A triphasic scaffold (TPS) for the regeneration of the bone-ligament interface was fabricated combining a 3D fiber deposited polycaprolactone structure and a polylactic co-glycolic acid electrospun. The scaffold presented a gradient of physical and mechanical properties which elicited different biological responses from human mesenchymal stem cells. Biological test were performed on the whole TPS and on scaffolds comprised of each single part of the TPS, considered as the controls. The TPS showed an increase of the metabolic activity with culturing time that seemed to be an average of the controls at each time point. The importance of differentiation media for bone and ligament regeneration was further investigated. Metabolic activity analysis on the different areas of the TPS showed a similar trend after 7 days in both differentiation media. Total alkaline phosphatase (ALP) activity analysis showed a statistically higher activity of the TPS in mineralization medium compared to the controls. A different glycosaminoglycans amount between the TPS and its controls was detected, displaying a similar trend with respect to ALP activity. Results clearly indicated that the integration of electrospinning and additive manufacturing represents a promising approach for the fabrication of scaffolds for the regeneration of tissue interfaces, such as the bone-to-ligament one, because it allows mimicking the structural environment combining different biomaterials at different scales.

The MPFL is a distinct structure that goes from patella to femur with a sail-like shape; its patellar insertion, that mostly occur via an aponeurosis tissue with VMO and VI, is at the proximal third of the patella but it may extend in some cases to the medial third patella or to the quadriceps tendon, or very rarely to the distal third of the patella. In the femoral side, the MPFL is inserted in its own site, in most cases distinct both from epicondyle and adductor tubercle, located on average at a 9.5 mm distance distally and anteriorly in respect to the adductor tubercle. Its lower margin was difficult to define. Given the importance of this structure, it must be reconstructed as anatomically as possible in its insertion and in its shape. Many attempts have been made to make functional reconstructions with less than excellent results.

Guiding bone regeneration poses still unmet challenges due to several drawbacks of current standard treatments in the clinics. A possible solution may rely on the use of three-dimensional scaffolds with optimized structural properties in combination with human mesenchymal stem cells (hMSCs). Bone presents a radial gradient structure from the outside, where the cortical bone is more compact (porosity ranging from 5% to 10%), toward the inner part, where the cancellous bone is more porous (porosity ranging from 50% to 90%). Here, we present a new scaffold design with a built-in gradient in porosity, which approximate the radial bone structure. The pores of the outer ring were 500 μm, the ones in the middle zone were 750 μm and the inner part presented pores of 1000 μm. The porosity of each scaffold region resembled the gradient present in bone, with the outer ring having a porosity of 29.6% ± 5%, the middle and inner regions a porosity of 50.8% ± 8.1% and 77.6% ± 3.2% respectively. hMSCs behavior was analyzed in terms of growth, extracellular matrix deposition and differentiation toward the osteogenic lineage. A trend was displayed by the hMSCs residing in different zones of the gradient scaffolds after 7, 14 and 28 days of culture in mineralization medium. Osteogenic differentiation was influenced by pore size and location in scaffolds displaying a radial porosity gradient. Cell differentiation was confirmed by gene expression with upregulation of Runx2 and bone sialoprotein markers. Mineralization staining further confirmed the maturation of cell differentiation, as indicated by the presence of calcium and phosphate mineral deposits.

Swift progress in biofabrication technologies has enabled unprecedented advances in the application of developmental biology design criteria in three-dimensional scaffolds for regenerative medicine. Considering that tissues and organs in the human body develop following specific physico-chemical gradients, in this study, we hypothesized that additive manufacturing (AM) technologies would significantly aid in the construction of 3D scaffolds encompassing such gradients. Specifically, we considered surface energy and stiffness gradients and analyzed their effect on adult bone marrow derived mesenchymal stem cell differentiation into skeletal lineages. Discrete step-wise macroscopic gradients were obtained by sequentially depositing different biodegradable biomaterials in the AM process, namely poly(lactic acid) (PLA), polycaprolactone (PCL), and poly(ethylene oxide terephthalate)/poly(butylene terephthalate) (PEOT/PBT) copolymers. At the bulk level, PEOT/PBT homogeneous scaffolds supported a higher alkaline phosphatase (ALP) activity compared to PCL, PLA, and gradient scaffolds, respectively. All homogeneous biomaterial scaffolds supported also a significantly higher amount of glycosaminoglycans (GAGs) production compared to discrete gradient scaffolds. Interestingly, the analysis of the different material compartments revealed a specific contribution of PCL, PLA, and PEOT/PBT to surface energy gradients. Whereas PEOT/PBT regions were associated to significantly higher ALP activity, PLA regions correlated with significantly higher GAG production. These results show that cell activity could be influenced by the specific spatial distribution of different biomaterial chemistries in a 3D scaffold and that engineering surface energy discrete gradients could be considered as an appealing criterion to design scaffolds for osteochondral regeneration.

Poly (l‐lactide) (PLLA) fibrous yarns were prepared by electrospinning of polymer solutions in 2,2,2‐trifluoroethanol. Applying spinning from two oppositely charged needles the spontaneous formed triangle of fibers at a grounded substrate could be assembled into fibrous yarns using a device consisting of a take‐up roller and twister. The effect of processing parameters on the morphology, diameter and mechanical properties of PLLA yarns was investigated by the response surface methodology (RSM). This method allowed evaluating a quantitative relationship between polymer concentration, voltage, take‐up rate and distance between the needles' center and the take‐up unit on the properties of the electrospun fibers and yarns. It was found that at increasing concentrations up to 9 wt % uniform fibers were obtained with increasing mean diameters. Conversely, the fiber diameter decreased slightly when the applied voltage was increased. The take‐up rate had a significant influence on the yarn diameter, which increased as the take‐up rate decreased. The tensile strength and modulus of the yarns were correlated with these variables and it was found that the polymer concentration had the largest influence on the mechanical properties of the yarns. By applying the RSM, it was possible to obtain a relationship between processing parameters which are important in the fabrication of electrospun yarns. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41388.