Purpose of review
To review optical imaging technologies in urologic surgery aimed to facilitate intraoperative imaging and tissue interrogation.
Emerging new optical imaging technologies can be integrated in the operating room environment during minimally invasive and open surgery. These technologies include macroscopic fluorescence imaging that provides contrast enhancement between normal and diseased tissue and microscopic imaging that provides tissue characterization.
Optical imaging technologies that have reached the clinical arena in urologic surgery are reviewed, including photodynamic diagnosis, near infrared fluorescence imaging, optical coherence tomography, and confocal laser endomicroscopy.
image-guided surgery; optical imaging; fluorescence imaging; in vivo microscopy; minimally invasive surgery
To develop the diagnostic criteria for benign and neoplastic conditions of the urinary tract using probe-based confocal laser endomicroscopy (pCLE), a new technology for dynamic, in vivo imaging with micron-scale resolution. The suggested diagnostic criteria will formulate a guide for pCLE image interpretation in urology.
Patients scheduled for transurethral resection of bladder tumor (TURBT) or nephrectomy were recruited. After white-light cystoscopy (WLC), fluorescein was administered as contrast. Different areas of the urinary tract were imaged with pCLE via direct contact between the confocal probe and the area of interest. Confocal images were subsequently compared with standard hematoxylin and eosin analysis.
pCLE images were collected from 66 participants, including 2 patients who underwent nephrectomy. We identified key features associated with different anatomic landmarks of the urinary tract, including the kidney, ureter, bladder, prostate, and urethra. In vivo pCLE of the bladder demonstrated distinct differences between normal mucosa and neoplastic tissue. Using mosaicing, a post hoc image-processing algorithm, individual image frames were juxtaposed to form wideangle views to better evaluate tissue microarchitecture.
In contrast to standard pathologic analysis of fixed tissue with hematoxylin and eosin, pCLE provides real time microscopy of the urinary tract to enable dynamic interrogation of benign and neoplastic tissues in vivo. The diagnostic criteria developed in this study will facilitate adaptation of pCLE for use in conjunction with WLC to expedite diagnosis of urinary tract pathology, particularly bladder cancer.
Background and Purpose
Emerging optical imaging technologies such as confocal laser endomicroscopy (CLE) hold promise in improving bladder cancer diagnosis. The purpose of this study was to determine the interobserver agreement of image interpretation using CLE for bladder cancer.
Experienced CLE urologists (n=2), novice CLE urologists (n=6), pathologists (n=4), and nonclinical researchers (n=5) were recruited to participate in a 2-hour computer-based training consisting of a teaching and validation set of intraoperative white light cystoscopy (WLC) and CLE video sequences from patients undergoing transurethral resection of bladder tumor. Interobserver agreement was determined using the κ statistic.
Of the 31 bladder regions analyzed, 19 were cancer and 12 were benign. For cancer diagnosis, experienced CLE urologists had substantial agreement for both CLE and WLC+CLE (90%, κ 0.80) compared with moderate agreement for WLC alone (74%, κ 0.46), while novice CLE urologists had moderate agreement for CLE (77%, κ 0.55), WLC (78%, κ 0.54), and WLC+CLE (80%, κ 0.59). Pathologists had substantial agreement for CLE (81%, κ 0.61), and nonclinical researchers had moderate agreement (77%, κ 0.49) in cancer diagnosis. For cancer grading, experienced CLE urologists had fair to moderate agreement for CLE (68%, κ 0.64), WLC (74%, κ 0.67), and WLC+CLE (53%, κ 0.33), as did novice CLE urologists for CLE (53%, κ 0.39), WLC (66%, κ 0.50), and WLC+CLE (61%, κ 0.49). Pathologists (65%, κ 0.55) and nonclinical researchers (61%, κ 0.56) both had moderate agreement for CLE in cancer grading.
