The nonradiative conversion of light energy into heat (photothermal therapy, PTT) or sound energy (photoacoustic imaging, PAI) has been intensively investigated for the treatment and diagnosis of cancer, respectively. By taking advantage of nanocarriers, both imaging and therapeutic functions together with enhanced tumour accumulation have been thoroughly studied to improve the pre-clinical efficiency of PAI and PTT. In this review, we first summarize the development of inorganic and organic nano photothermal transduction agents (PTAs) and strategies for improving the PTT outcomes, including applying appropriate laser dosage, guiding the treatment via imaging techniques, developing PTAs with absorption in the second NIR window, increasing photothermal conversion efficiency (PCE), and also increasing the accumulation of PTAs in tumours. Second, we introduce the advantages of combining PTT with other therapies in cancer treatment. Third, the emerging applications of PAI in cancer-related research are exemplified. Finally, the perspectives and challenges of PTT and PAI for combating cancer, especially regarding their clinical translation, are discussed. We believe that PTT and PAI having noteworthy features would become promising next-generation non-invasive cancer theranostic techniques and improve our ability to combat cancers.

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Photothermal therapy and photoacoustic imaging via nanotheranostics in fighting cancer

Reactive oxygen species (ROS) play an essential role in regulating various physiological functions of living organisms. The intrinsic biochemical properties of ROS, which underlie the mechanisms ne...

Reactive Oxygen Species (ROS)-Based Nanomedicine.

2D/2D Heterojunction of Ultrathin MXene/Bi2WO6 Nanosheets for Improved Photocatalytic CO2 Reduction

MXene, a new series of 2D material, has been steadily advancing its applications to a variety of fields, such as catalysis, supercapacitor, molecular separation, electromagnetic wave interference shielding. This work reports a carefully designed aqueous droplet light heating system along with a thorough mathematical procedure, which combined leads to a precise determination of internal light-to-heat conversion efficiency of a variety of nanomaterials. The internal light-to-heat conversion efficiency of MXene, more specifically Ti3C2, was measured to be 100%, indicating a perfect energy conversion. Furthermore, a self-floating MXene thin membrane was prepared by simple vacuum filtration and the membrane, in the presence of a rationally chosen heat barrier, produced a light-to-water-evaporation efficiency of 84% under one sun irradiation, which is among the state of art energy efficiency for similar photothermal evaporation system. The outstanding internal light-to-heat conversion efficiency and great light...

MXene Ti3C2: An Effective 2D Light-to-Heat Conversion Material

Conventionally, ceramics-based materials, fabricated by high-temperature solid-phase reaction and sintering, are preferred as bone scaffolds in hard-tissue engineering because of their tunable biocompatibility and mechanical properties. However, their possible biomedical applications have rarely been considered, especially the cancer phototherapeutic applications in both the first and second near-infrared light (NIR-I and NIR-II) biowindows. In this work, we explore, for the first time as far as we know, a novel kind of 2D niobium carbide (Nb2C), MXene, with highly efficient in vivo photothermal ablation of mouse tumor xenografts in both NIR-I and NIR-II windows. The 2D Nb2C nanosheets (NSs) were fabricated by a facile and scalable two-step liquid exfoliation method combining stepwise delamination and intercalation procedures. The ultrathin, lateral-nanosized Nb2C NSs exhibited extraordinarily high photothermal conversion efficiency (36.4% at NIR-I and 45.65% at NIR-II), as well as high photothermal stabi...

