Natural extract-functionalized titanium surfaces as biomimetic bioactive platforms for implantology: a critical narrative review

Abstract

Natural extract- and plant-derived compound-functionalized titanium surfaces are being investigated as multifunctional strategies to modulate cell responses, microbial colonization, oxidative stress, and peri-implant inflammation. This critical narrative review synthesized evidence published from January 2017 through June 25, 2026 using a structured literature search of PubMed/MEDLINE, Scopus, Web of Science Core Collection, ScienceDirect, and supplementary Google Scholar citation tracking. The mapped evidence comprised nine direct primary titanium studies, three indirect primary studies, and six secondary/contextual reviews. Direct experimental evidence was identified for green-tea polyphenols/Epigallocatechin gallate (EGCG), tannic acid/Mg2+, acemannan, curcumin-containing systems, propolis, quercitrin, and Calendula officinalis; chitosan was supported mainly as a coating/carrier matrix by secondary evidence, whereas Opuntia ficus-indica remained supported by indirect regenerative-biomaterial evidence. Across studies, interpretation was limited by heterogeneous titanium substrates, surface pretreatments, immobilization chemistries, co-components, biological models, doses, and outcome measures. Therefore, observed effects cannot generally be attributed to the natural compound alone. Current findings support promising preclinical bioactivity rather than established osteoinduction or improved clinical osseointegration. Future work should prioritize extract standardization, coating adhesion and stability, release kinetics, sterilization resistance, corrosion, cytocompatibility, biofilm selectivity, and appropriately controlled in vivo validation before clinical translation.