CLE is an adoptable technology for cancer diagnosis in novice CLE observers after a short training with moderate interobserver agreement and diagnostic accuracy similar to WLC alone. Experienced CLE observers may be capable of achieving substantial levels of agreement for cancer diagnosis that is higher than with WLC alone.
Rapid detection of bacterial pathogens is critical toward judicious management of infectious diseases. Herein, we demonstrate an in situ electrokinetic stringency control approach for a self-assembled monolayer-based electrochemical biosensor toward urinary tract infection diagnosis. The in situ electrokinetic stringency control technique generates Joule heating induced temperature rise and electrothermal fluid motion directly on the sensor to improve its performance for detecting bacterial 16S rRNA, a phylogenetic biomarker. The dependence of the hybridization efficiency reveals that in situ electrokinetic stringency control is capable of discriminating single-base mismatches. With electrokinetic stringency control, the background noise due to the matrix effects of clinical urine samples can be reduced by 60%. The applicability of the system is demonstrated by multiplex detection of three uropathogenic clinical isolates with similar 16S rRNA sequences. The results demonstrate that electrokinetic stringency control can significantly improve the signal-to-noise ratio of the biosensor for multiplex urinary tract infection diagnosis.
Urinary tract infection; Stringency control; Multiplex detection; Matrix effects; Self-assembled monolayers
Transforming microfluidics-based biosensing systems from laboratory research into clinical reality remains an elusive goal despite decades of intensive research. A fundamental obstacle for the development of fully automated microfluidic diagnostic systems is the lack of an effective strategy for combining pumping, sample preparation, and detection modules into an integrated biosensing platform. Herein, we report a universal electrode approach, which incorporates DC electrolytic pumping, AC electrokinetic sample preparation, and self-assembled monolayer based electrochemical sensing on a single microfluidic platform, to automate complicated molecular analysis procedures that will enable biosensing applications in non-traditional healthcare settings. Using the universal electrode approach, major microfluidic operations required in molecular analyses, such as pumping, mixing, washing, and sensing can be performed in a single platform. We demonstrate the universal electrode platform for detecting bacterial 16S rRNA, a phylogenetic marker, toward rapid diagnostics of urinary tract infection. Since only electronic interfaces are required to operate the platform, the universal electrode approach represents an effective system integration strategy to realize the potential of microfluidics in molecular diagnostics at the point of care.
System Integration; Electrochemical detection; Electrokinetics; 16S rRNA; Urinary Tract Infection
Advances in biosensor technologies for in vitro diagnostics have the potential to transform the practice of medicine. Despite considerable work in the biosensor field, there is still no general sensing platform that can be ubiquitously applied to detect the constellation of biomolecules in diverse clinical samples (for example, serum, urine, cell lysates or saliva) with high sensitivity and large linear dynamic range. A major limitation confounding other technologies is signal distortion that occurs in various matrices due to heterogeneity in ionic strength, pH, temperature and autofluorescence. Here we present a magnetic nanosensor technology that is matrix insensitive yet still capable of rapid, multiplex protein detection with resolution down to attomolar concentrations and extensive linear dynamic range. The matrix insensitivity of our platform to various media demonstrates that our magnetic nanosensor technology can be directly applied to a variety of settings such as molecular biology, clinical diagnostics and biodefense.
Urinary tract infection (UTI) is among the most common bacterial infections and poses a significant healthcare burden. The standard culture-based diagnosis of UTI has a typical delay of two to three days. In the absence of definitive microbiological diagnosis at the point of care, physicians frequently initiate empirical broad-spectrum antibiotic treatment, which has contributed to the emergence of resistant pathogens. Biosensors are emerging as a powerful diagnostic platform for infectious diseases. Similar to how blood glucose sensors revolutionized the management of diabetes and pregnancy tests are now conducted at home, biosensors are poised to significantly improve UTI diagnosis. Biosensors are amenable to integration with microfluidic technology for point-of-care applications. This review focuses on promising biosensor technology for UTI diagnosis, including pathogen identification and antimicrobial susceptibility testing and hurdles in the translation of biosensor technology from bench to bedside.
