{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,10]],"date-time":"2026-10-10T01:59:17Z","timestamp":1791597557597,"version":"4.3.4"},"reference-count":41,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2025,10,18]],"date-time":"2025-10-18T00:00:00Z","timestamp":1760745600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Gels"],"abstract":"<jats:p>Hydroxyapatite (HA) coatings improve implant bioactivity but suffer from brittleness and limited functionality. Here, we report a hybrid coating strategy combining flame-sprayed HA\/TiO2 with in situ hydrogel growth. TiO2 incorporated into the HA matrix acted as a photocatalytic initiator for acrylamide polymerization under UV. Unlike conventional hydrogel coatings that require added photoinitiators or separate surface modification steps, TiO2 incorporated into the HA layer serves as a built-in photocatalytic initiator, enabling direct polymerization of acrylamide monomers on the sprayed surface. The resulting HA\/TiO2\u2013hydrogel coatings exhibited a continuous hydrogel layer with intimate contact to the ceramic surface, as evidenced by SEM cross-sections and elemental mapping. The HA\/TiO2 1% coating produced a continuous coverage in close contact with the surface, while excessive TiO2(5%) led to uncontrolled hydrogel growth and partial coating failure. SEM cross-sections revealed a dense, well-adhered coating with homogeneously distributed Ca, P, O, and finely dispersed Ti. Upon immersion in simulated body fluid (SBF), submicron globular deposits progressively developed on the coating surface. EDS showed an increase in Ca\/P ratio from ~1.66 (as-sprayed) to ~1.92 (14 days). These findings highlight a straightforward approach for combining flame-sprayed ceramics with photocatalytic hydrogel growth, providing a practical route toward multifunctional implant surface modification.<\/jats:p>","DOI":"10.3390\/gels11100837","type":"journal-article","created":{"date-parts":[[2025,10,20]],"date-time":"2025-10-20T13:54:41Z","timestamp":1760968481000},"page":"837","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["In Situ Hydrogel Growth on Flame-Sprayed Hydroxyapatite (HA)\/TiO2-Coated Stainless Steel via TiO2-Photoinitiated Polymerization"],"prefix":"10.3390","volume":"11","author":[{"given":"Komsanti","family":"Chokethawai","sequence":"first","affiliation":[{"name":"Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nattawit","family":"Yutimit","sequence":"additional","affiliation":[{"name":"Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-9777-2814","authenticated-orcid":false,"given":"Burin","family":"Boonsri","sequence":"additional","affiliation":[{"name":"Faculty of Veterinary Medicine, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Parkpoom","family":"Jarupoom","sequence":"additional","affiliation":[{"name":"Department of Industrial Engineering, Faculty of Engineering, Rajamangala University of Technology Lanna (RMUTL), Chiang Mai 50300, Thailand"},{"name":"Materials and Medical Innovation Research Unit, Faculty of Engineering, Rajamangala University of Technology Lanna (RMUTL), Chiang Mai 50300, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ketmanee","family":"Muangchan","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sahadsawat","family":"Tonkaew","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pongpen","family":"Kaewdee","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand"},{"name":"Office of Research Administration, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sujitra","family":"Tandorn","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand"},{"name":"Office of Research Administration, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chamnan","family":"Randorn","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand"},{"name":"Center of Excellence in Materials Science and Technology, Chiang Mai University, Chiang Mai 50200, Thailand"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,10,18]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"112850","DOI":"10.1016\/j.matdes.2024.112850","article-title":"Titanium-Based alloys and composites for orthopedic implants Applications: A comprehensive review","volume":"241","author":"Darwish","year":"2024","journal-title":"Mater. Des."