The potential of an in situ gel-forming adhesive was examined as a hemostatic surgical sealant. The gel-forming mechanism for this adhesive mimics the last stages of blood coagulation but uses nonblood proteins. Specifically, gelatin is used as the structural protein and a calcium-independent microbial transglutaminase (mTG) is used as the crosslinking enzyme. In vitro burst pressure tests with porcine skin demonstrate that the gelatin-mTG adhesive forms a gel within 30 min under moist conditions and this gel can restrain pressures of 200 mmHg. In vivo tests with a rat liver wound model showed that the gelatin-mTG adhesive achieves complete hemostasis in 2.5 min and the gel (i.e., the biomimetic clot) offers substantial adhesive and cohesive strength. Complete hemostasis was also observed in 2.5 min after the gelatin-mTG adhesive was applied to a briskly bleeding rat femoral artery wound. In a large animal porcine model, a femoral artery wound that resulted in extensive bleeding was sealed in 4 min by (i) clamping the artery for temporary hemostasis, (ii) removing excess blood, and (iii) applying the gelatin-mTG adhesive. Thus, the biomimetic gelatin-mTG adhesive may provide a simple, safe, and cost-effective surgical sealant.

The current study examines the use of hand immersion in cold water to alleviate physiological strain caused by exercising in a hot climate while wearing NBC protective garments. Seventeen heat acclimated subjects wearing a semi-permeable NBC protective garment and a light bulletproof vest were exposed to a 125 min exercise-heat stress (35 degrees C, 50% RH; 5 km/h, 5% incline). The heat stress exposure routine included 5 min rest in the chamber followed by two 50:10 min work-rest cycles. During the control trial (CO), there was no intervention, whilst in the intervention condition the subjects immersed their hands and forearms in a 10 degrees C water bath (HI). The results demonstrated that hand immersion in cold water significantly reduced physiological strain. In the CO exposure during the first and second resting periods, the average rectal temperature (T (re)) practically did not decrease. With hand immersion, the mean (SD) T (re) decreased by 0.45 (0.05 degrees C) and 0.48 degrees C (0.06 degrees C) during the first and second rest periods respectively (P < 0.005). Significant decreases in skin temperature, sweat rate, heart rate, and heat storage was also noted in the HI vs. the CO trials. Tolerance time in the HI exposure were longer than in the CO exposure (only 12 subjects in the CO trial endured the entire heat exposure session, as opposed to all 17 subjects in the HI group). It is concluded that hand immersion in cold water for 10 min is an effective method for decreasing the physiological strain caused by exercising under heat stress while wearing NBC protective garments. The method is convenient, simple, and allows longer working periods in hot or contaminated areas with shorter resting periods.

Mechanical stimulation improves tissue-engineered cartilage development both in terms of biochemical composition and structural properties. However, the link between the compositional changes attributed to mechanical stimulation and the changing structural properties of the engineered cartilage is poorly understood. We hypothesize that transient events associated with construct stiffening can be documented and used to understand milestones in construct development. To do this, we designed and built a mechanical stimulation bioreactor that can continuously record the force response of the engineered construct in real time. This study documents the transient changes of the stiffness of tissue-engineered cartilage constructs over the first 14 days of their development under cyclic loading. Compressive strain stimulation (15%, 1 Hz) was applied to poly(ethylene glycol) (PEG) hydrogels seeded with primary articular chondrocytes. The average compressive modulus of strain-stimulated constructs was 12.7 +/- 1.45 kPa after 2 weeks, significantly greater (P < 0.01) than the average compressive moduli of both unstimulated constructs (10.7 +/- 0.94 kPa) and nonviable stimulated constructs (11.2 +/- 0.91 kPa). The system was able to document that nearly all of the stiffness increase occurred over the last 2 days of the experiment, where live-cell constructs demonstrated a rapid 20% increase in force response. The system's ability to track significant increases in stiffness over time was also confirmed by Instron testing. These results present a novel view of the early mechanical development of tissue-engineering cartilage constructs and suggest that the real-time monitoring of force response may be used to noninvasively track the development of engineered tissue.