Paper microchip with a graphene-modified silver nano-composite electrode for electrical sensing of microbial pathogens.

Rapid and sensitive point-of-care diagnostics are of paramount importance for early detection of infectious diseases and timely initiation of treatment. Here, we present cellulose paper and flexible plastic chips with printed graphene-modified silver electrodes as universal point-of-care diagnostic tools for the rapid and sensitive detection of microbial pathogens or nucleic acids through utilizing electrical sensing modality and loop-mediated isothermal amplification (LAMP). We evaluated the ability of the developed paper-based assay to detect (i) viruses on cellulose-based paper microchips without implementing amplification in samples with viral loads between 106 and 108 copies per ml, and (ii) amplified HIV-1 nucleic acids in samples with viral loads between 10 fg µl-1 and 108 fg µl-1. The target HIV-1 nucleic acid was amplified using the RT-LAMP technique and detected through the electrical sensing of LAMP amplicons for a broad range of RNA concentrations between 10 fg µl-1 and 108 fg µl-1 after 40 min of amplification time. Our assay may be used for antiretroviral therapy monitoring where it meets the sensitivity requirement of the World Health Organization guidelines. Such a paper microchip assay without the amplification step may also be considered as a simple and inexpensive approach for acute HIV detection where maximum viral replication occurs.

Electrical response of a B lymphoma cell line latently infected with Kaposi's sarcoma herpesvirus.

Certain viruses, such as herpesviruses, are capable of persistent and latent infection of host cells. Distinguishing and separating live, latently infected cells from uninfected cells is not easily attainable using current approaches. The ability to perform such separation would greatly enhance the ability to study primary, infected cells and potentially enable elimination of latently infected cells from the host. Here, the dielectrophoretic response of B cells infected with Kaposi's sarcoma-associated herpesvirus (KSHV) were investigated and compared to uninfected B cells. We evaluated the effect of applied voltage, signal frequency, and flow rate of the sample on the cell capture efficiency. We achieved 37.1% ± 8.5% difference in capture efficiencies between latently KSHV-infected and uninfected BJAB B lymphoma cells at the chip operational conditions of 1V, 50 kHz and 0.02 µl/min sample flow rate. Our results show that latently infected B lymphoma cells demonstrated significantly different electrical response compared to uninfected B cells and DEP-based microchips can be potentially used for sorting latently infected cells based on their electrical properties.

Biologic nanoparticles and platelet reactivity.

AIM: Nanosized particles (NPs) enriched in hydroxyapatite and protein isolated from calcified human tissue accelerate occlusion of endothelium-denuded arteries when injected intravenously into rabbits. Since platelet aggregation and secretory processes participate in normal hemostasis, thrombosis and vascular remodeling, experiments were designed to determine if these biologic NPs alter specific platelet functions in vitro. METHODS: Platelet-rich plasma was prepared from citrate anticoagulated human blood. Platelet aggregation and ATP secretion were monitored in response to thrombin receptor agonists peptide (10 microM) or convulxin (50 microg/ml) prior to and following 15 min incubation with either control solution, human-derived NPs, bovine-derived NPs or crystals of hydroxyapatite at concentrations of 50 and 150 nephelometric turbidity units. RESULTS: Incubation of platelets for 15 min with either human- or bovine-derived NPs reduced aggregation induced by thrombin receptor activator peptide and convulxin in a concentration-dependent manner. Hydroxyapatite caused a greater inhibition than either of the biologically derived NPs. Human-derived NPs increased ATP secretion by unstimulated platelets during the 15 min incubation period. CONCLUSION: Effects of bovine-derived and hydroxyapatite NPs on basal release of ATP were both time and concentration dependent. These results suggest that biologic NPs modulate both platelet aggregation and secretion. Biologically derived NPs could modify platelet responses within the vasculature, thereby reducing blood coagulability and the vascular response to injury.