3D Gel Structure Research Articles

Abstract 1505: Unraveling diepafitaxis: Investigating ECM stiffness and microarchitecture in tumor spheroid migration

Abstract Background: Metastasis, accounting for up to 90% of cancer-related deaths, remains one of the least understood aspects of cancer progression. Recent research has shifted focus from solely biological hallmarks to the physical characteristics of cancer, such as the stiffness and microarchitecture of the extracellular matrix (ECM), which play pivotal roles in metastatic advancement. We previously introduced the concept of 'diepafitaxis' to describe a unique mechanism driving the interface-mediated tropism of tumor spheroids at matrix-surface boundaries. This phenomenon suggests that cancer cells preferentially migrate along a 2D 'interfacial' track formed by heterogeneous 3D ECM structures, facilitating invasion and dispersion. However, the exact mechanisms by which interfacial components, stiffness, and structural attributes influence cell movement remain debated. To investigate this, we have developed a microfluidic chip with a precisely controlled stiffness of the hydrogel matrix-matrix interface (MMI), aiming to shed light on specific diepafitatic behaviors. Method: We developed a polydimethylsiloxane (PDMS)-based microfluidic chip using a traditional photolithographic process. This chip features three channels, with the center channel designed to precisely control various MMI stiffness combinations: stiff vs soft (t-o), stiff vs stiff (t-t) and soft vs soft (o-o). MDA-MB-231 breast cancer spheroids (BCS), representing an in vitro tumor model, were embedded in the top gel. We observed the dynamic behavior of these cancer spheroids over a 24-h period using differential interference contrast (DIC) microscopy. Result: The study revealed that BCS exhibited more pronounced dispersion in a soft homogeneous ECM compared to a stiff ECM in 3D environments. Interestingly, when BCS were near an MMI, a stiffer MMI (t-t) significantly enhanced BCS invasiveness and single-cell migration, more so than t-o, and notably more than o-o. We previously described this phenomenon as '2.5D migration,' where cells migrate in a ventral 2D manner within a sandwiched 3D gel structure. This diepafitatic behavior was further analyzed for its response to gravitational effects and the influence of chemotaxis, induced by introducing VEGF on one side of the microfluidic channel. Conclusion: Conclusively, our study demonstrates that the stiffness and structure of the ECM, particularly at MMI, significantly influence the invasive behavior and migration patterns of BCS, underscoring the critical role of mechanical microenvironments in cancer metastasis. Citation Format: Hsiang-Pei Chen, Ya-Chu Tsai, Ting-Yuan Tu. Unraveling diepafitaxis: Investigating ECM stiffness and microarchitecture in tumor spheroid migration [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1505.

Rheological Tunable Magnetic Fluids with Long-Term Stability.

Magnetic fluids have advantages such as flow ability and solid-like property in strong magnetic fields, but have to suffer from the tradeoff between suspension stability and flow resistance. In this work, a thermal/photo/magnetorheological water-based magnetic fluid is fabricated by using oleic acid-coated Fe3 O4 (Fe3 O4 @OA) nanoparticles as the magnetic particles and the amphiphilic penta block copolymer (PTMC-F127-PTMC)-based aqueous solution as the carrier fluid. Due to the hydrophobic self-assembly between Fe3 O4 @OA and PTMC-F127-PTMC, the Newtonian-like magnetic fluid has outstanding long-term stability and reversible rheological changes between the low-viscosity flow state and the 3D gel structure. In the linear viscoelastic region, the viscosity exhibits an abrupt increase from below 0.10Pa s at 20°C to ≈1.3×104 Pa s at 40°C. Benefitting from the photothermal and magnetocaloric effects of the Fe3 O4 @OA nanoparticles, the rheological change process also can be controlled by near infrared light and alternating magnetic field, which endows the magnetic fluid with the applications in the fields of mobile valves, moveable switches, buffer or damping materials in sealed devices, etc.

Preparation and characterization of chemically TEMPO-oxidized and mechanically disintegrated sacchachitin nanofibers (SCNF) for enhanced diabetic wound healing

TEMPO-oxidization and mechanical disintegration were utilized to develop sacchachitin nanofibers (SCNF) with a 3D gel structure for being an ideal scaffold. Mechanically disintegrated SCNF (MDSCNF) with NanoLyzer® at 20,000 psi for 5 cycles and TEMPO-oxidized SCNF (TOSCNF) produced with 5.0 and 10.0 mmole NaClO/g SC was designated as SCN5, T050SC, and T100SC, respectively. All 2% MDSCNF suspensions were demonstrated to be in gel form, while all except T100SC of 2% TOSCNF suspensions showed to be wet fiber-like hydrogel. In diabetic wound healing study, both SCN5 and T050SC incorporated in AMPS (2-acrylamide-2-methyl-propane sulfonate)-based wound dressing were showed to accelerate diabetic wound healing forming nearly the same as normal tissues. T050SC/H further provided the healed wound with growth of sweat glands and hair follicles indicating the wound had healed as functional tissue. Conclusively, TEMPO-oxidized SCNF-based hydrogel scaffolds showed greater potentials in tissue regeneration due to its unique physical and chemical properties.

