Biological Response of and Blood Plasma Protein Adsorption on Silver-Doped Hydroxyapatite

A plasma-3D print combined in vitro platform with implications for reliable materiobiological screening

Materiobiology is an emerging field focused on the physiochemical properties of biomaterials concerning biological outcomes which includes but is not limited to the biological responses and bioactivity of surface-modified biomaterials. Herein, we report a novel in vitro characterization platform for characterizing nanoparticle surface-modified 3D printed PLA scaffolds. We have introduced innovative design parameters that were practical for ubiquitous in vitro assays like those utilizing 96 and 24-well plates. Subsequently, gold and silica nanoparticles were deposited using two low-temperature plasma-assisted processes namely plasma electroless reduction (PER) and dusty plasma on 3D scaffolds. Materiobiological testing began with nanoparticle surface modification optimization on 96 well plate design 3D scaffolds. We have employed 3D laser confocal imaging and scanning electron microscopy to study the deposition of nanoparticles. It was found that the formation and distribution of the nanoparticles were time-dependent. In vitro assays were performed utilizing an osteosarcoma (MG-63) cell as a model. These cells were grown on both 96 and 24 well plate design 3D scaffolds. Subsequently, we performed different in vitro assays such as cell viability, and fluorescence staining of cytoskeletal actin and DNA incorporation. The actin cytoskeleton staining showed more homogeneity in the cell monolayer growing on the gold nanoparticle-modified 3D scaffolds than the control 3D PLA scaffold. Furthermore, the mineralization and protein adsorption experiments conducted on 96 well plate design scaffolds have shown enhanced mineralization and bovine serum albumin adsorption for the gold nanoparticle-modified scaffolds compared to the control scaffolds. Taken together, this study reports the efficacy of this new in vitro platform in conducting more reliable and efficient materiobiology studies. It is also worth mentioning that this platform has significant futuristic potential for developing as a high throughput screening platform. Such platforms could have a significant impact on the systematic study of biocompatibility and bioactive mechanisms of nanoparticle-modified 3D-printed scaffolds for tissue engineering. It would also provide unique ways to investigate mechanisms of biological responses and subsequent bioactive mechanisms for implantable biomaterials. Moreover, this platform can derive more consistent and reliable in vitro results which can improve the success rate of further in vivo experiments.

Correlation between biomedical and structural properties of Zn/Sr modified calcium phosphates

This study investigates the correlation between the biomedical and structural properties of Zn/Sr-modified Calcium Phosphates (ZnSr-CaPs) synthesized via the sol-gel combustion method. X-ray diffraction (XRD) analysis revealed the presence of Ca10(PO4)6(OH)2 (HAp), CaCO3, and Ca(OH)2 phases in the undoped sample, while the additional phase, Ca3(PO4)2 (β-TCP) was formed in modified samples. X-ray absorption near-edge structure (XANES) analysis demonstrated the incorporation of Sr into the lattice, with a preference for occupying the Ca1 sites in the HAp matrix. The introduction of Zn, furthermore, led to the formation of ZnO and CaZnO2 species. The ZnSr-CaPs exhibited significant antibacterial activity attributed to the generation of reactive oxygen species by ZnO, the oxidation reaction of CaZnO2, and the presence of Sr ions. Cytotoxicity tests revealed a correlation between the variation in ZnO content and cellular viability, with lower ZnO concentrations corresponding to higher cell viability. Additionally, the cooperative effects of Zn and Sr ions were found to enhance the bioactivity of CaPs, despite ZnO hindering the apatite formation process. These findings contribute to the deep understanding of the diverse role in modulating the antibacterial, cytotoxic, and bioactive properties of ZnSr-CaPs, offering potential applications in the field of biomaterials.

