hampered to date by the limited success in the development of clinical photothermal therapy agents. [6] PTT exploits heat generated locally by a photosensitizer, [7] in which both the photothermal agents and laser sources, as well as the matching between them, are essential. Laser thermal therapy generally employs continuouswave lasers with wavelengths of either 808 or 980 nm. [8,9] The wavelengths are in the near-IR (NIR, λ = 700-1100 nm) window so that photons can penetrate deep into biological tissue. [10][11][12] Certain nanoparticles (NPs) have proper carrier densities enabling them to exhibit localized surface plasmon resonances (LSPRs) that efficiently facilitate the conversion of NIR light into heat. [10][11][12] Several types of NPs are currently being developed as photosensitizers, including metallic and semiconductor NPs. Noble metal NPs, for example, Ag and Au NPs, have been extensively applied for the LSPRs in the visible spectrum. [5,[13][14][15] Semi conductor NPs have tunable carrier concentration and LSPRs typically in the NIR range. [10,11] A high photothermal conversion efficiency is key to effective NP photosensitizers to avoid thermal damage to healthy tissue, which is a serious problem in PTT. The NPs with a high photothermal conversion efficiency and tumor selectivity can thus effectively destroy the cancer cells at a low photon density and in a short treatment time, while keeping the surrounding healthy tissue at a safe temperature. [16] Other key factors to consider for developing Photothermal therapy requires efficient plasmonic nanomaterials with small size, good water dispersibility, and biocompatibility. This work reports a one-pot, 2-min synthesis strategy for ultrathin CuS nanocrystals (NCs) with precisely tunable size and localized surface plasmon resonance (LSPR), where a single-starch-layer coating leads to a high LSPR absorption at the near-IR wavelength 980 nm. The CuS NC diameter increases from 4.7 (1 nm height along [101]) to 28.6 nm (4.9 nm height along [001]) accompanied by LSPR redshift from 978 to 1200 nm, as the precursor ratio decreases from 1 to 0.125. Photothermal temperature increases by 38.6 °C in 50 mg L −1 CuS NC solution under laser illumination (980 nm, 1.44 W cm −2 ). Notably, 98.4% of human prostate cancer PC-3/Luc+ cells are killed by as little as 5 mg L −1 starch-coated CuS NCs with 3-min laser treatment, whereas CuS NCs without starch cause insignificant cell death. LSPR modeling discloses that the starch layer enhances the photothermal effect by significantly increasing the free carrier density and blue-shifting the LSPR toward 980 nm. This study not only presents a new type of photothermally highly efficient ultrathin CuS NCs, but also offers in-depth LSPR modeling investigations useful for other photothermal nanomaterial designs.
Noninvasive imaging of cardiac fibrosis is important for early diagnosis and intervention in chronic heart diseases. Here, we investigated whether noninvasive, contrast agent‐free MRI T2‐mapping can quantify myocardial fibrosis in preclinical models of aging and pressure overload. Myocardial fibrosis and remodeling were analyzed in two animal models: (i) aging (15‐month‐old male CF‐1 mice vs. young 6‐ to 8‐week‐old mice), and (ii) pressure overload (PO; by transverse aortic constriction in 4‐ to 5‐month‐old male C57BL/6 mice vs. sham‐operated for 14 days). In vivo T2‐mapping was performed by acquiring data during the isovolumic and early diastolic phases, with a modified respiratory and ECG‐triggered multiecho TurboRARE sequence on a 7‐T MRI. Cine MRI provided cardiac morphology and function. A quantitative segmentation method was developed to analyze the in vivo T2‐maps of hearts at midventricle, apex, and basal regions. The cardiac fibrosis area was analyzed ex vivo by picro sirius red (PSR) staining. Both aged and pressure‐overloaded hearts developed significant myocardial contractile dysfunction, cardiac hypertrophy, and interstitial fibrosis. The aged mice had two phenotypes, fibrotic and mild‐fibrotic. Notably, the aged fibrotic subgroup and the PO mice showed a marked decrease in T2 relaxation times (25.3 ± 0.6 in aged vs. 29.9 ± 0.7 ms in young mice, p = 0.002; and 24.3 ± 1.7 in PO vs. 28.7 ± 0.7 ms in shams, p = 0.05). However, no significant difference in T2 was detected between the aged mild‐fibrotic subgroup and the young mice. Accordingly, an inverse correlation between myocardial fibrosis percentage (FP) and T2 relaxation time was derived (R2 = 0.98): T2 (ms) = 30.45 – 1.05 × FP. Thus, these results demonstrate a statistical agreement between T2‐map–quantified fibrosis and PSR staining in two different clinically relevant animal models. In conclusion, T2‐mapping MRI is a promising noninvasive contrast agent‐free quantitative technique to characterize myocardial fibrosis.
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