Amorphous calcium polyphosphate (ACPP), an inorganic polymer ceramic, has shown promise as a drug delivery matrix following a repeat gelling protocol. This study described a simple method of preparing ACPP hydrogel in the presence of an excess volume of water. The increased water availability accelerates water molecule ingress and microstructural transformation of ACPP hydrogels. The impact of some experimental settings (soaking time, temperature, stirring, and ACPP particle size) on the physiochemical and rheological natures of ACPP hydrogel were investigated and from which possible hydrogel formation mechanisms were inferred. We believe that the formation of ACPP hydrogel is through the mechanisms of intermolecular ionic interaction and entanglement of polyphosphate chains. The potential application of ACPP hydrogel as a ceramic matrix for sustained drug release warrants further investigation.

Few studies have been reported that focus on developing implant surface nanofiber (NF) coating to prevent infection and enhance osseointegration by local drug release. In this study, coaxial doxycycline (Doxy)-doped polycaprolactone/polyvinyl alcohol (PCL/PVA) NFs were directly deposited on a titanium (Ti) implant surface during electrospinning. The interaction of loaded Doxy with both PVA and PCL NFs was characterized by Raman spectroscopy. The bonding strength of Doxy-doped NF coating on Ti implants was confirmed by a stand single-pass scratch test. The improved implant osseointegration by PCL/PVA NF coatings in vivo was confirmed by scanning electron microscopy, histomorphometry and micro computed tomography (μCT) at 2, 4 and 8 weeks after implantation. The bone contact surface (%) changes of the NF coating group (80%) is significantly higher than that of the no NF group (<5%, p < 0.05). Finally, we demonstrated that a Doxy-doped NF coating effectively inhibited bacterial infection and enhanced osseointegration in an infected (Staphylococcus aureus) tibia implantation rat model. Doxy released from NF coating inhibited bacterial growth up to 8 weeks in vivo. The maximal push-in force of the Doxy-NF coating (38 N) is much higher than that of the NF coating group (6.5 N) 8 weeks after implantation (p < 0.05), which was further confirmed by quantitative histological analysis and μCT. These findings indicate that coaxial PCL/PVA NF coating doped with Doxy and/or other drugs have great potential in enhancing implant osseointegration and preventing infection.

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The long head of the biceps tendon (LHBT) occupies a unique proximal intra-articular and distal extra-articular position within the human shoulder. In the presence of a rotator cuff (RC) tear, the LHBT is recruited into an accelerated role undergoing potential mechanical and biochemical degeneration. Intra-articular sections of the LHBT were harvested during primary shoulder arthroplasty from patients with an intact or deficient RC. LHBTs were stained (H&E, Alcian Blue) and subjected to histologic analysis using the semiquantitative Bonar scale and measurement of collagen orientation. LHBTs (n ¼ 12 per group) were also subjected to gene-expression analyses via an RT 2 -PCR Profiler Array quantifying 84 genes associated with cell-cell and cell-matrix interactions. LHBTs (n ¼ 18 per group) were biomechanically tested with both stress-relaxation and load-to-failure protocols and subsequently modeled with the Quasilinear Viscoelastic (QLV) and Structural-Based Elastic (SBE) models. While no histologic differences were observed, significant differences in mechanical testing, and viscoelastic modeling parameters were found. PCR arrays identified five genes that were differentially expressed between RC-intact and RC-deficient LHBT groups. LHBTs display signs of pathology regardless of RC status in the arthroplasty population, which may be secondary to both glenohumeral joint arthritis and the additional mechanical role of the LHBT in this population. Keywords: long head of the biceps tendon; rotator cuff pathology; tendon biomechanics; target gene expression; tendon histologic analysisThe long head of the biceps tendon (LHBT) occupies a unique proximal intra-articular position within the glenohumeral joint and a distal extra-articular position residing within the bicipital groove. 1 An association between pathology of the LHBT and rotator cuff (RC) tears has been well-established, 2-8 however, changes can occur either primarily, or secondarily in the setting of RC tears. Biomechanically, the LHBT may play the role of a secondary humeral head depressor during normal shoulder motion with an intact RC. 9 However, in the setting of a RC tear, it may be recruited into an accelerated load-bearing role and can subsequently undergo pathologic degeneration. 10 LHBT pathology may be a commonly overlooked cause of persistent anterior shoulder pain following RC repair.Prior histopathologic analyses of LHBT have demonstrated increased proteoglycan production and decreased collagen organization in the presence of RC tears. [11][12][13] Lakemeir et al. also demonstrated increased presence of vascular endothelial growth factor (VEGF) and matrix metalloproteinases (MMPs) in LHBTs in the presence of a RC tear or cuff arthropathy. 12,13 Joseph et al. 11 evaluated the intra-articular and extraarticular portions of the diseased LHBT concluding that the intra-articular portion of the LHBT displays many of the histological characteristics of tendinopathy, while, the extra-articular portion remains structurally similar to healthy te...