A Facile Method to Synthesize 3D Pomegranate-like Polydopamine Microspheres

Architecture of β-lactoglobulin coating modulates bioinspired alginate dialdehyde-gelatine/polydopamine scaffolds for subchondral bone regeneration

In this study, we developed polydopamine (PDA)-functionalized alginate dialdehyde-gelatine (ADA-GEL) scaffolds for subchondral bone regeneration. These polymeric scaffolds were then coated with β-Lactoglobulin (β-LG) at concentrations of 1 mg/ml and 2 mg/ml. Morphological analysis indicated a homogeneous coating of the β-LG layer on the surface of network-like scaffolds. The β-LG-coated scaffolds exhibited improved swelling capacity as a function of the β-LG concentration. Compared to ADA-GEL/PDA scaffolds, the β-LG-coated scaffolds demonstrated delayed degradation and enhanced biomineralization. Here, a lower concentration of β-LG showed long-lasting stability and superior biomimetic hydroxyapatite mineralization. According to the theoretical findings, the single-state, representing the low concentration of β-LG, exhibited a homogeneous distribution on the surface of the PDA, while the dimer-state (high concentration) displayed a high likelihood of uncontrolled interactions. β-LG-coated ADA-GEL/PDA scaffolds with a lower concentration of β-LG provided a biocompatible substrate that supported adhesion, proliferation, and alkaline phosphatase (ALP) secretion of sheep bone marrow mesenchymal stem cells, as well as increased expression of osteopontin (SPP1) and collagen type 1 (COL1A1) in human osteoblasts. These findings indicate the potential of protein-coated scaffolds for subchondral bone tissue regeneration. STATEMENT OF SIGNIFICANCE: This study addresses a crucial aspect of osteochondral defect repair, emphasizing the pivotal role of subchondral bone regeneration. The development of polydopamine-functionalized alginate dialdehyde-gelatine (ADA-GEL) scaffolds, coated with β-Lactoglobulin (β-LG), represents a novel approach to potentially enhance subchondral bone repair. β-LG, a milk protein rich in essential amino acids and bioactive peptides, is investigated for its potential to promote subchondral bone regeneration. This research explores computationally and experimentally the influence of protein concentration on the ordered or irregular deposition, unravelling the interplay between coating structure, scaffold properties, and in-vitro performance. This work contributes to advancing ordered protein coating strategies for subchondral bone regeneration, providing a biocompatible solution with potential implications for supporting subsequent cartilage repair.

Bovine serum albumin-modified 3D printed alginate dialdehyde-gelatin scaffolds incorporating polydopamine/SiO2-CaO nanoparticles for bone regeneration

Three-dimensional (3D) printing allows precise manufacturing of bone scaffolds for patient-specific applications and is one of the most recently developed and implemented technologies. In this study, bilayer and multimaterial alginate dialdehyde-gelatin (ADA-GEL) scaffolds incorporating polydopamine (PDA)/SiO2-CaO nanoparticle complexes were 3D printed using a pneumatic extrusion-based 3D printing technology and further modified on the surface with bovine serum albumin (BSA) for application in bone regeneration. The morphology, chemistry, and in vitro bioactivity of PDA/SiO2-CaO nanoparticle complexes were characterized (n = 3) and compared with those of mesoporous SiO2-CaO nanoparticles. Successful deposition of the PDA layer on the surface of the SiO2-CaO nanoparticles allowed better dispersion in a liquid medium and showed enhanced bioactivity. Rheological studies (n = 3) of ADA-GEL inks consisting of PDA/SiO2-CaO nanoparticle complexes showed results that may indicate better injectability and printability behavior compared to ADA-GEL inks incorporating unmodified nanoparticles. Microscopic observations of 3D printed scaffolds revealed that PDA/SiO2-CaO nanoparticle complexes introduced additional topography onto the surface of 3D printed scaffolds. Additionally, the modified scaffolds were mechanically stable and elastic, closely mimicking the properties of natural bone. Furthermore, protein-coated bilayer scaffolds displayed controllable absorption and biodegradation, enhanced bioactivity, MC3T3-E1 cell adhesion, proliferation, and higher alkaline phosphatase (ALP) activity (n = 3) compared to unmodified scaffolds. Consequently, the present results confirm that ADA-GEL scaffolds incorporating PDA/SiO2-CaO nanoparticle complexes modified with BSA offer a promising approach for bone regeneration applications.

