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(A) Photographs of expanded and contracted cylindrical and tube-shaped gels when heated above (contracted) and below (expanded) the LCST. (B) Swelling test of the gels at 37 and 33 1C. (C) SEM characterisation of contracted, top, and expanded, down, gels. (D) Pulsed illumination of the 3D printed AuNR -thermoresponsive gel with the heating plate set to 31 1C and laser density power of 2.5 W cm À2 .
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3D-printed cell models are currently in the spotlight of medical research. Whilst significant advances have been made, there are still aspects that require attention to achieve more realistic models which faithfully represent the in vivo environment. In this work we describe the production of an artery model with cyclic expansive properties, capabl...
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... a NIPAm:PEGDA range of 1 : 0.25-1 : 0.75, suggesting that PEGDA plays a major role regarding the temperature dependence of the modulus (Fig. S2, ESI †). The effect of PEGDA is also observed when altering the molecular weight of the PEGDA employed in the polymer formulation, with a trend of decreasing modulus as the molecular weight is increased (Fig. S3, ESI †). Although these findings suggest that low molecular weight PEGDA provides a more pronounced rheological response to temperature in the copolymer formulation, we observed poor stability in water of 700 Da PEGDAbased hydrogels, and thus the optimal formulation was fixed at a NIPAm:PEGDA (3400 Da) ratio of 1 : 0.5. We subsequently ...
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... macroscale properties of the thermoresponsive gel were studied, focusing on their porosity. Moreover, the cyclic nature of contraction and expansion of the gels was explored. Using a hot-plate heating setup, significant contraction was observed upon heating the thermoresponsive gel above its LCST (Fig. 3A). Indeed, when self-standing 8 cm tall cylinders were printed, a ca. 50% decrease in height was observed above 37 1C. Cyclic swelling studies conducted in aqueous media showed a similar trend; reproducible cycles of expansion and contraction were observed when varying the temperature between 32 1C and 37 1C (Fig. 3B). This behaviour is ...
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... gel above its LCST (Fig. 3A). Indeed, when self-standing 8 cm tall cylinders were printed, a ca. 50% decrease in height was observed above 37 1C. Cyclic swelling studies conducted in aqueous media showed a similar trend; reproducible cycles of expansion and contraction were observed when varying the temperature between 32 1C and 37 1C (Fig. 3B). This behaviour is consistent with the transitioning from hydrophilic to hydrophobic state above the LCST of pNIPAm-based hydrogels, subsequently resulting in expulsion of water and subsequent gel contraction. SEM imaging was used to observe the changes that occurred in the overall microstructure and porosity of the expanded and ...
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... S12, ESI †). When the gels were heated above their LCST, macroscale ripples with small pores were observed. In contrast, at temperatures below their LCST, smoother ripples with significantly larger pores were observed. As can be appreciated, the expanded and contracted states result in impressive differences in the porosity and surface morphology (Fig. 3C). In its contracted form, the surface shows folds measuring ca. 100 mm from crest to crest, and pores measuring o5 mm in ...
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... the starting temperature, controlled by placing the sample on a hot plate. As can be observed in Fig. S15 (ESI †), T max was directly proportional to the starting temperature. Therefore, the optimal heating setup involved pulsed (4s on/16s off) irradiation (2.5 W cm À2 ) of gels maintained at a baseline temperature of 28-30 1C using a heat-plate (Fig. 3D). The cyclic heating process was reproducible over time, suggesting that the system remains stable. Indeed, we observed that the absorbance spectra of the gels did not change significantly after heating (Fig. S16, ESI †), indicating negligible AuNR reshaping and thus confirming the non-invasive character of this technique during ...
