Calcium-Based Biomineralization: A Smart Approach for the Design of Novel Multifunctional Hybrid Materials

Osteogenic Potential of 3D-Printed Porous Poly(lactide-co-trimethylene carbonate) Scaffolds Coated with Mg-Doped Hydroxyapatite

Extrusion-based 3D printing of thermoplastic polymers presents significant potential for bone tissue engineering. However, a key limitation is the frequent absence of filament porosity and the inherent osteoconductive properties. This study addresses these challenges by fabricating poly(lactide-co-trimethylene carbonate) (PLATMC) scaffolds with dual-scale porosity: macroporosity achieved through controlled filament spacing and microporosity introduced via NaCl leaching. The inclusion of NaCl generated rough, porous surfaces that were well-suited for dip-coating with magnesium-carbonate-doped hydroxyapatite (MgCHA), thereby imparting osteoconductive functionality. Thermal analysis revealed that salt incorporation had minimal impact on the polymer's thermal stability. Rheological studies and computational modeling indicated that NaCl reduced the viscosity under shear, leading to enhanced printability and faster extrusion speeds. After leaching, the scaffolds exhibited approximately 34% microporosity, which significantly increased water uptake and swelling capacity, despite the roughened surfaces slightly elevating hydrophobicity. The mechanical properties of PLATMC (with nonporous filaments) and p-PLATMC (with porous filaments) scaffolds showed a modulus of elasticity of 566 ± 118 and 101 ± 20 MPa, respectively, with strain values of 178 ± 54% and 84 ± 28%. Biological evaluations highlighted the compatibility of the p-PLATMC scaffolds. Cell viability and proliferation assays confirmed sustained cellular interaction over a 14 day period. Notably, alkaline phosphatase (ALP) activity was elevated in the porous scaffolds, and the MgCHA coating significantly enhanced mineral deposition by day 28, suggesting improved osteogenic potential. In conclusion, this study presents a robust strategy for fabricating 3D-printed PLATMC scaffolds with integrated filament porosity, offering a viable platform for osteoconductive coatings in bone tissue engineering applications.

Vasculo-osteogenic keratin-based nanofibers containing merwinite nanoparticles and sildenafil for bone tissue regeneration

Vascularization of bone tissue constructs plays a pivotal role in facilitating nutrient transport and metabolic waste removal during the processes of osteogenesis and bone regeneration in vivo. In this study, a sildenafil (Sil)-loaded nanofibrous scaffold of keratin/Soluplus/merwinite (KS.Me.Sil) was fabricated through electrospinning and the effectiveness of the scaffold was assessed for bone tissue engineering applications. The KS.Me.Sil nanofibrous scaffold exhibited notably enhanced ultimate tensile strength (3.38 vs 2.61 MPa) and elastic modulus (69.83 vs 46.27 MPa) compared to the KS scaffold. The in vitro release of Ca2+, Si4+ and Mg2+ ions and the release of Sil from the nanofibers as well as biodegradability and bioactivity were evaluated for 14 days. Protein adsorption capability and cytocompatibility of the scaffolds were tested. Alkaline phosphatase activity test, Alizarin red staining and qRT-PCR analysis demonstrated that the KS.Me.Sil nanofibers had the best osteogenic activity among other samples. Also, the results of the chorioallantoic membrane assay showed an almost threefold increase in blood vessel density in the group treated with the KS.Me.Sil nanofibers extract compared to the KS. In conclusion, our findings suggest that the electrospun KS.Me.Sil nanofibrous scaffold offers a robust structure with exceptional osteogenic and angiogenic characteristics, making it a promising candidate for bone tissue engineering applications.

A Perspective on the Use of Hydroxyapatites to Improve the Dissolution Behavior of Poorly Water-Soluble Piretanide

BACKGROUND/OBJECTIVES

Interest in drug delivery systems (DDS) based on inorganic substrates has increased in parallel with the increase in the number of poorly water-soluble drugs. Hydroxyapatite is one of the ideal matrices for DDS due to its biocompatibility, low cost, and ease of preparation.

