Biomaterials are an important and integrated part of modern medicine, and their development and improvement are essential. The fundamental requirement of a biomaterial is found to be in its interaction with the surrounding environment, with which it must coexist. The aim of this study was to assess the biological characteristics of hydroxyapatite (HAp)-based coatings doped with Mg and Zn ions obtained by the pulsed galvanostatic electrochemical method on the surface of pure titanium (cp-Ti) functionalized with titanium dioxide nanotubes (NTs TiO₂) obtained by anodic oxidation. The obtained results highlighted that the addition of Zn or Mg into the HAp structure enhances the in vitro response of the cp-Ti surface functionalized with NT TiO₂. The contact angle and surface free energy showed that all the developed surfaces have a hydrophilic character in comparison with the cp-Ti surface. The HAp-based coatings doped with Zn registered superior values than the ones with Mg, in terms of biomineralization, electrochemical behavior, and cell interaction. Overall, it can be said that the addition of Mg or Zn can enhance the in vitro behavior of the HAp-based coatings in accordance with clinical requirements. Antibacterial tests showed that the proposed HAp-Mg coatings had no efficiency against Escherichia coli, while the HAp-Zn coatings registered the highest antibacterial efficiency.

Adipose-derived mesenchymal stromal cells (ADSC) are a promising source for cellular therapy of chronic wounds. However, the limited life span during in vitro expansion impedes their extensive use in clinical applications and basic research. We hypothesize that by introduction of an ectopic expression of telomerase into ADSC, the cells’ lifespans could be significantly extended. To test this hypothesis, we aimed at engineering an immortalized human ADSC line using a lentiviral transduction with human telomerase (hTERT). ADSC were transduced with a third-generation lentiviral system and a hTERT codifying plasmid (pLV-hTERT-IRES-hygro). A population characterized by increased hTERT expression, extensive proliferative potential and remarkable (potent) multilineage differentiation capacity was selected. The properties for wound healing of this immortalized ADSC line were assessed after 17 passages. Their secretome induced the proliferation and migration of keratinocytes, dermal fibroblasts, and endothelial cells similarly to untransduced ADSC. Moreover, they sustained the complete re-epithelialization of a full thickness wound performed on a skin organotypic model. In summary, the engineered immortalized ADSC maintain the beneficial properties of parent cells and could represent a valuable and suitable tool for wound healing in particular, and for skin regenerative therapy in general.

The purpose of coatings is to protect or enhance the functionality of the substrate material, irrespective of the field in which the material was designed. The use of coatings in medicine is rapidly expanding with the objective of enhancing the osseointegration ability of metallic materials such as titanium. The aim of this study was to obtain biomimetic hydroxyapatite (HAp)-based coatings on titanium by using the pulsed galvanostatic method. The morphology of the HAp-based coatings revealed the presence of very thin and wide plate-like crystals, grown perpendicular to the Ti substrate, while the chemical composition highlighted a Ca/P ratio of 1.66, which is close to that of stoichiometric HAp (1.67). The main phases and chemical bonds identified confirmed the presence of the HAp phase in the developed coatings. A roughness of 228 nm and a contact angle of approx. 17° were obtained for the HAp coatings, highlighting a hydrophilic character. In terms of biomineralization and electrochemical behavior, it was shown that the HAp coatings have significantly enhanced the titanium properties. Finally, the in vitro cell tests carried out with human mesenchymal stem cells showed that the Ti samples coated with HAp have increased cell viability, extracellular matrix, and Ca intracellular deposition when compared with the uncoated Ti, indicating the beneficial effect.

Introduction. Modern medicine depends on biomaterials. Thus, it is imperative that these materials continue to be developed and improved. Methods. This work aimed at designing hydroxyapatite-based coatings (HAp) with high osseointegration properties by developing a biomimetic morphology that resembles that of natural HAp found in bone tissue. The biomimetic HAp coatings with plate-like morphology were successfully obtained using the pulsed galvanostatic electrochemical approach on pure Ti discs. The coatings were investigated in terms of surface morphology, chemical and phasic composition, in vitro bioactivity, and cell interaction. Results and Discussion. The morphological investigations revealed that using electrochemical deposition, HAp-based coatings with very thin and wide plate-like crystals can be obtained. The chemical composition highlighted that both Ca and P are present, and that the Ca/P ratio registered values of 1.66, being close to that of the stoichiometric HAp of 1.67. The phasic composition analysis showed that the main phase consisted of hydroxyapatite (ICDD #09-0432), with a crystallinity of ~25%. The biomineralization ability of the cp-Ti substrate was improved by the HAp-based coatings, reaching a maximum value of 9.7 mg after 3 weeks of immersion in simulated body fluid (SBF) compared to the Ti samples which gained a mass of only 0.3 mg after the same period. The in vitro experiments using human mesenchymal stem cells demonstrated that the HAp-based coatings enhanced the extracellular matrix, the intracellular deposition of Ca, and cell viability when compared to the cp-Ti substrate, demonstrating the advantages of the developed coatings. Conclusions. Therefore, the outcomes confirm that coatings with improved and adjustable properties can be designed for medical applications by using the electrochemical deposition technique.