Abstract
The optical probes working in the second near-infrared (NIR-II) window have attracted increasing research interest for their advantages of high tissue penetration depth, low autofluorescence, and unprecedentedly improved imaging sensitivity and spatial resolution. Therefore, it is of great significance to design a new nanoplatform by integration of NIR-II optical imaging and drug delivery functions. Herein, a multifunctional nanoplatform based on GdPO4:Nd3+ yolk–shell sphere was developed for dual-modal in vivo NIR-II/X-ray bioimaging and pH-responsive drug delivery. The in vivo NIR-II bioimaging and real-time tracking presented that these probes were mainly accumulated in liver and spleen. Moreover, owing to the large X-ray absorption coefficient of Gd3+, these probes are successfully used as superior X-ray imaging agents than iobitridol. The in vivo toxicity assessments demonstrate the low biotoxicity of the GdPO4:Nd3+ spheres in living animals. More importantly, apart from the excellent dual-modal bioimaging, these yolk–shell-structured probes were also used as ideal nanotransducer for pH-responsive drug delivery of doxorubicin (DOX). These findings open up the opportunity of designing theranostic nanoplatform with integration of imaging-based diagnosis and therapy.
Highlights
IntroductionThe development of optical probes has opened up the new eld of bioimaging and promoted its applications for the early detection and diagnosis of diseased tissues, due to its advantages of high accuracy, high sensitivity, fast feedback and absence of radiation.[1,2,3,4,5] optical probes with short wavelength emissions such as the visible light region hold large absorption efficient and scattering losses in biotissues (blood, hemoglobin and lipids), limiting their imaging efficiency and tissue penetration depth.[6,7] Typically, the optical probes that emitting in the visible range (400–750 nm) can only penetrate approximately 1 mm into the tissue.[8,9] the penetration depth and imaging sensitivity can be improved by using the optical probes capable of emitting in the rst near-infrared (NIR-I) window (750–900 nm) owing to the reduced auto uorescence and scattering losses.[10,11,12,13,14] the imaging sensitivity, spatial resolution, and penetration depth of NIR-I emitting probes are still limited
The in vivo NIR-II bioimaging and realtime tracking presented that these probes were mainly accumulated in liver and spleen
In order to assess the feasibility of GdPO4:2% Nd3+ probe for in vivo bioimaging in the NIR-II window, the 250 mL solution (2 mg mLÀ1) of sample was intravenously injected into an anesthetized Kunming mouse which intraperitoneally injected with 150 mL of 10 wt% pentobarbital sodium aqueous solution, and in vivo NIR-II bioimaging at different time intervals from 1 h to 12 days a er injection was acquired by the InGaAs shortwavelength infrared (SWIR) detector under the excitation of 808 nm laser and the band-pass lter of 1200 nm to 1400 nm
Summary
The development of optical probes has opened up the new eld of bioimaging and promoted its applications for the early detection and diagnosis of diseased tissues, due to its advantages of high accuracy, high sensitivity, fast feedback and absence of radiation.[1,2,3,4,5] optical probes with short wavelength emissions such as the visible light region hold large absorption efficient and scattering losses in biotissues (blood, hemoglobin and lipids), limiting their imaging efficiency and tissue penetration depth.[6,7] Typically, the optical probes that emitting in the visible range (400–750 nm) can only penetrate approximately 1 mm into the tissue.[8,9] the penetration depth and imaging sensitivity can be improved by using the optical probes capable of emitting in the rst near-infrared (NIR-I) window (750–900 nm) owing to the reduced auto uorescence and scattering losses.[10,11,12,13,14] the imaging sensitivity, spatial resolution, and penetration depth of NIR-I emitting probes are still limited. These results indicate that the yolk–shell-structured GdPO4:Nd3+ probes are promising agents for simultaneously combining multimodal bioimaging, especially for the new advanced NIR-II bioimaging with drug delivery to form synergistic theranostic platform
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