Perspectives on the Novel Multifunctional Nerve Guidance Conduits: From Specific Regenerative Procedures to Motor Function Rebuilding.

Peripheral nerve injury potentially destroys the quality of life by inducing functional movement disorders and sensory capacity loss, which results in severe disability and substantial psychological, social, and financial burdens. Autologous nerve grafting has been commonly used as treatment in the clinic; however, its rare donor availability limits its application. A series of artificial nerve guidance conduits (NGCs) with advanced architectures are also proposed to promote injured peripheral nerve regeneration, which is a complicated process from axon sprouting to targeted muscle reinnervation. Therefore, exploring the interactions between sophisticated NGC complexes and versatile cells during each process including axon sprouting, Schwann cell dedifferentiation, nerve myelination, and muscle reinnervation is necessary. This review highlights the contribution of functional NGCs and the influence of microscale biomaterial architecture on biological processes of nerve repair. Progressive NGCs with chemical molecule induction, heterogenous topographical morphology, electroactive, anisotropic assembly microstructure, and self-powered electroactive and magnetic-sensitive NGCs are also collected, and they are expected to be pioneering features in future multifunctional and effective NGCs.

Electrospun Fibrous Membrane with Confined Chain Configuration: Dynamic Relaxation and Glass Transition.

Thermodynamic glass transition processes of electrospun membranes were first introduced to study their dynamic relaxation nature, which is not constantly in equilibrium. The relaxation modes of electrospun membranes are slow but measurable near and above the Tg, given the stretched chain over long distances. Based on differential scanning calorimetry (DSC) experiments and the general principle of mode-coupling theory (MCT), endothermic peak temperature and relaxation enthalpy were used to analyze the relaxation process by capturing these instantaneous "arrested" structures. The short- and long-wavelength relaxation modes could be identified with different annealing times and temperatures relative to DSC-measured Tg for electrospun membranes with different molecular weights. Results clearly showed the dynamic nature of a glass transition in polymeric materials. Tp and enthalpy loss initially increased and then directly decreased with the increase in annealing time. When Ta > Tg, regardless of the size of the molecular weight, the Tp and enthalpy loss of the PLGA fibers would directly decrease, and the curves would shift toward the melted one. Combination of electrospinningand normal DSC instrument can be used to investigating the dynamic relax process through an adequately designed kinetic scanning procedure. This result can be explained by the general principle of MCT-type dynamic theory.

Combinational application of metal-organic frameworks-based nanozyme and nucleic acid delivery in cancer therapy.

The rapid development of nanotechnology has generated numerous ideas for cancer treatment, and a wide variety of relevant nanoparticle platforms have been reported. Metal-organic frameworks (MOFs) have been widely investigated as an anti-cancer drug delivery vehicle owing to their unique porous hybrid structure, biocompatibility, structural tunability, and multi-functionality. MOF materials with catalytic activity, known as nanozymes, have applications in photodynamic and chemodynamic therapy. Nucleic acids have also attracted increasing research attention owing to their programmability, ease of synthesis, and versatility. A variety of functional DNAs and RNAs have been applied both therapeutically (gene-targeting drugs for cancer treatment) and nontherapeutically (used as modified materials to enhance the therapeutic effects of other nanomedicines). The combined use of MOFs and functional nucleic acids have been extensively investigated and has been associated with excellent tumor-suppressor activity in various treatment methods. In this review, we summarize the progress in the research and development of tumor therapy based on MOFs and nucleic acid delivery over recent years, focusing on the combinational use of different delivery and design strategies for MOF/therapeutic nucleic acid platforms. We further summarize the strategies for combining MOFs (universal carrier, functional carrier) and nucleic acids (therapeutic nucleic acids, nontherapeutic nucleic acids) and discuss the corresponding therapeutic effects in cancer treatment. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Dual-Functional Esophageal Stent Coating Composed of Paclitaxel-Loaded Electrospun Membrane and Protective Film.