Enhanced properties of nickel-silver codoped hydroxyapatite for bone tissue engineering: Synthesis, characterization, and biocompatibility evaluation

Hydroxyapatite (HAp) is the most well-known bioceramic and widely utilized in bone tissue regeneration. Hydroxyapatite is biocompatible and bioactive however, it lacks osteogenesis, angiogenesis, and antibacterial properties. In the current study, we synthesized and evaluated a novel nickel (Ni) and silver (Ag) codoped hydroxyapatite (HAp) in comparison to undoped HAp and individually doped HAp samples. Extensive physicochemical characterizations like XRD, TEM, FE-SEM/EDS, FTIR, Raman spectroscopy, and TGA were performed, confirming the crystal structure and morphology of the synthesized HAp samples. All HAp samples exhibited elongated spherical-like nanoparticle morphologies with lengths between 34 and 44 nm and widths between 21 and 26 nm. The presence of dopant atoms, Ag and Ni, were observed in the doped/codoped HAp samples by EDS elemental mapping. Biocompatibility assessments using pre-osteoblast cells indicated high cell viability for all the doped and undoped HAp samples. Osteoinduction potential through alkaline phosphatase (ALP) activity measurements and alizarin red S (ARS) staining revealed enhanced calcium deposition in the presence of Ni-Ag codoped HAp compared to other HAp samples and control groups. This highlights the importance of Ni-Ag co-doping in promoting osteogenesis, surpassing the effects of silver doped HAp and nickel doped HAp. The potential of this novel Ni-Ag codoped HAp to induce osteogenesis in pre-osteoblast cells makes it a promising material for various applications in bone tissue engineering.

Photothermal Conversion Efficiency of Silver and Gold Incorporated Nanosized Apatites for Biomedical Applications

The aim of this research was to investigate the photothermal ability of nanocrystalline hydroxyapatite (nHAp) incorporated with silver and gold. It was studied by using a recently developed technique evaluating the photothermal conversion efficiency. The heating performance of aqueous dispersions was examined under 445 and 532 nm excitation. The largest increase in temperature was found for the 2% Ag-nHAp and reached above 2 °C per mg/mL of sample (445 nm) under 90 mW laser continuous irradiation and an external light-to-heat conversion efficiency of 0.11 L/g cm. The obtained results have shown a new functionality of nanosized apatites that has not been considered before. The studied materials have also been characterized by XRPD, TEM, BET, and UV-Vis techniques. Finally, in this work, a new idea for their application was proposed: photothermal therapy.

In Vitro Evaluation of Ag- and Sr-Doped Hydroxyapatite Coatings for Medical Applications

Osseointegration plays the most important role in the success of an implant. One of the applications of hydroxyapatite (HAp) is as a coating for metallic implants due to its bioactive nature, which improves osteoconduction. The purpose of this research was to assess the in vitro behavior of HAp undoped and doped with Ag and/or Sr obtained by galvanostatic pulsed electrochemical deposition. The coatings were investigated in terms of chemical bonds, contact angle and surface free energy, electrochemical behavior, in vitro biomineralization in acellular media (SBF and PBS), and biocompatibility with preosteoblasts cells (MC3T3-E1 cell line). The obtained results highlighted the beneficial impact of Ag and/or Sr on the HAp. The FTIR spectra confirmed the presence of hydroxyapatite within all coatings, while in terms of wettability, the contact angle and surface free energy investigations showed that all surfaces were hydrophilic. The in vitro behavior of MC3T3-E1 indicated that the presence of Sr in the HAp coatings as a unique doping agent or in combination with Ag elicited improved cytocompatibility in terms of cell proliferation and osteogenic differentiation. Therefore, the composite HAp-based coatings showed promising potential for bone regeneration applications.

Antimicrobial activity of ion-substituted calcium phosphates: A systematic review

In this systematic review, the antimicrobial effect of ion-substituted calcium phosphate biomaterials was quantitatively assessed. The literature was systematically searched up to the 6th of December 2021. Study selection and data extraction was performed in duplo by two independent reviewers with a modified version of the OHAT tool for risk of bias assessment. Any differences were resolved by consensus or by a referee. A mixed effects model was used to investigate the relation between the degree of ionic substitution and bacterial reduction. Of 1016 identified studies, 108 were included in the analysis. The methodological quality of included studies ranged from 6 to 16 out of 18 (average 11.4). Selenite, copper, zinc, rubidium, gadolinium, silver and samarium had a clear antimicrobial effect, with a log reduction in bacteria count of 0.23, 1.8, 2.1, 3.6, 5.8, 7.4 and 10 per atomic% of substitution, respectively. There was considerable between-study variation, which could partially be explained by differences in material formulation, study quality and microbial strain. Future research should focus on clinically relevant scenarios in vitro and the translation to in vivo prevention of PJI.

