Tissue engineering with gellan gum.

Engineering complex tissues for research and clinical applications relies on high-performance biomaterials that are amenable to biofabrication, maintain mechanical integrity, support specific cell behaviours, and, ultimately, biodegrade. In most cases, complex tissues will need to be fabricated from not one, but many biomaterials, which collectively fulfill these demanding requirements. Gellan gum is an anionic polysaccharide with potential to fill several key roles in engineered tissues, particularly after modification and blending. This review focuses on the present state of research into gellan gum, from its origins, purification and modification, through processing and biofabrication options, to its performance as a cell scaffold for both soft tissue and load bearing applications. Overall, we find gellan gum to be a highly versatile backbone material for tissue engineering research, upon which a broad array of form and functionality can be built.

Pinocytic loading of cytochrome c into intact cells specifically induces caspase-dependent permeabilization of mitochondria: evidence for a cytochrome c feedback loop.

Previous studies introduced cytochrome c into intact cells via the disruptive techniques of microinjection or electroporation to provide support for the hypothesis that, in whole cells, cytochrome c release from mitochondria triggers caspase activation and other degradative changes. However, the types of measurements that could be undertaken with these techniques was limited. We used the simple and relatively gentle technique of pinocytic loading to demonstrate that, in intact cells, cytosolic cytochrome c specifically induced activation of caspase-3- and -9-like enzymes, and a loss of mitochondrial polarization coincident with an increase in mitochondrial permeability. Our results support the prediction from in vitro studies that activation of caspases-3 and -9 is downstream of cytochrome c release and provide the first direct evidence that, in whole cells, cytochrome c-dependent caspase-activation can exert a feedback effect to elicit mitochondrial permeabilization and collapse of the mitochondrial trans-membrane potential.

Peptide modification of purified gellan gum.

Gellan gum (GG) is an anionic polysaccharide with potential as a biopolymer for additive manufacturing (3D-bioprinting) and tissue engineering. Previous studies have shown GG to be highly cytocompatible, but lacking specific attachment sites required for anchorage-dependent cells. In this work, we modify purified-GG polymer with a short peptide containing the arginine-glycine-aspartic acid (RGD) sequence that is known to enhance integrin-mediated cell attachment. Radiolabelling of the peptide was used in optimisation of the conjugation procedure to achieve an overall efficiency of 40%. The purification of divalent cations from commercial GG samples was found to be critical for successful conjugation. Rheological studies revealed that the peptide coupling did not prevent gelation behaviour. C2C12 cells showed improved attachment on the surface of and encapsulated within RGD-GG hydrogels, differentiating to multinucleated myofibers after 5-7 days. PC12 cells showed minimal interactions with both GG and RGD-GG, with formation of cell clusters and impedance of terminal differentiation and neurite extension.

Validation of a photographic method of measuring corneal diameter.

A photographic method for measuring corneal diameter using the Medical-Nikkor f200 mm lens is described. Measurements were compared with those obtained by calipers (46 eyes of 25 patients) and by placing a ruler either near the eye (123 eyes of 64 patients) or on the nose (98 eyes of 55 patients). Over all we found good correlation between photographic and caliper measurements (r = 0.94). No significant correlation was found between photographic measurements and estimates made with the ruler either near the eye or on the nose (r = 0.65 and 0.31 respectively). Modifications to our system are suggested which may provide an accurate, simple, non-invasive method of measuring corneal diameter in ophthalmic clinics.

Creating conductive structures for cell growth: growth and alignment of myogenic cell types on polythiophenes.

Conducting polymers provide suitable substrates for the in vitro study of excitable cells, including skeletal muscle cells, due to their inherent conductivity and electroactivity. The thiophene family of conducting polymers offers unique flexibility for tailoring of polymer properties as a result of the ease of functionalization of the parent monomer. This article describes the preparation of films and electrospun fibers from an ester-functionalized organic solvent-soluble polythiophene (poly-octanoic acid 2-thiophen-3-yl-ethyl ester) and details the changes in properties that result from post-polymerization hydrolysis of the ester linkage. The polymer films supported the proliferation and differentiation of both primary and transformed skeletal muscle myoblasts. In addition, aligned electrospun fibers formed from the polymers provided scaffolds for the guided differentiation of linearly aligned primary myotubes, suggesting their suitability as three-dimensional substrates for the in vitro engineering of skeletal muscle tissue.

Slide and flex, tighten, extend (SAFTE): a safe, convenient, effective, and no-cost approach to rehabilitation after total knee arthroplasty.

Many of the clinical aspects of total knee arthroplasty (TKA) are now standardized; however, treatment protocols for rehabilitation vary according to surgeon and physical therapy departments. The purpose of this article was to determine if the slide and flex, tighten, extend (SAFTE) approach after TKA is a satisfactory method of achieving functional range of motion (full extension and at least 90 degrees of flexion). Of patients in the study group, 70% achieved functional range of motion by the 7-week evaluation period. SAFTE is a safe, effective, and no-cost approach to achieve functional range of motion in TKA using a single-radius, posterior-stabilized knee prosthesis.