There is a high need for covered esophageal stents as part of the palliative treatment for patients suffering from esophageal obstruction, a common symptom of esophageal cancer. This paper describes the development of a soft and flexible multi-functional bilayer membrane carrying paclitaxel, and the use of solution-casting and electrospinning to form this material into an esophageal stent coating. FDA-approved materials and established methods were used to shorten the certification process. A protective layer consisting of a polycaprolactone casting film and an electrospunpoly(lactide-coglycolide)/polycaprolactone/gelatin membrane was employed as a functional layer to enhance the material's hydrophilicity and cytocompatibility, as well as to control drug delivery behaviors. In vitro cytocompatibility indicated that cancer cells adhered and grew better than normal cells when competing for attachment on the surface of fibrous membranes. Cytotoxicity comparisons of paclitaxel-loaded membranes with various paclitaxel concentrations and corresponding paclitaxel solutions indicated that cancer cells were more sensitive than normal cells, and the controlled delivery of paclitaxel from drug-loaded membranes could maintain a sustained antitumor effect and cause less damage to normal cells. Animal experiments showed that the bilayered membrane increased the concentration of drug aggregation at the tumor, achieved efficient antitumor effects and reduced the side-effects of PTX. Bilayered membranes could be a promising stent coating to relieve dysphagia and improve the quality of life for esophageal cancer patients.

Relationship between morphologies and mechanical properties of hydroxypropyl methylcellulose/hydroxypropyl starch blends.

Edible films from the blending hydroxypropyl methylcellulose (HPMC) with hydroxypropyl starch (HPS) have been developed. This work focuses on the relationship between morphologies and mechanical properties of such systems. To aid understanding of blend morphology, a new technique used to identify the two phases through dying of the HPS by iodine has been developed, which provided a simple and convenient way to clearly distinguish between HPMC and HPS phases. It was found that the blend system is immiscible and there is phase transition point depending on blending ratio and solution concentration. The lower transparency point of the blend and phase transition reign of HPMC from continuous phase to separated phase correspond with the variation of tensile modulus. The modulus and elongation decreased with increased solution concentration, which is correlatable with the morphologies present, where it was found that the HPMC gradually changed from a continuous phase to a distinct phase.

Phase composition and interface of starch-gelatin blends studied by synchrotron FTIR micro-spectroscopy.

The well recognized complex issue of compatibility between starch and gelatin was investigated based on their interface and phase composition using synchrotron FTIR micro-spectroscope. A high amylose (80%) corn starch grafted with flexible and hydrophilic hydroxpropyl groups and plasticized by poly(ethylene glycol) (PEG) was used in this work. The FTIR beam focused on a 5 µm×5 µm detection region and the micro-spectroscope was scanned across the gelatin-starch interface. It was found that there was about a 20 µm thickness layer where gelatin and starch were in co-existence, indicating that gelatin and starch are compatible to a certain degree in this system. The ratio of the areas of the saccharide CO bands (1180-953 cm(-1)) and the amide I and II bands (1750-1483 cm(-1)) was used to monitor the relative distributions of the two components of the blends. FTIR 2 and 3-dimensional maps indicated that gelatin constituted the continuous phase up to 80% of starch content. The PEG was homogeneously distributed in both gelatin and starch phases, and blurred the interface between gelatin and starch in the chemical maps, indicating that PEG acted not only as a plasticizer but as a compatibilizer for the gelatin-starch blends.

Developing gelatin-starch blends for use as capsule materials.

Blends of gelatin with up to 50% hydroxypropylated high amylose (80%) corn starch were developed as capsule materials. Poly(ethylene glycol) (PEG) was used as both a plasticizer and a compatibilizer in the blends. In order to prepare hard capsules for pharmaceutical applications using the well-established method of dipping stainless steel mold pins into solution, solutions with higher solids concentrations (up to 30%) were developed. The solutions, films and capsules of the different gelatin-starch blends were characterized by viscosity, transparency, tensile testing, water contact angle and SEM. The linear microstructure of the high amylose starch, and the flexible and more hydrophilic hydroxylpropylene groups grafted onto the starch improved the compatibility between the gelatin and starch. SEM revealed a continuous phase of gelatin on the surface of films from all blends. The water contact angle of pure gelatin and the different blends were similar, indicating a continuous phase of gelatin. By optimizing temperature and incubation time to control viscosity, capsules of various blends were successfully developed. PEG increased the transparency and toughness of the various blends.