Electrodeposition of Calcium Phosphate Coatings on Metallic Substrates for Bone Implant Applications: A Review

This review summaries more than three decades of scientific knowledge on electrodeposition of calcium phosphate coatings. This low-temperature process aims to make the surface of metallic bone implants bioactive within a physiological environment. The first part of the review describes the reaction mechanisms that lead to the synthesis of a bioactive coating. Electrodeposition occurs in three consecutive steps that involve electrochemical reactions, pH modification, and precipitation of the calcium phosphate coating. However, the process also produces undesired dihydrogen bubbles during the deposition because of the reduction of water, the solvent of the electrolyte solution. To prevent the production of large amounts of dihydrogen bubbles, the current density value is limited during deposition. To circumvent this issue, the use of pulsed current has been proposed in recent years to replace the traditional direct current. Thanks to breaking times, dihydrogen bubbles can regularly escape from the surface of the implant, and the deposition of the calcium phosphate coating is less disturbed by the accumulation of bubbles. In addition, the pulsed current has a positive impact on the chemical composition, morphology, roughness, and mechanical properties of the electrodeposited calcium phosphate coating. Finally, the review describes one of the most interesting properties of electrodeposition, i.e., the possibility of adding ionic substituents to the calcium phosphate crystal lattice to improve the biological performance of the bone implant. Several cations and anions are reviewed from the scientific literature with a description of their biological impact on the physiological environment.

Investigation of Antibacterial Activity and Cell Viability of Ag/Mg and Ag/Zn Co-doped Hydroxyapatite Derived from Natural Limestone

Improving the antibacterial activity to avoid infections and keeping the biocompatibility at a safe level of HAp-based materials is highly important for biomedical applications. In this work, we investigate the antibacterial activity of 2.5Ag/2.5Mg co-doped HAp and 2.5Ag/2.5Zn co-doped HAp toward Escherichia coli bacteria. Moreover, their biocompatibility for osteoblastic cells (MC3T3-E1 cells) was also evaluated. The physical properties were characterized with necessary characterization tools such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Brunauer-Emmett-Teller. Both 2.5Ag/2.5Mg and 2.5Ag/2.5Zn co-doped HAp consist of hydroxyapatite (HAp) and beta calcium triphosphate (β-TCP) phases. The antibacterial test reveals that 2.5Ag/2.5Mg co-doped HAp or 2.5Ag/2.5Zn co-doped HAp has an outstanding antibacterial activity with a killing rate of 99 ± 1%. More importantly, the cell viability for osteoblast cells with 2.5Ag/2.5Mg and 2.5Ag/2.5Zn co-doped HAp promotes the proliferation much more effectively than 2.5Ag-doped HAp or 5Ag-doped HAp.

Quantitative detection of crystal violet using a surface-enhanced Raman scattering based on a flower-like HAp/Ag nanocomposite

Herein, we proposed a simple one-pot sol-thermal strategy to prepare a highly sensitive and reproducible SERS substrate. The silver-doped hydroxyapatite nanocomposite (HAp/Ag) could suppress the oxidation of silver nanoparticles, which endow the SERS substrate with good stability and reproducibility. Due to the strong interaction between the HAp/Ag substrate and the analytes, a stronger Raman signal generated during the process of SERS detection. In particular, the HAp/Ag substrate enabled the determination of rhodamine 6G (R6G) and crystal violet (CV), and the limits of detection (LOD) were low at 10^-6 M and 10^-5 M, respectively. In addition, the HAp/Ag substrate could be used for the quantitative analysis of CV in wastewater with a good linear relationship between 10^-2 and 10^-5 M. In this context, the HAp/Ag substrate combines the superior properties of both Ag NPs and HAp particles, providing a potential method for monitoring the environment and building a convenient SERS platform to detect pollutants in wastewater.

Label-free determination of liver cancer stages using surface-enhanced Raman scattering coupled with preferential adsorption of hydroxyapatite microspheres