Rapid, specific, and sensitive detection of bacterial pathogens is essential toward clinical management of infectious diseases. Traditional approaches for pathogen detection, however, often require time-intensive bacterial culture and amplification procedures. Herein, a microparticle enhanced double-stranded DNA probe is demonstrated for rapid species-specific detection of bacterial 16S rRNA. In this molecular assay, the binding of the target sequence to the fluorophore conjugated probe thermodynamically displaces the quencher probe and allows the fluorophore to fluoresce. By incorporation of streptavidin-coated microparticles to localize the biotinylated probes, the sensitivity of the assay can be improved by 3 orders of magnitude. The limit of detection of the assay is as few as eight bacteria without target amplification and is highly specific against other common pathogens. Its applicability toward clinical diagnostics is demonstrated by directly identifying bacterial pathogens in urine samples from patients with urinary tract infections.
Rapid diagnosis of infectious diseases and timely initiation of appropriate treatment are critical determinants that promote optimal clinical outcomes and general public health. Conventional in vitro diagnostics for infectious diseases are time-consuming and require centralized laboratories, experienced personnel and bulky equipment. Recent advances in biosensor technologies have potential to deliver point-of-care diagnostics that match or surpass conventional standards in regards to time, accuracy and cost. Broadly classified as either label-free or labeled, modern biosensors exploit micro- and nanofabrication technologies and diverse sensing strategies including optical, electrical and mechanical transducers. Despite clinical need, translation of biosensors from research laboratories to clinical applications has remained limited to a few notable examples, such as the glucose sensor. Challenges to be overcome include sample preparation, matrix effects and system integration. We review the advances of biosensors for infectious disease diagnostics and discuss the critical challenges that need to be overcome in order to implement integrated diagnostic biosensors in real world settings.
iosensor; infectious diseases; matrix effects; microfluidics; sample preparation; system integration
Multidrug-resistant pathogens are an emerging global health problem. In addition to the need of developing new antibiotics in the pipeline, the ability to rapidly determine the antibiotic resistance profiles of bacteria represents one of the most crucial steps toward the management of infectious diseases and the prevention of multidrug-resistant pathogens. Here, we report a single cell antimicrobial susceptibility testing (AST) approach for rapid determination of the antibiotic resistance of bacterial pathogens. By confining individual bacteria in gas permeable microchannels with dimensions comparable to a single bacterium, the antibiotic resistance of the bacteria can be monitored in real-time at the single cell level. To facilitate the dynamic loading of the bacteria into the confined microchannels for observation, AC electrokinetics is demonstrated for capturing bacteria to defined locations in high-conductivity AST buffer. The electrokinetic technique achieves a loading efficiency of about 75% with a negligible effect on the bacterial growth rate. To optimize the protocol for single cell AST, the bacterial growth rate of individual bacteria under different antibiotic conditions has been determined systematically. The applicability of single cell AST is demonstrated by the rapid determination of the antimicrobial resistant profiles of uropathogenic clinical isolates in Mueller-Hinton media and in urine. The antibiotic resistance profiles of bacteria can be determined in less than one hour compared to days in standard culture-based AST techniques.
To develop a portable point-of-care system based on biosensors for common infectious diseases such as urinary tract infection, the sensing process needs to be implemented within an enclosed fluidic system. On chip sample preparation of clinical samples remains a significant obstacle to achieve robust sensor performance. Herein AC electrokinetics is applied in an electrochemical biosensor cassette to enhance molecular convection and hybridization efficiency though electrokinetic induced fluid motion and Joule heating induced temperature elevation. Using E. coli as an exemplary pathogen, we determined the optimal electrokinetic parameters for detecting bacterial 16S rRNA in the biosensor cassette based on the current output, signal-to-noise ratio, and limit of detection. In addition, a panel of six probe sets targeting common uropathogenic bacteria was demonstrated. The optimized parameters were also validated using patient-derived clinical urine samples. The effectiveness of electrokinetic for on chip sample preparation will facilitate the implementation of point-of-care diagnosis of urinary tract infection in the future.
