Broad spectrum antimicrobial activity of Ca(Zn(OH)3)2·2H2O and ZnO nanoparticles synthesized by the sol–gel method

The process of biodeterioration is one of the main problems affecting historical monuments and buildings. On rock surfaces, different types of microorganisms establish in the most adequate niches and accelerate degradation, leading to the irreversible loss of cultural heritage. Therefore, new ways to preserve cultural heritage must be urgently studied to prevent such damage. In this study, the broad-spectrum antimicrobial activity of calcium zinc hydroxide dehydrate [Ca(Zn(OH)3)2·2H2O] (CZ) and zinc oxide (ZnO) nanoparticles synthesized by the sol–gel method is examined against fungal and bacterial model organisms. The selected microbes were inhibited by both nanoparticles, yet CZ was the most effective, with a bactericidal activity of 1.25 to 5 mg/mL and a fungicidal activity of 0.625 mg/mL. Both nanoparticles caused structural damage to the evaluated fungal cells, resulting in morphological changes and affecting the germination of conidia. For the first time in the literature, the antibacterial activity and the mode of action of CZ are reported. In conclusion, CZ nanoparticles are shown to be potential candidates for the treatment of rock surfaces of built cultural heritage.We are grateful for the financial support of the National Council for Science and Technology (Consejo Nacional de Ciencia y Tecnología [CONACyT]) of the “Fronteras de la Ciencia 138” project. Additional thanks are extended to CONACyT for the doctoral scholarship granted to MSC 282192.Peer reviewe

Effect of multiple interactions between fungal species on the colonization of two limestone lithotypes

Trabajo presentado en el 3rd International Congress on Science and Technology for the Conservation of Cultural Heritage (TechnoHeritage), celebrado en Cádiz (España), del 21 al 24 de mayo de 2017Peer reviewe

Calcium oxalates in biofilms on limestone walls of Maya buildings in Chichén Itzá, Mexico

Microbial biofilms frequently cause the esthetic and biological deterioration of stone monuments. Chichén Itzá, designated as a UNESCO World Heritage Site and as one of the seven new wonders of the world, is one Maya archeological site affected by biofilms. In the present study, we analyzed the biofilms at three different building complexes of Chichén Itzá: the Lower Temple of the Jaguars, the Temple of the Warriors, and Tzompantli. Samples of biofilms and detached rocks were taken from walls with abundant white-, green-, black-, and orange-colored biofilms. The morphology of rock fragments and dust was analyzed by electron and optical microscopy and was structurally characterized by X-ray diffraction. An HCl treatment (5% v/v) was subsequently applied to eliminate carbonates. The morphological analysis evidenced the presence of cyanobacteria, algae, and lichens. Some algae formed small nodules on orange- or black-colored rocks. Lichens were associated with a distinct mineral content on the inner surface of rocks versus on the outer surface. The presence of calcium oxalates such as weddellite (C2CaO4·2H2O) and whewellite (C2CaO4·H2O) and other minerals, including quartz and feldspars, was confirmed by X-ray diffraction. The lichens collected from the Lower Temple of the Jaguars and Tzompantli were therefore confirmed to disintegrate rock surfaces through biomineralization and the formation of oxalate crystals. At sites with greater solar radiation, a higher quantity of weddellite and a lower quantity of whewellite were observed. In conclusion, the establishment of microorganisms on the stone surfaces of Chichén Itzá causes esthetic damage and also leads to the biomineralization of these rock surfaces.Peer reviewe

Biomineralization of limestone for fungal interactions

Trabajo presentado en el 9th International Workshop on Interfaces: New frontiers in Biomaterials, celebrado en Santiago de Compostela (España), del 16 al 18 de abril de 2018Peer reviewe

Application of Zn-MgO nanoparticles as antifungal agent for stone conservation: implications for biomineralization

Trabajo presentado en el 9th International Workshop on Interfaces: New frontiers in Biomaterials, celebrado en Santiago de Compostela (España), del 16 al 18 de abril de 2018Peer reviewe