Citations
... To create a light-responsive hydrogel, researchers have incorporated nanomaterials, such as gold nanorods, carbon dot nanoparticles (CD NPs), gold-silver nanocores, gold-gold nanoshells, and SiO 2 -gold nanoshells into temperatureresponsive interpenetrating polymer networks. By absorbing light irradiation, the nanoparticles transfer heat to the polymer networks, resulting in a change in the printed structure [58,100,[123][124][125] Lu et al. designed injectable hybrid collagen hydrogels to enhance chondrogenesis by photodynamic therapy (PDT), where collagen was crosslinked with CD NPs using genipin as a linker (termed collagen-genipin-CD NPs (CGN)) [58]. The CGN hydrogel showed increased stiffness due to the cross-linking effect of genipin and the presence of CD NPs and could produce a moderate amount of reactive oxygen species (ROS) through PDT. ...
Bioink composition is a key consideration for the 3D-bioprinting of complex and stable structures used to model tissues and as tissue constructs for regenerative medicine. An emerging and industrially important area of research is the use of micro- and nanofillers to improve bioink performance without dramatically altering the physicochemical properties of the polymeric material that forms the bulk of the printed structure. The purpose of this review is to provide a comprehensive overview of emerging nanomaterial fillers designed to create heterogeneous and composite bioinks for 3D-bioprinting of complex functional tissues. We outline the criteria that must be considered when developing such a bioink and discuss applications where the fillers impart stimuli responsiveness, e.g., when exposed to magnetic fields, electrical fields, and light. We further highlight how the use of such fillers can enable non-destructive imaging to monitor scaffold placement and integrity following implantation.
... Additionally, there is evidence of the potential usage of 4D-printed biomaterials in the engineering of the cardiovascular system. Scientists are currently developing 4D-printed patches to aid heart function after myocardial infarction [89], as well as a model of an artery to study the pathomechanism of cardiovascular diseases [90]. Additionally, there are projects focused on creating 4D-printed heart valve implants [91]. ...
Biomimetic scaffolds imitate native tissue and can take a multidimensional form. They are biocompatible and can influence cellular metabolism, making them attractive bioengineering platforms. The use of biomimetic scaffolds adds complexity to traditional cell cultivation methods. The most commonly used technique involves cultivating cells on a flat surface in a two-dimensional format due to its simplicity. A three-dimensional (3D) format can provide a microenvironment for surrounding cells. There are two main techniques for obtaining 3D structures based on the presence of scaffolding. Scaffold-free techniques consist of spheroid technologies. Meanwhile, scaffold techniques contain organoids and all constructs that use various types of scaffolds, ranging from decellularized extracellular matrix (dECM) through hydrogels that are one of the most extensively studied forms of potential scaffolds for 3D culture up to 4D bioprinted biomaterials. 3D bioprinting is one of the most important techniques used to create biomimetic scaffolds. The versatility of this technique allows the use of many different types of inks, mainly hydrogels, as well as cells and inorganic substances. Increasing amounts of data provide evidence of vast potential of biomimetic scaffolds usage in tissue engineering and personalized medicine, with the main area of potential application being the regeneration of skin and musculoskeletal systems. Recent papers also indicate increasing amounts of in vivo tests of products based on biomimetic scaffolds, which further strengthen the importance of this branch of tissue engineering and emphasize the need for extensive research to provide safe for humansbiomimetic tissues and organs. In this review article, we provide a review of the recent advancements in the field of biomimetic scaffolds preceded by an overview of cell culture technologies that led to the development of biomimetic scaffold techniques as the most complex type of cell culture.
Being a vital organ exposed to the external environment, the lung is susceptible to a plethora of pathogens and pollutants. This is reflected in high incidences of chronic respiratory diseases, which remain a leading cause of mortality world-wide and pose a persistent global burden. It is thus of paramount importance to improve our understanding of these pathologies and provide better therapeutic options. This necessitates the development of representative and physiologically relevant in vitro models. Advances in bioengineering have enabled the development of sophisticated models that not only capture the three-dimensional architecture of the cellular environment but also incorporate the dynamics of local biophysical stimuli. However, such complex models also require novel approaches that provide reliable characterization. Within this review we explore how 3D bioprinting and nanoparticles can serve as multifaceted tools to develop such dynamic 4D printed in vitro lung models and facilitate their characterization in the context of pulmonary fibrosis and breast cancer lung metastasis.
