Au@Ag Core-shell Nanorods Self-assembled on Polyelectrolyte Multilayers for Ultra-High Sensitivity SERS Fiber Probes

We demonstrated a chemical process in the fabrication of a SERS fiber probe with an ultrahigh sensitivity.The synthesis was carried out by preparing Au@Ag core-shell nanorods (Au@Ag-NRs) selfassembled on polyelectrolyte (PE) multilayers,for which Au@Ag-NRs were controlled by adjusting the silver layer thickness.The effect of silver layer thickness of Au@Ag-NRs on the SERS performance of the fiber probe was investigated.The SERS fiber probe shows the best performance when the silver layer thickness is controlled at 8.57 nm.Under the condition of optimizing silver layer thickness,the fiber probe exhibits ultra-high sensitivity (i e,10^(-10) M crystalline violet,CV),good reproducibility (i e,RSD of 3.5%) and stability.Besides,electromagnetic field distribution of the SERS fiber probe was also investigated.The strongest enhancement is found within the core of fiber,whereas a weakened electromagnetic field exists in the fiber cladding layer.The SERS fiber probe can be a good candidate in ultra-trace detection for biomedical and environmental areas.

Probing surface interactions of underwater oleophobic polyelectrolyte multilayers

In the present work,the interaction mechanism of specific polyelectrolyte multilayers(PEMs),fabricated by layer-by-layer deposition of polydiallyldimethylammonium chloride(PDDA)and poly(sodium 4-styrenesulfonate)(PSS),is studied using atomic force microscopy.The underwater oil-repellency of PS S-capped PEMs was further explored by measuring the interaction forces between tetradecane droplets and PEMs-coated silica substrates under various salinities.The force curves were analyzed following the Stokes-Reynolds-Young-Laplace theoretical model.Desirable consistency was achieved between the experimental and theoretical calculations at low NaCl concentrations(0.1 mM and 1 mM);however,underestimation of the attractive force was found as the NaCl concentration increases to moderate(10 mM)and high(100 mM)levels.Discrepancy analyses and incorporated features toward a reduced surface charge density were considered based on the previous findings of the orientation of anionic benzenesulfonate moieties(Liu et al.in Angew Chem Int Ed 54(16):4851-4856,2015.https://doi.org/10.1002/anie.201411992).Short-range steric hindrance interactions were further introduced to simulate"brush"effect stemming from nanoscale surface roughness.It is demonstrated in our work that the PSS-capped PEMs remains a stable underwater lipophobicity against high salinity,which renders it potential application in surface wetting modification and anti-fouling.

Fiber Optic Humidity Sensor Based on Self-Assembled Polyelectrolyte Multilayers

Polyelectrolyte multilayers were self-assembled onto planar glass substrates and multimode optic fibers. The multilayer thin films deposited on glass substrates were characterized by using UV-vis spectroscopy and X-ray photoelectron spectroscope. The multilayer thin films containing hydrophilic side-groups possessed are affinity for uwer molecules. The adsorption and desorption of free water vapor gave rise to the changes in the refractive index and in the reflectance of the thin films. A multilayer thin film based fiber optic humidity sensor with an LED light source of 0.85 mum was designed. Under certain conditions, the rejected light intensity of the thin film sensor was a function of the humidity of air. About 30 bilayers was optimal for the multilayer thin film sensor working at wavelength of 0.85 mum. This sensor can work over almost the whole relative humidity range with very good sensitivity.

Polyelectrolyte Multilayer Patterns Created by Capillary Force and Their Impact on Cell Migration

Cell migration plays a crucial role in a variety of physiological and pathological processes.In this study a method of capillary force lithography was used to treat poly(sodium 4-styrenesulfonate) (PSS)/poly(diallyldimethylammonium) chloride (PDADMAC) multilayers with a PDMS stamp before or after etching by NaC1 solution,yielding physical patterns with various features such as double thin lines,double strips,meniscus-shaped ridges,and high ridges.The ridge height is controllable in the range of 25 and 1100 nm.Migration of smooth muscle cells (SMCs) was restrained by the double-line patterns in a ridge height-dependent manner.By contrast,the mobility of SMCs was controlled by both the hydration ratio of the multilayers and the pattern features.

