Highly piezoelectric, biodegradable, and flexible amino acid nanofibers for medical applications.

Amino acid crystals are an attractive piezoelectric material as they have an ultrahigh piezoelectric coefficient and have an appealing safety profile for medical implant applications. Unfortunately, solvent-cast films made from glycine crystals are brittle, quickly dissolve in body fluid, and lack crystal orientation control, reducing the overall piezoelectric effect. Here, we present a material processing strategy to create biodegradable, flexible, and piezoelectric nanofibers of glycine crystals embedded inside polycaprolactone (PCL). The glycine-PCL nanofiber film exhibits stable piezoelectric performance with a high ultrasound output of 334 kPa [under 0.15 voltage root-mean-square (Vrms)], which outperforms the state-of-the-art biodegradable transducers. We use this material to fabricate a biodegradable ultrasound transducer for facilitating the delivery of chemotherapeutic drug to the brain. The device remarkably enhances the animal survival time (twofold) in mice-bearing orthotopic glioblastoma models. The piezoelectric glycine-PCL presented here could offer an excellent platform not only for glioblastoma therapy but also for developing medical implantation fields.

Anionic ligand-induced chirality in perovskite nanoplatelets.

Perovskite materials passivated by chiral ligands have recently shown unique chiroptical activity with promising optoelectronic applications. However, the ligands have been limited to chiral amines. Here, chiral phosphate molecules have been exploited to synthesize CsPbBr3 nanoplatelets. The nanoplatelets showed a distinct circular dichroism signal and maintained their chiroptical properties after purification with anti-solvent.

Self-assembled materials from cellulose nanocrystals conjugated with a thermotropic liquid crystalline moiety.

Manipulating molecular and supramolecular interactions within cellulose nanocrystals (CNCs) to introduce different levels of assemblies combined with multiple functionalities is required for the development of degradable smart materials from renewable resources. To attain hierarchical structures and stimuli-responsive properties, a new class of liquid crystalline cellulosic hybrid materials is synthesized. Herein, main-chain rigid-rod-like oxidized cellulose (CNC-COOH) is prepared from a Cellulose Whatman filter paper (Cellulose W.P.) by acid hydrolysis and oxidized using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO). Thermotropic LC molecule, 4-cyano-4'-hydroxybiphenyl with a 12-methylene spacer (CB12-OH) is grafted onto the carboxylic acid group of CNC-COOH via Steglich esterification. The liquid crystalline functionalized CNCs cellulose nanocrystals (CNC-COO-CB12) are readily soluble in DMSO and ionic liquids. The extent of functionalization and structure of CNC-COO-CB12 are confirmed by solution-state 1H NMR and supported by other characterization techniques. We investigate the interplay of liquid crystalline orientational order of CNCs and cyanobiphenyl (CB12), and the supramolecular hydrogen bonding of CNCs within CNC-COO-CB12 and compare it with CNC-COOH. The introduction of thermotropic CB12 side chains onto rigid-rod CNCs shows the exclusive formation of smectic mesophases from the assemblies of CB12 with the absence of the cholesteric mesophase typically observed from CNC-COOH as verified by temperature-controlled SAXS (T-SAXS). This is further verified by UV-visible and SEM studies that show CNC-COO-CB12 forms smectic domains while CNC-COOH forms a visible light reflecting cholesteric mesophase in dried films. Thus, the interplay of liquid crystalline order of CNCs and CB12 and supramolecular hydrogen bonding of CNCs results in ordered, smectic-mesostructured CNCs for use in stimuli-responsive functional materials.

Biodegradable nanofiber-based piezoelectric transducer.

Piezoelectric materials, a type of "smart" material that generates electricity while deforming and vice versa, have been used extensively for many important implantable medical devices such as sensors, transducers, and actuators. However, commonly utilized piezoelectric materials are either toxic or nondegradable. Thus, implanted devices employing these materials raise a significant concern in terms of safety issues and often require an invasive removal surgery, which can damage directly interfaced tissues/organs. Here, we present a strategy for materials processing, device assembly, and electronic integration to 1) create biodegradable and biocompatible piezoelectric PLLA [poly(l-lactic acid)] nanofibers with a highly controllable, efficient, and stable piezoelectric performance, and 2) demonstrate device applications of this nanomaterial, including a highly sensitive biodegradable pressure sensor for monitoring vital physiological pressures and a biodegradable ultrasonic transducer for blood-brain barrier opening that can be used to facilitate the delivery of drugs into the brain. These significant applications, which have not been achieved so far by conventional piezoelectric materials and bulk piezoelectric PLLA, demonstrate the PLLA nanofibers as a powerful material platform that offers a profound impact on various medical fields including drug delivery, tissue engineering, and implanted medical devices.

Correction: A narrow amide I vibrational band observed by sum frequency generation spectroscopy reveals highly ordered structures of a biofilm protein at the air/water interface.

Correction for 'A narrow amide I vibrational band observed by sum frequency generation spectroscopy reveals highly ordered structures of a biofilm protein at the air/water interface' by Zhuguang Wang et al., Chem. Commun., 2016, 52, 2956-2959.

A narrow amide I vibrational band observed by sum frequency generation spectroscopy reveals highly ordered structures of a biofilm protein at the air/water interface.

We characterized BslA, a bacterial biofilm protein, at the air/water interface using vibrational sum frequency generation spectroscopy and observed one of the sharpest amide I bands ever reported. Combining methods of surface pressure measurements, thin film X-ray reflectivity, and atomic force microscopy, we showed extremely ordered BslA at the interface.