Recent developments in 3D printing (3DP) research have led to a variety of scaffold designs and techniques for osteochondral tissue engineering; however, the simultaneous incorporation of multiple types of gradients within the same construct remains a challenge. Herein, we describe the fabrication and mechanical characterization of porous poly(ε-caprolactone) (PCL) and PCLhydroxyapatite (HA) scaffolds with incorporated vertical porosity and ceramic content gradients via a multimaterial extrusion 3DP system. Scaffolds of 0 wt% HA (PCL), 15 wt% HA (HA15), or 30 wt% HA (HA30) were fabricated with uniform composition and porosity (using 0.2 mm, 0.5 mm, or 0.9 mm on-center fiber spacing), uniform composition and gradient porosity, and gradient composition (PCL-HA15-HA30) and porosity. Micro-CT imaging and porosity analysis demonstrated the ability to incorporate both vertical porosity and pore size gradients and a ceramic gradient, which collectively recapitulate gradients found in native osteochondral tissues. Uniaxial compression testing demonstrated an inverse relationship between porosity, ϕ, and compressive modulus, E, and yield stress, σ y , for uniform porosity scaffolds, however, no differences were

Background: Academic plastic surgery has a history of underrepresentation of ethnic and racial minority groups. Recent policy shifts by national medical groups and plastic surgery societies have focused on reversing these inequalities. This study seeks to measure ethnic and racial representation at academic and leadership positions following recent changes. Methods: A cross-sectional study was conducted in June of 2018, measuring ethnic and racial diversity of U.S. academic plastic surgery faculty. Among faculty, career qualifications, years of experience, faculty positions, and leadership ethnicity were compared. Results: A total of 930 academic plastic surgeons were included in the study. Classified collectively as nonwhite, this group graduated more recently than other academic plastic surgeons (2006 versus 2001; p < 0.0001) and had greater rates of clinical fellowship attainment (OR, 1.62; 95 percent CI, 1.16 to 2.26). Nonwhite individuals were less likely to be employed in the full professor position compared with their white colleagues (OR, 0.6; 95 percent CI, 0.42 to 0.88; p = 0.0077). However, after adjustment for differences in years of postresidency experience, this disparity was no longer significant (OR, 1.06; 95 percent CI, 0.62 to 1.83; p = 0.82), indicating the importance of current cohort experience differences. Assessment of program leadership found that nonwhite chairs employed significantly more nonwhite faculty (42.5 percent versus 20.9 percent; p < 0.0001). Conclusions: Academic plastic surgery continues to face disparities in representation of both ethnic and racial minorities. Current inequalities are most severe at senior academic positions and may be linked to cohort experience differences along with leadership and promotion biases.

To accurately mimic the native tissue environment, tissue engineered scaffolds often need to have a highly controlled and varied display of three-dimensional (3D) architecture and geometrical cues. Additive manufacturing in tissue engineering has made possible the development of complex scaffolds that mimic the native tissue architectures. As such, architectural details that were previously unattainable or irreproducible can now be incorporated in an ordered and organized approach, further advancing the structural and chemical cues delivered to cells interacting with the scaffold. This control over the environment has given engineers the ability to unlock cellular machinery that is highly dependent upon the intricate heterogeneous environment of native tissue. Recent research into the incorporation of physical and chemical gradients within scaffolds indicates that integrating these features improves the function of a tissue engineered construct. This review covers recent advances on techniques to incorporate gradients into polymer scaffolds through additive manufacturing and evaluate the success of these techniques. As covered here, to best replicate different tissue types, one must be cognizant of the vastly different types of manufacturing techniques available to create these gradient scaffolds. We review the various types of additive manufacturing techniques that can be leveraged to fabricate scaffolds with heterogeneous properties and discuss methods to successfully characterize them.

Synthetic hydrogels are investigated extensively in tissue engineering for their tunable physicochemical properties but are bioinert and lack the tissue-specific cues to produce appropriate biological responses. To introduce tissue-specific biochemical cues to these hydrogels, we have developed a modular hydrogel cross-linker, poly(glycolic acid)–poly(ethylene glycol)–poly(glycolic acid)-di(but-2-yne-1,4-dithiol) (PdBT), that can be functionalized with small peptide-based cues and large macromolecular cues simply by mixing PdBT in water with the appropriate biomolecules at room temperature. Cartilage- and bone-specific PdBT macromers were generated by functionalization with a cartilage-associated hydrophobic N-cadherin peptide, a hydrophilic bone morphogenetic protein peptide, and a cartilage-derived glycosaminoglycan, chondroitin sulfate. These biofunctionalized PdBT macromers can spontaneously cross-link polymers such as poly(N-isopropylacrylamide) to produce rapidly cross-linking, highly swollen, cytocompatible, and hydrolytically degradable hydrogels suitable for mesenchymal stem cell encapsulation. These favorable properties, combined with PdBT’s modular design and ease of functionalization, establish strong potential for its usage in tissue engineering applications.