METHODS

We propose two doped hydroxyapatites, one with Ba on Ca sites another with Si on P sites, with the aim of improving the dissolution rate of piretanide, a diuretic, poorly water-soluble drug. The hybrids were characterized by different physical-chemical techniques, and their formation was demonstrated by infrared spectroscopy, thermal analysis, and electron microanalysis, as well as by comparing the results with those obtained on physical mixtures of HAPs and properly prepared piretanide.

RESULTS

Both the hybrids improved the piretanide dissolution rate compared with the physical mixtures and the drug alone. The dose was completely solubilized from the Si-doped hybrid in about 5 min in the three fluids considered. This remarkable improvement can be explained by an increase in the wettability and solubility of the drug loaded in the drug-carrier systems.

CONCLUSIONS

Different experimental techniques, in particular spectroscopy and electronic microanalysis, proved the successful loading of piretanide onto doped HAP. Pharmaceutical measurements demonstrated rapid drug release in different fluids simulating gastrointestinal conditions after oral administration. These hybrid systems could be a very promising platform for drug delivery.

Chitosan biomineralized with ions-doped nano-hydroxyapatite tunes osteoblasts metabolism and DNA damage

Hydroxyapatite (HA) is a bioceramic material widely used as a bone biomimetic substitute and can be synthesized by biomineralization, according to which HA nanoparticles are formed on a polymer template. Nevertheless, little is known about the effect of ion doping and biomineralization on cell metabolism, oxidative stress, and DNA damage. In the present contribution, we report on synthesizing and characterizing biomineralized chitosan as a polymer template with HA nanoparticles doped with magnesium (MgHA) and iron ions (FeHA). The physical-chemical and morphological characterization confirmed the successful synthesis of low crystalline ions-doped HA nanoparticles on the chitosan template, whereas the biochemical activity of the resulting nanoparticles towards human osteoblasts-like cells (MG63 and HOBIT) was investigated considering their effect on cell metabolism, proliferation, colony formation, redox status, and DNA damage extent. Data obtained suggest that particles enhance cell metabolism but partially limit cell proliferation. The redox status of cells was measured suggesting a slight increase in Reactive Oxygen Species production with chitosan biomineralized with iron-doped HA, whereas no effect with magnesium-doped HA and no effect of all formulations on the oxidation level of Peroxiredoxin. On the other hand, DNA damage was investigated by COMET assay, and expression and foci γH2AX. These latter tests indicated that HA-based nanoparticles promote DNA damage which is enhanced by chitosan thus suggesting that chitosan favors the nanoparticles' internalization by cells and modulates their biological activity. The potential DNA damage should be considered - and potentially exploited for instance in anticancer treatment - when HA-based particles are used to devise biomaterials.

3D Tumor-Engineered Model Replicating the Osteosarcoma Stem Cell Niche and In Vivo Tumor Complexity

Osteosarcoma, among all bone sarcomas, remains a challenge despite the unwavering efforts of medical professionals and scientists. To address this, the scientific community is actively pursuing the development of three-dimensional (3D) in vitro models to faithfully replicate the heterogeneity of osteosarcoma, thereby facilitating the reliable preclinical screening of potential therapies. In this study, we present the latest advancements in engineering an in vitro 3D osteosarcoma model comprising enriched Cancer Stem Cells (CSCs) and a hybrid hydroxyapatite-based scaffold (MgHA/CoII). The improvement of the model occurred through two primary steps: (1) serial passaging of sarcospheres as the CSCs enrichment system and (2) the optimization of the structural configuration of the niche in the scaffold. Two injection-mediated approaches of sarcosphere seeding were designed and extensively characterized in vitro and in vivo Chorioallantoic Membrane (CAM) models to explore their biological properties and tumorigenic potential. The combination of the selected enriched-CSCs and custom-made seeding into the scaffold resulted in the development of 3D osteosarcoma models exhibiting tumor-like features in vitro and tumorigenic properties in vivo. The outcomes of this study offer prospects for future endeavors involving more complex systems capable of replicating specific malignant tumor behaviors (metastatic process and drug resistance), pushing the discovery of new therapeutic strategies for clinical applications.

