Florida Institute of Technology , Melbourne , Florida 32901 , United States.
J Phys Chem B. 2019 Jan 24;123(3):648-654. doi: 10.1021/acs.jpcb.8b11677. Epub 2019 Jan 11.
The pH of biological systems is important for the activity of enzymes, and abnormal cellular pH is related to many diseases. Spatial and temporal modulation of pH with light will be useful for studying the pH effects on enzymatic functions and disease mechanisms and may lead to new drug delivery and therapeutic methods. However, the pH of biological systems is maintained by pH buffers, which implies that only temporary pH change (pH pulse) can be induced in an open system. A key fundamental problem is whether a photoinduced pH pulse can be strong and long enough to generate a significant effect. In this work, a photoinduced pH pulse in a micrometer hydrophilic film in PBS buffer has been demonstrated. The thin film was made of an metastable-state photoacid (mPAH) polymer. It is an open system that allows exchange of protons. A quick release of the protons from the mPAHs and the proton exchange between the film and PBS resulted in a pH pulse generated by moderate visible-light irradiation. The magnitude of the pulse is 1.4-1.9 units with maximum pH change occurring after ∼18 s of the irradiation. Since the mPAH is a reversible photoacid, the pH pulse could be repeatedly generated after the photoacid recovered in the dark. This work shows that photochemical modulation of pH is possible even in buffered solutions.
生物体系的 pH 值对于酶的活性很重要，而细胞内 pH 值的异常与许多疾病有关。用光对 pH 值进行时空调控将有助于研究 pH 值对酶功能和疾病机制的影响，并可能导致新的药物输送和治疗方法。然而，生物体系的 pH 值是由 pH 值缓冲剂维持的，这意味着在开放体系中只能诱导暂时的 pH 值变化（pH 脉冲）。一个关键的基本问题是，光诱导的 pH 脉冲是否足够强且持续时间足够长，以产生显著的效果。在这项工作中，已经证明了 PBS 缓冲液中微米级亲水性薄膜中的光致 pH 脉冲。该薄膜由亚稳态光酸（mPAH）聚合物制成。它是一个允许质子交换的开放体系。mPAHs 快速释放质子以及薄膜与 PBS 之间的质子交换导致适度可见光照射下产生 pH 脉冲。脉冲的幅度为 1.4-1.9 个单位，最大 pH 值变化发生在照射后约 18 秒。由于 mPAH 是一种可逆的光酸，因此在光酸在黑暗中恢复后，可以重复产生 pH 脉冲。这项工作表明，即使在缓冲溶液中，光化学调节 pH 值也是可行的。
