Reductase-like Activity of Silicon Nanowire Arrays

The MTT (3-(4,5-dimethyl-2-thiazol)-2,5-diphenyl-2H-tetrazolium bromide) reduction method is widely used for measuring cell viability and proliferation. However, when MTT was used to study cells on silicon nanowire arrays (SiNWAs), the measured viability was much higher than normal values, resulting in a misleading estimate of cell viability. Our results demonstrated that the apparent high viability of cells is due to the fact that the SiNWAs itself was capable of reducing MTT in the absence of cells. In the presence of coenzyme, its reducing capacity was enhanced, thus showing the reductase-like function of SiNWAs. Furthermore, the chemical composition and nanostructure of Si surface had a strong influence on MTT reduction with the HF-treated SiNWAs (H-SiNWAs) showing significant reducing capacity. For example, the reduction capacity of H-SiNWAs samples was significantly higher than that of HF-treated planar silicon, whereas Piranha-treated SiNWAs and planar silicon did not reduce MTT. H-SiNWAs were also used for the reduction of azo dyes and showed a decolorization rate of more than 65% and as high as 90%. These findings suggest the potential use of SiNWAs as enzyme-mimics in biotechnology and environmental chemistry

Stimulation of Gene Transfection by Silicon Nanowire Arrays Modified with Polyethylenimine

In this work, a novel gene delivery strategy was proposed based on silicon nanowire arrays modified with high-molecular-weight 25 kDa branched polyethylenimine (SN-PEI). Both the plasmid DNA (pDNA) binding capacity and the in vitro gene transfection efficiency of silicon nanowire arrays (SiNWAs) were significantly enhanced after modification with high-molecular-weight bPEI. Moreover, the transfection efficiency was substantially further increased by the introduction of free pDNA/PEI complexes formed by low-molecular-weight branched PEI (bPEI, 2 kDa). Additionally, factors affecting the in vitro transfection efficiency of the novel gene delivery system were investigated in detail, and the transfection efficiency was optimized on SN-PEI with a bPEI grafting time of 3 h, an incubation time of 10 min for tethered pDNA/PEI complexes consisting of high-molecular-weight bPEI grafted onto SiNWAs, and with an N/P ratio of 80 for free pDNA/PEI complexes made of low-molecular-weight bPEI. Together, our results indicate that high-molecular-weight bPEI modified SiNWAs can serve as an efficient platform for gene delivery

Catalase-like and Peroxidase-like Catalytic Activities of Silicon Nanowire Arrays

Silicon nanowire arrays (SiNWAs) were found to have catalytic activities similar to those of biological enzymes catalase and peroxidase. Thus not only can these materials catalyze the decomposition reaction of H₂O₂ into water and oxygen, but they can also catalyze the oxidation of <i>o</i>-phenylenediamine (OPD), a common substrate for peroxidases, by H₂O₂. The presence of Si–H bonds and the morphology of the SiNWAs are found to be crucial to the occurrence of such catalytic activity. When the SiNWAs are reacted with H₂O₂, the data from Raman spectroscopy suggests the formation of (Si–H)₂···(O species) ((Si–H)₂···Os), which is presumably responsible for the catalytic activity. These findings suggest the potential use of SiNWAs as enzyme mimics in medicine, biotechnology, and environmental chemistry

Catalase-like and Peroxidase-like Catalytic Activities of Silicon Nanowire Arrays

Silicon nanowire arrays (SiNWAs) were found to have catalytic activities similar to those of biological enzymes catalase and peroxidase. Thus not only can these materials catalyze the decomposition reaction of H₂O₂ into water and oxygen, but they can also catalyze the oxidation of <i>o</i>-phenylenediamine (OPD), a common substrate for peroxidases, by H₂O₂. The presence of Si–H bonds and the morphology of the SiNWAs are found to be crucial to the occurrence of such catalytic activity. When the SiNWAs are reacted with H₂O₂, the data from Raman spectroscopy suggests the formation of (Si–H)₂···(O species) ((Si–H)₂···Os), which is presumably responsible for the catalytic activity. These findings suggest the potential use of SiNWAs as enzyme mimics in medicine, biotechnology, and environmental chemistry

Summary of effect sizes of pooled estimates of uptake from meta-analysis.

