Rational design of poly(peptide-ester) block copolymers for enzyme-specific surface resorption.

Tissue resorption and remodeling are pivotal steps in successful healing and regeneration, and it is important to design biomaterials that are responsive to regenerative processes in native tissue. The cell types responsible for remodeling, such as macrophages in the soft tissue wound environment and osteoclasts in the bone environment, utilize a class of enzymes called proteases to degrade the organic matrix. Many hydrophobic thermoplastics used in tissue regeneration are designed to degrade and resorb passively through hydrolytic mechanisms, leaving the potential of proteolytic-guided degradation underutilized. Here, we report the design and synthesis of a tyrosol-derived peptide-polyester block copolymer where protease-mediated resorption is tuned through changing the chemistry of the base polymer backbone and protease specificity is imparted through incorporation of specific peptide sequences. Quartz crystal microbalance was used to quantify polymer surface resorption upon exposure to various enzymes. Aqueous solubility of the diacids and the thermal properties of the resulting polymer had a significant effect on enzyme-mediated polymer resorption. While peptide incorporation at 2 mol% had little effect on the final thermal and physical properties of the block copolymers, its incorporation improved polymer resorption significantly in a peptide sequence- and protease-specific manner. To our knowledge, this is the first example of a peptide-incorporated linear thermoplastic with protease-specific sensitivity reported in the literature. The product is a modular system for engineering specificity in how polyesters can resorb under physiological conditions, thus providing a potential framework for improving vascularization and integration of biomaterials used in tissue engineering.

Polymer Texture Influences Cell Responses in Osteogenic Microparticles.

Introduction: Polymer materials used in medical devices and treatments invariably encounter cellular networks. For the device to succeed in tissue engineering applications, the polymer must promote cellular interactions through adhesion and proliferation. To predict how a polymer will behave in vitro, these material-cell interactions need to be well understood. Methods: To study polymer structure-property relationships, microparticles of four chemically distinct tyrosol-derived poly(ester-arylate) polymers and a commercially available poly(lactic acid-co-glycolic acid) (PLGA) copolymer were prepared and their interactions with cells investigated. Cell loading concentration was optimized and cell adhesion and proliferation evaluated. Particles were also tested for their ability to adsorb bone morphogenetic protein-2 (BMP-2) and differentiate a myoblast cell line towards an osteoblast lineage through BMP-2 loading and release. Results: While cell adhesion was observed on all particles after 24 h of incubation, the highest degree of cell adhesion occurred on polymers with smaller crystallites. At longer incubation times, cells proliferated on all particle formulations, regardless of the differences in polymer properties. High BMP-2 loading was achieved for all particle formulations and all formulations showed a burst release. Even with the burst release, cells cultured on all formulations showed an upregulation in alkaline phosphatase (ALP) activity, a measure of osteoblast differentiation. Conclusions: As with cell adhesion, the polymer with the smaller crystallite showed the most ALP activity. We suggest that smaller crystallites serve as a proxy for topographical roughness to elicit the observed responses from cells. Furthermore, we have drawn a correlation between the polymer crystallite with the hydration potential using surface analysis techniques. Supplementary Information: The online version contains supplementary material available at 10.1007/s12195-022-00729-9.

In Vitro Evaluation of Recombinant Bone Morphogenetic Protein-2 Bioactivity for Regenerative Medicine.

IMPACT STATEMENT: This work is a systematic evaluation of the experimental parameters of the most widely used in vitro recombinant human bone morphogenetic protein-2 (rhBMP-2) activity assays. The variations in assays reported in the literature have challenged the reproducibility and translation of work using rhBMP-2 as a bone-inducing growth factor. By elucidating the effect of model cell line on the dose-dependent alkaline phosphatase response to rhBMP-2 induction and by establishing a correlation between protein activity and protein concentration by enzyme-linked immunosorbent assay using commercially available rhBMP-2, this work is a significant step toward developing an in vitro-in vivo correlation between quantified activity and clinical efficacy.

Polyester-based ink platform with tunable bioactivity for 3D printing of tissue engineering scaffolds.

In this work, we synthesized a novel polymeric biomaterial platform with tunable functionalizability for extrusion-based 3D printing. Biodegradable polymers were synthesized using 4-hydroxyphenethyl 2-(4-hydroxyphenyl)acetate (HTy), which is derived from Tyrosol and 2-(4-hydroxyphenyl)acetic acid. p-Phenylenediacetic acid (PDA) was introduced to enhance crystallinity. To enable functionalizability without deteriorating printability, glutamic acid derivatives were introduced into the polymer design, forming copolymers including poly(HTy-co-45%PDA-co-5%Gluhexenamide ester) (HP5GH), poly(HTy-co-45%PDA-co-5%Glupentynamide ester) (HP5GP), and poly(HTy-co-45%PDA-co-5%BocGlu ester) (HP5BG). The resulting polymers have: two melting temperatures (125-131 °C and 141-147 °C), Young's moduli of 1.9-2.4 GPa, and print temperatures of 170-190 °C. The molecular weight (Mw) loss due to hydrolytic degradation was gradual with ∼30% Mw retained after 25 weeks for HP5BG, whereas it was much faster for HP5GP and HP5GH with only 18% Mw retained after 8 weeks. HP5GH and HP5GP were successfully functionalized in solution (bulk) or on the surface using click-based chemistry. Finally, the utilization of this novel platform was demonstrated by studying osteogenic differentiation of human mesenchymal stem cells (hMSCs) using 3D printed scaffolds from HP5GP. Scaffolds were functionalized with azide-Heparin (az-Heparin) to bind and deliver bone morphogenetic protein 2 (BMP-2). This sample group significantly enhanced osteogenic differentiation of hMSCs as compared to unfunctionalized scaffolds incubated directly with az-Heparin or BMP-2 prior to cell culture. This novel polymer platform with tunable functionalizability could be utilized for additive manufacturing of biodegradable devices and scaffolds with tailored mechanical and bioactive properties for a wide range of medical applications including bone fixation devices and scaffolds for bone regeneration.

Self-control training in children: a review of interventions for anxiety and depression and the role of parental involvement.

This review critically evaluates self-control skills interventions in the treatment of childhood anxiety and depression, outlining conditions under which these interventions are successful and the specific role of parents. Findings indicated that self-control skills interventions are successful with both children and adolescents, in the context of other cognitive behavioral techniques and as the primary treatment component, and with and without parental involvement. However, despite consistent evidence of success in both pre-post and waitlist control designs, self-control skills treatments have not demonstrated superior efficacy when compared to other active treatments. Continued application and evaluation of these interventions amongst children and adolescents are recommended.