Hybrid Hydroxyapatite-Metal Complex Materials Derived from Amino Acids and Nucleobases

Calcium phosphates (CaPs) and their substituted derivatives encompass a large number of compounds with a vast presence in nature that have aroused a great interest for decades. In particular, hydroxyapatite (HAp, Ca10(OH)2(PO4)6) is the most abundant CaP mineral and is significant in the biological world, at least in part due to being a major compound in bones and teeth. HAp exhibits excellent properties, such as safety, stability, hardness, biocompatibility, and osteoconductivity, among others. Even some of its drawbacks, such as its fragility, can be redirected thanks to another essential feature: its great versatility. This is based on the compound's tendency to undergo substitutions of its constituent ions and to incorporate or anchor new molecules on its surface and pores. Thus, its affinity for biomolecules makes it an optimal compound for multiple applications, mainly, but not only, in biological and biomedical fields. The present review provides a chemical and structural context to explain the affinity of HAp for biomolecules such as proteins and nucleic acids to generate hybrid materials. A size-dependent criterium of increasing complexity is applied, ranging from amino acids/nucleobases to the corresponding macromolecules. The incorporation of metal ions or metal complexes into these functionalized compounds is also discussed.

Effect of the Sr-Fe layered double hydroxide coating based on the microenvironment response on implant osseointegration in osteoporotic rats

Osteoporosis is a disease that manifests itself as an abnormality of bone metabolism and is characterized by low bone mass and destruction of the bone microstructure. Since bone resorption occurs more rapidly than new bone formation, osteoporosis leads to reduced orthopedic implant stability. From a microenvironmental point of view, the rationale for this outcome is that osteoclasts are overactive in the bone tissue of patients with osteoporosis, and the large amount of H+ they produce leads to local chronic acidosis, which promotes bone mineral loss. Therefore, we designed a weakly alkaline layered double hydroxide (LDH) coating to modulate the pathologically acidic microenvironment and the osteogenic-osteoclastic coupling by releasing Sr2+. We prepared Sr-Fe LDH coatings on pure titanium implants using a hydrothermal method in this study and characterized the material using SEM, AFM, XRD, XPS, EDS, ICP, pH acidimeter, etc. We found that the coatings had good nanomorphology and were able to efficiently neutralize H+ as well as steadily release Sr2+ for up to 21 days. In vitro, the coating not only significantly promoted the adhesion, proliferation, and differentiation of osteoblasts, but also inhibited the differentiation of osteoclasts at the same time. In addition, in animal experiments, the coating significantly improved the mechanical stability of the implant in osteoporotic rats, increasing Sr-Fe LDH@Ti maximal push-out force by 72.2% compared to Ti. At the same time, the coating was effective in reversing the osteoporotic state, resulting in a 58.5% increase in BV/TV (%), and a 12.4% increase in Tb. N (1 mm-1), a 31.6% increase in Tb. Th (μm), and a 30.9% increase in BA (%). Our results suggest that this Sr-Fe LDH nanocoating material with acid-neutralizing, as well as long-term Sr2+-releasing capabilities, is a novel and effective orthopedic implant coating material under osteoporotic conditions.

Recent Advances in the Development of Biomimetic Materials

In this review, we focused on recent efforts in the design and development of materials with biomimetic properties. Innovative methods promise to emulate cell microenvironments and tissue functions, but many aspects regarding cellular communication, motility, and responsiveness remain to be explained. We photographed the state-of-the-art advancements in biomimetics, and discussed the complexity of a "bottom-up" artificial construction of living systems, with particular highlights on hydrogels, collagen-based composites, surface modifications, and three-dimensional (3D) bioprinting applications. Fast-paced 3D printing and artificial intelligence, nevertheless, collide with reality: How difficult can it be to build reproducible biomimetic materials at a real scale in line with the complexity of living systems? Nowadays, science is in urgent need of bioengineering technologies for the practical use of bioinspired and biomimetics for medicine and clinics.