Gelation in solutions of low deacetylated chitosan initiated by high shear stresses

A new process of mechanically initiated formation of chitosan physical hydrogels in aqueous solution, without a cross-linking agent, was studied. Physical hydrogel is formed by mechanical activation of solutions of chitosan with a low deacetylation degree (58%) in situ in a rotor-stator device for 10 s. The formation of 3D gel structure has been proven by rotational viscometry and dynamic rheometry methods. Gelation is caused by the action of high shear stresses initiating the formation of hydrophobic associates from residual chitinous blocks. In comparison with the films from untreated chitosan, the films obtained by drying hydrogel have a lower degree of crystallinity and a higher sorption capacity towards water vapor and Cu2+ ions, as well as the ability to retain up to 5000% of water during re-swelling without destruction.

Solvothermal fabrication of TiO2/sepiolite composite gel with exposed {0 0 1} and {1 0 1} facets and its enhanced photocatalytic activity

A novel TiO2/sepiolite composite gel (TiSG) was fabricated in the presence of cetyltrimethylammonium bromide (CTAB) through a simple solvothermal reaction in an acetic acid–water solvent. A homogeneous anchoring of TiO2 nanoparticles with exposed {0 0 1} and {1 0 1} facets on sepiolite nanofibers was achieved. CTAB content, solvothermal temperature/time, and HAc content play crucial roles in the morphological and facet formation of TiSG. A possible mechanism for the formation of TiSG was further proposed. CTAB as capping/shape-controlling agent can strongly bind to the more reactive (0 0 1) facet of TiO2 and then mitigate the thermodynamically favored (0 0 1) plane growth. Eventually, the truncated octahedral TiO2 was obtained by controlling the growth rates in 〈0 0 1〉 and 〈1 0 1〉 directions. Sepiolite as a cross-linking agent provides sufficient crosslinking sites for TiO2 to induce three-dimensional (3D) network formation, thereby generating the composite gel. The synthesized TiSG samples were then used as photocatalysts, which exhibited increased methyl orange removal under UV–vis light (350–780 nm) by the synergistic effect of adsorption and in-situ photocatalytic degradation as compared to P25 and bare TiO2. The excellent photocatalytic performance of TiSG was mainly ascribed to the formations of 3D gel structure and surface heterojunctions between (0 0 1) and (1 0 1) facets.

The development of cell-adhesive hydrogel for 3D printing

Biofabrication has gained tremendous attention for manufacturing functional organs or tissues. To fabricate functional organs or tissues, it is necessary to reproduce tissue-specific micro to macro structures. Previously, we developed a custom-made 3D-bioprinter with the capability to print and fabricate 3D complicated hydrogel structures composed of living cells. Through the gelation reaction, fine and complicated 3D gel structures can be fabricated via layer by layer printing. Alginate hydrogel has been used mainly due to its good fabricating properties. However, it is not a reliable platform for tissue regeneration because of its inadequate cell-adhesiveness. Therefore, our laboratory is interested to explore more suitable hydrogels for bioprinting and 3D tissue fabrication. In this study, we tried to fabricate 3D gel structures with enough cell-adhesive properties. We focused on hydrogel formation through enzymatic reaction by incorporating materials bearing phenolic hydroxyl moieties and horseradish peroxidase. We examined Alg-Ph and Alg-Ph/Gelatin-Ph gels. We used a mixed solution of applied materials as bioink and printed into H2O2 solution. We successfully fabricated the 3D gel sheet structures including fibroblasts cultures. Fibroblast proliferation and viability were also observed in the 3D gel sheet for more than one week. In conclusion, the hydrogel obtained through enzymatic reaction is a biocompatible bioink material which can be applied to fabricate 3D cell-adhesive gel structures using a 3D-bioprinter.

