Design of nanostructured siloxane-gelatin coatings: Immobilization strategies and dissolution properties

Owing to the outstanding service life of metallic prostheses, a substantial effort has been put into their surface modification to improve biocompatibility and reduce metallic ion diffusion. To satisfy these requirements, the coating materials obtained using the sol-gel method, with its wide range of tuning properties, have been extensively explored. The well-known biocompatibility of these materials makes them good candidates for different biomedical applications. We designed a series of siloxane-gelatin hybrids to be used as coatings for metallic implants or in controlled delivery systems. Two different matrixes were designed based on methyltrimethoxysilane (MTMOS), tetraethoxysilane (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) alkoxysilane precursors. In one hybrid coating gelatin was physically entrapped and in the other it was linked to the siloxane network by covalent bonds. Synthesis parameters were established by studying the sol-gel reaction using 29Si nuclear magnetic resonance (29Si NMR), which also allowed quantification of the network connectivity. Dissolution and degradation studies showed the effectiveness of GPTMS as a covalent coupling agent between the silica and gelatin phases; it increased the stability of the coatings in aqueous media. The aim of this study was to design a set of hybrid materials with highly tailorable properties, suitable for their potential biomedical application

The design and characterisation of sol–gel coatings for the controlled-release of active molecules

The controlled release of active agents from a matrix has become increasingly important for oral, transdermal or implantable therapeutic systems, due to the advantages of safety, efficacy and patient convenience. Controlled-release hybrid (organic-inorganic) sol-gel coating synthesis has been performed to create a sol with an active molecule included (procaine). Synthesis procedures included acid-catalysed hydrolysis, sol preparation, the addition of a procaine solution to the sol, and the subsequent gelation and drying. The alkoxide precursors used were triethoxyvinylsilane and tetraethyl-orthosilicate (TEOS) in molar ratios of 1:0, 9:1, 8:2 and 7:3. After the determination of the optimal synthesis parameters, the material was physicochemically characterised by silicon-29 nuclear magnetic resonance (²⁹Si-NMR) and Fourier transform infrared spectroscopy, contact angle analysis and electrochemical impedance spectroscopy tests. Finally, the materials were assayed in vitro for their ability to degrade by hydrolysis and to release procaine in a controlled manner. The sustained release of procaine over a 3-day period was demonstrated. A close correlation between release and degradation rates suggests that film degradation is the main mechanism underlying the control of release. Electrochemical analysis reveals the formation of pores and water uptake during the degradation. The quantity of TEOS is one of the principal parameters used to determine the kinetics of degradation and procaine release.The supports of the Spanish Ministry of Economy and Competitiveness through project IPT-010000-2010-004 and of the University of the Basque Country (UPV/EHU) through ‘‘UFI11/56’’ are kindly acknowledge

Advances in the slow freezing cryopreservation of microencapsulated cells

Over the past few decades, the use of cell microencapsulation technology has been promoted for a wide range of applications as sustained drug delivery systems or as cells containing biosystems for regenerative medicine. However, difficulty in their preservation and storage has limited their availability to healthcare centers. Because the preservation in cryogenic temperatures poses many biological and biophysical challenges and that the technology has not been well understood, the slow cooling cryopreservation, which is the most used technique worldwide, has not given full measure of its full potential application yet. This review will discuss the different steps that should be understood and taken into account to preserve microencapsulated cells by slow freezing in a successful and simple manner. Moreover, it will review the slow freezing preservation of alginate-based microencapsulated cells and discuss some recommendations that the research community may pursue to optimize the preservation of microencapsulated cells, enabling the therapy translate from bench to the clinic

Proteomic Analysis of Mesenchymal Stem Cells and Monocyte Co-Cultures Exposed to a Bioactive Silica-Based Sol–Gel Coating

