4D Printed Protein-AuNR Nanocomposites with Photothermal Shape Recovery.

4D printing is the 3D printing of objects that change chemically or physically in response to an external stimulus over time. Photothermally responsive shape memory materials are attractive for their ability to undergo remote activation. While photothermal methods using gold nanorods (AuNRs) have been used for shape recovery, 3D patterning of these materials into objects with complex geometries using degradable materials has not been addressed. Here, we report on the fabrication of 3D printed shape memory bioplastics with photo-activated shape recovery. Protein-based nanocomposites based on bovine serum albumin (BSA), poly (ethylene glycol) diacrylate and gold nanorods were developed for vat photopolymerization. These 3D printed bioplastics were mechanically deformed under high loads, and the proteins served as mechanoactive elements that unfolded in an energy-dissipating mechanism that prevented fracture of the thermoset. The bioplastic object maintained its metastable shape-programmed state under ambient conditions. Subsequently, up to 99% shape recovery was achieved within 1 min of irradiation with near-infrared light. Mechanical characterization and small angle X-ray scattering (SAXS) analysis suggest that the proteins mechanically unfold during the shape programming step and may refold during shape recovery. These composites are promising materials for the fabrication of biodegradable shape-morphing devices for robotics and medicine.

Physicochemical Characterization and In Vitro Activity of Poly(ε-Caprolactone)/Mycophenolic Acid Amorphous Solid Dispersions.

The obtention of amorphous solid dispersions (ASDs) of mycophenolic acid (MPA) in poly(ε-caprolactone) (PCL) is reported in this paper. An improvement in the bioavailability of the drug is possible thanks to the favorable specific interactions occurring in this system. Differential scanning calorimetry (DSC) was used to investigate the miscibility of PCL/MPA blends, measuring glass transition temperature (Tg) and analyzing melting point depression to obtain a negative interaction parameter, which indicates the development of favorable inter-association interactions. Fourier transform infrared spectroscopy (FTIR) was used to analyze the specific interaction occurring in the blends. Drug release measurements showed that at least 70% of the drug was released by the third day in vitro in all compositions. Finally, preliminary in vitro cell culture experiments showed a decreased number of cancerous cells over the scaffolds containing MPA, presumably arising from the anti-cancer activity attributable to MPA.

3D-Printed Bioplastics with Shape-Memory Behavior Based on Native Bovine Serum Albumin.

Bio-based plastics that can supplant petroleum-derived materials are necessary to meet the future demands of sustainability in the life cycle of plastic materials. While there are significant efforts to develop protein-based plastic materials for commercial use, their application is limited by poor processability and limitations in mechanical performance. Here, we present a bovine serum albumin (BSA)-based resin for stereolithographic apparatus (SLA) 3D printing that affords bioplastic objects with shape-memory behavior. We demonstrate that the native conformation of these globular proteins is largely retained in the 3D-printed constructs and that each protein molecule possesses a "stored length" that could be revealed during mechanical deformation (extension or compression) of the 3D bioplastic objects. While the plastically deformed objects could retain this state for an indefinite period of time, heating the object or submerging in water allowed it to return to its original 3D-printed shape.

Novel biodegradable and non-fouling systems for controlled-release based on poly(ε-caprolactone)/Quercetin blends and biomimetic bacterial S-layer coatings.

Quercetin is a strong antioxidant with low bioavailability due to its high crystallinity. A further drawback is that Quercetin has potentially toxic effects at high concentrations. To improve this low water solubility, as well as control the concentration of the flavonoid in the body, Quercetin is incorporated into a polymeric matrix to form an amorphous solid dispersion (ASD) stable enough to resist the recrystallization of the drug. For this purpose, miscible poly(ε-caprolactone) (PCL) and Quercetin (Q) blends are prepared, provided that they have complementary interacting groups. For compositions in which the flavonoid remains in an amorphous state thanks to the interactions with polymer chains, various PCL/Q drug release platforms are fabricated: micrometric films by solvent casting, nanometric films by spin coating, and nanofibers by electrospinning. Then, the potential use of bacterial S-layer proteins as release-preventive membranes is tested on PCL-Quercetin blends, due to their ability to construct a biomimetic coating including nanometric pores. For all the platforms, the SbpA coating can maintain a stable release under the toxicity level of Quercetin. Accordingly, a PCL/Q system with an S-layer coating allows the design of versatile bioavailable Quercetin eluting devices that prevent toxicity and biofouling issues.

Correction: Novel biodegradable and non-fouling systems for controlled-release based on poly(ε-caprolactone)/Quercetin blends and biomimetic bacterial S-layer coatings.

[This corrects the article DOI: 10.1039/C9RA04398E.].

The conformation of chloramphenicol in the ordered and disordered phases.

The conformational behavior of chloramphenicol (CHL) in the solid, liquid and vapor phases is revisited here by means of FTIR spectroscopy and QM methods. In the crystalline phase, both the IR analysis and QM computations discard the conformer proposed by Acharya et al. (Acta Cryst., 1979, B35:1360-1363) and support the one proposed by Chatterjee et al. (J. Cryst. Mol. Struct., 1979, 9:295-304), characterized by an intramolecular OH⋯O hydrogen bond in which the primary hydroxyl group acts as hydrogen bond donor. The conformational behavior of CHL in the liquid and gas phases has been analyzed using QM calculations. The Self-Consistent Reaction Field (SCRF) method with the Onsager solvation model has been used for the initial optimizations in solution, and the lowest energy conformers have been refined using the Solvation Model based on Density (SMD). In solution environment the intramolecular OH⋯O hydrogen bond in CHL is reversed so that the secondary hydroxyl group acts as hydrogen bond donor. In addition, the dichloroacetamide group folds back further over the phenyl ring to form an intramolecular CCl⋯π halogen bond. Two different halogen bonds are actually observed (each one with a different chlorine atom) resulting in two different stable conformers, that can be detected by FTIR spectroscopy due to the conformational sensitivity of the CO group to the conformation of the dichloroacetyl group. Finally, the stability of the conformers with the polarity of the medium is also discussed.

Recent developments in drug eluting devices with tailored interfacial properties.

Drug eluting devices have greatly evolved during past years to become fundamental products of great marketing importance in the biomedical field. There is currently a large diversity of highly specialized devices for specific applications, making the development of these devices an exciting field of research. The replacement of the former bare metal devices by devices loaded with drugs allowed the sustained and controlled release of drugs, to achieve the desired local therapeutic concentration of drug. The newer devices have been "engineered" with surfaces containing micro- and nanoscale features in a well-controlled manner, that have shown to significantly affect cellular and subcellular function of various biological systems. For example, the topography can be structured to form an antifouling surface mimicking the defense mechanisms found in nature, like the skin of the shark. In the case of bone implants, well-controlled nanostructured interfaces can promote osteoblast differentiation and matrix production, and enhance short-term and long-term osteointegration. In any case, the goal of current research is to design implants that induce controlled, guided, and rapid healing. This article reviews recent trends in the development of drug eluting devices, as well as recent developments on the micro/nanotechnology scales, and their future challenges. For this purpose medical devices have been divided according to the different systems of the body they are focused to: orthopedic devices, breathing stents, gastrointestinal and urinary systems, devices for cardiovascular diseases, neuronal implants, and wound dressings.