Reduced graphene oxide-based field effect transistors for the detection of E7 protein of human papillomavirus in saliva.

Several challenging biological sensing concepts have been realized using electrolyte-gated reduced graphene oxide field effect transistors (rGO-FETs). In this work, we demonstrate the interest of rGO-FET for the sensing of human papillomavirus (HPV), one of the most common sexually transmitted viruses and a necessary factor for cervical carcinogenesis. The highly sensitive and selective detection of the HPV-16 E7 protein relies on the attractive semiconducting characteristics of pyrene-modified rGO functionalized with RNA aptamer Sc5-c3. The aptamer-functionalized rGO-FET allows for monitoring the aptamer-HPV-16 E7 protein binding in real time with a detection limit of about 100 pg mL-1 (1.75 nM) for HPV-16 E7 from five blank noise signals (95% confidence level). The feasibility of this method for clinical application in point-of-care technology is evaluated using HPV-16 E7 protein suspended in saliva and demonstrates the successful fabrication of a promising field effect transistor biosensor for HPV diagnosis.Graphical abstract.

In vitro fibroblast and pre-osteoblastic cellular responses on laser surface modified Ti-6Al-4V.

The success of any implant, dental or orthopaedic, is driven by the interaction of implant material with the surrounding tissue. In this context, the nature of the implant surface plays a direct role in determining the long term stability as physico-chemical properties of the surface affect cellular attachment, expression of proteins, and finally osseointegration. Thus to enhance the degree of integration of the implant into the host tissue, various surface modification techniques are employed. In this work, laser surface melting of titanium alloy Ti-6Al-4V was carried out using a CO2 laser with an argon gas atmosphere. Investigations were carried out to study the influence of laser surface modification on the biocompatibility of Ti-6Al-4V alloy implant material. Surface roughness, microhardness, and phase development were recorded. Initial knowledge of these effects on biocompatibility was gained from examination of the response of fibroblast cell lines, which was followed by examination of the response of osteoblast cell lines which is relevant to the applications of this material in bone repair. Biocompatibility with these cell lines was analysed via Resazurin cell viability assay, DNA cell attachment assay, and alamarBlue metabolic activity assay. Laser treated surfaces were found to preferentially promote cell attachment, higher levels of proliferation, and enhanced bioactivity when compared to untreated control samples. These results demonstrate the tremendous potential of this laser surface melting treatment to significantly improve the biocompatibility of titanium implants in vivo.

Study on the productivity of silicon nanoparticles by picosecond laser ablation in water: towards gram per hour yield.

An investigation on the productivity of silicon nanoparticles by picosecond laser ablation in water is presented. A systematic experimental study is performed as function of the laser wavelength, fluence and ablation time. In case of ablation at 1064 nm silicon nanoparticles with a mean diameter of 40 nm are produced. Instead, ablation at 355 nm results in nanoparticles with a mean diameter of 9 nm for short ablation time while the mean diameter decreases to 3 nm at longer ablation time. An original model based on the in-situ ablation/photo-fragmentation physical process is developed, and it very well explains the experimental productivity findings. The reported phenomenological model has a general validity, and it can be applied to analyze pulsed laser ablation in liquid in order to optimize the process parameters for higher productivity. Finally, an outlook is given towards gram per hour yield of ultra-small silicon nanoparticles.

Influence of organic solvent on optical and structural properties of ultra-small silicon dots synthesized by UV laser ablation in liquid.

Ultra small silicon nanoparticles (Si-NPs) with narrow size distribution are prepared in a one step process by UV picosecond laser ablation of silicon bulk in liquid. Characterization by electron microscopy and absorption spectroscopy proves Si-NPs generation with an average size of 2 nm resulting from an in situ photofragmentation effect. In this context, the current work aims to explore the liquid medium (water and toluene) effect on the Si-NPs structure and on the optical properties of the colloidal solution. Si-NPs with high pressure structure (s.g. Fm3m) and diamond-like structure (s.g. Fd3m), in water, and SiC moissanite 3C phase (s.g. F4[combining macron]3m) in toluene are revealed by the means of High-Resolution TEM and HAADF-STEM measurements. Optical investigations show that water-synthesized Si-NPs have blue-green photoluminescence emission characterized by signal modulation at a frequency of 673 cm(-1) related to electron-phonon coupling. The synthesis in toluene leads to generation of Si-NPs embedded in the graphitic carbon-polymer composite which has intrinsic optical properties at the origin of the optical absorption and luminescence of the obtained colloidal solution.

Bioconjugated silicon quantum dots from one-step green synthesis.

Biofunctionalized silicon quantum dots were prepared through a one step strategy avoiding the use of chemical precursors. UV-Vis spectroscopy, Raman spectroscopy and HAADF-STEM prove oligonucleotide conjugation to the surface of silicon nanoparticle with an average size of 4 nm. The nanoparticle size results from the size-quenching effect during in situ conjugation. Photoemissive properties, conjugation efficiency and stability of these pure colloids were studied and demonstrate the bio-application potential, e.g. for nucleic acid vector delivery with semiconducting, biocompatible nanoparticles.