This study reports a hybrid electrokinetic technique for label-free manipulation of pathogenic bacteria in biological samples toward medical diagnostic applications. While most electrokinetic techniques only function in low-conductivity buffers, hybrid electrokinetics enables effective operation in high-conductivity samples, such as physiological fluids (~1 S m−1). The hybrid electrokinetic technique combines short-range electrophoresis and dielectrophoresis, and long-range AC electrothermal flow to improve its effectiveness. The major technical hurdle of electrode instability for manipulating high conductivity samples is tackled by using a Ti–Au–Ti sandwich electrode and a 3-parallel-electrode configuration is designed for continuous isolation of bacteria. The device operates directly with biological samples including urine and buffy coats. We show that pathogenic bacteria and biowarfare agents can be concentrated for over 3 orders of magnitude using hybrid electrokinetics.
This study reports a multifunctional electrode approach which directly implements electrokinetic enhancement on a self-assembled-monolayer-based electro-chemical sensor for point-of-care diagnostics. Using urinary tract infections as a model system, we demonstrate that electrokinetic enhancement, which involves in situ stirring and heating, can enhance the sensitivity of the strain specific 16S rRNA hybridization assay for 1 order of magnitude and accelerate the time-limiting incubation step with a 6-fold reduction in the incubation time. Since the same electrode platform is used for both electrochemical signal enhancement and electrochemical sensing, the multifunctional electrode approach provides a highly effective strategy toward fully integrated lab-on-a-chip systems for various biomedical applications.
A significant barrier to efficient antibiotic management of infection is that the standard diagnostic methodologies do not provide results at the point of care. The delays between sample collection and bacterial culture and antibiotic susceptibility reporting have led to empirical use of antibiotics, contributing to the emergence of drug resistant pathogens. As a key step toward the development of a point of care device for determining the antibiotic susceptibility of urinary tract pathogens, we report on a biosensor based antimicrobial susceptibility test.
Materials and Methods
For assay development bacteria were cultured with or without antibiotics, and growth was quantitated by determining viable counts and electrochemical biosensor measurement of bacterial 16S rRNA. To determine antibiotic susceptibility directly from patient samples, urine was cultured on antibiotic plates for 2.5 hours and growth was determined by electrochemical measurement of bacterial 16S rRNA. For assay validation 252 urine samples were collected from patients at the Spinal Cord Injury Service at Veterans Affairs Palo Alto Health Care System. The biosensor based antimicrobial susceptibility test was completed for samples containing gram-negative organisms. Pathogen identification and antibiotic susceptibility results were compared between our assay and standard microbiological analysis.
A direct biosensor quantitation of bacterial 16S rRNA can be used to monitor bacterial growth for a biosensor based antimicrobial susceptibility test. Clinical validation of a biosensor based antimicrobial susceptibility test with patient urine samples demonstrated that this test was 94% accurate in 368 pathogen-antibiotic tests compared to standard microbiological analysis.
This biosensor based antimicrobial susceptibility test, in concert with our previously described pathogen identification assay, can provide culture and susceptibility information directly from a urine sample within 3.5 hours.
urinary tract infections; biosensing techniques; microbial sensitivity tests; point-of-care systems
Bladder cancer presents as a spectrum of different diatheses. Accurate assessment for individualized treatment depends on initial diagnostic accuracy. Detection relies on white light cystoscopy accuracy and comprehensiveness. Aside from invasiveness and potential risks, white light cystoscopy shortcomings include difficult flat lesion detection, precise tumor delineation to enable complete resection, inflammation and malignancy differentiation, and grade and stage determination. Each shortcoming depends on surgeon ability and experience with the technology available for visualization and resection. Fluorescence cystoscopy/photodynamic diagnosis, narrow band imaging, confocal laser endomicroscopy and optical coherence tomography address the limitations and have in vivo feasibility. They detect suspicious lesions (photodynamic diagnosis and narrow band imaging) and further characterize lesions (optical coherence tomography and confocal laser endomicroscopy). We analyzed the added value of each technology beyond white light cystoscopy and evaluated their maturity to alter the cancer course.
