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Carol M Cleetus,1 Fabian Alvarez Primo,1 Gisel Fregoso,2 Nivedita Lalitha Raveendran,3 Juan C Noveron,4 Charles T Spencer,5 Chinatalapalle V Ramana,3 Binata Joddar1 1Department of Metallurgical, Materials and Biomedical Engineering, The University of Texas at El Paso, El Paso, TX 79968, USA; 2Department of Electrical and Computer Engineering, The University of Texas at El Paso, El Paso, TX 79968, USA; 3Department of Mechanical Engineering, The University of Texas at El Paso, El Paso, TX 79968, USA; 4Department of Chemistry and Biochemistry, The University of Texas at El Paso, El Paso, TX 79968, USA; 5Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX 79968, USACorrespondence: Binata Joddar Email bjoddar@utep.eduIntroduction: In this in-vitro study, we designed a 3D printed composite of zinc oxide (ZnO) nanoparticles (NPs) with photocatalytic activities encapsulated within hydrogel (alginate) constructs, for antibacterial purposes applicable towards wound healing. We primarily sought to confirm the mechanical properties and cell compatibility of these ZnO NP infused scaffolds.Methods: The antibacterial property of the ZnO NPs was confirmed by hydroxyl radical generation using ultraviolet (U.V.) photocatalysis. Titanium dioxide (TiO2), a well-known antibacterial compound, was used as a positive control (1% w/v) for the ZnO NP-based alginate constructs and their antibacterial efficacies compared. Among the ZnO group, 3D printed gels containing 0.5% and 1% w/v of ZnO were analyzed and compared with manually casted samples via SEM, swelling evaluation, and rheological analysis. Envisioning an in-vivo application for the 3D printed ZnO NP-based alginates, we studied their antibacterial properties by bacterial broth testing, cytocompatibility via live/dead assay, and moisture retention capabilities utilizing a humidity sensor.Results: 3D printed constructs revealed significantly greater pore sizes and enhanced structural stability compared to manually casted samples. For all samples, the addition of ZnO or TiO2 resulted in significantly stiffer gels in comparison with the alginate control. Bacterial resistance testing on Staphylococcus epidermidis indicated the addition of ZnO NPs to the gels decreased bacterial growth when compared to the alginate only gels. Cell viability of STO-fibroblasts was not adversely affected by the addition of ZnO NPs to the alginate gels. Furthermore, the addition of increasing doses of ZnO NPs to the alginate demonstrated increased humidity retention in gels.Discussion: The customization of 3D printed alginates containing antibacterial ZnO NPs leads to an alternative that allows accessible mobility of molecular exchange required for improving chronic wound healing. This scaffold can provide a cost-effective and durable antibacterial treatment option.Keywords: zinc oxide nanoparticles, chronic wound healing, 3D printing, antibacterial, hydroxyl radicals, alginate hydrogels/scaffolds