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Aim: Platelet-rich plasma (PRP) is an autologous blood-derived material that has been used to enhance bone regeneration. Clinical studies, however, reported inconsistent outcomes. This study aimed to assess the effect of changes in leucocyte and PRP (L-PRP) composition on bone defect healing.Materials and Methods: L-PRPs were prepared using different centrifugation methods and their regenerative potential was assessed in an in-vivo rat model. Bilateral critical-size tibial bone defects were created and filled with single-spin L-PRP, double-spin L-PRP, or filtered L-PRP. Empty defects and defects treated with collagen scaffolds served as controls. Rats were euthanized after 2 weeks, and their tibias were collected and analysed using micro-CT and histology.Results: Double-spin L-PRP contained higher concentrations of platelets than singlespin L-PRP and filtered L-PRP. Filtration of single-spin L-PRP resulted in lower concentrations of minerals and metabolites. In vivo, double-spin L-PRP improved bone

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Brushite cements are promising bone regeneration materials with limited biological and mechanical properties. Here, we engineer a mechanically improved brushite–collagen type I cement with enhanced biological properties by use of chiral chemistry; d - and l -tartaric acid were used to limit crystal growth and increase the mechanical properties of brushite–collagen cements. The impact of the chiral molecules on the cements was examined with Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). A 3-point bend test was utilized to study the fracture toughness, and cell attachment and morphology studies were carried out to demonstrate biocompatibility. XRD and SEM analyses showed that l -, but not d -tartaric acid, significantly restrained brushite crystal growth by binding to the {010} plane of the mineral and increased brushite crystal packing and the collagen interaction area. l -Tartaric acid significantly improved fracture toughness compared to traditional brushite by 30%. Collagen significantly enhanced cell morphology and focal adhesion expression on l -tartaric acid-treated brushite cements.

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Systemically circulating microbubbles are used as contrast agents to aid both drug targeting and delivery using ultrasound. Exploiting their acoustic behaviour in small diameter vessels is critical for both applications, but the highly controlled experiments required to support this are not possible in vivo and challenging in vitro. Experimental platforms with small diameter channels (below 200 microns) are not readily available nor able to represent vascular geometries, leaving the existence and extent of microbubble-microvessel interactions incompletely defined. In this work we present a 3D-printed microchannel platform using tissue-mimicking hydrogels featuring radii down to 75 microns. We demonstrate application to study microbubble behaviour via acoustic backscatter under controlled environments in physiologically-relevant conditions.