Materials and Methods
Detailed PubMed® searches were done using the terms “fluorescence cystoscopy,” “photodynamic diagnosis,” “narrow band imaging,” “optical coherence tomography” and “confocal laser endomicroscopy” with “optical imaging,” “bladder cancer” and “urothelial carcinoma.” Diagnostic accuracy reports and all prospective studies were selected for analysis. We explored technological principles, preclinical and clinical evidence supporting nonmuscle invasive bladder cancer detection and characterization, and whether improved sensitivity vs specificity translates into improved correlation of diagnostic accuracy with recurrence and progression. Emerging preclinical technologies with potential application were reviewed.
Photodynamic diagnosis and narrow band imaging improve nonmuscle invasive bladder cancer detection, including carcinoma in situ. Photodynamic diagnosis identifies more papillary lesions than white light cystoscopy, enabling more complete resection and fewer residual tumors. Despite improved treatment current data on photodynamic diagnosis do not support improved high risk diathetic detection and characterization or correlation with disease progression. Prospective recurrence data are lacking on narrow band imaging. Confocal laser endomicroscopy and optical coherence tomography potentially grade and stage lesions but data are lacking on diagnostic accuracy. Several emerging preclinical technologies may enhance the diagnostic capability of endoscopic imaging.
New optical imaging technologies may improve bladder cancer detection and characterization, and transurethral resection quality. While data on photodynamic diagnosis are strongest, the clinical effectiveness of these technologies is not proven. Prospective studies are needed, particularly of narrow band imaging, confocal laser endomicroscopy and optical coherence tomography. As each technology matures and new ones emerge, cost-effectiveness analysis must be addressed in the context of the various bladder cancer types.
urinary bladder neoplasms; fluorescence; cystoscopy; lasers; tomography; optical coherence
Rapid diagnosis of urinary tract infection would have a significant beneficial impact on clinical management, particularly in patients with structural or functional urinary tract abnormalities who are highly susceptible to recurrent polymicrobial infections. We examined the analytical validity of an electrochemical biosensor array for rapid molecular diagnosis of urinary tract infection in a prospective clinical study in patients with neurogenic bladder.
Materials and Methods
The electrochemical biosensor array was functionalized with DNA probes against 16S rRNA of the most common uropathogens. Spinal cord injured patients at a Veterans Affairs hospital were recruited into the study. Urine samples were generally tested on the biosensor within 1 to 2 hours of collection. Biosensor results were compared with those obtained using standard clinical microbiology laboratory methods.
We successfully developed a 1-hour biosensor assay for multiplex identification of pathogens. From July 2007 to December 2008 we recruited 116 patients, yielding a total of 109 urine samples suitable for analysis and comparison between biosensor assay and standard urine culture. Of the samples 74% were positive, of which 42% were polymicrobial. We identified 20 organisms, of which Escherichia coli, Pseudomonas aeruginosa and Enterococcus species were the most common. Biosensor assay specificity and positive predictive value were 100%. Pathogen detection sensitivity was 89%, yielding a 76% negative predictive value.