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"914","DOI":"10.1016\/j.dental.2025.05.007","article-title":"Titanium-Zirconia abutment-implant assemblies: Are they alternatives for single material implants?","volume":"41","author":"Austin","year":"2025","journal-title":"Dent. Mater."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"3780","DOI":"10.1016\/j.jmrt.2024.04.136","article-title":"From clinic to lab: Advances in porous titanium-based orthopedic implant research","volume":"30","author":"Li","year":"2024","journal-title":"J. Mater. Res. Technol."},{"key":"ref_4","first-page":"100019","article-title":"Classification and applications of titanium and its alloys: A review","volume":"3","author":"Najafizadeh","year":"2024","journal-title":"J. Alloys Compd. Commun."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"109466","DOI":"10.1016\/j.engfailanal.2025.109466","article-title":"Failure analysis of a fractured stainless steel femoral bone plate","volume":"173","author":"Fantin","year":"2025","journal-title":"Eng. Fail. Anal."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"465","DOI":"10.1023\/A:1008992807888","article-title":"Bioactive nanocrystalline sol-gel hydroxyapatite coatings","volume":"10","author":"Chai","year":"1999","journal-title":"J. Mater. Sci. Mater. Med."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"111038","DOI":"10.1016\/j.triboint.2025.111038","article-title":"Tribological and microstructural evaluation of HVOF-sprayed hydroxyapatite coatings with machine learning-based wear rate prediction","volume":"213","author":"Jagadeeshanayaka","year":"2026","journal-title":"Tribol. Int."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"100914","DOI":"10.1016\/j.nxmate.2025.100914","article-title":"Nano carbon dot-collagen peptide\u2014Hydroxyapatite composite coating for bone tissue regeneration","volume":"8","author":"Ashraf","year":"2025","journal-title":"Next Mater."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"36182","DOI":"10.1016\/j.ceramint.2025.05.339","article-title":"Hydroxyapatite ceramic coatings with Ag, Mg, and Si additives via plasma electrolytic oxidation: Advancing antibacterial and multi-functional properties for biomedical implants","volume":"51","author":"Logesh","year":"2025","journal-title":"Ceram. Int."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"28935","DOI":"10.1016\/j.ceramint.2025.04.103","article-title":"Advanced hydroxyapatite- DLC bilayer coatings for improved performance of NiTi biomedical alloys","volume":"51","author":"Shanaghi","year":"2025","journal-title":"Ceram. Int."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"14002","DOI":"10.1016\/j.jmrt.2020.10.005","article-title":"Study of HVOF-Sprayed Hydroxyapatite\/Titania Graded Coatings under in-Vitro Conditions","volume":"9","author":"Henao","year":"2020","journal-title":"J. Mater. Res. Technol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"113307","DOI":"10.1016\/j.optlastec.2025.113307","article-title":"Dual surface modification of medical-grade PEEK: Nanosecond laser pre-treatment and hydrothermal hydroxyapatite coating","volume":"191","author":"Zhang","year":"2025","journal-title":"Opt. Laser Technol."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"42565","DOI":"10.1016\/j.ceramint.2025.07.002","article-title":"In vitro tribological behavior of plasma-sprayed hydroxyapatite composite coatings reinforced with graphene nanosheets","volume":"51","author":"Lu","year":"2025","journal-title":"Ceram. Int."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"105948","DOI":"10.1016\/j.surfin.2025.105948","article-title":"Effect of morphologies of hydroxyapatite powders on thermal sprayed hydroxyapatite coatings","volume":"60","author":"Lin","year":"2025","journal-title":"Surf. Interfaces"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"142","DOI":"10.1016\/j.matlet.2017.01.098","article-title":"Preparation of hydroxyapatite hydrogel for bone-like materials via novel self-initiated photocatalytic polymerization","volume":"193","author":"Han","year":"2017","journal-title":"Mater. Lett."