pH and glucose dual-responsive injectable hydrogels were prepared through the cross-linking of Schiff's base and phenylboronate ester using phenylboronic-modified chitosan, poly(vinyl alcohol) and benzaldehyde-capped poly(ethylene glycol). Protein drugs and live cells could be incorporated into the hydrogels during the in situ cross-linking, displaying sustained and pH/glucose-triggered drug release from the hydrogels and cell viability and proliferation in the three-dimensional hydrogel matrix as well. Hence, the hydrogels with insulin and fibroblasts were considered as bioactive dressings for diabetic wound healing. A streptozotocin-induced diabetic rat model was used to evaluate the efficacy of hydrogel dressings in wound repair. The results revealed that the incorporation of insulin and L929 in the hydrogels could promote neovascularization and collagen deposition and enhance the wound-healing process of diabetic wounds. Thus, the drug- and cell-loaded hydrogels have promising potential in wound healing as a medicated system for various therapeutic proteins and live cells.

Developing methods that provide adequate vascular perfusion is an important step toward engineering large functional tissues. Meanwhile, an imaging modality to assess the three-dimensional (3-D) structures and functions of the vascular channels is lacking for thick matrices (>2~3mm). Herein, we report on an original approach to construct and image 3-D dynamically perfused vascular structures in thick hydrogel scaffolds. In this work, we integrated a robotic 3-D cell-printing technology with a mesoscopic fluorescence molecular tomography imaging system, and demonstrated the capability of the platform to construct perfused collagen scaffolds with endothelial lining and to image both the fluid flow and fluorescent-labeled living endothelial cells at high-frame rates, with high sensitivity and accuracy. These results establish the potential of integrating both 3-D cell-printing and fluorescence mesoscopic imaging for functional and molecular studies in complex tissue engineered tissues.

The conjugation of anti-cancer drugs to endogenous ligands has proven to be an effective strategy to enhance their pharmacological selectivity and delivery towards neoplasic tissues. Since cell proliferation has a strong requirement for iron, cancer cells express high levels of transferrin receptors (TfnR), making its ligand, transferrin (Tfn), of great interest as a delivery agent for therapeutics. However, a critical gap exists in the ability to non-invasively determine whether drugs conjugated to Tfn are internalized into target cells in vivo. Due to the enhanced permeability and retention (EPR) effect, it remains unknown whether these Tfn-conjugated drugs are specifically internalized into cancer cells or are localized non-specifically as a result of a generalized accumulation of macromolecules near tumors. By exploiting the dimeric nature of the TfnR that binds two molecules of Tfn in close proximity, we utilized a Förster Resonance Energy Transfer (FRET) based technique that can discriminate bound and internalized Tfn from free, soluble Tfn. In order to non-invasively visualize intracellular amounts of Tfn in tumors through live animal tissues, we developed a novel near infrared (NIR) fluorescence lifetime FRET imaging technique that uses an active wide-field time gated illumination platform. In summary, we report that the NIR fluorescence lifetime FRET technique is capable of non-invasively detecting bound and internalized forms of Tfn in cancer cells and tumors within a live small animal model, and that our results are quantitatively consistent when compared to well-established intensity-based FRET microscopy methods used in in vitro experiments.

Hypoxic-ischemic encephalopathy (HIE) is one of the leading causes of morbidity and mortality in neonates. Because of high concentrations of sensitive immature cells, metal-catalyzed free radicals, non-saturated fatty acids, and low concentrations of antioxidant enzymes, the brain requires high levels of oxygen supply and is, thus, extremely sensitive to hypoxia. Strong evidence indicates that oxidative stress plays an important role in pathogenesis and progression. Following hypoxia and ischemia, reactive oxygen species (ROS) production rapidly increases and overwhelms antioxidant defenses. A large excess of ROS will directly modify or degenerate cellular macromolecules, such as membranes, proteins, lipids, and DNA, and lead to a cascading inflammatory response, and protease secretion. These derivatives are involved in a complex interplay of multiple pathways (e.g., inflammation, apoptosis, autophagy, and necrosis) which finally lead to brain injury. In this review, we highlight the molecular mechanism for oxidative stress in HIE, summarize current research on therapeutic strategies utilized in combating oxidative stress, and try to explore novel potential clinical approaches.