Although microfluidic approaches for liposomes preparation have been developed, fabricating microfluidic devices remains expensive and time-consuming. Also, owing to the traditional layout of microchannels, the volumetric throughput of microfluidics has been greatly limited. Herein an ultra-high volumetric throughput nanoliposome preparation method using 3D printed microfluidic chips is presented. A high-resolution projection micro stereolithography (PμSL) 3D printer is applied to produce microfluidic chips with critical dimensions of 400 µm. The microchannels of the microfluidic chip adopt a three-layer layout, achieving the total flow rate (TFR) up to 474 ml min−1, which is remarkably higher than those in the reported literature. The liposome size can be as small as 80 nm. The state of flows in microchannels and the effect of turbulence on liposome formation are explored. The experimental results demonstrate that the 3D printed integrated microfluidic chip enables ultra-high volumetric throughput nanoliposome preparation and can control size efficiently, which has great potential in targeting drug delivery systems.

Targeted liposomes, as a promising carrier, have received tremendous attention in COVID‐19 vaccines, molecular imaging, and cancer treatment, due to their enhanced cellular uptake and payload accumulation at target sites. However, the conventional methods for preparing targeted liposomes still suffer from limitations, including complex operation, time‐consuming, and poor reproducibility. Herein, a facile and scalable strategy is developed for one‐step construction of targeted liposomes using a versatile microfluidic mixing device (MMD). The engineered MMD provides an advanced synthesis platform for multifunctional liposome with high production rate and controllability. To validate the method, a programmed death‐ligand 1 (PD‐L1)‐targeting aptamer modified indocyanine green (ICG)‐liposome (Apt‐ICG@Lip) is successfully constructed via the MMD. ICG and the PD‐L1‐targeting aptamer are used as model drug and targeting moiety, respectively. The Apt‐ICG@Lip has high encapsulation efficiency (89.9 ± 1.4%) and small mean diameter (129.16 ± 5.48 nm). In vivo studies (PD‐L1‐expressing tumor models) show that Apt‐ICG@Lip can realize PD‐L1 targeted photoacoustic imaging, fluorescence imaging, and photothermal therapy. To verify the versatility of this approach, various targeted liposomes with different functions are further prepared and investigated. These experimental results demonstrate that this method is concise, efficient, and scalable to prepare multifunctional targeted liposomal nanoplatforms for molecular imaging and disease theranostics.

Current Photoacoustic tomography (PAT) approaches are based on a single-element transducer that exhibits compromised performance in clinical imaging applications. For example, vascular, tumors are likely to have complicated shapes and optical absorptions, covering relatively wide spectra in acoustic signals. The wide ultrasonic spectra make it difficult to set the detection bandwidth optimally in advance. In this work, we propose a stack-layer dual-element ultrasonic transducer for PAT. The central frequencies of the two piezoelectric elements are 3.06 MHz (99.3% bandwidth at –6 dB) and 11.07 MHz (85.2% bandwidth at –6 dB), respectively. This transducer bridges the sensitivity capability of ultrasound and the high contrast of optical methods in functional photoacoustic tomography. The dual-element transducer enabled multiscale analysis of the vascular network in rat brains. Using a multi-wavelength imaging scheme, the blood oxygen saturation was also detected. The preliminary results showed the great potential of broad-bandwidth functional PAT on vascular network visualization. The method can also be extended to whole-body imaging of small animals, breast cancer detection, and finger joint imaging.

Recently, indocyanine green (ICG), as an FDA-approved dye, has been widely used for phototherapy. It is essential to obtain information on the migration and aggregation of ICG in deep tissues. However, existing fluorescence imaging platforms are not able to obtain the structural information of the tissues. Here, we prepared ICG liposomes (ICG-Lips) and built a dual-wavelength photoacoustic computed tomography (PACT) system with piezoelectric ring-array transducer to image the aggregation of ICG-Lips in tumors to guide phototherapy. Visible 780 nm light excited the photoacoustic (PA) effects of the ICG-Lips and near-infrared 1064 nm light provided the imaging of the surrounding tissues. The aggregation of ICG-Lips within the tumor and the surrounding tissues was visualized by PACT in real time. This work indicates that PACT with piezoelectric ring-array transducer has great potential in the real-time monitoring of in vivo drug distribution.