To our knowledge we report the first prospective clinical study to successfully identify pathogens within a point of care time frame using an electrochemical biosensor platform. Additional efforts to improve the limit of detection and probe design are needed to further enhance assay sensitivity.
urinary bladder; neurogenic; spinal cord injuries; urinary tract infections; biosensing techniques; RNA; ribosomal; 16S
We demonstrate feasibility of endoscopic imaging of Cerenkov light originated when charged nuclear particles, emitted from radionuclides, travel through a biological tissue of living subjects at superluminal velocity. The endoscopy imaging system consists of conventional optical fiber bundle/ clinical endoscopes, an optical imaging lens system, and a sensitive low-noise charge coupled device (CCD) camera. Our systematic studies using phantom samples show that Cerenkov light from as low as 1 µCi of radioactivity emitted from 18F-Fluorodeoxyglucose (FDG) can be coupled and transmitted through conventional optical fibers and endoscopes. In vivo imaging experiments with tumor bearing mice, intravenously administered with 18F-FDG, further demonstrated that Cerenkov luminescence endoscopy is a promising new tool in the field of endoscopic molecular imaging.
(170.2150) Endoscopic imaging; (170.0110) Imaging systems; (170.4580) Optical diagnostics for medicine
Medical imaging is an invaluable tool for diagnosis, surgical guidance, and assessment of treatment efficacy. The Network for Translational Research (NTR) for Optical Imaging consists of four research groups working to “bridge the gap” between lab discovery and clinical use of fluorescence- and photoacoustic-based imaging devices used with imaging biomarkers. While the groups are using different modalities, all the groups face similar challenges when attempting to validate these systems for FDA approval and, ultimately, clinical use. Validation steps taken, as well as future needs, are described here. The group hopes to provide translational validation guidance for itself, as well as other researchers.
(170.0110) Imaging systems; (170.3880) Medical and biological imaging
Electrothermal flow is a promising technique in microfluidic manipulation toward laboratory automation applications, such as clinical diagnostics and high throughput drug screening. Despite the potential of electrothermal flow in biomedical applications, relative little is known about electrothermal manipulation of highly conductive samples, such as physiological fluids and buffer solutions. In this study, the characteristics and challenges of electrothermal manipulation of fluid samples with different conductivities were investigated systematically. Electrothermal flow was shown to create fluid motion for samples with a wide range of conductivity when the driving frequency was above 100 kHz. For samples with low conductivities (below 1 S/m), the characteristics of the electrothermal fluid motions were in quantitative agreement with the theory. For samples with high conductivities (above 1 S/m), the fluid motion appeared to deviate from the model as a result of potential electrochemical reactions and other electrothermal effects. These effects should be taken into consideration for electrothermal manipulation of biological samples with high conductivities. This study will provide insights in designing microfluidic devices for electrokinetic manipulation of biological samples toward laboratory automation applications in the future.
Urinary tract infection (UTI) is a common infection that poses a substantial healthcare burden, yet its definitive diagnosis can be challenging. There is a need for a rapid, sensitive and reliable analytical method that could allow early detection of UTI and reduce unnecessary antibiotics. Pathogen identification along with quantitative detection of lactoferrin, a measure of pyuria, may provide useful information towards the overall diagnosis of UTI. Here, we report an integrated biosensor platform capable of simultaneous pathogen identification and detection of urinary biomarker that could aid the effectiveness of the treatment and clinical management.
The integrated pathogen 16S rRNA and host lactoferrin detection using the biosensor array was performed on 113 clinical urine samples collected from patients at risk for complicated UTI. For pathogen detection, the biosensor used sandwich hybridization of capture and detector oligonucleotides to the target analyte, bacterial 16S rRNA. For detection of the protein biomarker, the biosensor used an analogous electrochemical sandwich assay based on capture and detector antibodies. For this assay, a set of oligonucleotide probes optimized for hybridization at 37°C to facilitate integration with the immunoassay was developed. This probe set targeted common uropathogens including E. coli, P. mirabilis, P. aeruginosa and Enterococcus spp. as well as less common uropathogens including Serratia, Providencia, Morganella and Staphylococcus spp. The biosensor assay for pathogen detection had a specificity of 97% and a sensitivity of 89%. A significant correlation was found between LTF concentration measured by the biosensor and WBC and leukocyte esterase (p<0.001 for both).
