"Photothermal therapy is a new tumor treatment model, and its effect depends on the performance of the photothermal conversion agent. The BxC/C dihedral quantum tablets prepared in this article have ultra-high photothermal conversion efficiency and are expected to show certain application prospects in tumor photothermal therapy." Regarding his new paper, Liu Hui, associate professor of , School of Materials and Energy, Southwest University, said.
Figure | Liu Hui (Source: Liu Hui)
The background of this study is that cancer has become one of the major diseases that seriously threaten human health due to its complexity, diversity and heterogeneity. Photothermal therapy (PTT) is a promising choice for clinical treatment of tumors due to its advantages of good space-time controllability, non-invasiveness or minimally invasiveness, and is called "tumor green therapy".
In addition, photothermal therapy can synergistically and sensitize conventional radiotherapy, chemotherapy and traditional Chinese medicine treatment, and can also activate the body's immunity and enhance the body's rejection response to tumor cells. Therefore, malignant tumors, especially advanced malignant tumors, can not only kill tumor cells, but also maintain the patient's quality of life.
Therefore, the development of high-performance photothermal agents (PTAs) with near-infrared (NIR) photoresponsiveness has important clinical guiding significance for achieving efficient tumor photothermal treatment. At present, experts and scholars from all over the world are working hard to explore and synthesize new photothermal converters, through functional modification, in order to achieve ideal tumor treatment effects. Typical examples include self-assembled gold chains, selective etching of platinum cubes, polypyrrole nanoparticles, conjugated small molecules, and carbon nanomaterials.
It is worth mentioning that carbon dots (CDs), because it has a relatively narrow HOMO and LOMO energy band gap (0.4~1.2 eV), under near-infrared laser irradiation, it can absorb light and excitation electrons, transform from a low-excited state to an excited state, and has developed into a widely concerned photothermal conversion agent.
For carbon dots, the absorbed energy generates heat by non-radiative vibration relaxation dissipation when returning from the excited state to the low excited state. However, there is a considerable amount of absorption energy dispersed in the form of fluorescence emission, which tends to significantly reduce the photothermal conversion efficiency (PCE), limiting it to around 36-38%.
(Source: Small Methods)
Generally speaking, in order to generate sufficient heat in the tumor area, a strong energy density (1.5 W cm-2) and a high dose of photothermal converter are required, but this will lead to poor biosafety problems. Based on this, Liu Hui's team hopes to suppress fluorescence performance by regulating its electronic structure, in order to achieve the goal of improving the photothermal conversion efficiency. But the strategy is quite challenging and beyond the scope of reported nanotechnology.
Recently, the relevant paper was published on Small Methods Small Methods [1], Shi-Yu Lu He served as the first author, and Liu Hui served as the last corresponding author of .
Figure | Related papers (Source: Small Methods)
This article reports a class of BxC/C dihedral quantum sheets (BxC/C JQSs) modified by polyethylene glycol (PEG) that completely inhibit fluorescence emission through Z-type photogenerated electron-hole separation in the near infrared region. The heterostructure of Z-type BxC/C dihedral quantum sheet allows NIR-driven thermal electrons to be quickly injected from C into the conjugated BxC/C, achieving a specific conversion from light to heat.
(Source: Small Methods)
Among them, BxC/C dihedral quantum sheets can achieve ultra-high photothermal conversion efficiency of 60.6%, exceeding most reported non-metallic photothermal conversion agents, and even close to the best metal-based photothermal conversion agents reported. In addition, BxC/C-PEG dihedral quantum tablets show good photothermal stability and biocompatibility in vivo, showing good potential in photothermal therapy. After injection, under laser irradiation, BxC/C dihedral quantum tablets can achieve effective tumor elimination effect through synergistic photothermal immunotherapy, while no adverse reactions to normal tissues.
During the review process, the reviewer believed that: "The material design is interesting. The photothermal performance and biocompatibility of BxC/C JQSs were well evaluated. In addition, this new Z-type BxC/C-PEG JQS showed effective tumor elimination results in vitro and in vivo through the collaborative photothermal immunotherapy of the biological window, and the damage to normal tissue is negligible. This work contributes to the application of carbon materials in tumor treatment."
also reviewer commented: "New Z Type BxC/C-PEG JQSs exhibit excellent biocompatibility due to their metal-free structure and show effective tumor elimination effects in vitro and in vivo through synergistic photothermal immunotherapy. "
During the implementation of this project, it mainly involves several stages such as material design and preparation, surface modification, photothermal performance testing, cytotoxicity detection, and live anti-tumor performance research. The most important thing is the design and preparation stage of the material. Based on the current defects of carbon materials in photothermal therapy, Liu Hui's team believes that from the perspective of electron transfer, it is expected to solve and improve the photothermal conversion efficiency of carbon materials.
(Source: Small Methods)
Z type heterostructure is a type of material structure with unique properties. Through design, the organic integration of two different components is expected to change the behavior of the electronics and then regulate the performance of the material. Unlike the methods reported in the literature, Liu Hui's team innovatively developed a method for preparing heterojunctions. Using biomass gelatin as the carbon source and boric acid as the boron source, dissolve and recrystallize at high temperature, and then annealing treatment . During the experiment, the growth mechanism of the product was explored by regulating the ratio of carbon source /boron source, and the morphology of the product was optimized. It is then surface modified to improve water solubility and biocompatibility, and finally obtains a BxC/C dihedral quantum sheet with excellent performance.
(Source: Small Methods)
After preparing uniform morphological BxC/C dihedral quantum slices, the explanation of its growth mechanism plagued the team for a long time. I was suddenly inspired during a rest and thinking, and I creatively proposed the "cut tofu" growth model. The initial biomass gelatin carbon is compared to a piece of “tofu” and the melted boric acid liquid is compared to “scissors.”
Under high temperature conditions, the liquid "scissors" cut the solid "tofu". The more "scissors", the easier it is to cut the "tofu" evenly. Since "scissors" are flowing, they will be combined with "tofu" after cooling down. Therefore, different product morphology at different boron/carbon ratios are created. In particular, "scissors" and "tofu" combine to form a heterojunction product with uniform morphology under appropriate proportions.
(Source: Small Methods)
This new metal-free photothermal agent shows great potential in further multifunctional tumor treatment, such as drug delivery, metal ion loading, immune adjuvant integration, etc., and can be further explored and explored. For example, in photothermal therapy, the cellular damage caused releases tumor-associated antigens, causing immunogenic cell death. These antigens are presented to dendritic cells, which in turn activate T lymphocytes .Activation of the immune system can prevent tumor migration and eliminate metastases. This can be used as a potential research direction to explore the performance of BxC/C dihedral quantum sheets in the elimination of metastasis tumor models.
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Reference:
1, Lu, S. Y., Wang, J., Wang, X., Yang, W., Jin, M., Xu, L., ... & Liu, H. (2022). Janus-like BxC/C Quantum Sheets with Z-Scheme Mechanism Strengthen Tumor Photothermal-Immunotherapy in NIR‐II Biowindow. Small Methods, 2101551.
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