Timely detection of infectious agents is critical in early diagnosis and treatment of infectious diseases. Conventional pathogen detection methods, such as enzyme linked immunosorbent assay (ELISA), culturing or polymerase chain reaction (PCR) require long assay times, and complex and expensive instruments, which are not adaptable to point-of-care (POC) needs at resource-constrained as well as primary care settings. Therefore, there is an unmet need to develop simple, rapid, and accurate methods for detection of pathogens at the POC. Here, we present a portable, multiplex, inexpensive microfluidic-integrated surface plasmon resonance (SPR) platform that detects and quantifies bacteria, i.e., Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) rapidly. The platform presented reliable capture and detection of E. coli at concentrations ranging from ~105 to 3.2 × 107 CFUs/mL in phosphate buffered saline (PBS) and peritoneal dialysis (PD) fluid. The multiplexing and specificity capability of the platform was also tested with S. aureus samples. The presented platform technology could potentially be applicable to capture and detect other pathogens at the POC and primary care settings.

This letter demonstrates a biosensing platform for naked eye detection of miRNA, fabricated using a poly(vinylidene fluoride) thin paper impregnated with positively charged poly(3-alkoxy-4-methylthiophene) as luminescent reporters. The miRNA assay is based on the formation of a duplex and a triplex species between the "reporter and miRNA" and "reporter and miRNA-peptide nucleic acid (PNA) hybrid", which yields two significantly different optical signals, thereby facilitating naked eye detection. This letter illustrates the successful validation of the proposed methodology via a mir21 assay (miRNA sequence associated with lung cancer). Furthermore, this facile platform enables rapid, sensitive, and selective detection of miRNA, at clinically relevant concentration levels as well as single base pair mismatch, without requiring complex and expensive instrumentation.

In this study, complexes of DNA with different organic di- and tetravalent counterions were systematically investigated in solution and on a surface. The complexation behavior was studied by dynamic light scattering, static light scattering, atomic force microscopy, analytical ultracentrifugation, and UV-vis spectroscopy. Results show that both divalent and tetravalent counterions can induce the formation of DNA complexes. Divalent counterions cause aggregation only at high counterion excess, with charge ratios of 50:1 for supercoiled DNA and 200:1 for linear DNA, while for different tetravalent counterions aggregation is already observed for charge ratios of about 1:1. Flower-like aggregates are observed with divalent counterions. For a tetravalent perylene based counterion, a transition from flower-like aggregates at low charge ratios to toroids and rods at high charge ratios is observed. A transition regime for intermediate charge ratios is found. The influence of concentration, added salt, and preparation method is also discussed. It is concluded that it is the interplay of electrostatics and component architectures that directs the structure formation.

Recent advances in biosensing technologies present great potential for medical diagnostics, thus improving clinical decisions. However, creating a label-free general sensing platform capable of detecting multiple biotargets in various clinical specimens over a wide dynamic range, without lengthy sample-processing steps, remains a considerable challenge. In practice, these barriers prevent broad applications in clinics and at patients' homes. Here, we demonstrate the nanoplasmonic electrical field-enhanced resonating device (NE 2 RD), which addresses all these impediments on a single platform. The NE 2 RD employs an immunodetection assay to capture biotargets, and precisely measures spectral color changes by their wavelength and extinction intensity shifts in nanoparticles without prior sample labeling or preprocessing. We present through multiple examples, a label-free, quantitative, portable, multitarget platform by rapidly detecting various protein biomarkers, drugs, protein allergens, bacteria, eukaryotic cells, and distinct viruses. The linear dynamic range of NE 2 RD is five orders of magnitude broader than ELISA, with a sensitivity down to 400 fg/mL This range and sensitivity are achieved by self-assembling gold nanoparticles to generate hot spots on a 3D-oriented substrate for ultrasensitive measurements. We demonstrate that this precise platform handles multiple clinical samples such as whole blood, serum, and saliva without sample preprocessing under diverse conditions of temperature, pH, and ionic strength. The NE 2 RD's broad dynamic range, detection limit, and portability integrated with a disposable fluidic chip have broad applications, potentially enabling the transition toward precision medicine at the pointof-care or primary care settings and at patients' homes.iosensing platforms have enabled various applications in different fields of clinical medicine such as biomarker/drug discovery and initiation and monitoring of therapy (1-3). However, material cost, accessibility, ease of operation, lack of portability, and complexity in readout remain major challenges for developing robust diagnostic assays (SI Appendix, Table S1). Recent advances in nanotechnology and biosensing have created new avenues to address these issues (4-9). Technically, they have provided integration of high-throughput sampling with readout systems for quantitative detection of disease-specific biotargets. Therefore, they have demonstrated great potential to revolutionize medical diagnostics. However, from a clinical and technological perspective, existing platforms still face several challenges. First, lengthy assay time hinders physicians from making early clinical decisions. Second, examining clinical samples with diverse pH range, ionic content, and ionic strength requires SignificanceBiosensing technologies have significant impact on medical diagnostics but difficulties in the handling of complex biospecimens, portability, and nonlinearity in dynamic detection range present considerable technical bottlenecks in their tran...