New methodologies capable of extensively analyzing the cell-material interactions are necessary to improve current in vitro characterization methods, and proteomics is a viable alternative. Also, many studies are focused on monocultures, even though co-cultures model better the natural tissue. For instance, human mesenchymal stem cells (MSCs) modulate immune responses and promote bone repair through interaction with other cell types. Here, label-free liquid chromatography tandem mass spectroscopy proteomic methods were applied for the first time to characterize HUCPV (MSC) and CD14+ monocytes co-cultures exposed to a bioactive sol–gel coating (MT). PANTHER, DAVID, and STRING were employed for data integration. Fluorescence microscopy, enzyme-linked immunosorbent assay, and ALP activity were measured for further characterization. Regarding the HUCPV response, MT mainly affected cell adhesion by decreasing integrins, RHOC, and CAD13 expression. In contrast, MT augmented CD14+ cell areas and integrins, Rho family GTPases, actins, myosins, and 14-3-3 expression. Also, anti-inflammatory (APOE, LEG9, LEG3, and LEG1) and antioxidant (peroxiredoxins, GSTO1, GPX1, GSHR, CATA, and SODM) proteins were overexpressed. On co-cultures, collagens (CO5A1, CO3A1, CO6A1, CO6A2, CO1A2, CO1A1, and CO6A3), cell adhesion, and pro-inflammatory proteins were downregulated. Thus, cell adhesion appears to be mainly regulated by the material, while inflammation is impacted by both cellular cross-talk and the material. Altogether, we conclude that applied proteomic approaches show its potential in biomaterial characterization, even in complex systems.This work was supported by MINECO [MAT2017-86043-R; RTC-2017-6147-1], Generalitat Valenciana [GRISOLIAP/2018/091, BEFPI/2021/043, PROMETEO/2020/069], Universitat Jaume I [UJI-B2017-37], and the University of the Basque Country [GIU18/189]. Andreia Cerqueira was supported by the Margarita Salas postdoctoral contract MGS/2022/10 (UP2022-024) financed by the European Union-NextGenerationEU. The University Medical Centre Hamburg-Eppendorf (Hamburg, Germany) and the Clinics for Gynecology AGAPLESION BETHESDA Hospital provided the blood and tissue for cell isolation. The authors would like to thank Raquel Oliver, Jose Ortega, Iraide Escobés, and Anke Borkam-Schuster for their valuable technical assistance and Antonio Coso (GMI-Ilerimplant) for producing the titanium discs

Sol-gel coatings for metallic prosthesis from methyl-modified alkoxysilanes: balance between protection and bioactivation

The reported osteogenic properties of the hybrid silica sol-gel materials make these compositions perfect candidates for bone tissue engineering applications. The aim of this study was the synthesis and characterisation of hybrid silica coatings, obtained using mixtures of tetraethyl orthosilicate (TEOS) and three different methyl-modified alkoxysilanes: trimethoxymethylsilane (MTMS), dimethyldiethoxysilane (DMDES) or polydimethylsiloxane (PDMS). A comparison of the properties of these materials can reveal the best candidate for the coatings on metallic prostheses. After optimising the synthesis parameters, the developed coatings were characterised using Fourier transform infrared spectrometry (FT-IR), 1H and 29Si solid-state nuclear magnetic resonance (1H-NMR and 29Si-MNR), cross-cut tests, scanning electron microscopy (SEM), contact angle measurements, optical profilometry, hydrolytic degradation tests and electrochemical corrosion analysis. Homogeneous and well-adhering coatings were obtained using the three methyl-modified reagents. However, different degrees of protection against corrosion, different hydrophilicity and varying degradation kinetics were observed for different precursors. The MTMS-based coating showed the highest hydrophilicity and degradation kinetics; these properties can be associated with increased bioactivity (Si release). In contrast, the PDMS and DMDES-based coatings showed augmented resistance to corrosion and lower permeability to water and, consequently, improved protection of metallic surfaces. From the physicochemical point of view, all these materials displayed interesting characteristics, relevant for coatings to be used in biomedical applications

Proteomic analysis of silica hybrid sol-gel coatings: a potential tool for predicting the biocompatibility of implants in vivo

