Enviro Nmental-response Near-infrared Fluorescent Probe For Tumor Dia Gnosis And Treatment

Intracellular pH plays a pivotal role in many cellular events.Under normal physiological conditions extracellular hydrogen ion concentration is about 40 nmol/L(pH 7.40).Deviation by 0.10-0.20 pH units in either direction can cause diseases su ch as inflammation,alzheimer’s disease, cancer, etc. It has been verified solid tumors tend to have a more acidic extracellular microenvironment than normal tissues.Therefore, it is important to visualize the tumor microenvironment pH for better tumor diagnosis and prognosis. Fluorescence imaging has many advantages, such as non-invasive, nonionic, low energy radiation, high sensitivity and selectivity, so widely used in pH detection In Vivo.NIR fluorophores, such as heptamethine cyanine have the advantage that light in the NIR region(around 650-900 nm) is relatively poorly absorbed by biomolecules, so it can penetrate deeply into tissues. There is also less autofluorescence in thisregion.Thus, NIR pH probes based on heptamethine cyanine are expected to be suitable for monitoring pH and in Vivo imaging.In this paper, a heptamethine cyanine Cy.7.Cl was first synthesized, then five other aminocyanine bearing a diamine moiety were achieved by nucleophilic reaction at the chlorine of the dye. On the basis of these near-infrared fluorescent dye, we would explore their applications to the tumor microenvironment pH detect. On the basis of these NIR fluorescent dye, after the investigation of the spectroscopic properties in different pH solution, we found that these NIR fluorescent dyes exhibited a wealth of spectroscopic response toward the change of p H value, so can be used as p H probes. According to the calculated pKa values o f these NIR fluorescent dye 1a-5a, NIR probe 3a was chosen with a pKa of 6.4 and was suitable for monitoring tumor pH and in Vivo imaging. Due to the strong pH-dependent absorption of the NIR probe 3a, photoacoustic(PA) imaging of the NIR probe 3a dispersed in citrate buffer solutions with different pH values and captured at 680 nm and 760 nm was carried out.Interestingly, 760nm/680 nm PA signalratios showed excellent pH dependence in the range of 5.5–7.8. We detected pH using our NIR probe 3a by photoacoustic imaging, covered by pork tissues with different thicknesses. Importantly, the 760nm/680 nm PA signal ratios, which were used to determine the pH values, showed no significant change, suggesting that our ratiometric photoacoustic pH sensing method remains to be accurate for targets covered by tissues with considerable depth, potentially suitable for detecting pH values in the tumor microenvironment by ratiometric photoacoustic imaging. It is a good dual modality pH imaging probe by fluorescent imaging and photoacoustic imaging. Meanwhile animal experiments showed that the probe 3a had a good effect for photothermal therapy. This study showed that the NIR probe 3a can be used a good dual modality pH imaging probe to more accurate detect the tumor microenvironment pH and guide better photothermal therapy in fluorescent imaging and photoacoustic imaging.The near-infrared(NIR) dyes such as heptamethine cyanine, whose biological application is critically hampered by the low photostability and solubility in aqueous media. We designed and synthesized a system of the NIR pH probe CP encapsulated in the triblock polypeptide copolymers PE G5000-PLL30-PLLeu40(DNPs).Experiments showed that the DNPs had better stability in aqueous media compared with the free NIR pH probe CP. The photobleaching properties of the DNPs and the free NIR pH probe was explored, the results showed that fluorescence intensity of the free NIR pH probe CP was almost completely quenched after only irradiating 60 s,can be very clearly saw the color of the solution had been completely faded. The fluorescence intensity of the DNPs only descended 25% after high-energy irradiating, and hardly observe colour fading by the naked eye.After high-energy light, the solution of the fluorescence intensity fell by only about 25%, and the solution of fade hardly observed with the naked eye. These phenomena again confirmed the low photostability of cyanine, and can be obviously improved by the NIR pH probe CP encapsulated in the triblock polypeptide copolymers(DPNs). This study we designed and synthesized a pH-response nanoprobes, obviously enhanced the stability and the water soluble of cyanine dyes, it can be used to used to detect intracellular pH change, has good application prospect in the tumor early diagnosis and imaging.