Highly Flexible Multifunctional Biopaper Comprising Chitosan Reinforced by Ultralong Hydroxyapatite Nanowires

Highly flexible multifunctional biopaper comprising ultralong hydroxyapatite nanowires and chitosan (UHANWs/CS), with high weight fractions of ultralong hydroxyapatite nanowires (UHANWs) up to 100 wt. %, is reported. The as-prepared UHANWs/CS composite biopaper has high flexibility and superior mechanical properties even when the weight fraction of UHANWs is as high as 90 wt. %. In contrast, the control samples consisting of hydroxyapatite nanorods and chitosan (HANRs/CS) with weight fractions of HANRs higher than 66.7 wt.% cannot be obtained in the form of the flexible membrane. The ultimate tensile strength and Young's modulus of the UHANWs/CS composite biopaper are about 3.2 times and 4.3 times those of the HANRs/CS membrane with the same weight fraction of HAP, respectively. In addition, the UHANWs/CS composite biopaper (90 wt. % UHANWs) can be used for color printing using a commercial ink-jet printer. The surface wettability, swelling ratio, and water vapor transmission rate of the UHANWs/CS composite biopaper are adjustable by changing the addition amount of UHANWs. In vitro experiments indicate that the UHANWs/CS composite biopaper has good degradability, high acellular bioactivity and high biocompatibility. The as-prepared UHANWs/CS composite biopaper is therefore promising for various biomedical applications such as wound dressing, bone-fracture fixation, and bone-defect repair.