Abstract
Nanocomposite hydrogels capable of undergoing manufacturing process have recently attracted attention in biomedical applications due to their desired mechanical properties and high functionality. 3D printing nanocomposite hydrogels of hyaluronic acid (HA)/nanodiamond (ND) revealed that the addition of ND with the low weight ratio of 0.02 wt% resulted in higher compressive force and gel breaking point, compared with HA only nanocomposites. These HA nanocomposite hydrogels loaded with surface functionalized ND allowed for the enforced compressive stress to be tuned in a pH-dependent manner. HA nanocomposite hydrogels with ND-OH at pH 8 showed an increase of 1.40-fold (0.02%: 236.18 kPa) and 1.37-fold (0.04%: 616.72 kPa) the compressive stress at the composition of 0.02 wt% and 0.04 wt, respectively, compared to those of ND-COOH (0.02%: 168.31 kPa, 0.04%: 449.59 kPa) at the same pH. Moreover, the compressive stress of HA/ND-OH (0.04 wt%) at pH 8 was mechanically enhanced 1.29-fold, compared to that of HA/ND-OH (0.04 wt%) at pH 7. These results indicate that the tunable buffering environment and interaction with the long chains of HA at the molecular level have a critical role in the dependency of the mechanical properties on pH. Due to the pH stability of the ND-OH nanophase, filament-based processing and layer-based deposition at microscale attained enforced mechanical properties of hydrogel. Fine surface tuning of the inorganic ND nanophase and controlled 3D printing leads to improved control over the pH-dependent mechanical properties of the nanocomposite hydrogels reported herein.
Highlights
Three-dimensional (3D) printing of biomaterials has gained attention in the pharmaceutics to direct development toward customized therapeutics that increase patient compliance
To prepare nanocomposite hydrogel precursors, 0.02 wt% carboxylated or hydroxyl ND were mixed with 2 wt% of Methacrylated hyaluronic acid (MeHA) at pH 7 and pH 8
The nanocomposite hyaluronic acid (HA) hydrogel precursors showed higher viscosity at pH 8, compared to those at pH 7. Rheological characteristics such as viscosity may vary depending on the degree of polymerization of HA, but by using ND, it was possible to form a viscosity suitable for printing despite the use of a lower content of HA
Summary
Three-dimensional (3D) printing of biomaterials has gained attention in the pharmaceutics to direct development toward customized therapeutics that increase patient compliance. Computation-based manufacturing processes, including tablets [1], medical devices [2, 3], tissue engineering [4,5,6], and tumor modeling [7] have benefited from 3D printing. Modified nanocomposite hydrogels with enhanced mechanical and functional properties have been beneficial in the fields of tissue engineering, medical devices, and depot formulation. Enhanced biomaterials and natural biopolymers have been composited with metal [15], carbon based materials [15,16,17,18,19], glass [20,21,22], cellulose crystal [23, 24], and clay [25, 26] to form nanocomposites for a variety of applications. The specific functionality granted by nanocomposite hydrogels with inorganic materials would lead to improved electrical conductivity [27, 28], energy absorbance [29,30,31], as well as cellular [18, 26, 32, 33] and protein interactions [2], in addition to mechanical enhancement
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