Using type III recombinant human collagen to construct a series of highly porous scaffolds for tissue regeneration.

As an alternative biopolymer material without the risks of the use of animal-derived collagens in soft tissue engineering applications, recombinant human collagen polypeptide (RHC) was used to construct three-dimensional porous scaffolds. RHC and RHC-chitosan (RHC-CHI) porous scaffolds were fabricated using a freeze-drying method to create highly porous internal structures and then cross-linked with 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC). All scaffolds had interconnected porous structures with high porosity (90%), and pore size that ranged from 111 µm to 159 µm. The swelling ability and in vitro degradation of the prepared scaffolds were investigated. The mechanical properties could be tailored to meet the requirements of end-use application by adjusting the concentrations of the polymer or cross-linking agent, and the resulting mechanical strengths were comparable to those of biological soft tissues. The cytocompatibility of the fabricated porous scaffolds was investigated by seeding 3T3 fibroblasts into the porous structures, and then cell proliferation, distribution, morphology, and synthesis of extra cellular matrix-associated proteins were assessed. The results indicated that RHC-based porous scaffolds were non-cytotoxic and promoted the attachment and proliferation of the seeded cells. Finally, the in vivo study proved these porous scaffolds were able to accelerate the cell infiltration and collagen deposition that promoted the wound closure. Overall, the results indicate that RHC-based porous scaffolds show promise for use in soft tissue engineering due to their excellent in vitro cytocompatibility and adjustable mechanical properties.

Physiological Parameter Response to Variation of Mental Workload.

OBJECTIVE: To examine the relationship between experienced mental workload and physiological response by noninvasive monitoring of physiological parameters. BACKGROUND: Previous studies have examined how individual physiological measures respond to changes in mental demand and subjective reports of workload. This study explores the response of multiple physiological parameters and quantifies their added value when estimating the level of demand. METHOD: The study presented was conducted in laboratory conditions and required participants to perform a visual-motor task that imposed varying levels of demand. The data collected consisted of physiological measurements (heart interbeat intervals, breathing rate, pupil diameter, facial thermography), subjective ratings of workload (Instantaneous Self-Assessment Workload Scale [ISA] and NASA-Task Load Index), and the performance. RESULTS: Facial thermography and pupil diameter were demonstrated to be good candidates for noninvasive workload measurements: For seven out of 10 participants, pupil diameter showed a strong correlation ( R values between .61 and .79 at a significance value of .01) with mean ISA normalized values. Facial thermography measures added on average 47.7% to the amount of variability in task performance explained by a regression model. As with the ISA ratings, the relationship between the physiological measures and performance showed strong interparticipant differences, with some individuals demonstrating a much stronger relationship between workload and performance measures than others. CONCLUSION: The results presented in this paper demonstrate that physiological and pupil diameter can be used for noninvasive real-time measurement of workload. APPLICATION: The methods presented in this article, with current technological capabilities, are better suited for workplaces where the person is seated, offering the possibility of being applied to pilots and air traffic controllers.

Comparison of glutaraldehyde and procyanidin cross-linked scaffolds for soft tissue engineering.

Soft tissue injuries are among the most difficult orthopaedic conditions to treat, and regenerative medicine holds the promise of better treatments of these injuries. There is therefore a requirement for substrates and porous scaffolds which provide an appropriate chemical and mechanical environment for cell attachment, growth, proliferation and differentiation. In this study, cross-linked porous gelatin-chitosan (Gel/Chi) scaffolds with high porosity (>90%) were fabricated and their internal morphology, pore sizes and porosities were characterized using scanning electron microscopy (SEM), micro computed tomography (micro-CT) and mercury intrusion porosimetry. The cross-linking agents chosen for this study were Procyanidin (PA), chosen for its biocompatibility, and glutaraldehyde (GA), chosen for comparison as a highly effective cross-linker. Concentrations of these cross-linkers varied from 0.1% to 1% (w/v) and controls had the same gelatin-chitosan blend but were untreated. It was found that the water absorption of cross-linked scaffolds decreased as the cross-linker concentration increased and in vitro collagenase degradation test showed both cross-linkers increased the biostability of the scaffolds. Scaffolds were also tested under compressive load to investigate their resistance to deformation. The results indicated that both cross-linkers increase the stiffness of the scaffolds both initially and at higher strains, but GA cross-linked scaffolds had a higher compressive stiffness than scaffolds cross-linked with PA for a given concentration. Results from cyclic compression and stress relaxation tests showed that PA cross-linked scaffolds recover more rapidly after deformation. 3T3 fibroblasts were cultured on the scaffolds to assess cytotoxicity and biocompatibility. The results indicated that PA was non-cytotoxic and promoted the attachment and proliferation of the seeded cells, while fewer cells were seen on GA cross-linked scaffolds, indicating that the GA had conferred some cytotoxicity. PA cross-linked Gel/Chi porous scaffolds show promise as three dimentional porous scaffolds in tissue engineering, as porous substrates for biomimetic culture environments, and for regenerative medicine applications, due to their excellent biocompatibility and easily adaptable mechanical properties, as well as their lower cost compared to collagen and fibrin based substrates.

Development of an elastic cell culture substrate for a novel uniaxial tensile strain bioreactor.

Bioreactors can be used for mechanical conditioning and to investigate the mechanobiology of cells in vitro. In this study a polyurethane (PU), Chronoflex AL, was evaluated for use as a flexible cell culture substrate in a novel bioreactor capable of imparting cyclic uniaxial tensile strain to cells. PU membranes were plasma etched, across a range of operating parameters, in oxygen. Contact angle analysis and X-ray photoelectron spectroscopy showed increases in wettability and surface oxygen were related to both etching power and duration. Atomic force microscopy demonstrated that surface roughness decreased after etching at 20 W but was increased at higher powers. The etching parameters, 20 W 40 s, produced membranes with high surface oxygen content (21%), a contact angle of 66° ± 7° and reduced topographical features. Etching and protein conditioning membranes facilitated attachment, and growth to confluence within 3 days, of MG-63 osteoblasts. After 2 days with uniaxial strain (1%, 30 cycles/min, 1500 cycles/day), cellular alignment was observed perpendicular to the principal strain axis, and found to increase after 24 h. The results indicate that the membrane supports culture and strain transmission to adhered cells.