A photoresponsive amphiphilic gold nanoparticle (AuNP) is achieved through the decoration of AuNP with hydrophilic poly(ethylene glycol) (PEG) and hydrophobic photoresponsive polymethacrylate containing spiropyran units (PSPMA). Owing to the photoresponsive property of spiropyran units, the amphiphilic AuNPs can easily achieve the controllable assembly/disassembly behaviors under the trigger by light. Under visible light, spiropyran units provide weak intermolecular interactions between neighbored AuNPs, leading to isolated AuNPs in the solution. While under UV light irradiation, spiropyran units in the polymer brushes transform into merocyanine isomer with conjugated structure and zwitterionic state, promoting the integration of adjacent AuNPs through π-π stacking and electrostatic attractions, further leading to the formation of Au oligomers. The smart reversible AuNP oligomers exhibited switchable plasmonic coupling for tuning surface-enhanced Raman scattering (SERS) activity, which is promising for the application of SERS based sensors and optical imaging.

Gold nanoparticles (AuNPs) labeled lateral-flow test strip immunoassay (LFTS) has been widely used in biomedical, feed/food, and environmental analysis fields. Conventional ILFS assay usually uses spherical AuNPs as labeled probes and shows low detection sensitivity, which further limits its widespread practical application. Unlike spherical AuNP used as labeled probe in conventional ILFS, in our present study, a hierarchical flowerlike AuNP specific probe was designed for LFTS and further used to detect Escherichia coli O157:H7 (E. coli O157:H7). Three types of hierarchical flowerlike AuNPs, such as tipped flowerlike, popcornlike, and large-sized flowerlike AuNPs were synthesized in a one-step method. Compared with other two kinds of Au particles, tipped flowerlike AuNPs probes for LFTS particularly exhibited highly sensitive detection of E. coli O157:H7. The remarkable improvement of detection sensitivity of tipped flowerlike AuNPs probes can be achieved even as low as 10(3) colony-forming units (CFU)/mL by taking advantages of its appropriate size and hierarchical structures, which is superior over the detection performance of conventional LFTS. Using this novel tipped flower AuNPs probes, quantitative detection of E. coli O157:H7 can be obtained partially in a wide concentration range with good repeatability. This hierarchical tipped flower-shaped AuNPs probe for LFTS is promising for the practical applications in widespread analysis fields.

Background HIV-infected women need highly effective contraception to reduce unintended pregnancies and mother-to-child HIV transmission. Previous studies report conflicting results regarding the effect of hormonal contraception (HC) on HIV disease progression. Methods HIV-infected women in Uganda and Zimbabwe were recruited immediately after seroconversion; CD4 testing and clinical exams were conducted quarterly. The study endpoint was time to AIDS (two successive CD4 ≤200 cells/mm3 or WHO advanced stage 3 or stage 4 disease). We used marginal structural Cox survival models to estimate the effect of cumulative exposure to depot-medroxyprogesterone acetate (DMPA) and oral contraceptives (OC) on time to AIDS. Results 303 HIV-infected women contributed 1,408 person-years (py). 111 women (37%) developed AIDS. Cumulative probability of AIDS was 50% at 7 years and did not vary by country. AIDS incidence was 6.6, 9.3 and 8.8 per 100py for DMPA, OC and non-hormonal users. Neither DMPA (adjusted hazard ratio (AHR) = 0.90; 95% CI 0.76-1.08) nor OCs (AHR =1.07; 95% CI 0.89-1.29) were associated with HIV disease progression. Alternative exposure definitions of HC use during the year prior to AIDS or at time of HIV infection produced similar results. STI symptoms were associated with faster progression while young age at HIV infection (18-24 years) was associated with slower progression. Adding baseline CD4 level and setpoint viral load to models did not change the HC results but subtype D infection became associated with disease progression. Conclusion Hormonal contraceptive use was not associated with more rapid HIV disease progression but older age, STI symptoms and subtype D infection were.

Because of the distinctive features of ease-of-use, low cost and portable detection, a gold nanoparticle (AuNP) based lateral flow immunoassay (LFA) is an effective and currently used method for the detection of Escherichia coli O157:H7; however, its low sensitivity limits its practical use. In the present study, the size and uniformity of AuNPs have been systematically optimized to maximally amplify both the visual inspection signals (the color of test line) and the quantitative data (light intensity) recorded using a bioassay reader. The remarkable enhancement of detection sensitivity can be increased to 10 2 colony forming units per mL by taking advantage of the optimized AuNPs and the separated incubation of the AuNPs/antibody/E. coli O157:H7 complex. Quantitative detection of E. coli O157:H7 was partially obtained in a wide concentration range with good repeatability. The new, optimized AuNPs-based LFA is well suited to fast quantitative and qualitative food analysis.