Crosslinked poly tannic acid) micro particles, p(TA), were synthesized using trimethylolpropane triglycidyl ether (TMPGDE) as crosslinker in a single step with high yield (73 perpendicular to 6%). The obtained p(TA) microgels possessed negative zeta potential, -27 mV, and the surface charge can be tuned by chemical modification using various modifying agents, such as 3-chloro-2-hydroxypropyl ammonium chloride (CHPACl) and chloro sulfonic acid (CSA) to generate microgels with different zeta potentials, e.g., -18 mV and -36 mV, respectively. Modified p(TA) microgels are found to be thermally less stable than bare p(TA) particles. Additionally, upon chemical modification of p(TA) particles, the antioxidant capacity of the p(TA) microgels decreased confirming the utilization of some of the phenolic groups, the main functional groups responsible for the antioxidant property of TA moieties. Moreover, the antimicrobial properties increased approximately four fold against three common bacterial strains; Escherichia coli ATCC 8739, Staphylococcus aureus ATCC 6538, and Bacillus subtilis ATCC 6633. P(TA) microgels as TA molecules have a natural capability to reduce metal ions, allowing in situ reduction of absorbed Ag and Cu ions to the corresponding metal nanoparticles within the p(TA) microgel network. The composite p(TA)-M (M:Ag or Cu) nanoparticle demonstrated superior antimicrobial activity against the mentioned bacteria compared to the bare p(TA) microgels. Moreover, bare and modified p(TA) microgels are shown to be drug carrier materials by loading three model drugs, phenylephrine HCl (PHE), trimethoprim (TMP), and naproxen (NP), and releasing them in phosphate buffer saline PBS (pH 7.4) at 37.5 degrees C. (C) 2015 Elsevier B.V. All rights reserved.