3D Printing of Biocompatible Shape-Memory Double Network Hydrogels

Abstract

Shape-memory hydrogels can be fixed to an arbitrary temporary shape and recover their permanent shape under appropriate stimulus conditions. Their shape-memory behavior and biocompatible mechanical and chemical properties impart them with many biomedical applications. However, like most hydrogels, traditional shape-memory hydrogels suffer from intrinsic brittleness due to the network inhomogeneity and high water content. In the past, the double network (DN) scheme has been proved a robust method to improve the mechanical performance of hydrogels. Although 3D printing of DN hydrogels has been realized before, 3D printable shape-memory DN hydrogels have not been achieved so far. In this work, we propose a one-pot method for printing a biocompatible shape-memory DN hydrogel via fused deposition method. The two networks incorporated to the hydrogel ink are polyacrylamide (PAAm) and gelatin. The PAAm network is covalently cross-linked and responsible for the permanent shape, while the gelatin network has thermoreversible cross-links and responsible for fixing the temporary shape. The DN hydrogel shows 3 to 7 times higher fracture toughness than a single network gelatin or PAAm hydrogel and can be fixed to 300% of its original length under tension and 10% of its original thickness under compression. The ink compositions are tuned for optimal printing quality and shape-memory performance. The robust mechanical integrity and dramatic shape transformation capability of the 3D-printed shape-memory DN hydrogel will open-up new potential applications in transformative medical robots and self-deployable devices.

Progress in Gelatin as Biomaterial for Tissue Engineering

“…Within this framework, gelatin is classified as a smart biomaterial, owing to its ability to reshape itself in changing physical conditions such as wettability, or electric or magnetic field. The latter holds great promise in bone tissue engineering applications as it is a stimuli-responsive polymer, which can lead to rigorous drug delivery as well as opening up the opportunity for biosensing and monitoring [44,45] Pharmaceutics 2022, 14, x FOR PEER REVIEW 5 of 19 with electrical stimuli. The system responded to electrical changes, and cells were lined to form fibrous structures that simulated skeletal muscle (Figure 2b).…”

“…Within this framework, gelatin is classified as a smart biomaterial, owing to its ability to reshape itself in changing physical conditions such as wettability, or electric or magnetic field. The latter holds great promise in bone tissue engineering applications as it is a stimuli-responsive polymer, which can lead to rigorous drug delivery as well as opening up the opportunity for biosensing and monitoring [44,45] Another strategy to improve bone tissue regeneration is the incorporation of inorganic molecules within gelatin using different approaches and technologies such as 3D bioprinting [19,46,47]. In this way, it is possible to merge the latest technological advances, which provides homogeneity and accuracy to the system, with gelatin and inorganic molecules present in the mineralized part of the bone [22].…”

Photo-responsive hydrogel-based re-programmable metamaterials

“…Hydrogels are comprised of cross-linked polymer networks and solvents. Their good bio-compatibility (41,42) and large deformability (43,44) impart them with many important applications such as drug delivery (45), wound dressing (46), arti cial organ (47), soft sensors, actuators, and soft robots (48, 49). Many hydrogels are made stimuli-responsive that can swell or shrink in response to external stimuli such as temperature (50), humidity (51), pH (52), light (53)(54)(55), electric eld (56), and other information inputs (57).…”

Development of a 3D Printable and Highly Stretchable Ternary Organic-Inorganic Nanocomposite Hydrogel

“…The developed POx-based hydrogel in this work is studied with respect to printability and mechanical flexibility, and exhibited a comparable performance to the hydrogels prepared with traditional materials which have achieved significant achievements in tissue engineering and soft robotics but requiring additional support bath or rheology modifiers to realize the printability. [34][35][36] In this system, the thermogelling POx-b-POzi copolymer acts as the first and rapid-response physical network, which not only gives the hydrogel a satisfactory printability but also maintains the integrity of the printing structures temporarily. The second component PDMAA allows the formation of the interpenetrating network (IPN) hydrogel to improve significantly its long-term stability and mechanical properties.…”