Tunable and label-free virus enrichment for ultrasensitive virus detection using carbon nanotube arrays.

Viral infectious diseases can erupt unpredictably, spread rapidly, and ravage mass populations. Although established methods, such as polymerase chain reaction, virus isolation, and next-generation sequencing have been used to detect viruses, field samples with low virus count pose major challenges in virus surveillance and discovery. We report a unique carbon nanotube size-tunable enrichment microdevice (CNT-STEM) that efficiently enriches and concentrates viruses collected from field samples. The channel sidewall in the microdevice was made by growing arrays of vertically aligned nitrogen-doped multiwalled CNTs, where the intertubular distance between CNTs could be engineered in the range of 17 to 325 nm to accurately match the size of different viruses. The CNT-STEM significantly improves detection limits and virus isolation rates by at least 100 times. Using this device, we successfully identified an emerging avian influenza virus strain [A/duck/PA/02099/2012(H11N9)] and a novel virus strain (IBDV/turkey/PA/00924/14). Our unique method demonstrates the early detection of emerging viruses and the discovery of new viruses directly from field samples, thus creating a universal platform for effectively remediating viral infectious diseases.

pKa determination of graphene-like materials: Validating chemical functionalization.

We report a novel pKa determination for different graphene-like samples: graphene oxide (GO), reduced GO (rGO), graphene nanoribbons (GNR), oxidized GNR (GONR), thiol- and imidazole-functionalized GO (GOSH and GOIMZ, respectively) and thiol-functionalized GONR (GONRSH). Using the specialized computational program BEST7 for treating titration curves, pKas for different functional groups were discriminated (confirmed by infrared spectra) and their composition quantified. Overall, three equilibria were distinguished, two relative to carboxylic acids exhibiting different acidic degrees (pKa1∼4.0 and pKa2∼6.0) and one relative to alcohols (pKa4∼10.0). Upon functionalization on carboxylate sites, thiol (pKa(GOSH/GONRSH)=6.7) and imidazole (pKa(GOIMZ)=6.6) moieties were discerned, followed by a decrease of their carboxylate percentage (compared to the precursors), thus allowing determining the degree of functionalization (48% and 36% of thiol content for GOSH and GONRSH respectively, and 29% of imidazole for GOIMZ). The proposed method is innovative and simpler when compared to the traditional tools usually employed to quantify chemical functionalization.