A critical review on polydopamine surface-modified scaffolds in musculoskeletal regeneration

Increasing concern about age-related diseases, particularly musculoskeletal injuries and orthopedic conditions, highlights the need for strategies such as tissue engineering to address them. Surface modification has been developed to create pro-healing interfaces, personalize scaffolds and provide novel medicines. Polydopamine, a mussel-inspired adhesive polymer with highly reactive functional groups that adhere to nearly all substrates, has gained attention in surface modification strategies for biomaterials. Polydopamine was primarily developed to modify surfaces, but its effectiveness has opened up promising approaches for further applications in bioengineering as carriers and nanoparticles. This review focuses on the recent discoveries of the role of polydopamine as a surface coating material, with focus on the properties that make it suitable for tackling musculoskeletal disorders. We report the evolution of using it in research, and discuss papers involving the progress of this field. The current research on the role of polydopamine in bone, cartilage, muscle, nerve, and tendon regeneration is discussed, thus giving comprehensive overview about the function of polydopamine both in-vitro and in-vivo. Finally, the report concludes presenting the critical challenges that must be addressed for the clinical translation of this biomaterial while exploring future perspectives and research opportunities in this area.

The effects of process parameters on polydopamine coatings employed in tissue engineering applications

The biomaterials’ success within the tissue engineering field is hinged on the capability to regulate tissue and cell responses, comprising cellular adhesion, as well as repair and immune processes’ induction. In an attempt to enhance and fulfill these biomaterials’ functions, scholars have been inspired by nature; in this regard, surface modification via coating the biomaterials with polydopamine is one of the most successful inspirations endowing the biomaterials with surface adhesive properties. By employing this approach, favorable results have been achieved in various tissue engineering-related experiments, a significant one of which is the more rapid cellular growth observed on the polydopamine-coated substrates compared to the untreated ones; nonetheless, some considerations regarding polydopamine-coated surfaces should be taken into account to control the ultimate outcomes. In this mini-review, the importance of coatings in the tissue engineering field, the different types of surfaces requiring coatings, the significance of polydopamine coatings, critical factors affecting the result of the coating procedure, and recent investigations concerning applications of polydopamine-coated biomaterials in tissue engineering are thoroughly discussed.

Mussel-inspired polydopamine decorated alginate dialdehyde-gelatin 3D printed scaffolds for bone tissue engineering application

This study utilized extrusion-based 3D printing technology to fabricate calcium-cross-linked alginate dialdehyde-gelatin scaffolds for bone regeneration. The surface of polymeric constructs was modified with mussel-derived polydopamine (PDA) in order to induce biomineralization, increase hydrophilicity, and enhance cell interactions. Microscopic observations revealed that the PDA layer homogeneously coated the surface and did not appear to induce any distinct change in the microstructure of the scaffolds. The PDA-functionalized scaffolds were more mechanically stable (compression strength of 0.69 ± 0.02 MPa) and hydrophilic (contact angle of 26) than non-modified scaffolds. PDA-decorated ADA-GEL scaffolds demonstrated greater durability. As result of the 18-days immersion in simulated body fluid solution, the PDA-coated scaffolds showed satisfactory biomineralization. Based on theoretical energy analysis, it was shown that the scaffolds coated with PDA interact spontaneously with osteocalcin and osteomodulin (binding energy values of −35.95 kJ mol⁻¹ and −46.39 kJ mol⁻¹, respectively), resulting in the formation of a protein layer on the surface, suggesting applications in bone repair. PDA-coated ADA-GEL scaffolds are capable of supporting osteosarcoma MG-63 cell adhesion, viability (140.18% after 7 days), and proliferation. In addition to increased alkaline phosphatase secretion, osteoimage intensity also increased, indicating that the scaffolds could potentially induce bone regeneration. As a consequence, the present results confirm that 3D printed PDA-coated scaffolds constitute an intriguing novel approach for bone tissue engineering.

Protein-Based Hydrogels: Promising Materials for Tissue Engineering

The successful design of a hydrogel for tissue engineering requires a profound understanding of its constituents' structural and molecular properties, as well as the proper selection of components. If the engineered processes are in line with the procedures that natural materials undergo to achieve the best network structure necessary for the formation of the hydrogel with desired properties, the failure rate of tissue engineering projects will be significantly reduced. In this review, we examine the behavior of proteins as an essential and effective component of hydrogels, and describe the factors that can enhance the protein-based hydrogels' structure. Furthermore, we outline the fabrication route of protein-based hydrogels from protein microstructure and the selection of appropriate materials according to recent research to growth factors, crucial members of the protein family, and their delivery approaches. Finally, the unmet needs and current challenges in developing the ideal biomaterials for protein-based hydrogels are discussed, and emerging strategies in this area are highlighted.