With the copolymer micelles being widely used in the field of tumor therapy, environmental responding copolymers had gained large interest. In our previous work, we synthesized the nanovehicle N-succinyl-N’-4-(2-nitrobenzyloxy)-succinyl-chitosan micelles (SNSC) that were composed of a light-sensitive triggering group 2-nitrobenzyl alcohol on the hydrophobic block and succinyl group modified chitosan. We have demonstrated that the use of a continuous-wave diode near-infrared (NIR) laser could cleave the amphiphilic block copolymer micelles and trigger the release of their “payloads”. In the present study, SNSC were further optimized and characterized by UV-visible spectroscopy, fluorescence spectroscopy and transmission electron microscopy (TEM) that was used to display the two-photon photolysis of SNSC micelles under the NIR irradiation (765nm) . Later on, laser confocal fluorescence microscopy was used to investigate the fluorescein (Ex/Em: 490/520 nm)-loaded SNSC imaging ability. As a result, the optimized SNSCs exhibited higher loading efficiency and smaller size which contributed to an improved stability, drug delivery and cell imaging abilities.
KEYWORDS: Photodynamic therapy, Luminescence, Nanoparticles, In vivo imaging, Near infrared, Upconversion, Imaging systems, Oxygen, Signal detection, Tissues
Upconversion nanoparticles (UCNPs) have attracted much attention as novel contrast agents for low-background biomedical imaging and potential photosensitizer carriers for photodynamic therapy (PDT) in deep tissues. In this work, firstly we synthesized NaYF4:Yb3+,Tm3+@NaYF4:Yb3+,Er3+ core-shell structured UCNPs with multiple emission peaks (e.g. 480, 539, 654 and 800 nm) by a seeded growth approach. By coating folate-modified amphiphilic chitosan (FASOC) on UCNPs, the as-prepared UCNPs were favorably endowed with good water solubility and the enhanced tumor-selectivity to cancer cells that overexpressed folate receptor. Then, water-insoluble photosensitizer zinc(II) phthalocyanine (ZnPc) was loaded into the FASOC-UCNPs via hydrophobic interactions for potential near-infrared light induced photodynamic therapy (PDT). Our results indicate that the multifunctional FASOC-UCNP-ZnPc nanoconstruct has efficient NIR-to-NIR upconversion luminescence and PDT abilities, which could be potentially employed as a theranostic platform for cancer treatment.
In this manuscript, a new near-infrared (NIR) light-breakable amphiphilic block copolymer containing light-sensitive triggering group on the hydrophobic block was developed. By encapsulating NIR dye cypate inside micelles of poly (N-succinyl-N'-4- (2-nitrobenzyloxy)-succinyl chitosan) and exposing the micellar solution to 765.9 nm light, the photo-cleavage reaction was activated and leading to the dissociation of micelles and release of co-loaded hydrophobic species. The UV-vis absorption spectra, fourier transform infrared (FTIR) spectra and 1H nuclear magnetic resonance (1H NMR) spectra of micelles were characterized. Triggered burst release of the payload upon NIR irradiation and subsequent degradation of the micelles were observed by transmission electron microscopy (TEM).
This system represents a general and efficient method to circumvent the need for UV or visible light excitation that is a common drawback for light-responsive polymeric systems developed for potential biomedical applications.
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