Sol-Gel synthesis, characterization and antifungal properties of MgO, ZnO and Mg/Zn oxide nanoparticles developed for the protection of stone heritage

Trabajo presentado en la 19th International Sol-Gel Conference, celebrada en Liege (Belgica), del 3 al 8 de septiembre de 2017Peer reviewe

Synthesis, Photocatalytic, and Antifungal Properties of MgO, ZnO and Zn/Mg Oxide Nanoparticles for the Protection of Calcareous Stone Heritage

More recently, the biological colonization of stone heritage and consequently its biodeterioration has become the focus of numerous studies. Among all microorganisms, fungi are considered to be one of the most important colonizers and biodegraders on stone materials. This is why the development of new antifungal materials requires immediate action. ZnMgO nanoparticles (NPs) have several exciting applications in different areas, highlighting as an efficient antimicrobial agent for medical application. In this research, the application of Zn-doped MgO (Mg1–xZnxO, x = 0.096) NPs obtained by sol–gel method as antifungal coatings on dolomitic and calcitic stones has been explored as a means to develop effective protective coatings for stone heritage. Moreover, the photocatalytic and antifungal activity of Mg1–xZnxO NPs were comparatively studied with single ZnO and MgO NPs. Thus, compared to the MgO and ZnO nanomaterials, the Mg1–xZnxO NPs exhibited an enhanced photocatalytic activity. After UV irradiation for 60 min, 87% methylene blue was degraded over Zn-doped MgO NPs, whereas only 58% and 38% of MB was degraded over ZnO and MgO NPs, respectively. These nanoparticles also displayed a better antifungal activity than that of single pure MgO or ZnO NPs, inhibiting the growth of fungi Aspergillus niger, Penicillium oxalicum, Paraconiothyrium sp., and Pestalotiopsis maculans, which are especially active in the bioweathering of stone. The improved photocatalytic and antifungal properties detected in the Mg1–xZnxO NPs was attributed to the formation of crystal defects by the incorporation of Zn into MgO. The application of the MgO- and Zn-doped MgO NPs as protective coatings on calcareous stones showed important antifungal properties, inhibiting successfully the epilithic and endolithic colonization of A. niger and P. oxalicum in both lithotypes, and indicating a greater antifungal effectiveness on Zn-doped MgO NPs. The use of Zn-doped MgO NPs may thus represent a highly efficient antifungal protection for calcareous stone heritage.This research has been financially supported under projects FOMIX-Yuc 2008–108160, CONACYT LAB-2009-01-123913, 188345, Fronteras de la Ciencia No. 138, by the Community of Madrid under the Geomaterials 2 Programme (S2013/MIT_2914), Climortec, BIA2014–53911-R and MAT2013-47460-C5-5-P, and the Autonomous Region Program of Madrid, MULTIMAT CHALLENGE (S2013/MIT-2862). A.S.-F. would like to gratefully acknowledge the financial support of Santander Universidades through “Becas Iberoamérica Jóvenes Profesores e Investigadores, España 2015” scholarship program.Peer reviewe

Study of biodeterioration and bioweathering on lime Stone in buildings of the Mayan culture at Chichén Itzá and Edzna, México: New strategies for their conservation

Trabajo presentado en el 42nd International Symposium on Archaometry (ISA), celebrado en Mérida (México) del 20 al 26 de mayo de 2018Peer reviewe

Multifunctional inorganic nanomaterials based on magnesium and calcium hydroxides for heritage conservation

Trabajo presentado en el 3rd International Congress on Science and Technology for the Conservation of Cultural Heritage (TechnoHeritage), celebrado en Cádiz (España), del 21 al 24 de mayo de 2017Peer reviewe

Magnesium and calcium hydroxide nanoparticles: Multifunctional nanomaterials for the stone heritage conservation

Trabajo presentado en Green Conservation of Cultural Heritage - 2nd International Conference, celebrada en Palermo (Italia) del 16 al 18 de noviembre de 2017Peer reviewe