Fig. 1: A comparative analysis of tissue penetration depths achieved with different excitation sources.
From: X-ray-activated polymerization expanding the frontiers of deep-tissue hydrogel formation
Ultraviolet/visible (UV/Vis) light exhibits restricted tissue penetration, typically reaching only a few millimeters, thus severely hampering its utility in biological systems. Near infrared ray (NIR) light with longer wavelengths can enhance penetration depth to some extent. Nonetheless, existing photo-crosslinking methods fall short in achieving deep-tissue penetration, especially within bone structures. Compared to light, X-rays, a form of electromagnetic waves extensively utilized in biomedical applications, exhibit remarkable penetration capabilities through both bones and human tissue. Herein, we present a breakthrough X-ray-controlled polymer crosslinking system consisted of containing polyethyleneglycoldiacrylate (PEGDA), complex of camphorquinone and methyl-β-cyclodextrin (MCD/CQ), and halloysite nanotubes-based X-ray-activated visible persistent luminescent emitting phosphors (HNTs@YF3:Tb3+), referred to as Xcrosslinking, that achieves hydrogel formation within deep tissues and bone structures with advantages including highly spatial controllability, noncontact external stimuli, and uncritical demand for the environment.
