Enzyme-induced Aggregation of Plasmonic Nanoparticles for the Development of Label-free and Ultrasensitive Detection of Bacterial DNA

Sensitive detection of pathogens is critical to ensure the safety of food supplies and to prevent bacterial disease infection and outbreak at the first onset. While conventional techniques such as cell culture, ELISA, PCR, etc. have been used as the predominant detection workhorses, they are however limited by either time-consuming procedure, complicated sample pre-treatment, expensive analysis and operation, or inability to be implemented at point-of-care testing. Here, we present our recently developed assay exploiting enzyme-induced aggregation of plasmonic gold nanoparticles (AuNPs) for label-free and ultrasensitive detection of bacterial DNA. In the experiments, AuNPs are first functionalized with specific, single-stranded RNA probes so that they exhibit high stability in solution even under high electrolytic condition thus exhibiting red color. When bacterial DNA is present in a sample, a DNA-RNA heteroduplex will be formed and subsequently prone to the RNase H cleavage on the RNA probe, allowing the DNA to liberate and hybridize with another RNA strand. This continuously happens until all of the RNA strands are cleaved, leaving the nanoparticles ‘unprotected’. The addition of NaCl will cause the ‘unprotected’ nanoparticles to aggregate, initiating a colour change from red to blue. The reaction is performed in a multi-well plate format, and the distinct colour signal can be discriminated by naked eye or simple optical spectroscopy. As a result, bacterial DNA as low as pM could be unambiguously detected, suggesting that the enzyme-induced aggregation of AuNPs assay is very easy to perform and sensitive, it will significantly benefit to development of fast and ultrasensitive methods that can be used for disease detection and diagnosis.

Endonuclease Controlled Aggregation of Gold Nanoparticles for the Ultrasensitive Detection of Pathogenic Bacterial DNA

The development of an ultrasensitive biosensor for the low-cost and on-site detection of pathogenic DNA could transform detection capabilities within food safety, environmental monitoring and clinical diagnosis. Herein, we present an innovative approach exploiting endonuclease-controlled aggregation of plasmonic gold nanoparticles (AuNPs) for label-free and ultrasensitive detection of bacterial DNA. The method utilizes RNA-functionalized AuNPs which form DNA-RNA heteroduplex structures through specific hybridization with target DNA. Once formed, the DNA-RNA heteroduplex is susceptible to RNAse H enzymatic cleavage of the RNA probe, allowing the target DNA to liberate and hybridize with another RNA probe. This continuously happens until all of the RNA probes are cleaved, leaving the nanoparticles unprotected and thus aggregated upon exposure to a high electrolytic medium. The assay is ultrasensitive, allowing the detection of target DNA at femtomolar level by simple spectroscopic analysis (40.7 fM and 2.45 fM as measured by UV-vis and dynamic light scattering (DLS), respectively). The target DNA spiked food matrix (chicken meat) is also successfully detected at a concentration of 1.2 pM (by UV-vis) or 18.0 fM (by DLS). In addition to the ultra-high sensitivity, the total analysis time of the assay is less than 3 hours, thus demonstrating its practicality for food analysis.

Equipping young people to engage with media driven science experiences: beyond science knowledge to science literacy and discerning consumers of news.

This paper reports on a study of a curricular intervention for pupils (age 10-13 years) in the UK aimed at supporting critical engagement with science based media reports. In particular the study focused on core elements of knowledge, skills and attitudes identified in previous studies that characterize critical consumers of science presented as news. This was an empirical study based on classroom observation. Data included responses from individual pupils, in addition video recording of group activity and intentional conversations between pupils and teachers were scrutinised. Analysis focused on core tasks relating to different elements of critical reading. Pupils demonstrated a grasp of questioning and evaluating text, however the capacity to translate this experience in support of a critical response to a media report with a science component is limited in assessing the credibility of text and as an element in critical reading.

Knowledge and acceptance of Human Papillomavirus (HPV) and HPV vaccination in adolescent boys worldwide: a systematic review

Aim

To determine HPV and HPV vaccine awareness, knowledge and acceptance in male adolescents worldwide.

Methods

A mixed methods systematic review was conducted. In accordance with PRISMA guidelines, relevant literature was identified through an electronic database search using specified keywords from inception to September 2015. Non-interventional studies presented in English that assessed HPV knowledge and provided data on male adolescents were included. If available, data on HPV and HPV vaccine perceptions, attitudes and/or HPV vaccine acceptance were also extracted. All studies were critically appraised to provide an indication of methodological quality. Results were compiled using a convergent synthesis.

Results

22 papers were included. The majority of studies were cross-sectional and conducted in the US and Europe. Across continents, regardless of a country’s HPV vaccination programme status, boys’ knowledge of HPV and/or HPV vaccination was generally low to moderate and significantly lower than female knowledge or awareness. There was a disagreement in the association of knowledge and vaccine acceptance, with higher knowledge not always being predictive of acceptance.

Conclusions

Comparison and synthesis of research concerning HPV knowledge and attitudes was made difficult due to the lack of universal definition of vaccine acceptance, and no universally accepted tool for its measurement or for the measurement of HPV knowledge. It is imperative that future research utilises consistent measures of HPV knowledge and attitudes to facilitate interpretation and comparison across studies internationally. Prospective longitudinal studies would be more informative providing data on factors that influenced the move from vaccine intention to uptake.