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2401296","DOI":"10.1002\/adhm.202401296","article-title":"Hydrogel Coatings of Implants for Pathological Bone Repair","volume":"13","author":"Li","year":"2024","journal-title":"Adv. Healthc. Mater."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"727","DOI":"10.1080\/10667857.2018.1475143","article-title":"Bioactive conformable hydrogel-carbonated hydroxyapatite nanocomposite coatings on Ti-6Al-4V substrates","volume":"35","author":"Kwon","year":"2020","journal-title":"Mater. Technol."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Moreau, D., Villain, A., Ku, D.N., and Corte, L. (2014). Poly(vinyl alcohol) hydrogel coatings with tunable surface exposure of hydroxyapatite. Biomatter, 4.","DOI":"10.4161\/biom.28764"},{"key":"ref_19","first-page":"9440956","article-title":"A novel hydroxyapatite modified MXene-based hydrogel coating on Ti6Al4V alloy with improved biotribological properties and corrosion resistance","volume":"13","author":"Cao","year":"2024","journal-title":"Friction"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"667","DOI":"10.1016\/j.jconrel.2023.05.022","article-title":"Osteoimmunomodulatory GelMA\/liposome coatings to promote bone regeneration of orthopedic implants","volume":"358","author":"Jahanmard","year":"2023","journal-title":"J. Control. Release"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"109197","DOI":"10.1016\/j.isci.2024.109197","article-title":"Preparation of biocompatibility coating on magnesium alloy surface by sodium alginate and carboxymethyl chitosan hydrogel","volume":"27","author":"Jia","year":"2024","journal-title":"Iscience"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"157088","DOI":"10.1016\/j.cej.2024.157088","article-title":"Enhancing Bone-Titanium integration through hydrogel coating mediated sequential M1\/M2 polarization of interfacial macrophages","volume":"500","author":"Wang","year":"2024","journal-title":"Chem. Eng. J."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"910","DOI":"10.1002\/jbm.a.37521","article-title":"Polyacrylamide-based hydrogel coatings improve biocompatibility of implanted pump devices","volume":"111","author":"Chan","year":"2023","journal-title":"J. Biomed. Mater. Res. A"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"136659","DOI":"10.1016\/j.matlet.2024.136659","article-title":"Highly bioactive hydroxyapatite coating made by flame spray technique","volume":"368","author":"Yutimit","year":"2024","journal-title":"Mater. Lett."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"18232","DOI":"10.1039\/C9RA01473J","article-title":"Phase-specific bioactivity and altered Ostwald ripening pathways of calcium carbonate polymorphs in simulated body fluid","volume":"9","author":"Myszka","year":"2019","journal-title":"RSC Adv."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1038\/ijos.2017.13","article-title":"Evaluation of the osseointegration of dental implants coated with calcium carbonate: An animal study","volume":"9","author":"Liu","year":"2017","journal-title":"Int. J. Oral Sci."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"124393","DOI":"10.1016\/j.ijpharm.2024.124393","article-title":"Alginate microparticles containing silver@hydroxyapatite functionalized calcium carbonate composites","volume":"661","author":"Nocchetti","year":"2024","journal-title":"Int. J. Pharm."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Medrano-David, D., Lopera, A.M., Londono, M.E., and Araque-Marin, P. (2021). Formulation and Characterization of a New Injectable Bone Substitute Composed PVA\/Borax\/CaCO3 and Demineralized Bone Matrix. J. Funct. Biomater., 12.","DOI":"10.20944\/preprints202106.0545.v1"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"6109","DOI":"10.1039\/C9TB00897G","article-title":"Chitosan\/Hydroxyapatite Composite Bone Tissue Engineering Scaffolds with Dual and Decoupled Therapeutic Ion Delivery: Copper and Strontium","volume":"7","author":"Gritsch","year":"2019","journal-title":"J. Mater. Chem. B"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"6617","DOI":"10.1016\/j.ceramint.2013.11.119","article-title":"Bioactive HA\/TiO2 Coating on Magnesium Alloy for Biomedical Applications","volume":"40","author":"Amaravathy","year":"2014","journal-title":"Ceram. Int."