Tough Hydrogels with Programmable and Complex Shape Deformations by Ion Dip‐Dyeing and Transfer Printing

Stimuli‐responsive hydrogels with high mechanical strength, programmable deformation, and simple preparation are essential for their practical applications. Here the preparation of tough hydrogels with programmable and complex shape deformations is reported. Janus hydrogels with different compositions and hydrophilic natures on the two surfaces are first prepared, and they exhibit reversible bending/unbending upon swelling/deswelling processes. More impressively, the deformation rate and extent of the hydrogels can further be easily controlled through an extremely simple and versatile ion dip‐dyeing (IDD) and/or ion transfer printing (ITP) method. By selectively printing proper patterns on 1D gel strips, 2D gel sheets and 3D gel structures, the transformations from 1D to 2D, 2D to 3D, and 3D to more complicated 3D shapes can be achieved after swelling the ion‐patterned hydrogels in water. The swelling‐deformable Janus and ion‐patterned hydrogels with high mechanical strengths and programmable deformations can find many practical applications, such as soft machines.

Carbon xerogels as model materials: toward a relationship between pore texture and electrochemical behavior as anodes for lithium-ion batteries

The mechanisms of Li+ insertion in porous hard carbons used as anodes for Li-ion batteries are still a matter of debate, especially considering the divergence of electrochemical performances observed in the literature. Since these materials usually exhibit several levels of porosity, the pore texture versus electrochemical behavior relationship is difficult to establish. In this paper, we propose to use carbon xerogels, prepared from aqueous resorcinol–formaldehyde mixtures, as model materials for Li-ion battery anodes to study the influence of the pore texture on the overall electrochemical behavior. Indeed, carbon xerogels are described as microporous nodules linked together to form meso- or macroporous voids inside a 3D gel structure; the size of these voids can be tuned by changing the synthesis conditions without affecting other parameters such as the micropore volume. The materials are chosen so as to obtain identical average particle sizes, homogeneous coatings with similar thicknesses, and a comparable surface chemistry. The electrochemical behaviors of carbon xerogels as Li-ion anodes are correlated with the surface accessible to the electrolyte and are not dependent on the total specific surface area calculated by the BET method from nitrogen adsorption isotherms. The key parameter proposed to understand their behavior is the external surface area of the nodules, which corresponds to the surface of the meso/macropores.

A rapid polymerisation process realizing 3D biocompatible structures in a microfluidic channel suitable for genetic analysis

Surface probe immobilisation is a complex and time consuming task undertaken prior to microfluidic integration, this requires surface functionalisation, biomolecule spotting, incubation and blocking steps. Traditional bonding techniques (anodic, thermal, etc.) or adhesives (UV cured) used to seal fluidic systems may denature biomolecules due to high temperature or vapour effects, thus bonding techniques such as thin film laminate or PDMS are used to seal systems, with substrate-fluidic alignment required prior to bonding. We propose a technique allowing probe DNA molecules to be immobilised in a sealed microfluidic system using (3D) hydrogel structures without any alignment steps. A prepolymer solution is introduced to the channels where photo-polymerisation is undertaken forming 3D structures covalently attached to the channel surface. We use a photo-initiated prepolymer material poly-ethylene-glycol (PEG) to form structures containing probe DNA. This process is fast compared to conventional biomolecule immobilisation techniques and is also biocompatible, this direct write approach removes overnight immobilisation/incubation of the probe DNA, it also facilitates immobilisation within a sealed fluidic system where conventionally DNA probe spots must be immobilised prior to channel sealing. We consider the transport of target DNA from bulk analyte to the 3D gel structure and evaluate hybridisation within the microfluidic system.

Development of a Three-Dimensional Bioprinter: Construction of Cell Supporting Structures Using Hydrogel and State-Of-The-Art Inkjet Technology

We have developed a new technology for producing three-dimensional (3D) biological structures composed of living cells and hydrogel in vitro, via the direct and accurate printing of cells with an inkjet printing system. Various hydrogel structures were constructed with our custom-made inkjet printer, which we termed 3D bioprinter. In the present study, we used an alginate hydrogel that was obtained through the reaction of a sodium alginate solution with a calcium chloride solution. For the construction of the gel structure, sodium alginate solution was ejected from the inkjet nozzle (SEA-Jet, Seiko Epson Corp., Suwa, Japan) and was mixed with a substrate composed of a calcium chloride solution. In our 3D bioprinter, the nozzle head can be moved in three dimensions. Owing to the development of the 3D bioprinter, an innovative fabrication method that enables the gentle and precise fixation of 3D gel structures was established using living cells as a material. To date, several 3D structures that include living cells have been fabricated, including lines, planes, laminated structures, and tubes, and now, experiments to construct various hydrogel structures are being carried out in our laboratory.