Collagen biomaterial doped with colominic acid for cell culture applications with regard to peripheral nerve repair

Neurofilament degradation is involved in laparotomy-induced cognitive dysfunction in aged rats

Excessive neuroinflammatory responses play important roles in the development of postoperative cognitive dysfunction (POCD). Neurofilaments (NFs) were essential to the structure of axon and nerve conduction; and the abnormal degradation of NFs were always accompanied with degenerative diseases, which were also characterized by excessive neuroinflammatory responses in brain. However, it is still unclear whether the NFs were involved in the POCD. In this study, the LC-MS/MS method was used to explore the neuroinflammatory response and NFs of POCD in aged rats. Moreover, trichostatin A (TSA), an inflammation-related drug, was selected to test whether it could improve the surgery-induced cognitive dysfunction, inflammatory responses and NFs. Evident cognitive dysfunction, excessive microglia activation, neuroinflammatory responses and upregulated NFs in hippocampus were observed in the POCD group. TSA pretreatment could significantly mitigate these changes. The KEGG analysis revealed that nine pathways were enriched in the TSA + surgery group (versus the surgery group). Among them, two signaling pathways were closely related with the changes of NFs proteins. In conclusion, surgery could impair the cognitive function and aggravate neuroinflammation and NFs. The TSA could significantly improve these changes which might be related to the activation of the “focal adhesion” and “ECM-receptor interaction” pathways.

Poly(3,4-ethylenedioxythiophene) nanoparticle and poly(ɛ-caprolactone) electrospun scaffold characterization for skeletal muscle regeneration

Injuries to peripheral nerves and/or skeletal muscle can cause scar tissue formation and loss of function. The focus of this article is the creation of a conductive, biocompatible scaffold with appropriate mechanical properties to regenerate skeletal muscle. Poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles (Np) were electrospun with poly(ɛ-caprolactone) (PCL) to form conductive scaffolds. During electrospinning, ribboning, larger fiber diameters, and unaligned scaffolds were observed with increasing PEDOT amounts. To address this, PEDOT Np were sonicated prior to electrospinning, which resulted in decreased conductivity and increased mechanical properties. Multi-walled carbon nanotubes (MWCNT) were added to the 1:2 solution in an effort to increase conductivity. However, the addition of MWCNT had little effect on scaffold conductivity, and the elastic modulus and yield stress of the scaffold increased as a result. Rat muscle cells attached and were active on the 1-10, 1-2, 3-4, and 1-1 PCL-PEDOT scaffolds; however, the 3-4 scaffolds had the lowest level of metabolic activity. Although the scaffolds were cytocompatible, further development of the fabrication method is necessary to produce more highly aligned scaffolds capable of promoting skeletal muscle cell alignment and eventual regeneration.

Nanoporous silica nanoparticles as biomaterials: evaluation of different strategies for the functionalization with polysialic acid by step-by-step cytocompatibility testing

Nanoporous silica materials have become a prominent novel class of biomaterials which are typically applied as nanoparticles or thin films. Their large surface area combined with the rich surface chemistry of amorphous silica affords the possibility to equip this material with variable functionalities, also with several different ones on the same particle or coating. Although many studies have shown that nanoporous silica is apparently non-toxic and basically biocompatible, any surface modification may change the surface properties considerably and, therefore, the modified materials should be checked for their biocompatibility at every step. Here we report on different silane-based functionalization strategies, firstly a conventional succinic anhydride-based linker system and, secondly, copper-catalyzed click chemistry, to bind polysialic acid, a polysaccharide important in neurogenesis, onto nanoporous silica nanoparticles (NPSNPs) of MCM-41 type. At each of the different modification steps, the materials are characterized by cell culture experiments. The results show that polysialic acid can be immobilized on the surface of NPSNPs by using different strategies. The cell culture experiments show that the kind of surface immobilization has a strong influence on the toxicity of the material versus the cells. Whereas most modifications appear inoffensive, NPSNPs modified by click reactions are toxic, probably due to residues of the Cu catalyst used in these reactions.

