Paper-Based Electrochemiluminescent Screening for Genotoxic Activity in the Environment

A low cost, microfluidic paper electrochemical device (μPED) was fabricated using screen printing of electrodes and heat transfer of patterned wax paper onto filter paper. The μPED features films of a light-emitting ruthenium metallopolymer, microsomal metabolic enzymes, and DNA to detect potential genotoxic pollutant activity in environmental samples. Unlike conventional analytical methods that detect specific pollutant compounds, the μPED was designed to rapidly measure the presence of genotoxic equivalents in environmental samples with the signal related to benzo­[a]­pyrene (B­[<i>a</i>]­P) as a reference standard. The analytical end point is the detection of DNA damage from metabolites produced in the device using an electrochemiluminescence output measured with a charge-coupled device (CCD) camera. Proof-of-concept of this measurement was established for smoke, water, and food samples. The μPED provides a rapid screening tool for on-site environmental monitoring that specifically monitors the genotoxic reactivity of metabolites of toxic compounds present in the samples

Highly Efficient Binding of Paramagnetic Beads Bioconjugated with 100 000 or More Antibodies to Protein-Coated Surfaces

We report here the first kinetic characterization of 1 μm diameter superparamagnetic particles (MP) decorated with over 100 000 antibodies binding to protein antigens attached to flat surfaces. Surface plasmon resonance (SPR) was used to show that these antibody-derivatized MPs (MP-Ab₂) exhibit irreversible binding with 100-fold increased association rates compared to free antibodies. The estimated upper limit for the dissociation constant of MP-Ab₂ from the SPR sensor surface is 5 fM, compared to 3–8 nM for the free antibodies. These results are explained by up to 2000 interactions of MP-Ab₂ with protein-decorated surfaces. Findings are consistent with highly efficient capture of protein antigens in solution by the MP-Ab₂ and explain in part the utility of these beads for ultrasensitive protein detection into the fM and aM range. Aggregation of these particles on the SPR chip, probably due to residual magnetic microdomains in the particles, also contributes to ultrasensitive detection and may also help drive the irreversible binding

The Exosome Total Isolation Chip

Circulating tumor-derived extracellular vesicles (EVs) have emerged as a promising source for identifying cancer biomarkers for early cancer detection. However, the clinical utility of EVs has thus far been limited by the fact that most EV isolation methods are tedious, nonstandardized, and require bulky instrumentation such as ultracentrifugation (UC). Here, we report a size-based EV isolation tool called ExoTIC (exosome total isolation chip), which is simple, easy-to-use, modular, and facilitates high-yield and high-purity EV isolation from biofluids. ExoTIC achieves an EV yield ∼4–1000-fold higher than that with UC, and EV-derived protein and microRNA levels are well-correlated between the two methods. Moreover, we demonstrate that ExoTIC is a modular platform that can sort a heterogeneous population of cancer cell line EVs based on size. Further, we utilize ExoTIC to isolate EVs from cancer patient clinical samples, including plasma, urine, and lavage, demonstrating the device’s broad applicability to cancers and other diseases. Finally, the ability of ExoTIC to efficiently isolate EVs from small sample volumes opens up avenues for preclinical studies in <i>small</i> animal tumor models and for point-of-care EV-based clinical testing from fingerprick quantities (10–100 μL) of blood