Here, we explored a label-free albumin targeted analysis method by utilizing hydroxyapatite (HAp) to adsorb-release serum albumin, in conjunction with surface-enhanced Raman scattering (SERS) for screening liver cancer (LC) at different tumor (T) stages. Excitingly, albumin can be preferentially adsorbed by HAp as compared with other serum proteins. Moreover, we developed a novel strategy using a high concentration of PO₄^3- solution as the albumin-release agent. This method overcomes the shortcomings of the traditional purification technology of serum albumin, which requires acid to release protein, and ensures that the structure and properties of albumin are not damaged. The SERS spectra of serum albumin obtained from three sample groups were analyzed to verify the feasibility of this new method: healthy volunteers (n = 35), LC patients with T1 stage (n = 25) and LC patients with T2-T4 stage (n = 23). Furthermore, principal component analysis (PCA) combined with linear discriminant analysis (LDA) was employed to classify the early T (T1) stage LC vs. normal group and advanced T (T2-T4) stage LC vs. normal group, yielding high diagnostic accuracies of 90.00% and 96.55%, respectively, which showed a 10% improvement in diagnostic accuracy for the early stage detection of cancer as compared with previous studies. The results of this exploratory work demonstrated that HAp-adsorbed-released serum albumin combined with SERS analysis has great potential for label-free, noninvasive and sensitive detection of different T stages of liver cancer.

Biomineralization at fluid interfaces

Biomineralization is of paramount importance for life on Earth. The delicate balance of physicochemical interactions at the interface between organic and inorganic matter during all stages of biomineralization resembles an extremely high complexity. The coordination of this sophisticated biological machinery and physicochemical scenarios is certainly a wonderful show of nature. Understanding of the biomineralization processes is still far from complete. The recent advances in biomineralization research from the Colloid and Interface Science perspective are reviewed herein. The synergy between this two fields of research is demonstrated. The unique opportunities offered by purposefully designed fluid interfaces, mainly Langmuir monolayers are presented. Biomedical applications of biomineral-based nanostructures are discussed, showing their improved biocompatibility and on-demand delivery features. A brief guide to the array of state-of-the-art experimental techniques for unraveling the mechanisms of biomineralization using fluid interfaces is included. In summary, the fruitful and exciting crossroad between Colloid and Interface Science with Biomineralization is exhibited.

Unraveling the mechanism for an amelogenin-derived peptide regulated hydroxyapatite mineralization via specific functional domain identification

Amelogenin and its various derived peptides play important roles in promoting biomimetic mineralization of enamel. Previously, an amelogenin-derived peptide named QP5 was proved to be able to repair demineralized enamel. The objective here was to interpret the mechanism of QP5 by elucidating the specific function of each domain for further sequence and efficacy improvement. Peptide QP5 was separated into domains (QPX)5 and C-tail. (QPX)3 was also synthesized to investigate how QPX repeats affect the mineralization process. Circular dichroism spectroscopy showed that two (QPX) repeats adopted a β-sheet structure, while C-tail exhibited a disordered structure. (QPX)5 showed more absorption in confocal laser scanning microscopy observation and a higher K value in Langmuir adsorption isotherms compared to C-tail, while (QPX)3 with better hydropathy had greater adsorption capability than (QPX)5. Meanwhile, calcium consumption kinetics, transmission electron microscopy and selected area electron diffraction indicated that (QPX)5, C-tail and (QPX)3 had similar inhibitory effects on the spontaneous calcium consumption and the morphology of their nucleation products were alike, while QP5 had a greater inhibitory effect than them and induced elongated plate-like crystals. X-Ray diffraction further showed that both C-tail and (QPX)3 had greater potential in improving the apatite crystal orientation degree. In conclusion, (QPX)5 was the major adsorption region, both (QPX)5 and C-tail inhibited the nucleation, and C-tail contributed more to improve the HAP orientation degree, so QP5 could exert a significant remineralization effect. By reducing two repeats, (QPX)3 showed higher hydropathicity than (QPX)5 and achieved higher binding affinity, and it was more potential in improving the HAP orientation degree with lower economic cost.

Surface-enhanced Raman scattering analysis of serum albumin via adsorption-exfoliation on hydroxyapatite nanoparticles for noninvasive cancers screening

Combining serum albumin via adsorption-exfoliation on hydroxyapatite particles (HAp) with surface-enhanced Raman scattering (SERS), we developed a novel quantitative analysis of albumin method from blood serum for cancers screening applications. The quantitatively analysis obtained by our HAp method had a good linear relationship from 1 to 10 g/dL, and the lower limit of detection was less than the albumin prognostic factor for disease (3.5 g/dL). Serum albumin was adsorbed and exfoliated by HAp from serum samples of liver cancer patients, breast cancer patients and healthy volunteers and mixed with silver colloids to perform SERS spectral analysis. Based on the PLS-SVM algorithm, the diagnostic accuracies of liver cancer patients and breast cancer patients were 100% and 96.68%, respectively. Moreover, this algorithm successfully predicted the unidentified subjects with a diagnostic accuracy of 93.75%. This exploratory work demonstrated that HAp-adsorbed-exfoliated serum proteins combined with SERS spectroscopy has great potential for cancer screening.