Effects of polysialic acid on sensory innervation of the cornea

Sensory trigeminal growth cones innervate the cornea in a coordinated fashion during embryonic development. Polysialic acid (polySia) is known for its important roles during nerve development and regeneration. The purpose of this work is to determine whether polySia, present in developing eyefronts and on the surface of sensory nerves, may provide guidance cues to nerves during corneal innervation. Expression and localization of polySia in embryonic day (E)5-14 chick eyefronts and E9 trigeminal ganglia were identified using Western blotting and immunostaining. Effects of polySia removal on trigeminal nerve growth behavior were determined in vivo, using exogenous endoneuraminidase (endoN) treatments to remove polySia substrates during chick cornea development, and in vitro, using neuronal explant cultures. PolySia substrates, made by the physical adsorption of colominic acid to a surface coated with poly-d-lysine (PDL), were used as a model to investigate functions of the polySia expressed in axonal environments. PolySia was localized within developing eyefronts and on trigeminal sensory nerves. Distributions of PolySia in corneas and pericorneal regions are developmentally regulated. PolySia removal caused defasciculation of the limbal nerve trunk in vivo from E7 to E10. Removal of polySia on trigeminal neurites inhibited neurite outgrowth and caused axon defasciculation, but did not affect Neural Cell Adhesion Molecule (NCAM) expression or Schwann cell migration in vitro. PolySia substrates in vitro inhibited outgrowth of trigeminal neurites and promoted their fasciculation. In conclusion, polySia is localized on corneal nerves and in their targeting environment during early developing stages of chick embryos. PolySias promote fasciculation of trigeminal axons in vivo and in vitro, whereas, in contrast, their removal promotes defasciculation.

Type I collagen nerve conduits for median nerve repairs in the forearm

PURPOSE

To evaluate patients with median nerve damage in the distal forearm treated with type 1 collagen nerve conduits.

METHODS

Nine patients with damage to the median nerve in the distal forearm underwent treatment with a type 1 collagen nerve conduit. The nerve gaps ranged between 1 and 2 cm. An independent observer reexamined patients after treatment at a minimal follow-up of 14 months and a mean follow-up of 21 months. Residual pain was evaluated using a visual analog scale. Functional outcome was quantified by assessing static 2-point discrimination, nerve conduction velocity relative to the uninjured limb, and Disabilities of the Arm, Shoulder, and Hand outcome measure scoring. We also recorded quality of life measures including patients' perceived satisfaction with the results and return to work latency.

RESULTS

We observed no implant-related complications. Of 9 patients, 7 were free of pain, and the mean visual analog scale was 0.6. The mean Disabilities of the Arm, Shoulder, and Hand score was 6. The static 2-point discrimination was less than 6 mm in 3 patients, between 6 and 10 mm in 4 patients, and over 10 mm in 2 patients. Six patients reached a status of M4 or higher. Eight patients were satisfied with the procedure and would undergo surgery again.

CONCLUSIONS

This study indicates that purified type 1 bovine collagen conduits are a practical and efficacious method for the repair of median nerves in the distal forearm.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

ADDITION OF CONDUCTIVE ELEMENTS TO POLYMERIC SCAFFOLDS FOR MUSCLE TISSUE ENGINEERING

Cardiac and skeletal muscles are two tissues that would benefit from an electrically conductive scaffold to regenerate lost or lower functioning areas. By augmenting polymeric scaffolds with conductive elements, the contractile process for both muscles could increase. In this review, the components reviewed include polyaniline (PANi), gold (Au) nanoparticles, and carbon nanotubes (CNT). PANi has been combined with several polymers and increased the conductivity of the scaffolds. It is biocompatible, but increases mechanical properties and decreases scaffold elongation. Tissue engineering using nanoparticles is an emerging area and considerable research focuses on determining possible toxicity due to nanoparticle concentration. Contradicting data exists for both Au nanoparticles and CNT. Smaller Au nanoparticles damage cardiac tissue in vivo while larger ones do not. By comparison, in vitro data shows no harmful results for skeletal muscle cells. Data for CNT is just as diverse as the amount, orientation and further purification or functionalization could all play a role in determining biocompatibility. Future research should focus on establishing the conductivity level needed for each muscle tissue to ascertain the amount of conductive element needed so the most suitable one can be utilized.

Silk fibroin protein from mulberry and non-mulberry silkworms: cytotoxicity, biocompatibility and kinetics of L929 murine fibroblast adhesion

Silks fibers and films fabricated from fibroin protein of domesticated mulberry silkworm cocoon have been traditionally utilized as sutures in surgery and recently as biomaterial films respectively. Here, we explore the possibility of application of silk fibroin protein from non-mulberry silkworm cocoon as a potential biomaterial aid. In terms of direct inflammatory potential, fibroin proteins from Antheraea mylitta and Bombyx mori are immunologically inert and invoke minimal immune response. Stimulation of murine peritoneal macrophages and RAW 264.7 murine macrophages by these fibroin proteins both in solution and in the form of films assayed in terms of nitric oxide and TNFalpha production showed comparable stimulation as in collagen. Kinetics of adhesion of L929 murine fibroblasts, for biocompatibility evaluation, monitored every 4 h from seeding and studied over a period of 24 h, reveal A. mylitta fibroin film to be a better substrate in terms of rapid and easier cellularization. Cell viability studies by MTT assay and flow cytometric analyses indicate the ability of fibroin matrices to support cell growth and proliferation comparable to collagen for long-term culture. This matrix may have potential to serve in those injuries where rapid cellularization is essential.