3D-printed collagen/chitosan/secretome derived from HUCMSCs scaffolds for efficient neural network reconstruction in canines with traumatic brain injury

The secretome secreted by stem cells and bioactive material has emerged as a promising therapeutic choice for traumatic brain injury (TBI). We aimed to determine the effect of 3D-printed collagen/chitosan/secretome derived from human umbilical cord blood mesenchymal stem cells scaffolds (3D-CC-ST) on the injured tissue regeneration process. 3D-CC-ST was performed using 3D printing technology at a low temperature (−20°C), and the physical properties and degeneration rate were measured. The utilization of low temperature contributed to a higher cytocompatibility of fabricating porous 3D architectures that provide a homogeneous distribution of cells. Immediately after the establishment of the canine TBI model, 3D-CC-ST and 3D-CC (3D-printed collagen/chitosan scaffolds) were implanted into the cavity of TBI. Following implantation of scaffolds, neurological examination and motor evoked potential detection were performed to analyze locomotor function recovery. Histological and immunofluorescence staining were performed to evaluate neuro-regeneration. The group treated with 3D-CC-ST had good performance of behavior functions. Implanting 3D-CC-ST significantly reduced the cavity area, facilitated the regeneration of nerve fibers and vessel reconstruction, and promoted endogenous neuronal differentiation and synapse formation after TBI. The implantation of 3D-CC-ST also markedly reduced cell apoptosis and regulated the level of systemic inflammatory factors after TBI.

Electro-deposition synthesis of tube-like collagen-chitosan hydrogels and their biological performance

Electro-deposition is a smart, safe and efficient method for biomaterial manufacturing. Collagen, a functional protein with excellent biocompatibility and biosafety, is a promising candidate for tissue engineering and biomedical applications. However, there are few reports on electro-deposition of biomaterials using collagen without electrically or magnetically active nanoparticles. In this study, electro-deposition was employed to swiftly fabricate tube-like collagen-chitosan hydrogels in a mild environment. Fourier transform infrared spectroscopy was employed to analyze the ingredients of the tube-like hydrogels. The result showed that the hydrogels contained both collagen and chitosan. The distribution and content of collagen in the hydrogels was further measured by hematoxylin-eosin staining and hydroxyproline titration. Collagen was distributed homogeneously and its content was related to the initial collagen:chitosan ratio. The tension resistance of the composite gels and the thermal stability of collagen in the composites were obviously enhanced by the chitosan doping. Meanwhile, the tube-like hydrogels retained a good ability to promote cell proliferation of collagen. This method offers a convenient approach to the design and fabrication of collagen-based materials, which could effectively retain the bioactivity and biosafety of collagen and furnish a new way to enhance the stability of collagen and the tensile strength of collagen-based materials.

Review of Electrochemically Triggered Macromolecular Film Buildup Processes and Their Biomedical Applications

Macromolecular coatings play an important role in many technological areas, ranging from the car industry to biosensors. Among the different coating technologies, electrochemically triggered processes are extremely powerful because they allow in particular spatial confinement of the film buildup up to the micrometer scale on microelectrodes. Here, we review the latest advances in the field of electrochemically triggered macromolecular film buildup processes performed in aqueous solutions. All these processes will be discussed and related to their several applications such as corrosion prevention, biosensors, antimicrobial coatings, drug-release, barrier properties and cell encapsulation. Special emphasis will be put on applications in the rapidly growing field of biosensors. Using polymers or proteins, the electrochemical buildup of the films can result from a local change of macromolecules solubility, self-assembly of polyelectrolytes through electrostatic/ionic interactions or covalent cross-linking between different macromolecules. The assembly process can be in one step or performed step-by-step based on an electrical trigger affecting directly the interacting macromolecules or generating ionic species.

Enzyme-responsive multifunctional surfaces for controlled uptake/release of (bio)molecules

The current trend in the development of biomaterials is towards bioactive and biodegradable systems. In particular, enzyme-responsive structures are useful tools to realize biodegradable surfaces for the controlled delivery of biomolecules/drugs through a triggered surface erosion process. Up to now, enzyme-responsive structures have been designed by covalent linkage between synthetic polymers and biodegradable functionalities that are responsive to chemical and biological cues (i.e. proteases or pH) [1-4]. Here, we present a novel approach to achieve enzyme-responsive surface-attached networks by exploiting the non-covalent interaction between streptavidin and biotin. The functional component of this three-dimensional (3D) structure is a layer of biotinylated peptides that are degraded by the action of specific proteases. The system was stable under typical physiological conditions; however, it was efficiently degraded upon enzyme exposure. Further, the controlled release of biomolecules and drugs--previously entrapped into the surface-attached network--was demonstrated to occur as a consequence of the enzymatic cleavage. This versatile approach does not require complex chemical procedures. Interestingly, it can be easily adapted to different enzyme-peptide partners and therefore is very attractive for tissue replacement, drug delivery and biosensing.