Bio-Inspired Nanomaterials for Micro/Nanodevices: A New Era in Biomedical Applications

Exploring bio-inspired nanomaterials (BINMs) and incorporating them into micro/nanodevices represent a significant development in biomedical applications. Nanomaterials, engineered to imitate biological structures and processes, exhibit distinctive attributes such as exceptional biocompatibility, multifunctionality, and unparalleled versatility. The utilization of BINMs demonstrates significant potential in diverse domains of biomedical micro/nanodevices, encompassing biosensors, targeted drug delivery systems, and advanced tissue engineering constructs. This article thoroughly examines the development and distinctive attributes of various BINMs, including those originating from proteins, DNA, and biomimetic polymers. Significant attention is directed toward incorporating these entities into micro/nanodevices and the subsequent biomedical ramifications that arise. This review explores biomimicry's structure-function correlations. Synthesis mosaics include bioprocesses, biomolecules, and natural structures. These nanomaterials' interfaces use biomimetic functionalization and geometric adaptations, transforming drug delivery, nanobiosensing, bio-inspired organ-on-chip systems, cancer-on-chip models, wound healing dressing mats, and antimicrobial surfaces. It provides an in-depth analysis of the existing challenges and proposes prospective strategies to improve the efficiency, performance, and reliability of these devices. Furthermore, this study offers a forward-thinking viewpoint highlighting potential avenues for future exploration and advancement. The objective is to effectively utilize and maximize the application of BINMs in the progression of biomedical micro/nanodevices, thereby propelling this rapidly developing field toward its promising future.

Nanomaterial genotoxicity evaluation using the high-throughput p53-binding protein 1 (53BP1) assay

Toxicity evaluation of engineered nanomaterials is challenging due to the ever increasing number of materials and because nanomaterials (NMs) frequently interfere with commonly used assays. Hence, there is a need for robust, high-throughput assays with which to assess their hazard potential. The present study aimed at evaluating the applicability of a genotoxicity assay based on the immunostaining and foci counting of the DNA repair protein 53BP1 (p53-binding protein 1), in a high-throughput format, for NM genotoxicity assessment. For benchmarking purposes, we first applied the assay to a set of eight known genotoxic agents, as well as X-ray irradiation (1 Gy). Then, a panel of NMs and nanobiomaterials (NBMs) was evaluated with respect to their impact on cell viability and genotoxicity, and to their potential to induce reactive oxygen species (ROS) production. The genotoxicity recorded using the 53BP1 assay was confirmed using the micronucleus assay, also scored via automated (high-throughput) microscopy. The 53BP1 assay successfully identified genotoxic compounds on the HCT116 human intestinal cell line. None of the tested NMs showed any genotoxicity using the 53BP1 assay, except the positive control consisting in (CoO)(NiO) NMs, while only TiO2 NMs showed positive outcome in the micronucleus assay. Only Fe3O4 NMs caused significant elevation of ROS, not correlated to DNA damage. Therefore, owing to its adequate predictivity of the genotoxicity of most of the tested benchmark substance and its ease of implementation in a high throughput format, the 53BP1 assay could be proposed as a complementary high-throughput screening genotoxicity assay, in the context of the development of New Approach Methodologies.

Biomineralization: A new tool for developing eco-sustainable Ti-doped hydroxyapatite-based hybrid UV filters

It is well known that the prolonged exposure to UV radiation from sunlight can compromise human health and is particularly damaging to the skin, leading to sunburn, photo-aging and skin cancer. Sunscreen formulations containing UV-filters present a barrier against solar UV and help to mitigate the harmful effects however, concern about their safety for both human and environmental health is still a much-debated topic. EC regulations classify UV-filters depending on their chemical nature, particle size, and mechanism of action. Furthermore, it regulates their use in cosmetic products with specific limitations in terms of concentration (organic UV filters) and particle size and surface modification to reduce their photo-activity (mineral UV filters). The regulations have prompted researchers to identify new materials that show promise for use in sunscreens. In this work, biomimetic hybrid materials composed of titanium-doped hydroxyapatite (TiHA) grown on two different organic templates, derived from animal (gelatin - from pig skin) and vegetable (alginate - from algae) sources. These novel materials were developed and characterized to obtain sustainable UV-filters as a safer alternative for both human and ecosystem health. This 'biomineralization' process yielded TiHA nanoparticles that demonstrated high UV reflectance, low photoactivity, good biocompatibility and an aggregate morphology which prevents dermal penetration. The materials are safe for topical application and for the marine environment; moreover, they can protect organic sunscreen components from photodegradation and yield long-lasting protection.

Editorial for the Special Issue on Bioceramic Composites

This Special Issue on bioceramic composites and its published papers, addressing a number of current topics from industry and academia, are intended to be a reference for students and scholars in the field of biomaterials science, giving an insight into challenges and research topics in the field bioceramic composites [...]