Analysis of Airborne Biomarkers for Point-of-Care Diagnostics.

Treatable diseases continue to exact a heavy burden worldwide despite powerful advances in treatment. Diagnostics play crucial roles in the detection, management, and ultimate prevention of these diseases by guiding the allocation of precious medical resources. Motivated by globalization and evolving disease, and enabled by advances in molecular pathology, the scientific community has produced an explosion of research on miniaturized integrated biosensor platforms for disease detection. Low-cost, automated tests promise accessibility in low-resource settings by loosening constraints around infrastructure and usability. To address the challenges raised by invasive and intrusive sample collection, researchers are exploring alternative biomarkers in various specimens. Specifically, patient-generated airborne biomarkers suit minimally invasive collection and automated analysis. Disease biomarkers are known to exist in aerosols and volatile compounds in breath, odor, and headspace, media that can be exploited for field-ready diagnostics. This article reviews global disease priorities and the characteristics of low-resource settings. It surveys existing technologies for the analysis of bioaerosols and volatile organic compounds, and emerging technologies that could enable their translation to the point of care. Engineering advances promise to enable appropriate diagnostics by detecting chemical and microbial markers. Nonetheless, further innovation and cost reduction are needed for these technologies to broadly affect global health.

Quantitative detection of PfHRP2 in saliva of malaria patients in the Philippines.

BACKGROUND: Malaria is a global health priority with a heavy burden of fatality and morbidity. Improvements in field diagnostics are needed to support the agenda for malaria elimination. Saliva has shown significant potential for use in non-invasive diagnostics, but the development of off-the-shelf saliva diagnostic kits requires best practices for sample preparation and quantitative insight on the availability of biomarkers and the dynamics of immunoassay in saliva. This pilot study measured the levels of the PfHRP2 in patient saliva to inform the development of salivary diagnostic tests for malaria. METHODS: Matched samples of blood and saliva were collected between January and May, 2011 from eight patients at Palawan Baptist Hospital in Roxas, Palawan, Philippines. Parasite density was determined from thick-film blood smears. Concentrations of PfHRP2 in saliva of malaria-positive patients were measured using a custom chemiluminescent ELISA in microtitre plates. Sixteen negative-control patients were enrolled at UCLA. A substantive difference between this protocol and previous related studies was that saliva samples were stabilized with protease inhibitors. RESULTS: Of the eight patients with microscopically confirmed P. falciparum malaria, seven tested positive for PfHRP2 in the blood using rapid diagnostic test kits, and all tested positive for PfHRP2 in saliva. All negative-control samples tested negative for salivary PfHRP2. On a binary-decision basis, the ELISA agreed with microscopy with 100 % sensitivity and 100 % specificity. Salivary levels of PfHRP2 ranged from 17 to 1,167 pg/mL in the malaria-positive group. CONCLUSION: Saliva is a promising diagnostic fluid for malaria when protein degradation and matrix effects are mitigated. Systematic quantitation of other malaria biomarkers in saliva would identify those with the best clinical relevance and suitability for off-the-shelf diagnostic kits.

Electrochemical properties and myocyte interaction of carbon nanotube microelectrodes.

Arrays of carbon nanotube (CNT) microelectrodes (nominal geometric surface areas 20-200 µm(2)) were fabricated by photolithography with chemical vapor deposition of randomly oriented CNTs. Raman spectroscopy showed strong peak intensities in both G and D bands (G/D = 0.86), indicative of significant disorder in the graphitic layers of the randomly oriented CNTs. The impedance spectra of gold and CNT microelectrodes were compared using equivalent circuit models. Compared to planar gold surfaces, pristine nanotubes lowered the overall electrode impedance at 1 kHz by 75%, while nanotubes treated in O(2) plasma reduced the impedance by 95%. Cyclic voltammetry in potassium ferricyanide showed potential peak separations of 133 and 198 mV for gold and carbon nanotube electrodes, respectively. The interaction of cultured cardiac myocytes with randomly oriented and vertically aligned CNTs was investigated by the sectioning of myocytes using focused-ion-beam milling. Vertically aligned nanotubes deposited by plasma-enhanced chemical vapor deposition (PECVD) were observed to penetrate the membrane of neonatal-rat ventricular myocytes, while randomly oriented CNTs remained external to the cells. These results demonstrated that CNT electrodes can be leveraged to reduce impedance and enhance biological interfaces for microelectrodes of subcellular size.

Engineering novel diagnostic modalities and implantable cytomimetic nanomaterials for next-generation medicine.

The advent of 21st century medicine will be based on a comprehensive approach to achieving the highly sensitive and specific detection of diseases, as well as the development of novel materials and devices based on biotic-abiotic interfacing as interventional modalities. Novel technologies that enable early identification of physiological changes will serve as a gateway tool for the proper treatment of these disorders. Toward the realization of these technologies, microfabrication and nanofabrication methods have been applied to biomedical systems that allow scientists to interact with cellular and molecular systems on their native size scales. Future enabling systems will build on the foundation composed of such devices. With respect to the envisioned fruition of biofunctional nanomaterials and systems, foundational studies of biological systems and molecules, as well as their interfacing with biocompatible materials, have produced a domain of components that can be integrated and engineered toward eventual cytomimetic materials for transplantation. In addition, the potential underscoring of their future applications in nanoscale medicine is based on the ability to engineer and design intelligent membrane/protein self-assembling and organization phenomena that are typically found in nature into these artificial composite systems. These devices will provide a powerful suite of solutions with broad applicabilities in nanomedicine, for example, (1) the use of concomitant protein functionality toward energy production and the powering of medical implants and (2) replacement of damaged cells (e.g., heart and neuron) with implantable biologically intelligent engineered materials. This work will examine key advances in the areas of diagnostics and synthetic biology that have led to visionary contributions to next-generation medicine. Furthermore, we present 2 devices that will contribute to the realization of compelling biosensing and biofunctional material technologies. These systems include advanced diagnostic platforms for whole-cell detection, as well as copolymeric materials that have been functionalized by the coupled activity of their embedded membrane proteins. They are envisioned to successfully bridge the gap between foundational scientific progress and the realization of rapid point-of-care disease assessment and biofunctional devices with higher-order behavior.