Research on mathematics education has shown that learners’ actions can influence how they think and vice versa. Much of this work has been rooted in the use of manipulatives, gestures, and body movements. Our article dissects the mechanisms that underscore the impact of embodied activities and applies this lens to explore how to harness the affordances of new technology to enhance mathematical thinking. This is especially crucial given the increasing accessibility of technology—such as digital touch devices, 3D printers, and location sensors—for constructing embodied experiences. Providing guidance for incorporating those tools, we focus on the role that embodied cognition can play in communicating mathematical concepts as well as in allowing learners to experiment and evolve their ideas. To inspire future integration of theory in the development of technologically enhanced embodied mathematics experiences, we provide examples of how this can be done. Finally, we outline future directions in the areas of design, implementation, and assessment of embodied learning of mathematics.

3D printing has emerged as an important technique for fabricating tissue engineered scaffolds. However, systematic evaluations of biomaterials for 3D printing have not been widely investigated. We evaluated poly­(propylene fumarate) (PPF) as a model material for extrusion-based printing applications. A full-factorial design evaluating the effects of four factors (PPF concentration, printing pressure, printing speed, and programmed fiber spacing) on viscosity, fiber diameter, and pore size was performed layer-by-layer on 3D scaffolds. We developed a linear model of printing solution viscosity, where concentration of PPF had the greatest effect on viscosity, and the polymer exhibited shear thinning behavior. Additionally, linear models of pore size and fiber diameter revealed that fiber spacing and pressure had the greatest effect on pore size and fiber diameter, respectively, but interplay among the factors also influenced scaffold architecture. This study serves as a platform to determine if novel biomaterials are suitable for extrusion-based 3D printing applications.

The primary focus of this work is to present the current challenges of printing scaffolds with concentration gradients of nanoparticles with an aim to improve the processing of these scaffolds. Furthermore, we address how print fidelity is related to material composition and emphasize the importance of considering this relationship when developing complex scaffolds for bone implants. The ability to create complex tissues is becoming increasingly relevant in the tissue engineering community. For bone tissue engineering applications, this work demonstrates the ability to use extrusion-based printing techniques to control the spatial deposition of hydroxyapatite (HA) nanoparticles in a 3D composite scaffold. In doing so, we combined the benefits of synthetic, degradable polymers, such as poly(propylene fumarate) (PPF), with osteoconductive HA nanoparticles that provide robust compressive mechanical properties. Furthermore, the final 3D printed scaffolds consisted of well-defined layers with interconnected pores, two critical features for a successful bone implant. To demonstrate a controlled gradient of HA, thermogravimetric analysis was carried out to quantify HA on a per-layer basis. Moreover, we non-destructively evaluated the tendency of HA particles to aggregate within PPF using micro-computed tomography (µCT). This work provides insight for proper fabrication and characterization of composite scaffolds containing particle gradients and has broad applicability for future efforts in fabricating complex scaffolds for tissue engineering applications.

Reconstruction of large bone defects can be complicated by the presence of both infection and local antibiotic administration. This can be addressed through a two-stage reconstructive approach, called the Masquelet technique, that involves the generation of an induced osteogenic membrane over a temporary poly(methyl methacrylate) (PMMA) space maintainer, followed by definitive reconstruction after the induced membrane is formed. Given that infection and antibiotic delivery each have independent effects on local tissue response, the objective of this study is to evaluate the interaction between local clindamycin release and bacterial contamination with regards to infection prevention and the restoration of pro-osteogenic gene expression in the induced membrane. Porous PMMA space maintainers with or without clindamycin were implanted in an 8 mm rat femoral defect model with or without Staphylococcus aureus inoculation for 28 days in a full-factorial study design (four groups, n = 8/group). Culture results demonstrated that 8/8 animals in the inoculated/no antibiotic group were infected at 4 weeks, which was significantly reduced to 1/8 animals in the inoculated/antibiotic group. Quantitative polymerase chain reaction analysis demonstrated that clindamycin treatment restores inflammatory cytokine and growth factor expression to the same levels as the no inoculation/no antibiotic group, demonstrating that clindamycin can ameliorate the negative effects of bacterial inoculation and does not itself negatively impact the expression of important cytokines. Main effect analysis shows that bacterial inoculation and clindamycin treatment have independent and interacting effects on the gene expression profile of the induced membrane, further highlighting that antibiotics play an important role in the regeneration of infected defects apart from their antimicrobial properties.