Antibacterial hydrogel coating by electrophoretic co-deposition of chitosan/alkynyl chitosan

Despite much effort has been paid to develop aseptic implant devices, the infection associated with medical implant still remains a significant problem. Here, we report a potential coating material derived from a natural biopolymer chitosan. Firstly, chitosan functionalized with alkynyl moiety (ACS) was prepared by reaction between chitosan and 3-bromopropyne. The structure of the alkynyl chitosan was characterized by FT-IR, (1)H NMR, XRD, TGA and element analysis. The minimum inhibitory concentration (MIC) of ACS with a degree of substitution (DS) of 0.40 was 0.03% against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Subsequently, the alkynyl chitosan was co-deposited with chitosan on stainless steel wire to fabricate a composite hydrogel. The composite hydrogel exhibited better antibacterial activities than pure chitosan hydrogel.

Chitosan electrodeposition for microrobotic drug delivery

A method to functionalize steerable magnetic microdevices through the co-electrodeposition of drug loaded chitosan hydrogels is presented. The characteristics of the polymer matrix have been investigated in terms of fabrication, morphology, drug release and response to different environmental conditions. Modifications of the matrix behavior could be achieved by simple chemical post processing. The system is able to load and deliver 40-80 μg cm(-2) of a model drug (Brilliant Green) in a sustained manner with different profiles. Chitosan allows a pH responsive behavior with faster and more efficient release under slightly acidic conditions as can be present in tumor or inflamed tissue. A prototype of a microrobot functionalized with the hydrogel is presented and proposed for the treatment of posterior eye diseases.

Chitosan: an integrative biomaterial for lab-on-a-chip devices

Chitosan is a naturally derived polymer with applications in a variety of industrial and biomedical fields. Recently, it has emerged as a promising material for biological functionalization of microelectromechanical systems (bioMEMS). Due to its unique chemical properties and film forming ability, chitosan serves as a matrix for the assembly of biomolecules, cells, nanoparticles, and other substances. The addition of these components to bioMEMS devices enables them to perform functions such as specific biorecognition, enzymatic catalysis, and controlled drug release. The chitosan film can be integrated in the device by several methods compatible with standard microfabrication technology, including solution casting, spin casting, electrodeposition, and nanoimprinting. This article surveys the usage of chitosan in bioMEMS to date. We discuss the common methods for fabrication, modification, and characterization of chitosan films, and we review a number of demonstrated chitosan-based microdevices. We also highlight the advantages of chitosan over some other functionalization materials for micro-scale devices.

In situ generation of pH gradients in microfluidic devices for biofabrication of freestanding, semi-permeable chitosan membranes

We report the in situ generation of pH gradients in microfluidic devices for biofabrication of freestanding, semi-permeable chitosan membranes. The pH-stimuli-responsive polysaccharide chitosan was enlisted to form a freestanding hydrophilic membrane structure in microfluidic networks where pH gradients are generated at the converging interface between a slightly acidic chitosan solution and a slightly basic buffer solution. A simple and effective pumping strategy was devised to realize a stable flow interface thereby generating a stable, well-controlled and localized pH gradient. Chitosan molecules were deprotonated at the flow interface, causing gelation and solidification of a freestanding chitosan membrane from a nucleation point at the junction of two converging flow streams to an anchoring point where the two flow streams diverge to two output channels. The fabricated chitosan membranes were about 30-60 microm thick and uniform throughout the flow interface inside the microchannels. A T-shaped membrane formed by sequentially fabricating orthogonal membranes demonstrates flexibility of the assembly process. The membranes are permeable to aqueous solutions and are removed by mildly acidic solutions. Permeability tests suggested that the membrane pore size was a few nanometres, i.e., the size range of antibodies. Building on the widely reported use of chitosan as a soft interconnect for biological components and microfabricated devices and the broad applications of membrane functionalities in microsystems, we believe that the facile, rapid biofabrication of freestanding chitosan membranes can be applied to many biochemical, bioanalytical, biosensing applications and cellular studies.