The interactions of implanted biomaterials with the host organism determine the success or failure of an implantation. Normally, their biocompatibility is assessed using in vitro tests. Unfortunately, in vitro and in vivo results are not always concordant; new, effective methods of biomaterial characterisation are urgently needed to predict the in vivo outcome. As the first layer of proteins adsorbed onto the biomaterial surfaces might condition the host response, mass spectrometry analysis was performed to characterise these proteins. Four distinct hybrid sol-gel biomaterials were tested. The in vitro results were similar for all the materials examined here. However, in vivo, the materials behaved differently. Six of the 171 adsorbed proteins were significantly more abundant on the materials with weak biocompatibility; these proteins are associated with the complement pathway. Thus, protein analysis might be a suitable tool to predict the in vivo outcomes of implantations using newly formulated biomaterials

Control of the degradation of silica sol-gel hybrid coatings for metal implants prepared by the triple combination of alkoxysilanes

Hybrid materials obtained by sol-gel process are able to degrade and release Si compounds that are useful in regenerative medicine due to their osteoinductive properties. The present work studies the behavior of new organic-inorganic sol-gel coatings based on triple mixtures of alkoxysilanes in different molar ratios. The precursors employed are methyl-trimethoxysilane (MTMOS), 3-glycidoxypropyl-trimethoxysilane (GPTMS) and tetraethyl-orthosilicate (TEOS). After optimization of the synthesis conditions, the coatings were characterized using 29Si nuclear magnetic resonance (29Si-MNR), Fourier transform infrared spectrometry (FT-IR), contact angle measurements, hydrolytic degradation assays, electrochemical impedance spectroscopy (EIS) and mechanical profilometry. The degradation and EIS results show that by controlling the amount of TEOS precursor in the coating it is possible to tune its degradation by hydrolysis, while keeping properties such as wettability at their optimum values for biomaterials application. The corrosion properties of the new coatings were also evaluated when applied to stainless steel substrate. The coatings showed an improvement of the anticorrosive properties of the steel which is important to protect the metal implants at the early stages of the regeneration process.The financial support of MAT2014-51918-C2-2-R, P11B2014-19 and Plan de Promoción de la Investigación from the Universitat Jaume I (Predoc/2014/25) is gratefully acknowledged. J. García-Cañadas acknowledge financial support from Ramón y Cajal programme (RYC-2013-13970). The experimental support of Raquel Oliver Valls and José Ortega Herreros is also acknowledged

Development and characterisation of strontium-doped sol-gel coatings to optimise the initial bone regeneration processes

Strontium plays an important role in bone regeneration; it promotes the differentiation and maturation of osteoblasts and inhibits the activity of osteoclasts. Our principal objective in this study was to formulate new organic-inorganic hybrid sol-gel coatings applied to titanium discs. These coatings were functionalised with different amounts of SrCl2 and examined using in vitro tests and proteomics. The chemical and morphological characteristics of obtained coatings were scrutinised. The in vitro evaluation using the MC3T3-E1 osteoblasts and RAW264.7 macrophages showed the osteogenic and anti-inflammatory effects of strontium doping. The proteomic assay identified 111 different proteins adhering to the coatings. Six of these proteins reduced their adhesion affinity as a result of Sr-doping, whereas 40 showed increased affinity. Moreover, the proteomic analysis revealed osteogenic and anti-inflammatory properties of these biomaterials. The analysis also showed increased adhesion of proteins related to the coagulation system. We can conclude that proteomic methods are invaluable in developing new biomaterials and represent an important tool for predicting the biocompatibility of dental implants

Osteointegración de implantes de titanio con superficies activas. Un estudio proteómico

