Disposable Device for Bacterial Vaginosis Detection.

Due to the increasing demand for clinical testing of infectious diseases at the point-of-care, the global market claims alternatives for rapid diagnosis tools such as disposable biosensors, avoiding the need for specialized laboratories and skilled personnel. Bacterial vaginosis (BV) is an infectious disease that commonly affects reproductive-age women and predisposes the infection of sexually transmitted diseases. Especially in asymptomatic cases, BV can lead to pelvic inflammatory conditions, postpartum endometritis, and preterm labor. Conventionally, BV diagnosis involves the microscopic analysis of vaginal swab samples; it thus requires highly trained personnel. In response, we report a novel microfluidic paper-based analytical device for BV diagnosis. Sialidase, a biomarker overexpressed in BV, was detected by exploiting an immunosensing mechanism previously discovered by our team. This technology employs a graphene oxide-coated surface as a quencher of fluorescence; the fluorescence of the immunoprobes that do not experiment immunoreactions (antibody-antigen) are deactivated by graphene oxide via non-radiative energy transfer, whereas those immunoprobes undergoing immunoreactions preserve their photoluminescence due to the distance and the low affinity between the immunocomplex and the graphene oxide-coated surface. Our paper-based test was typically carried out within 20 min, and the sample volume was 6 µL. Besides, it was tested with 14 vaginal swabs specimens to discriminate clinical samples of women with normal microbiota from those with BV. Our disposable device represents a new tool to prevent the consequences of BV.

Facile Determination of COVID-19 Seroconversion via Nonradiative Energy Transfer.

Serological tests are crucial in a pandemic scenario, since they are a valuable tool to spot those citizens with potential immunity, specific regions with herd immunity or particular at-risk populations, as well as acquired immunity after vaccination. Hence, high-throughput, fast, cost-effective, and straightforward technologies facilitating interrogation of COVID-19 seroconversion are an existing need. Herein, we developed an innovative assay for the determination of COVID-19 seroconversion. Fluorophore-labeled SARS-CoV-2 spike receptor-binding domain recombinant protein (F-RBD) was discovered to operate as a bioprobe that emits a strong fluorescence upon COVID-19 antibody detection; however, F-RBD fluorescence was deactivated by graphene oxide-decorated surfaces when COVID-19 antibodies are absent in the sample. With a cost of less than 0.5 USD per test (at laboratory scale), the biosensing system offers optimum results within 42 min. To demonstrate that this technology is technically sound in a relevant environment, 34 human serum samples were analyzed and clearly differentiated, requiring a tiny amount of serum (1 µL to be later diluted in saline buffer).

Nanophotonic Sialidase Immunoassay for Bacterial Vaginosis Diagnosis.

Bacterial vaginosis (BV) affects reproductive-age women and can lead to pelvic inflammatory disease, postpartum endometritis, and preterm labor/delivery and predisposes the infection of sexually transmitted diseases. Typically, BV diagnosis involves the analysis of vaginal swab samples via microscopy operated by highly skilled personnel. Hence, novel approaches for BV diagnosis are an existing need. In response, the first immunosensing platform targeting sialidase, a BV biomarker, is reported. The nanophotonic operational principle of this biosensing platform allows for a cheaper, faster, and simpler analysis when compared with an indirect enzyme-linked immunosorbent assay (ELISA). The clinical evaluation of such a nanotechnology is highlighted, where 162 vaginal swab samples were analyzed with high sensitivity and specificity (96.29%, respectively). The resulting nanoimmunosensing platform offers a resourceful approach to perform a timely BV diagnosis.

Real-Time Photoluminescent Biosensing Based on Graphene Oxide-Coated Microplates: A Rapid Pathogen Detection Platform.

Pathogenic bacterial contamination is a major threat to safety, human health, and ecosystems. Herein, we report an advantageous single-step, wash-free, and real-time bacterial detection platform operating with a single antibody. Escherichia coli was detected as a model analyte. This technology is based on graphene oxide-coated microplates (GOMs) and photoluminescent bioprobes (PLBs). On the one hand, using nonradiative energy transfer, GOMs are conceived to deactivate the photoluminescence of those PLBs that are not experimenting immunoreactions via antibody-bacterial membrane affinity. On the other hand, those PLBs experimenting immunoreactions preserve their photoluminescence because of both (i) the distance between the complex (PLBs-bacteria) and GOMs and (ii) the low affinity between the same complex and GOMs. With an optimal analytical performance of ∼30 min, the resulting bacterial detection platform was demonstrated to be fast and highly sensitive, exhibiting a limit of detection of ∼2 CFU mL-1. Industrial real samples were also successfully analyzed in a widely used format that is amenable to high-throughput applications. Moreover, the proposed technology is highly transformative, as graphene oxide is able to quench different fluorophores, and other analytes can be detected by simply changing the specific antibody.

Microwell plates coated with graphene oxide enable advantageous real-time immunosensing platform.

Immunoassays are fundamental analytical tools in molecular diagnostics, therapy monitoring and drug discovery. Nevertheless, they often take around 6 h and require cumbersome procedures. We introduce a breakthrough in immunosensing based on the photoluminescence quenching capabilities of graphene oxide (GO) and the versatile format offered by the famous microwell plates. Taking advantage of the highly efficient non-radiative energy transfer occurring between photoexcited fluorophores (donors) and GO (acceptor), we discovered that flurophore-labelled antibodies (Fl-Abs) are quickly and strongly quenched by the studied GO-coated microwell, whereas Fl-Abs complexed with the respective analyte are weakly quenched by the same surface due to the low affinity between the GO-coated surface and the relatively long distance between these photoluminescent complexes and the GO-coated surface. In doing so, we developed a conceptually innovative single-step immunosensing platform, avoiding blocking, separation and washing steps and exploiting a single antibody. Importantly, the biosensing response can be interrogated in real time. This leads to an advantageous immunodetection phenomenon which is observable in few minutes (e.g. 5 min). The resulting highly transformative biosensing platform operates with different photoluminescent agents and different analytes. Besides, this biosensing platform was demonstrated to operate with real samples of human urine doped with different concentrations of prostate specific antigen.