biomarkers for OvCa. Systematic evolution of ligands by exponential enrichment (SELEX) and phage display technology are two powerful technologies for identifying affinity reagent biomarkers. However, the benchtop protocols for both screening technologies are relatively lengthy and require well-trained personnel. We therefore developed a novel, integrated microfluidic system capable of automating SELEX and phage display technology. Instead of using cancer cell lines, it is the first work which used tissue slides as screening targets, which possess more complicated and uncovered information for affinity reagents to recognize. This allowed for the identification of aptamer (nucleic acid) and peptide probes specific to OvCa cells and tissues. Furthermore, this developed system could be readily modified to uncover affinity reagents for diagnostics or even target therapy of other cancer cell types in the future.

Thermometry of photosensitive and optically induced electrokinetics chips

Optically induced electrokinetics (OEK)-based technologies, which integrate the high-resolution dynamic addressability of optical tweezers and the high-throughput capability of electrokinetic forces, have been widely used to manipulate, assemble, and separate biological and non-biological entities in parallel on scales ranging from micrometers to nanometers. However, simultaneously introducing optical and electrical energy into an OEK chip may induce a problematic temperature increase, which poses the potential risk of exceeding physiological conditions and thus inducing variations in cell behavior or activity or even irreversible cell damage during bio-manipulation. Here, we systematically measure the temperature distribution and changes in an OEK chip arising from the projected images and applied alternating current (AC) voltage using an infrared camera. We have found that the average temperature of a projected area is influenced by the light color, total illumination area, ratio of lighted regions to the total controlled areas, and amplitude of the AC voltage. As an example, optically induced thermocapillary flow is triggered by the light image-induced temperature gradient on a photosensitive substrate to realize fluidic hydrogel patterning. Our studies show that the projected light pattern needs to be properly designed to satisfy specific application requirements, especially for applications related to cell manipulation and assembly.

A nitrocellulose membrane-based integrated microfluidic system for bacterial detection utilizing magnetic-composite membrane microdevices and bacteria-specific aptamers

Bacteria such as Acinetobacter baumannii (AB) can cause serious infections, resulting in high mortality if not diagnosed early and treated properly; there is consequently a need for rapid and accurate detection of this bacterial species. Therefore, we developed a new, nitrocellulose-based microfluidic system featuring AB-specific aptamers capable of automating the bacterial detection process via the activity of microfluidic devices composed of magnetic-composite membranes. Electromagnets were used to actuate these microfluidic devices such that the entire diagnostic process could be conducted in the integrated microfluidic system within 40 minutes with a limit of detection as low as 450 CFU per reaction for AB. Aptamers were used to capture AB in complex samples on nitrocellulose membranes, and a simple colorimetric assay was used to estimate bacterial loads. Given the ease of use, portability, and sensitivity of this aptamer-based microfluidic system, it may hold great promise for point-of-care diagnostics.

Automatic cell fusion via optically-induced dielectrophoresis and optically-induced locally-enhanced electric field on a microfluidic chip

Cell fusion technology has been exploited in a wide variety of biomedical applications, and physical, chemical, and biological approaches can all be used to fuse two different types of cells; however, no current technique is adept at inducing both cell pairing and fusion at high efficiencies and yields. Hence, we developed a new method featuring the use of optically induced dielectrophoresis (ODEP) in conjunction with an optically induced, locally enhanced electric field for accurate and automatic cell pairing and fusion on a microfluidic device. After pairing cells via ODEP, a locally enhanced electric field generated by "virtual electrodes" by projecting light patterns was enacted to induce a proper transmembrane potential at the cell contact area such that cell fusion could be triggered by white light exposure. As a fusion yield of 9.67% was achieved between Pan1 and A549 cells, we believe that this may be a promising technique for automatically fusing different cell types.