Titanium is a biomaterial largely used on dental implant manufacturing. However, as a consequence of its intrinsically low bioactivity, the development of distinct superficial treatments in order to enhance its osseointegration properties is being studied. In this sense, the use of titanium implants with a higher level of roughness has been broadened, recurring to the application of sand-blasted acid-etched surface treatments. In this article, a study of two distinct titanium surface treatments has been carried out, regarding the physico-chemical properties (roughness, hydrophilicity and chemical composition) of each, as well as the pattern of adhered proteins onto each surface (proteomic study). Hence, mass spectrometry analysis allowed the detection of 2 18 d istinct a dsorbed p roteins, being 37 of those related to bone regenerative processes and dental implant integration. Moreover, using differential quantification between associated proteins, comparing surfaces, it was observable a greater affinity of APOE, ANT3 and PROC proteins to the treated surface, directly linked to the bone regenerative process. On the other hand, the treated surface displays lower affinity of CO3 protein. The variations between the adsorbed protein profiles could be an explanation for distinct in vivo outcomes.El titanio es un biomaterial ampliamente empleado en la fabricación de implantes dentales, sin embargo, como consecuencia de su baja bioactividad se han desarrollado distintos tratamientos superficiales buscando una mejora en su capacidad de osteintegración. De esta forma, se ha extendido el uso de implantes de titanio con un mayor grado de rugosidad gracias a la aplicación de un tratamiento de granallado, al que le sigue un tratamiento de ataque ácido. En este artículo se ha llevado a cabo un estudio de discos de titanio con dos tipos de superficie: sin tratamiento alguno y con tratamiento de granallado más ataque ácido. El estudio reveló diferencias físico-químicas (rugosidad, hidrofilia y composición química) tras la aplicación del tratamiento superficial, pero también en cuanto al perfil de proteínas adheridas a cada superficie (estudio proteómico). Así, la espectrometría de masas permitió la caracterización de las proteínas adsorbidas en ambos tipos de superficies. El análisis permitió la identificación de 218 proteínas distintas, pudiendo relacionar 37 de ellas con el proceso de regeneración ósea y en consecuencia con la osteointegración de un implante dental. Además, tras la cuantificación diferencial entre proteínas asociadas, antes y después de aplicar el tratamiento superficial mencionado, se observó que tras su aplicación se producía un aumento en la afinidad de las proteínas APOE, ANT3 y PROC, directamente relacionadas con el proceso de regeneración ósea. Por el contrario, la proteína CO3 se adhería a esta superficie en menor proporción. Estas variaciones de los perfiles de proteínas podrían explicar la diferencia encontrada en la respuesta de las distintas superficies al ser caracterizadas en cuanto a su comportamiento in vivo

Complement proteins regulating macrophage polarisation on biomaterials

[EN] One of the events occurring when a biomaterial is implanted in an host is the protein deposition onto its surface, which might regulate cell responses. When a biomaterial displays a compromised biocompatibility, distinct complement pathways can be activated to produce a foreign body reaction. In this article, we have designed different types of biomaterial surfaces to study the inflammation process. Here, we used different concentrations of (3-glycidoxypropyl)-trimethoxysilane (GPTMS), an organically-modified alkoxysilane as a precursor for the synthesis of various types of sol-gel materials functionalizing coatings for titanium implants to regulate biological responses. Our results showed that greater GPTMS surface concentrations induced greater secretion of TNF-alpha and IL-10 on RAW 264.7 macrophages. When implanted into rabbit tibia, osseointegration decreased with higher GPTMS concentrations. Interestingly, higher deposition of complement-related proteins C-reactive protein (CRP) and ficolin-2 (FCN2), two main activators of distinct complement pathways, was observed. Taking all together, inflammatory potential increase seems to be GPTMS concentration-dependent. Our results show that a greater adsorption of complement proteins can condition macrophage polarization.This work was supported by MINECO [MAT2017-86043-R]; Universitat Jaume I [Predoc/2014/25, UJI-B2017-37]; Basque Government [IT611-13, Predoc/2016/1/0141]; University of the Basque Country [UFI11/56]; CIC bioGUNE is supported by Basque Department of Industry, Tourism and Trade (Etortek and Elkartek programs), ProteoRed-ISCIII [PRB3 IPT17/0019]; CIBERehd Network and Severo Ochoa Grant [SEV-2016-0644]. Authors would like to thank Antonio Coso and Jaime Franco (GMI-Ilerimplant) for their inestimable contribution to this study, and Raquel Oliver, Jose Ortega (UJI), René van Rheden, Vicent Cuijpers (Radboudumc) and Iraide Escobes (CIC bioGUNE) for their valuable technical assistance.Araújo-Gomes, N.; Romero-Gavilán, F.; Zhang, Y.; Martínez-Ramos, C.; Elortza, F.; Azkargorta, M.; Martín De Llano, JJ.... (2019). Complement proteins regulating macrophage polarisation on biomaterials. Colloids and Surfaces B Biointerfaces. 181:125-133. https://doi.org/10.1016/j.colsurfb.2019.05.039S12513318