We successfully demonstrate simultaneous detection of nucleic acid and host immune marker on a single biosensor array in clinical samples. This platform can be used for multiplexed detection of nucleic acid and protein as the next generation of urinary tract infection diagnostics.
Urine is the most abundant and easily accessible of all body fluids and provides an ideal route for non-invasive diagnosis of human diseases, particularly of the urinary tract. Electrochemical biosensors are well suited for urinary diagnostics due to their excellent sensitivity, low cost, and ability to detect a wide variety of target molecules including nucleic acids and protein biomarkers. We report the development of an electrochemical immunosensor for direct detection of the urinary tract infection (UTI) biomarker lactoferrin from infected clinical samples. An electrochemical biosensor array with alkanethiolate self-assembled monolayer (SAM) was used. Electrochemical impedance spectroscopy was used to characterize the mixed SAM, consisted of 11-mercaptoundecanoic acid and 6-mercapto-1-hexanol. A sandwich amperometric immunoassay was developed for detection of lactoferrin from urine, with a detection limit of 145 pg/ml. We validated lactoferrin as a biomarker of pyuria (presence of white blood cells in urine), an important hallmark of UTI, in 111 patient-derived urine samples. Finally, we demonstrated multiplex detection of urinary pathogens and lactoferrin through simultaneous detection of bacterial nucleic acid (16S rRNA) and host immune-response protein (lactoferrin) on a single sensor array. Our results represent first integrated sensor platform capable of quantitative pathogen identification and measurement of host immune response, potentially providing clinical diagnosis that is not only more expeditious but more informative than the current standard.
Electrochemical biosensor; Amperometry; Urinary diagnostics; Urinary tract infections; Biomarkers
Microfluidics holds great promise to revolutionize various areas of biological engineering, such as single cell analysis, environmental monitoring, regenerative medicine, and point-of-care diagnostics. Despite the fact that intensive efforts have been devoted into the field in the past decades, microfluidics has not yet been adopted widely. It is increasingly realized that an effective system integration strategy that is low cost and broadly applicable to various biological engineering situations is required to fully realize the potential of microfluidics. In this article, we review several promising system integration approaches for microfluidics and discuss their advantages, limitations, and applications. Future advancements of these microfluidic strategies will lead toward translational lab-on-a-chip systems for a wide spectrum of biological engineering applications.
This study reports the use of microfluidics, which intrinsically has a large surface-to-volume ratio, toward rapid antimicrobial susceptibility testing at the point of care. By observing the growth of uropathogenic E. coli in gas permeable polymeric microchannels with different dimensions, we demonstrate that the large surface-to-volume ratio of microfluidic systems facilitates rapid growth of bacteria. For microchannels with 250 micrometer or less in depth, the effective oxygenation can sustain the growth of E. coli to over 109 cfu/ml without external agitation or oxygenation, which eliminates the requirement of bulky instrumentation and facilitates rapid bacterial growth for antimicrobial susceptibility testing at the point of care. The applicability of microfluidic rapid antimicrobial susceptibility testing is demonstrated in culture media and in urine with clinical bacterial isolates that have different antimicrobial resistance profiles. The antimicrobial resistance pattern can be determined as rapidly as 2 hours compared to days in standard clinical procedures facilitating diagnostics at the point of care.
Cartridge-based microfluidics is a promising technology for clinical diagnostics. By miniaturizing the fluid-handling processes required for genomic and proteomic analyses, reagent and specimen volume is minimized along with the size of the system. We demonstrate an automated microfluidic system capable of performing six multiplexed genomic and proteomic analyses simultaneously, by means of an integrated electrochemical sensor and embedded controls.
microfluidics; electrochemical sensor; multiplexed assay; quantitative; molecular analysis; point of care; clinical diagnostics