An antibody-free dual-biomarker rapid enrichment workflow (AnDREW) improves the sensitivity of malaria rapid diagnostic tests.

Rapid diagnostic tests (RDTs) are critical to the success of malaria elimination campaigns. These tests are rapid, user-friendly, and field-deployable to resource-limited regions. However, RDTs demonstrate poor sensitivity because they can only tolerate a small (5 µL) volume of blood, which limits the amount of protein biomarker delivered to the test. We have developed the Antibody-free Dual-biomarker Rapid Enrichment Workflow (AnDREW) for purifying histidine-rich protein 2 (HRP2) and Plasmodium lactate dehydrogenase (PLDH) from large volume (150 µL) blood samples. We used Zn(II)NTA and aptamer-conjugated magnetic beads to capture HRP2 and PLDH, respectively. Both biomarkers were then eluted into RDT-compatible volumes using ethylene diamine tetraacetic acid (EDTA). We optimized both bead conjugates individually by enzyme-linked immunosorbent assays (ELISAs) and then combined the optimized capture and elution assays for both biomarkers to produce the AnDREW. The AnDREW-enhanced RDTs exhibited a 11-fold and 9-fold improvement in analytical sensitivity for detection of HRP2 and PLDH, respectively, when compared to unenhanced RDTs. Moreover, the limit of detection for PLDH was improved 11-fold for the AnDREW-enhanced RDTs (3.80 parasites/µL) compared to unenhanced RDTs (42.31 parasites/µL). Importantly, the AnDREW utilizes a pan-specific PLDH aptamer and improves upon existing methods by eluting both biomarkers without complexed antibodies.

Inorganic Complexes and Metal-Based Nanomaterials for Infectious Disease Diagnostics.

Infectious diseases claim millions of lives each year. Robust and accurate diagnostics are essential tools for identifying those who are at risk and in need of treatment in low-resource settings. Inorganic complexes and metal-based nanomaterials continue to drive the development of diagnostic platforms and strategies that enable infectious disease detection in low-resource settings. In this review, we highlight works from the past 20 years in which inorganic chemistry and nanotechnology were implemented in each of the core components that make up a diagnostic test. First, we present how inorganic biomarkers and their properties are leveraged for infectious disease detection. In the following section, we detail metal-based technologies that have been employed for sample preparation and biomarker isolation from sample matrices. We then describe how inorganic- and nanomaterial-based probes have been utilized in point-of-care diagnostics for signal generation. The following section discusses instrumentation for signal readout in resource-limited settings. Next, we highlight the detection of nucleic acids at the point of care as an emerging application of inorganic chemistry. Lastly, we consider the challenges that remain for translation of the aforementioned diagnostic platforms to low-resource settings.

Ten-atom silver cluster signaling and tempering DNA hybridization.

Silver clusters with ∼10 atoms are molecules, and specific species develop within DNA strands. These molecular metals have sparsely organized electronic states with distinctive visible and near-infrared spectra that vary with cluster size, oxidation, and shape. These small molecules also act as DNA adducts and coordinate with their DNA hosts. We investigated these characteristics using a specific cluster-DNA conjugate with the goal of developing a sensitive and selective biosensor. The silver cluster has a single violet absorption band (λ(max) = 400 nm), and its single-stranded DNA host has two domains that stabilize this cluster and hybridize with target oligonucleotides. These target analytes transform the weakly emissive violet cluster to a new chromophore with blue-green absorption (λ(max) = 490 nm) and strong green emission (λ(max) = 550 nm). Our studies consider the synthesis, cluster size, and DNA structure of the precursor violet cluster-DNA complex. This species preferentially forms with relatively low amounts of Ag(+), high concentrations of the oxidizing agent O2, and DNA strands with ≳20 nucleotides. The resulting aqueous and gaseous forms of this chromophore have 10 silvers that coalesce into a single cluster. This molecule is not only a chromophore but also an adduct that coordinates multiple nucleobases. Large-scale DNA conformational changes are manifested in a 20% smaller hydrodynamic radius and disrupted nucleobase stacking. Multidentate coordination also stabilizes the single-stranded DNA and thereby inhibits hybridization with target complements. These observations suggest that the silver cluster-DNA conjugate acts like a molecular beacon but is distinguished because the cluster chromophore not only sensitively signals target analytes but also stringently discriminates against analogous competing analytes.

Trifluoropropynyl as a surrogate for the cyano ligand and intense, room-temperature, metal-centered emission from its Rh(III) complex.

The trifluoropropynyl ligand -C≡CCF(3) was studied as a possible surrogate for the cyano ligand. Complexes of the type trans-[M(cyclam)(C≡CCF(3))(2)]OTf (where M = Cr(3+), Co(3+), and Rh(3+); OTf = trifluoromethanesulfonate) were prepared and then characterized by electronic spectroscopy and by cyclic voltammetry for the Co(3+) complex. The UV-vis spectra for all three bear a remarkable similarity to that of the trans-M(cyclam)(CN)(2)(+) cations. The trifluoropropynyl complex of Co(3+) shows electrochemical behavior nearly identical with that of its dicyano analogue. Metal-centered phosphorescence from the Rh(III) complex in room-temperature aqueous solution has a quantum yield of 0.12 and a lifetime of 73 µs, nearly 10 times higher than those of its dicyano analogue.