A Bright NIR-II Fluorescence Probe for Vascular and Tumor Imaging

High-resolution vascular and tumor imaging was realized by the near-infrared to fluorescent nanoprob, providing an accurate and effective method for directing vascular diseases and cancer. In vivo imaging in the NIR-II window, which enables us to look deeply into living subject, produces opportunities for biomedical research and our clinical applications. Prepare for the near-infrared II or NIR-II imaging by placing commercially available black cardboard in the center of the carrier of the imaging device.

Then, place the sample on top of the black cardboard, so it is in the center of the carrier. After selecting the appropriate filter, perform the platform height adjustment. Long press the option of platform up on the touchscreen interface of the carrier console control area to move it upwards.

And long press the platform down to move it downwards. After synthesizing the NIR-II dye HLY1, prepare the HLY1 dots by nanoprecipitation method using DSPE-PEG-2K as an encapsulation matrix. To do so, place a beaker containing a solution of 10 milligrams of DSPE-PEG-2K in nine milliliters of water for sonication at 25 degrees Celsius.

Then, dissolve one milligram of HLY1 in one milliliter of tetrahydrofuran or THF. And slowly add the solution into the DSPE-PEG-2K aqueous solution undergoing sonication. Subsequently, remove THF from the mixture by dialysis.

After concentrating the above solution centrifugally with ultrafiltration at 7, 100 G for 10 minutes, place it in a four degree Celsius refrigerator for future use. For in vivo imaging, inject the HLY1 dots intravenously into the anesthetized mice. And three minutes later, proceed to perform NIR-II fluorescence imaging of the blood vessels of the whole body of the mice using an optical NIR-II imaging system.

Focus further on the mouse's head to collect brain vascular imaging. Set the instrument parameters of the optical NIR-II imaging system at 90 milliwatts per square centimeter and 808 nanometer laser. Collect the images five minutes after the injection of HLY1 dots in mice and process the data using ImageJ software.

The fluorescence intensity of HLY1 in the 90%THF solution containing 90%water was five times that in the THF solution, indicating a prominent aggregation-induced emission or AIE feature of HLY1. The HLY1 dots emitted strong fluorescent signals under a 1, 500 nanometer low pass or LP filter establishing its suitability for NIR-IIb imaging. The maximum absorption and emission wavelength of HLY1 dots were 740 nanometers and 1, 040 nanometers, respectively.

Additionally, the hydrodynamic size of HLY1 dots was determined to be 145 nanometers by dynamic light scattering. In mice administered with HLY1 dots, the cerebral vessels and the micro vessels in the hind limb were identified clearly by NIR-II imaging under a 1, 500 nanometer LP filter. Further, the four T1 tumor of the tumor-bearing mice was also clearly visible by NIR-II imaging, indicating the enhanced permeability and retention or EPR effect of HLY1 dots.

All these results suggested that HLY1 dots are a bright NIR-II fluorescence probe applicable for vascular and tumor imaging. Preparation of the water-suspendable nanoprobe under the in vivo and NIR-II fluorescence imaging are the most important part of the procedure.