Endothelialized microrods for minimally invasive in situ neovascularization

Despite the significant advancements in fabricating various scaffolding systems over the past decades, generation of functional tissues towards vascularization remains challenging for the currently available biofabrication approaches. On the other hand, the applicability of traditional surgical transplantation of vascularized tissue constructs is sometimes limited due to the sophisticated surgical procedures, which are invasive, leading to increased risks of scar formation and infection. Considering these facts, we present an innovative platform, the angiogenic microrods composed of sodium alginate/gelatin harboring proliferating endothelial cells using a specially designed double T-junction microfluidic device with an expansion chamber, for achieving minimally invasive neovascularization in situ. Such vessel-like microarchitectures could be derived through controlled penetration of the crosslinker genepin for the gelatin phase, ensuing differential degrees in crosslinking of peripheral and central portions of the microstructures, thus resulting in the formation of vascular lumen-like hollow cavities via endothelial cell migration and proliferation during culture in vitro. Furthermore, in vivo performance of the microrods was explored. We believe that the development of these modular microrods for minimally invasive delivery is of great interest and offers a convenient approach for vascularization in situ.

Carbon-Doped TiO2 Activated by X-Ray Irradiation for the Generation of Reactive Oxygen Species to Enhance Photodynamic Therapy in Tumor Treatment

Traditional photodynamic therapy (PDT) is limited by the penetration depth of visible light. Although the light source has been changed to near infrared, infrared light is unable to overcome the penetration barrier and it is only effective at the surface of the tumors. In this study, we used X-ray as a light source for deep-seated tumor treatment. A particle with a narrow band gap when exposed to soft X-rays would produce reactive oxygen species (ROS) to kill tumor cell, with less damage to the normal tissues. Anatase TiO₂ has been studied as a photosensitizer in PDT. In the experiment, C was doped into the anatase lattice at an optimum atomic ratio to make the band gap narrower, which would be activated by X-ray to produce more ROS and kill tumor cells under stress. The results showed that the synthesized TiO₂:C particles were identified as crystal structures of anatase. The synthesized particles could be activated effectively by soft X-rays to produce ROS, to degrade methylene blue by up to 30.4%. Once TiO₂:C was activated by X-ray irradiation, the death rate of A549 cells in in vitro testing was as high as 16.57%, on day 2. In the animal study, the tumor size gradually decreased after treatment with TiO₂:C and exposure to X-rays on day 0 and day 8. On day 14, the tumor declined to nearly half of its initial volume, while the tumor in the control group was twice its initial volume. After the animal was sacrificed, blood, and major organs were harvested for further analysis and examination, with data fully supporting the safety of the treatment. Based on the results of the study, we believe that TiO₂:C when exposed to X-rays could overcome the limitation of penetration depth and could improve PDT effects by inhibiting tumor growth effectively and safely, in vivo.