Controllable Synthesis of Au NRs and Its Flexible SERS Optical Fiber Probe with High Sensitivity

The surface-enhanced Raman scattering(SERS) optical fiber probes were successfully prepared by self-assembling on polyelectrolyte multilayers. Gold nanorods(Au NRs) were used as SERS enhancement material to give excellent biological affinity and stability to the SERS optical fiber probes. Au NRs were synthesized by seed growth method. The synergistic effect between AgNO_(3) and surfactant was investigated, and the highest yield was found when AgNO_(3) was 500 uL. Meanwhile, different SERS optical fiber probes were obtained by selecting silane coupling agent, polyelectrolyte multilayer and graphene oxide(GO) to treat quartz fiber. It was found that the SERS optical fiber probes obtained by the self-assembled on polyelectrolyte multilayers method performed better than those by other methods. In addition, Mapping was combined with finite element simulation to analyze the electromagnetic field distribution at the fiber end face.The electromagnetic field distribution of Au NRs was investigated, the difference of electromagnetic field intensity around the Au NRs with different arrangements was compared, the strongest signal was obtained when the Au NRs were head-to-head. Finally, sensitivity of the optimized SERS optical fiber probes could reach 10^(-9)mol/L, with excellent stability and repeatability.

In situ Molecular Self-assembly and Sensitive Label-free Detection of Streptavidin via a Wavelength Interrogated Surface Plasmon Resonance Sensor

The sensing sensitivity of wavelength interrogated surface plasmon resonance（WISPR） biosensor is improved by self-assembly of polyelectrolyte multilayer（PEM） film of poly（allylamine hydrochloride）（PAH）/ poly（sodium-p-styrenesulfonate）（PSS） on the Au film coated glass chip via the layer-by-layer（LBL） technique. The home-made WISPR with Krestchmann configuration consists of a tungsten-halogen lamp as a photon source and a charge coupled device（CCD） camera as the detector. The influence of PEM film thickness on the optical properties of WISPR biosensors was investigated theoretically and experimentally. In order to achieve higher sensing sensitivity, the PEM film thickness has to be designed as ca.14 nm at an Au layer thickness of 50 nm and an incidental angle of 11.8°. Furthermore, the PEM coated WISPR biosensor can serve as highly sensitive biosensor, in which the biotin-streptavidin is used as bioconjugate pair. After deposition of the PEM film of （biotin/PAH）（PSS/PAH）3, the modified WISPR biosensor is more sensitive to the low concentration（〈0.01 mg/mL） of streptavidin. And the sensing sensitivity can be further increased by one order of magnitude compared with that of the biotin/PAH coated WISPR biosensor. Thus, such low-cost, high-performance and efficient PEM-coated WISPR biosensors have great potentials in a diverse array of fields such as medical diagnostics, drug screening, food safety analysis, environmental monitoring, and homeland security.

3D porous acellular cartilage matrix scaffold with surface mediated sustainable release of TGF-β3 for cartilage engineering

Acellular tissue matrix scaffolds are much closer to tissue’s complex natural structure and biological characteristics,thus assess great advantages in cartilage engineering.We used rabbit costal cartilage to prepare acellular microfilaments and further 3D porous acellular cartilage scaffold via crosslinking.Poly(_L-lysine)/hyaluronic acid(PLL/HA)multilayer film was then built up onto the surface of the resulting porous scaffold.Furthermore,TGF-β3 was loaded into the PLL/HA multilayer film coated scaffold to obtain a 3D porous acellular cartilage scaffold with sustained releasing of TGF-β3 up to 60 days.The success of this project will provide a new way for the treatment of articular cartilage defects.Meanwhile,the anchoring and on-site sustained releasing of growth factors mediated by polyelectrolyte multilayered film can also provide a new method for improving the biocompatibility and the biofunctionality for other implanted biomaterials.