A Two-Dimensional Biodegradable Niobium Carbide (MXene) for Photothermal Tumor Eradication in NIR-I and NIR-II Biowindows

Ceramic biomaterials have been investigated for several decades, but their potential biomedical applications in cancer therapy have been paid much less attentions, mainly due to their lack of related material functionality for combating the cancer. In this work, we report, for the first time, that MAX ceramic biomaterials exhibit the unique functionality for the photothermal ablation of cancer upon being exfoliated into ultrathin nanosheets within atomic thickness (MXene). As a paradigm, biocompatible Ti3C2 nanosheets (MXenes) were successfully synthesized based on a two-step exfoliation strategy of MAX phase Ti3AlC2 by the combined HF etching and TPAOH intercalation. Especially, the high photothermal-conversion efficiency and in vitro/in vivo photothermal ablation of tumor of Ti3C2 nanosheets (MXenes) were revealed and demonstrated, not only in the intravenous administration of soybean phospholipid modified Ti3C2 nanosheets but also in the localized intratumoral implantation of a phase-changeable PLGA/Ti...

Two-Dimensional Ultrathin MXene Ceramic Nanosheets for Photothermal Conversion

ZrC ceramics with additions of MC (M = V, Nb, and Ta) were prepared by hot pressing, and the effect of MC additions on densification was analyzed in terms of the solubility limit and kinetics of formation of MC solid solutions with ZrC. VC additions of 2.5–10 vol% (3.5–13.5 mol%), which is higher than its solid solubility limit of 1.3 vol% (1.8 mol%), effectively promoted the densification process and nearly fully dense ZrC ceramics were obtained by hot-pressing at 1900 °C. In contrast, both NbC and TaC additions, which can form unlimited solid solutions with ZrC, have no obvious contribution to ZrC densification. This is because formation of the solid solution of NbC and TaC with ZrC matrix requires higher temperature and longer time due to their stronger bonding energy, compared to VC. SEM observation demonstrated that the VC addition resulted in larger grains, compared to ZrC ceramics with NbC and TaC additions.

Effect of solid solution formation on densification of hot-pressed ZrC ceramics with MC (M = V, Nb, and Ta) additions

Densifications of hot-pressed ZrC ceramics with Zr and graphite additives were studied at 1800–2000 °C. ZrC with 8.94 wt% Zr additive (named ZC10) sintered at 1900–2000 °C achieved higher relative densities (>98.4%) than that of additive-free ZrC (<83%). The densification improvement was attributed to the formation of non-stoichiometric ZrC0.9, whereas there had rapid grain growth with grain size about 50–100 μm in ZC10. By adding co-doped additive of Zr plus C and adjusting the molar ratio of Zr/C, ZrC with co-doped additives with Zr/C molar ratio at 1:2 (named ZC12), ZrC ceramics with both high relative density (98.4%) and fine microstructures (grain size about 5–10 μm) were obtained at 1900–2000 °C. Effect of formation of non-stoichiometric ZrC1−x on densification of ZrC was discussed. The Vickers hardness and indentation toughness of ZC10 and ZC12 samples sintered at 1900 °C were 17.8 GPa and 3.0 MPa m1/2, 16.2 GPa and 4.7 MPa m1/2, respectively.

Densification behavior and properties of hot-pressed ZrC ceramics with Zr and graphite additives

Composites of ZrC–SiC with relative densities in excess of 98% were prepared by reactive hot pressing of ZrC and Si at temperature as low as 1600°C. The reaction between ZrC and Si resulted in the formation of ZrC1−x, SiC, and ZrSi. Low-temperature densification of ZrC−SiC ceramics is attributed to the formed nonstoichiometric ZrC1−x and Zr–Si liquid phase. Adding 5 wt% Si to ZrC, the three-point bending strength of formed ZrC0.8–13.4 vol%SiC ceramics reached 819 ± 102 MPa with hardness and toughness being 20.5 GPa and 3.3 MPa·m1/2, respectively.

Xin-Gang Wang

Papers

Two-Dimensional Ultrathin MXene Ceramic Nanosheets for Photothermal Conversion

Effect of solid solution formation on densification of hot-pressed ZrC ceramics with MC (M = V, Nb, and Ta) additions

Densification behavior and properties of hot-pressed ZrC ceramics with Zr and graphite additives

Reactive Hot Pressing of ZrC–SiC Ceramics at Low Temperature

Pressureless sintering mechanism and microstructure of ZrB2–SiC ceramics doped with boron