Ibrahim Shimaa, Hussein Rageh K, Abdulla Hesham, Omar Ghada, Abu Alrub Sharif, Grenni Paola, Atwa Dina M
Department of Botany, Faculty of Science, Cairo University, Giza P.O. Box 12613, Egypt.
Physics Department, College of Science, Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh 11623, Saudi Arabia.
Int J Mol Sci. 2025 Aug 20;26(16):8064. doi: 10.3390/ijms26168064.
Stone cleaning for cultural heritage monuments is a critical conservation intervention that must effectively eliminate harmful surface contaminants while preserving the material's physical, chemical, and historical integrity. This study investigated the removal of tenacious black biofilms formed by species previously isolated from deteriorated limestone from the Bastet tomb in Tell Basta, Zagazig City, Egypt, using a Q-switched 1064 nm Nd:YAG laser. Experimental limestone specimens were systematically inoculated with sp. under controlled laboratory conditions to simulate biodeterioration processes. Comprehensive testing revealed that a laser fluence of 0.03 J/cm with a 5 ns pulse duration, applied under wet conditions with 500 pulses, achieved the complete elimination of the biological black film without damaging the underlying stone substrate. The cleaning efficacy was evaluated through an integrated analytical framework combining stereomicroscopy, scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDX), X-ray diffraction (XRD), and laser-induced plasma spectroscopy (LIPS). These analyses demonstrated a remarkable transformation from a compromised mineralogical composition dominated by gypsum (62%) and anhydrite (13%) to a restored state of 98% calcite, confirming the laser treatment's effectiveness in reversing biodeterioration processes. SEM micrographs revealed the complete elimination of mycelial networks that had penetrated to depths between 984 μm and 1.66 mm, while LIPS analysis confirmed the restoration of elemental signatures to near-control levels. The successful application of LIPS for real-time monitoring during cleaning provides a valuable tool for preventing overcleaning, addressing a significant concern in laser conservation interventions. This research establishes evidence-based protocols for the non-invasive removal of -induced black biofilms from limestone artifacts, offering conservation professionals a precise, effective, and environmentally sustainable alternative to traditional chemical treatments for preserving irreplaceable cultural heritage.
文化遗产古迹的石材清洁是一项关键的保护干预措施，必须在保持材料的物理、化学和历史完整性的同时，有效去除有害的表面污染物。本研究使用调Q 1064 nm Nd:YAG激光，研究了去除先前从埃及扎加齐格市泰勒巴斯塔的巴斯女神墓中劣化石灰石分离出的物种形成的顽固黑色生物膜的方法。在受控实验室条件下，将实验石灰石标本系统接种上该物种，以模拟生物劣化过程。综合测试表明，在潮湿条件下施加500个脉冲，激光能量密度为0.03 J/cm²、脉冲持续时间为5 ns时，可完全消除生物黑色膜，且不会损坏下层石材基质。通过结合立体显微镜、扫描电子显微镜与能量色散X射线分析（SEM-EDX）、X射线衍射（XRD）和激光诱导等离子体光谱（LIPS）的综合分析框架评估清洁效果。这些分析表明，矿物成分从以石膏（62%）和硬石膏（13%）为主的受损状态显著转变为方解石含量达98%的恢复状态，证实了激光处理在逆转生物劣化过程方面的有效性。SEM显微照片显示，已完全消除了深入到984μm至1.66mm深度的菌丝网络，而LIPS分析证实元素特征已恢复到接近对照水平。LIPS在清洁过程中成功用于实时监测，为防止过度清洁提供了一种有价值的工具，解决了激光保护干预中的一个重大问题。本研究建立了从石灰石文物中无创去除生物诱导黑色生物膜的循证方案，为保护专业人员提供了一种精确、有效且环境可持续的替代传统化学处理方法，以保护不可替代的文化遗产。
