Nano LIFE

Gold nanoparticles are the most extensively studied nanomaterials for biomedical application due to their unique properties, such as rapid and simple synthesis, large surface area, strong adsorption ability and facile conjugation to various biomolecules. The remarkable photophysical properties of gold nanoparticles have provided plenty of opportunities for the preparation of gold nanoparticles-based optical biosensors, while the excellent biocompatibility, conductivity, catalytic properties and large surface-to-volume ratio have facilitated the application of gold nanoparticles in the construction of electrochemical biosensors. In this review, we mainly detail the gold nanoparticles-based optical and electrochemical biosensors for biomedical application in the recent two years, which have exhibited greatly enhanced analytical performances in the detection of DNA, proteins and some important small molecules.

Electrospinning is a process for generating micrometer or nanometer scale polymer fibers with large surface areas and high porosity. For tissue engineering research, the electrospinning technique provides a quick way to fabricate fibrous scaffolds with dimensions comparable to the extracellular matrix (ECM). A variety of materials can be used in the electrospinning process, including natural biomaterials as well as synthetic polymers. The natural biomaterials have advantages such as excellent biocompatibility and biodegradability, which can be more suitable for making biomimic scaffolds. In the last two decades, there have been growing numbers of studies of biomaterial fibrous scaffolds using the electrospinning process. In this review, we will discuss biomaterials in the electrospinning process and their applications in tissue engineering.

Inactivation of pathogens from environment and inhibition of biofilm formation on various surfaces are important for biosafety, biosecurity and public health. Carbon nanotubes (CNTs) possess antimicrobial effects in addition to their unique optical, electrical, mechanical and thermal properties. This review summarizes the antimicrobial effects of single walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) in suspensions and on CNT contained surfaces. To increase antimicrobial effects, CNT composites containing other antimicrobial reagents are introduced. Also described are the possible antimicrobial mechanisms of CNTs.

The objective of this study is to characterize the pH sensing performance of carbon nanotube-based thin films and compare them to their non-carbon nanotube-based counterparts. A layer-by-layer technique is employed for fabricating the nanocomposites, and pH sensitivity is encoded by incorporating polyaniline (PANI) by itself or with single-walled carbon nanotubes during film fabrication. In particular, polyaniline is doped with different counter ions such as hydrochloric acid (HCl) and methane sulfonic acid (MeSA) for fabricating four different thin film sample sets. The as fabricated films are subjected to various pH buffer solutions ranging from pH 1 to 13 while their electrical properties are simultaneously measured using two different techniques. First, time-domain bulk film resistance measurements have been conducted, and the findings show that all four types of films exhibit pH sensitivity. Their bulk film resistances increase in tandem with increasing pH. Second, frequency-domain electrical impedance spectroscopy (EIS) has also been conducted when the films are exposed to different pH buffers. The recorded EIS spectra have been fit to a proposed equivalent circuit model consisting of resistors, capacitors and a constant-phase element. The results suggest that the MeSA-based films exhibit linear sensitivity, whereas the HCl-based films exhibit a bilinear sensitivity in the time-domain case. Both HCl- and MeSA-based films exhibit a bilinear pH response in the frequency domain. The equivalent circuit has also revealed that the equivalent parallel capacitor and the constant-phase element of the HCl-and MeSA-doped films also exhibit an inverse bilinear sensitivity to pH buffer solutions.

The proposed design uses Quantum Dots (QDs) and basic MEMS fabrication techniques to create a flexible thin-film optical heart rate sensor. Fields including health sciences, fitness sciences and psychophysiological studies can benefit from a biosensor that detects heart rate (HR) in a noninvasive manner. Optical heart rate sensors achieve this by being able to collect signals simply through contact with the user. While the sensing method itself is nothing new, the nature of the flexible thin-film structure will allow the device to achieve maintained unobtrusive contact with minimal effort.