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"24683","DOI":"10.1039\/C7RA02157G","article-title":"Enhanced Photocatalytic Removal of NO over Titania\/Hydroxyapatite (TiO2\/HAp) Composites with Improved Adsorption and Charge Mobility Ability","volume":"7","author":"Yao","year":"2017","journal-title":"RSC Adv."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"101072","DOI":"10.1016\/j.surfin.2021.101072","article-title":"In Vitro Study: Evaluation of Mechanical Behavior, Corrosion Resistance, Antibacterial Properties and Biocompatibility of HAp\/TiO2\/Ag Coating on Ti6Al4V\/TiO2 Substrate","volume":"24","author":"Ahmadi","year":"2021","journal-title":"Surf. Interfaces"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"622","DOI":"10.1016\/j.saa.2013.09.037","article-title":"Structural, optical and morphological analyses of pristine titanium di-oxide nanoparticles\u2014Synthesized via sol\u2013gel route","volume":"117","author":"Praveen","year":"2014","journal-title":"Spectrochim. Acta Part A Mol. Biomol. Spectrosc."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"4971","DOI":"10.1016\/j.ijleo.2013.03.040","article-title":"Effect of annealing on TiO2 nanoparticles","volume":"124","author":"Sugapriya","year":"2013","journal-title":"Optik"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"106624","DOI":"10.1016\/j.rineng.2025.106624","article-title":"Titanium Dioxide-Grafted Polyacrylamide Nanocomposites Ameliorate the Rheology and High-Pressure High-Temperature Fluid Loss of Water-Based Drilling Fluids","volume":"27","author":"Sarokolai","year":"2025","journal-title":"Results Eng."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"2153","DOI":"10.1016\/j.rinp.2017.06.027","article-title":"Spectroscopic and Thermal Analysis of Polyacrylamide\/Chitosan (PAM\/CS) Blend Loaded by Gold Nanoparticles","volume":"7","author":"Gaabour","year":"2017","journal-title":"Results Phys."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"118","DOI":"10.1016\/j.eurpolymj.2018.08.004","article-title":"Green Synthesis of Titanium Dioxide\/Acrylamide-Based Hydrogel Composite, Self Degradation and Environmental Applications","volume":"107","author":"Kangwansupamonkon","year":"2018","journal-title":"Eur. Polym. J."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"490","DOI":"10.1016\/j.msec.2012.09.019","article-title":"Calcite as a bone substitute. Comparison with hydroxyapatite and tricalcium phosphate with regard to the osteoblastic activity","volume":"33","author":"Monchau","year":"2013","journal-title":"Mater. Sci. Eng. C"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"292","DOI":"10.1016\/j.materresbull.2014.08.052","article-title":"Carbonated hydroxyapatite starting from calcite and different orthophosphates under moderate hydrothermal conditions: Synthesis and surface reactivity in simulated body fluid","volume":"60","author":"Nzihou","year":"2014","journal-title":"Mater. Res. Bull."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"25","DOI":"10.1590\/S1516-14392011005000012","article-title":"Development and characterization of a novel bioresorbable and bioactive biomaterial based on polyvinyl acetate, calcium carbonate and coralline hydroxyapatite","volume":"14","author":"Fuentes","year":"2011","journal-title":"Mater. Res."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"5594","DOI":"10.1016\/j.ceramint.2014.12.139","article-title":"Fabrication of dense biocompatible hydroxyapatite ceramics with high hardness using a peroxide-based route: A potential process for scaling up","volume":"41","author":"Randorn","year":"2015","journal-title":"Ceram. Int."}],"container-title":["Gels"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2310-2861\/11\/10\/837\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,20]],"date-time":"2025-10-20T14:23:29Z","timestamp":1760970209000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2310-2861\/11\/10\/837"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,10,18]]},"references-count":41,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2025,10]]}},"alternative-id":["gels11100837"],"URL":"https:\/\/doi.org\/10.3390\/gels11100837","relation":{},"ISSN":["2310-2861"],"issn-type":[{"value":"2310-2861","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,10,18]]}}}