Peptide-based solutions for light-triggered delivery of macromolecular therapeutics and nanoparticles

许多重要药物的有效性大大降低，因为它们不能充分地输送到细胞内的液体中，而细胞内正是它们的生物靶点所在。这意味着需要更高的剂量，从而导致潜在副作用的增加和患者生活质量的降低。这类药物通常很难被人体吸收，因为它们是通过胞吞作用被细胞吸收的，在胞吞作用中，细胞壁或细胞膜包裹着药物分子，使它们被困在细胞内的小隔室（核内体、溶酶体）中，为了到达细胞的正确部分（如细胞核），它们必须从中逃脱。如果药物不能有效地逃逸，它可能会被酶分解或从细胞中排出。光化学内化技术（PCI）是解决这一问题的一种新方法。在这里，感兴趣的药物与光敏剂一起施用，光敏剂是一种被光激活时可以促进逃逸过程的分子。理想情况下，光敏剂用低剂量的红光激活，这对健康组织造成的损害最小，并且由于组织对红光波长的吸收较弱，也允许在目标组织深处进行光激活。相比之下，紫外光激活的药物释放不能有效地在组织中使用，不仅是因为它的诱变作用，而且因为组织对紫外光的吸收太强，限制了作用在距离表面几层细胞的深度。可以通过PCI输送的药物范围从用于癌症治疗的毒素到用于基因治疗的分子制剂，光可以直接照射到目标组织上，也可以从放置在组织内的光纤中通过激光引导，以允许更大体积的照明。当细胞暴露在PCI光处理下，为了激活光敏剂，这些分子吸收能量并产生短寿命的反应性化合物，这些化合物会破坏含有药物的隔室的壁，释放药物，使其达到目标。然而，为了使PCI有效地起作用，所使用的药物和光敏剂必须结合到细胞内的同一隔间中，当然，首先必须有效地进入细胞。因此，我们项目的最初目标是开发用于PCI的新型光敏剂分子，这些分子是水溶性的，可以有效地穿过细胞膜，并且可以通过内吞作用进入细胞，这样它们就可以与同时施用的药物一起定位在正确的细胞区室中。我们已经证明，这种原型分子比简单的光敏剂提供更有效的PCI效果。为了进一步改进PCI方法，我们希望开发一种系统，其中药物和光敏剂都与相同的载体分子相关联，从而增强两种成分的吸收，并保证它们在完全相同的细胞区室中的定位。为了使这种方法尽可能通用和灵活，我们的目标是开发一种系统，其中载体和光敏剂可以很容易地互换，并且可以以一种一旦PCI光治疗进行后就可以从细胞内的载体中释放出各种药物分子的方式结合。作为最后的改进，我们还将研究制造针对身体特定部位的输送系统的可能性，并仅在病变组织中特异性地启动，以便PCI治疗可以精确地在需要的地方进行定点选择性。该项目的所有结果将通过提供一种新的方法来更有效地提供各种化疗药物，提高疗效，降低剂量，并最大限度地减少副作用，从而直接造福于医疗保健领域。

The effectiveness of many important drugs is much reduced because they cannot be adequately delivered to the fluid inside cells where their biological targets are located. This means that higher doses are needed, leading to an increase in potential side effects and reduced patient quality of life. Such drugs are often poorly absorbed in the body because they are taken up into cells by endocytosis, where the cell wall or membrane envelops drug molecules leaving them trapped inside small compartments (endosomes, lysosomes) within the cell from which they must escape in order to reach the right part of the cell (e.g. the nucleus). If the drug cannot escape efficiently, it may instead be broken down by enzymes, or expelled from the cell. The technique of photochemical internalisation (PCI) is a novel way to get around this problem. Here, the drug of interest is administered along with a photosensitiser, a molecule that can facilitate the escape process when activated by light. Ideally, the photosensitiser is activated with a low dose of red light which causes minimal damage to healthy tissue and also allows light-activation to take place deep within the target tissue, as tissue absorption at red light wavelengths is weak. In contrast, UV light-activated drug release cannot be used effectively in tissue not only due its mutagenic effects, but also because tissue absorption of UV light is too strong and limits the effect to a depth of few cell layers from the surface. Drugs that can be delivered with PCI range from toxins for cancer treatment to molecular agents for gene therapy, and light can either be shone directly onto the target tissue or guided from a laser down optical fibres placed within the tissue to allow illumination of larger volumes. When cells are exposed to PCI light treatment, to activate the photosensitiser, these molecules absorb energy and generate short-lived reactive chemical compounds that break down the walls of the drug-containing compartments, releasing the drug to allow it to reach its target. However, in order for PCI to work effectively, the drug and photosensitiser employed must be incorporated into the same compartment inside the cell and must of course both efficiently enter the cell in the first place. The initial aim of our project is therefore to develop new photosensitiser molecules for PCI that are water-soluble, cross cell membranes effectively, and are also taken up into cells by endocytosis so that they may be localised in the right cell compartments with drugs that are administered at the same time. We have already shown that prototype molecules of this sort give a much more efficient PCI effect than that obtained with a simple photosensitiser. To further improve the PCI approach, we then want to develop systems where both a drug and a photosensitiser are associated with the same carrier molecule so that the uptake of both components is enhanced and their localisation in exactly the same cell compartment is guaranteed. To make this approach as general and as flexible as possible, we aim to develop systems where the carrier and photosensitiser can be easily interchanged, and a wide range of drug molecules can be incorporated in such a way that they can be released from the carrier inside the cell once the PCI light treatment has been carried out. As a final refinement, we will also look at the possibility of making delivery systems that can be targeted to a specific part of the body and switched on specifically in diseased tissue only, so that the PCI therapy can be performed with pin-point selectivity, exactly where it is required.All the results of this project will be of direct benefit to the healthcare field by providing a new means to more effectively deliver diverse chemotherapeutic agents, improving efficacy, lowering dosage, and minimising side-effects.