A versatile method for constructing nonbiofouling and micropatterned surfaces bearing brush type poly(2-methacryloyloxyethyl phosphorylcholine) (MPC) on polymeric substrates using living radical polymerization with N,N-diethyldithiocarbamate moiety as a photoiniferter for microbiodevices was demonstrated. The polymeric photoiniferters comprised of 4-vinyl benzyl N,N-diethyldithiocarbamate (VBDC) and 2-ethylhexyl methacrylate (EHMA) were synthesized with variation of VBDC contents from 10% to 40% to easily tune the chain density of poly(MPC) grafted while the chain length was regulated by changing photoirradiation time. The characterizations of the poly(MPC)-modified surfaces were conducted by using attenuated total reflection infrared (ATR-IR), X-ray photoelectron spectroscopy (XPS), ellipsometric measurements, along with atomic force microscopy (AFM). The nonspecific protein adsorption from single and binary solutions of bovine plasma fibrinogen and bovine serum albumin was greatly suppressed on moderate to high chain density, moderate chain length of poly(MPC) and on smooth surfaces. The modified surfaces excellently eliminate cell adhesion of fibroblast-like cell L929 as well. Further, micropatterned-nonbiofouling poly(MPC) brush surface could be constructed using photomask with high fidelity.

Bacterial pathogens, such as Pseudomonas aeruginosa, readily form biofilms on surfaces, limiting the efficacy of antimicrobial and antibiotic treatments. To mitigate biofilm formation, surfaces are often treated with antimicrobial agents, which have limited lifetime and efficacy. Recent studies have shown that well-ordered topographic patterns can limit bacterial attachment to surfaces and limit biofilm formation. In this study, nano and microscale patterned poly(dimethylsiloxane) surfaces were evaluated for their ability to affect adhesion and biofilm formation by Pseudomonas aeruginosa. Feature size and spacing were varied from 500 nm to 2 μm and included repeating arrays of square pillars, holes, lines and biomimetc Sharklet™ patterns. Bacterial surface adhesion and biofilm formation was assessed in microfluidic flow devices and under static conditions. Attachment profiles under static and fluid flow varied within topography types, sizes and spacing. Pillar structures of all sizes yielded lower surface attachment than line-based patterns and arrays of holes. This trend was also observed for biomimetic Sharklet™ patterns, with reduced bacterial attachment to "raised" features as compared to "recessed" features. Notably, none of the topographically patterned surfaces outperformed smooth surfaces (without topography) for resisting cell adhesion. Initial surface attachment patterns were indicative of subsequent biofilm formation and coverage, suggesting a direct role of surface topography in biofilm-based biofouling.

We presented a new approach to produce Chitosan–Glutaraldehyde–Chitosan–Alginate (CGCA) hollow fiber with the capability of cell capture and adhesion for vascular tissue engineering. The CGCA hollow fiber was generated by sacrificing the inner part of alginate/chitosan (A/C) solid fiber using sodium citrate, followed by glutaraldehyde (GA) cross-linking chitosan to form stable imine bonds on the fiber surface. Furthermore, human umbilical vein endothelial cells (HUVEC) were captured by the CGCA hollow fiber surface and adhesive as layer pattern with good viability and normal morphology. This strategy facilitated the lumen structure formation with good biocompatibility by biomaterials modification, providing a promising and facile technique for blood vessel regeneration in vitro and in vivo.

One of the major limitations in producing transgenic soybeans using the agrobacterium-mediated cotyledonary-node method is low regeneration frequency. An improved highly efficient regeneration system of soybean was established herein. Cotyledonary node explants were placed in shoot initiation medium with single-wall carbon nanotube (SWNT) for adventitious shoots regeneration, and adventitious shoots were subcultured in shoot elongation medium with SWNT for shoot elongation and rooting. 40 mg/L SWNT supplemented in shoot initiation medium was found to be the optimal concentration with shoots regeneration frequency significantly increased by 21.5% compared with the control treatment, while for 4 mg/L and 400 mg/L, the increase was 4.6% and 6.5%, respectively. Faster elongation and rooting of adventitious shoots was observed in shoot elongation medium with 40 mg/L SWNT. Soybean plantlet formation frequency within the limited four weeks supplemented with 40 mg/L SWNT reached 48.4% while in the other three treatments: 4 mg/L, 400 mg/L and control, 0% were observed. These results indicate that supplement of SWNT in the soybean medium can efficiently promote adventitious shoots formation frequency, increase plantlet formation frequency and shorten the regeneration period.