Fabrication of Microporous Coatings on Titanium Implants with Improved Mechanical, Antibacterial, and Cell-Interactive Properties

The success of an orthopedic implant therapy depends on successful bone integration and the prevention of microbial infections. In this work, plasma electrolytic oxidation (PEO) was performed to deposit TiO₂ coatings enriched with Ca, P, and Ag on titanium to improve its surface properties and antibacterial efficacy while maintaining normal biological functions and thus to enhance the performance of orthopedic implants. After PEO treatment, the surface of Ti was converted to anatase and rutile TiO₂, hydroxyapatite, and calcium titanate phases. The presence of these crystalline phases was further increased with an increased Ag content in the coatings. The developed coatings also exhibited a more porous morphology with an improved surface wettability, roughness, microhardness, and frictional coefficient. In vitro antibacterial assays indicated that the Ag-doped coatings can significantly prevent the growth of both Staphylococcus aureus and Escherichia coli by releasing Ag⁺ ions, and the ability to prevent these bacteria was enhanced by increasing the Ag content in the coatings, resulting in a maximal 6-log reduction of E. coli and a maximal 5-log reduction of S. aureus after 24 h of incubation. Moreover, the in vitro cytocompatibility evaluation of the coatings showed that the osteoblast (MC3T3) cell integration on the PEO-based coatings was greatly improved compared to untreated Ti and no notable impact on their cytocompatibility was observed on increasing the amount of Ag in the coating. In conclusion, the coating with favorable physicochemical and mechanical properties along with controlled silver ion release can offer an excellent antibacterial performance and osteocompatibility and can thus become a prospective coating strategy to face current challenges in orthopedics.

Rolling or Two-Stage Aggregation of Platelets on the Surface of Thin Ceramic Coatings under in Vitro Simulated Blood Flow Conditions

The process of modern cardiovascular device fabrication should always be associated with an investigation of how surface properties modulate its hemocompatibility through plasma protein adsorption as well as blood morphotic element activation and adhesion. In this work, a package of novel assays was used to correlate the physicochemical properties of thin ceramic coatings with hemocompatibility under dynamic conditions. Different variants of carbon-based films were prepared on polymer substrates using the magnetron sputtering method. The microstructural, mechanical, and surface physicochemical tests were performed to characterize the coatings, followed by investigation of whole human blood quality changes under blood flow conditions using the "Impact R" test, tubes' tester, and radial flow chamber assay. The applied methodology allowed us to determine that aggregate formation on hydrophobic and hydrophilic carbon-based coatings may follow one of the two different mechanisms dependent on the type and conformational changes of adsorbed blood plasma proteins.

Bioactive Coating on Ti Alloy with High Osseointegration and Antibacterial Ag Nanoparticles

Titanium alloys have advanced mechanical properties jointly with high biocompatibility that make them eminently suitable for biomedical applications such as dental and orthopedic implants. Improvement in their osseointegration with human bone can be achieved by the development of hydroxyapatite (HAp) on a Ti alloy surface using different methods of deposition. However, plasma electrolytic oxidation (PEO) treatment has been found to be one of the most promising techniques, due to the formation of high bonding between the bone and the Ti surface. Along with this high bonding, an antibacterial ability of the surface to prevent bacterial infection is also essential. Silver, which is a widely applicable antibacterial agent, was used in this work. First, a titanium oxide coating containing calcium and phosphorus and Ag nanoparticles was formed by PEO treatment. Then, Ti alloy was subjected to hydrothermal treatment to ensure a crystalline formation of HAp. Morphology and phase composition investigations detected the presence of HAp crystals in the coating along with antibacterial agents of silver nanoparticles. The biocompatibility and bioactivity of the created coating were examined by contact angle (CS) measurement and electrochemical impedance spectroscopy (EIS). It was shown that the coating was extensively grown after exposure of the alloy to simulated body fluid (SBF) solution for 7 days with no effect on the Ag nanoparticles. An antibacterial test using Staphylococcus aureus and Escherichia coli revealed that the coating containing Ag nanoparticles has more significant antibacterial effectiveness compared to a coating that does not contain silver.