Cellulose nanocrystals (CNCs) are one of the most promising natural derived nanomaterials that possess a number of advantages such as nanoscale size, rich of surface functional groups, biodegradability, low cost, and desirable biocompatibility. Considering the above characteristics, CNCs and their composites have raised considerable research attention for various applications. On the other hand, the surface modification of nanomaterials plays a crucial role in adjusting their surface properties and endow novel functions for specific applications. However, to the best of our knowledge, direct surface modification of CNCs with hyperbranched polymers and their biomedical applications are largely underexplored. In this work, we reported a novel method for the preparation of hyperbranched polymers-functionalized CNCs through direct anionic polymerization using surface hydroxyl groups of CNCs as initiators and glycidol as the monomer. The peripheral end functional groups of these functionalized CNCs were further transformed to hydrazide groups, which could be utilized for loading anticancer drugs, such as epirubicin (EPI), through the formation of hydrazone bonds with pH-responsiveness. Based on the characterization data such as 1 H NMR spectra, Fourier transform infrared spectra, transmission electron microscopy images, etc., we demonstrated that CNCs could be successfully surface-functionalized with hyperbranched polymers. The drug release behavior, cell viability, and cell imaging results suggested that EPI could be released from these CNCs-based carriers with pH-responsive behavior and that the resultant drug-containing complexes could maintain their anticancer capability. In conclusion, a novel strategy based on anionic polymerization has been developed for direct surface functionalization of CNCs with pH-responsive hyperbranched polymers. These resultant functionalized CNCs could serve as promising candidates for controlled intracellular drug-delivery applications.
Hydroxyapatite (HAP) materials are widely applied as biomedical materials due to their stable performance, low cost, good biocompatibility and biodegradability. Here, a green, fast and efficient strategy was designed to construct a fluorescent nanosystem for cell imaging and drug delivery based on polyethyleneimine (PEI) and functionalized HAP via simple physical adsorption. First, HAP nanorods were functionalized with riboflavin sodium phosphate (HE) to provide them with fluorescence properties based on ligand-exchange process. Next, PEI was attached on the surface of HE-functionalized HAP (HAP-HE@PEI) via electrostatic attraction. The fluorescent HAP-HE@PEI nanosystem could be rapidly taken up by NIH-3T3 fibroblast cells and successfully applied to for cell imaging. Additionally, doxorubicin hydrochloride (DOX) containing HAP-HE@PEI with high loading capacity was prepared, and in-vitro release results show that the maximum release of DOX at pH 5.4 (31.83%) was significantly higher than that at pH 7.2 (9.90%), which can be used as a drug delivery tool for cancer therapy. Finally, HAP-HE@PEI as the 3D inkjet printing ink were printed with GelMA hydrogel, showing a great biocompatible property for 3D cell culture of RAW 264.7 macrophage cells. Altogether, because of the enhanced affinity with the cell membrane of HAP-HE@PEI, this green, fast and efficient strategy may provide a prospective candidate for bio-imaging, drug delivery and bio-printing.
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