Curcumin-loaded bovine serum albumin (BSA) nanoparticles: photoreactivity and photodynamic action against Acinetobacter baumannii and Staphylococcus aureus
Juliana Guerra Pinto, Francesca Laneri, Isabelle de Paula Ribeiro Brambilla, Maria Clara Barbosa Silva de Azevedo, Jéssica A. R. Ambrósio, Andreza R. Simioni, Aurore Fraix, Salvatore Sortino and Juliana Ferreira-Strixino
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引用次数: 0
Abstract
Curcumin (CUR) is a naturally occurring pigment, poorly soluble in water and an object of intense interest due to its multifaceted therapeutic and phototherapeutic activity. In this contribution, bovine serum albumin nanoparticles (BSA-NPs) with oppositely charged surfaces have been used as suitable nanocarriers both to overcome the poor water solubility of CUR and to encourage its interaction with Gram-positive and Gram-negative bacteria. The different surface charges of the BSA-NPs do not affect either the spectroscopic or the photochemical behaviour of the encapsulated CUR which in all cases is almost exclusively present in a diketo form rather than the enolic one. This strictly dictates the response of CUR to blue light excitation which, under these conditions, exhibits the usual reactivity of carbonyl compounds toward molecules that behave as hydrogen donors such as the BSA-NP components. Steady-state and time-resolved photochemical experiments show that the encapsulated CUR undergoes photodecomposition with rate basically independent of the presence of oxygen. The photodecomposition seems to be mediated mainly by an intermolecular H-abstraction from the components of the nanocarrier by the lowest excited triplet state of CUR with the formation of the corresponding ketyl radical occurring in less than 0.5 μs. This radical is oxidized by molecular oxygen, likely leading to peroxyl and hydroperoxyl radical species, probably responsible for the photodynamic action. Accordingly, with the short triplet lifetime, no singlet oxygen photogeneration is observed. Concentrations of 0.2, 0.3 and 0.4 μM were selected for in vitro tests. Internalization of both formulations was observed in strains of A. baumannii and S. aureus, after 15 minutes of interaction. After irradiation, a reduction in the viability of bacteria was observed, at the different concentrations tested, with concentrations of 0.4 and 0.3 μM being the most efficient.
姜黄素(CUR)是一种天然色素,难溶于水,因其具有多方面的治疗和光疗活性而备受关注。在本文中,具有相反电荷表面的牛血清白蛋白纳米颗粒(BSA-NPs)被用作合适的纳米载体,既克服了 CUR 水溶性差的问题,又促进了 CUR 与革兰氏阳性和革兰氏阴性细菌的相互作用。BSA-NPs 不同的表面电荷既不会影响封装 CUR 的光谱特性,也不会影响其光化学特性。这严格决定了 CUR 对蓝光激发的反应,在这些条件下,CUR 对 BSA-NPs 成分等作为氢供体的分子表现出通常的羰基化合物反应性。稳态和时间分辨光化学实验表明,封装的 CUR 会发生光分解,分解速率基本不受氧气存在的影响。光分解似乎主要是由 CUR 的最低激发三重态从纳米载体成分中分子间萃取 H 介导的,在不到 0.5 µs 的时间内就会形成相应的酮基自由基。这种自由基被分子氧氧化后,可能会产生过氧自由基和氢过氧自由基,从而产生光动力作用。由于三重态寿命较短,因此没有观察到单线态氧的光生成。体外试验选择的浓度分别为 0.2、0.3 和 0.4 μM。经过 15 分钟的相互作用后,在鲍曼尼杆菌和金黄色葡萄球菌菌株中观察到了两种制剂的内化。辐照后,在不同的测试浓度下,细菌的存活率都有所下降,其中 0.4 和 0.3 μM 的浓度最为有效。