Injury from blunt head impacts causes acute neurological deficits and may lead to chronic neurodegeneration. A head impact detection device can serve both as a research tool for studying head injury mechanisms and a clinical tool for real-time trauma screening. The simplest approach is an acceleration thresholding algorithm, which may falsely detect high-acceleration spurious events such as manual manipulation of the device. We designed a head impact detection system that distinguishes head impacts from nonimpacts through two subsystems. First, we use infrared proximity sensing to determine if the mouthguard is worn on the teeth to filter out all off-teeth events. Second, on-teeth, nonimpact events are rejected using a support vector machine classifier trained on frequency domain features of linear acceleration and rotational velocity. The remaining events are classified as head impacts. In a controlled laboratory evaluation, the present system performed substantially better than a 10-g acceleration threshold in head impact detection (98% sensitivity, 99.99% specificity, 99% accuracy, and 99.98% precision, compared to 92% sensitivity, 58% specificity, 65% accuracy, and 37% precision). Once adapted for field deployment by training and validation with field data, this system has the potential to effectively detect head trauma in sports, military service, and other high-risk activities.

Vascularization of tissue engineering constructs (TECs) in vitro is of critical importance for ensuring effective and satisfactory clinical outcomes upon implantation of TECs. Biomechanical properties of TECs have remarkable influence on the in vitro vascularization of TECs. This work utilized in vitro experiments and finite element analysis to investigate endothelial patterns in hybrid constructs of soft collagen gels and rigid macroporous poly(ε-caprolactone)-β-tricalcium phosphate (PCL-β-TCP) scaffold seeded/embedded with human umbilical vein endothelial cells (HUVECs) for bone tissue engineering applications. We first fabricated and characterized well-defined porous PCL-β-TCP scaffolds with identical pore size (500µm) but different strut sizes (200 and 400µm) using additive manufacturing (AM) technology, and then assessed the HUVEC׳s proliferation and morphogenesis within collagen, PCL-β-TCP scaffold, and the collagen-scaffold hybrid construct. Results showed that, in the hybrid construct, the cell population in the collagen component dropped by day 7 but then increased by day 14. Also, cells migrated onto the struts of the scaffold component, proliferated over time, and formed networks on the thinner struts (i.e., 200µm). Also, the thinner struts resulted in formation of long linear cellular cords structures within the pores. Finite element simulation demonstrated principal stress patterns similar to the observed cell-network pattern. It is probable that the scaffold component modulated patterns of principal stresses in the collagen component as biomechanical cues for reorganization of cell network patterns. Also, the scaffold component significantly improved the mechanical integrity of hydrogel component in the hybrid construct for weight-bearing applications. These results have collectively indicated that the manipulation of micro-architecture of scaffold could be an effective means to further regulate and guide desired cellular response in hybrid constructs.

Vitrification is an increasingly popular method of embryo cryopreservation that is used in assisted reproductive technology. Although vitrification has high post-thaw survival rates compared to other freezing techniques, its long-term effects on embryo development are still poorly understood. We demonstrate an application of full-field optical coherence tomography (FF-OCT) to visualize the effects of vitrification on live single-cell (2 pronuclear) mouse embryos without harmful labels. Using FF-OCT, we observed that vitrification causes a significant increase in the aggregation of structures within the embryo cytoplasm, consistent with reports in literature based on fluorescence techniques. We quantify the degree of aggregation with an objective metric, the cytoplasmic aggregation (CA) score, and observe a high degree of correlation between the CA scores of FF-OCT images of embryos and of fluorescence images of their mitochondria. Our results indicate that FF-OCT shows promise as a label-free assessment of the effects of vitrification on embryo mitochondria distribution. The CA score provides a quantitative metric to describe the degree to which embryos have been affected by vitrification and could aid clinicians in selecting embryos for transfer.

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