Pooled RR effect sizes ranged from near 1.0 (indicating no improvement in uptake of HTS) through nearly 7.0 (indicating a large effect size); not important improvements (RR p p > 0.05). CI, confidence interval; HTS, HIV testing service; RR, relative risk; SMS, short message service; vs., versus.</p

PRISMA flowchart.

BackgroundHIV testing services (HTS) are the first steps in reaching the UNAIDS 95-95-95 goals to achieve and maintain low HIV incidence. Evaluating the effectiveness of different demand creation interventions to increase uptake of efficient and effective HTS is useful to prioritize limited programmatic resources. This review was undertaken to inform World Health Organization (WHO) 2019 HIV testing guidelines and assessed the research question, “Which demand creation strategies are effective for enhancing uptake of HTS?” focused on populations globally.Methods and findingsThe following electronic databases were searched through September 28, 2021: PubMed, PsycInfo, Cochrane CENTRAL, CINAHL Complete, Web of Science Core Collection, EMBASE, and Global Health Database; we searched IAS and AIDS conferences. We systematically searched for randomized controlled trials (RCTs) that compared any demand creation intervention (incentives, mobilization, counseling, tailoring, and digital interventions) to either a control or other demand creation intervention and reported HTS uptake. We pooled trials to evaluate categories of demand creation interventions using random-effects models for meta-analysis and assessed study quality with Cochrane’s risk of bias 1 tool. This study was funded by the WHO and registered in Prospero with ID CRD42022296947.We screened 10,583 records and 507 conference abstracts, reviewed 952 full texts, and included 124 RCTs for data extraction. The majority of studies were from the African (N = 53) and Americas (N = 54) regions. We found that mobilization (relative risk [RR]: 2.01, 95% confidence interval [CI]: [1.30, 3.09], p p N = 4 RCTs), couple-oriented counseling (RR: 1.98, 95% CI [1.02, 3.86], p p N = 4 RCTs), peer-led interventions (RR: 1.57, 95% CI [1.15, 2.15], p p N = 10 RCTs), motivation-oriented counseling (RR: 1.53, 95% CI [1.07, 2.20], p p N = 4 RCTs), short message service (SMS) (RR: 1.53, 95% CI [1.09, 2.16], p p N = 5 RCTs), and conditional fixed value incentives (RR: 1.52, 95% CI [1.21, 1.91], p p N = 11 RCTs) all significantly and importantly (≥50% relative increase) increased HTS uptake and had medium risk of bias.Lottery-based incentives and audio-based interventions less importantly (25% to 49% increase) but not significantly increased HTS uptake (medium risk of bias). Personal invitation letters and personalized message content significantly but not importantly (ConclusionsMobilization, couple- and motivation-oriented counseling, peer-led interventions, conditional fixed value incentives, and SMS are high-impact demand creation interventions and should be prioritized for programmatic consideration. Reduced duration counseling and video-based interventions are an efficient and effective alternative to address staffing shortages. Investment in demand creation activities should prioritize those with undiagnosed HIV or ongoing HIV exposure. Selection of demand creation interventions must consider risks and benefits, context-specific factors, feasibility and sustainability, country ownership, and universal health coverage across disease areas.</div

Subgroup analyses for meta-analyses with high statistical heterogeneity.

Subgroup analyses for meta-analyses with high statistical heterogeneity.</p

Trim-and-fill adjusted estimates of uptake and yield.

Trim-and-fill adjusted estimates of uptake and yield.</p

Geographic distribution of included trials.

Key and bar chart identify the total number of trials included from each country on the map. The rworldmap [cran.r-project.org] package in R was used to obtain the publicly available map (South A (2011). “rworldmap: A New R package for Mapping Global Data.” The R Journal, 3(1), 35–43. ISSN 2073-4859); the base layer map file can be found: https://code.google.com/archive/p/rworld/source/default/source. (DOCX)</p

Funnel plots and Egger’s tests to assess publication bias.

Funnel plots and Egger’s tests to assess publication bias.</p