Patterning porosity in hydrogels by arresting phase separation

Poly (ethylene glycol) (PEG) hydrogels have been used extensively in biological and tissue engineering, because of their outstanding biocompatibility and processability. However, it is not yet possible to process soft materials like PEG hydrogels with the requisite precision and throughput needed to recapitulate macroscopic biological tissue with control over every hierarchical scale. In this study, porous PEG hydrogels are processed by a phase separation method and patterned in a single photolithographic step. The thermodynamics of the temperature triggered spinodal decomposition of a ternary mixture of water, salt, and polymer are studied resulting in a ternary phase diagram and a spinodal temperature plot. Importantly, the state of porosity can be frozen by exposing the hydrogel to UV light to form a crosslinked hydrogel network. The average pore size can be tuned by changing delay between the application of heat and UV exposure. By utilizing grey-scale photomasks, a single process can be used to define regions of pure hydrogel, porous hydrogel with a programmed average pore size, and blank substrate with no hydrogel. In addition to representing a combination of a top-down and a bottom-up processes that enables the realization of complex samples, the simplicity of this process and the versatility of the resultant patterns could provide a useful capability for the definition of hydrogel samples for the development of advanced biomaterials

Fabrication of drug-loaded hydrogels with stereolithographic 3D printing

3D printing (3DP) technologies have been attracting much recent interest as new methods of fabricating medicines and medical devices. Of the many types of 3DP available, stereolithographic (SLA) printing offers the unique advantage of being able to fabricate objects by cross-linking resins to form networked polymer matrices. Because water can be entrapped in these matrices, it is possible in principle to fabricate pre-wetted, drug-loaded hydrogels and devices. Here, SLA printing was used to prepare ibuprofen-loaded hydrogels of cross-linked polyethylene glycol diacrylate. Hydrogels containing up to 30% w/w water, and 10% w/w ibuprofen, were successfully printed. Dissolution profiles showed that drug release rates were dependent on water content, with higher water content hydrogels releasing drug faster. The conclusion is that SLA 3DP offers a new manufacturing route to pharmaceutical hydrogels

Poly(Ethylene glycol) diacrylate hydrogel with silver nanoclusters for water Pb(II) ions filtering

Poly(ethylene glycol) diacrylate (PEGDA) hydrogels modified with luminescent silver nanoclusters (AgNCs) are synthesized by a photo-crosslinking process. The hybrid material thus obtained is employed to filter Pb(II) polluted water. Under the best conditions, the nanocomposite is able to remove up to 80–90% of lead contaminant, depending on the filter composition. The experimental results indicate that the adsorption process of Pb(II) onto the modified filter can be well modeled using the Freundlich isotherm, thus revealing that the chemisorption is the driving process of Pb(II) adsorption. In addition, the parameter n in the Freundlich model suggests that the adsorption process of Pb(II) ions in the modified hydrogel is favored. Based on the obtained remarkable contaminant uptake capacity and the overall low cost, this hybrid system appears to be a promising sorbent material for the removal of Pb(II) ions from aqueous media

Study on the Chemical and Mechanical Stability of Polymer Nanofluidic Biosensors

Polymer nanofluidic devices have great potential to replace silicon (Si) and glass-based nanofluidic devices in biomedical applications due to their advantages such as low material and fabrication cost, various physicochemical properties, well-developed surface modification protocol, and low electrical noises for electrical measurements. In nanofluidic sensing applications, single molecules such as DNA are introduced into the fabricated nanochannel or nanopore, measuring their physicochemical properties optically or electrically. The properties of materials for nanofluidic devices have a significant role in the performance of the devices, such as DNA translocation and device stability. Among several nanoscale fluidic physics, surface charge density is a key material property of nanofluidic devices related to the capture of single molecules because it determines the magnitude of electrophoresis and electroosmosis in the nanostructures. To facilitate the capture of single molecules into nanofluidic devices, polymers containing poly(ethylene glycol) (PEG) are preferred due to their low surface charge density and reduction of surface fouling of biomolecules. However, a drawback of PEG-based polymers is a weak chemical and mechanical stability due to swelling effect and low surface hardness when in contact with electrolytes. This work presents an improvement in the chemical and mechanical stability of a nanofluidic device formed in poly(ethylene glycol) diacrylate (PEGDA), a PEG-based UV resin for UV-NIL, by adding a cross-linking agent (e.g. TMPTA). First, we defined the surface charge density of polymers such as PMMA, COC 6013, and PEGDA with the different O2 treatment time because these three polymers have low surface charge density compared to other polymers. Then, we studied the effect of the cross-linking agent content on the surface charge density of PEGDA-TMPTA material and on the translocation of DNA molecules through the nanopore. Five different compositions of PEGDA resins with varied amounts of a cross-linking 1 agent, trimethylolpropane triacrylate (TMPTA), were used (pure PEGDA, ratio 5:1, 1:1, 1:2, and 1:5). The surface hardness of PEGDA-TMPTA resin increases according to the crosslinking agent concentration from 139 MPa (pure PEGDA resin) to 205 MPa (1:5 resin). To be specific, the surface hardnesses of pure PEGDA, 5:1, 1:1, 1:2, and 1:5 were 139 MPa, 158 MPa, 196 GPa, 204 MPa, and 205 MPa, respectively. The surface charge densities at 0.001M KCl (pH 8.0) of pure PEGDA, 5:1, 2:1, 1:1, and 1:5 were −9.5 ± 0.09 / ! , −7.9 ± 0.97 / ! , −7.1 ± 1.06 / ! , −7.5 ± 1.10 / ! , and −7.4 ± 0.57 / ! , respectively. These observed surface charge densities of PEGDA-TMPTA resin exhibit a decreasing trend which is beneficial for DNA translocation into nanostructures. In conclusion, this approach has a positive influence on the chemical and mechanical stability of nanofluidic devices concerning DNA translocation into a nanopore or a nanochannel

Rapid Fabrication of Hydrogel Microstructures Using UV-Induced Projection Printing

Fabrication of hydrogel microstructures has attracted considerable attention. A large number of applications, such as fabricating tissue engineering scaffolds, delivering drugs to diseased tissue, and constructing extracellular matrix for studying cell behaviors, have been introduced. In this article, an ultraviolet (UV)-curing method based on a digital micromirror device (DMD) for fabricating poly(ethylene glycol) diacrylate (PEGDA) hydrogel microstructures was presented. By controlling UV projection in real-time using a DMD as digital dynamic mask instead of a physical mask, polymerization of the pre-polymer solution could be controlled to create custom-designed hydrogel microstructures. Arbitrary microstructures could also be fabricated within several seconds (<5 s) using a single-exposure, providing a much higher efficiency than existing methods, while also offering a high degree of flexibility and repeatability. Moreover, different cell chains, which can be used for straightforwardly and effectively studying the cell interaction, were formed by fabricated PEGDA microstructures

Rapid Fabrication of Hydrogel Microstructures Using UV-Induced Projection Printing

Fabrication of hydrogel microstructures has attracted considerable attention. A large number of applications, such as fabricating tissue engineering scaffolds, delivering drugs to diseased tissue, and constructing extracellular matrix for studying cell behaviors, have been introduced. In this article, an ultraviolet (UV)-curing method based on a digital micromirror device (DMD) for fabricating poly(ethylene glycol) diacrylate (PEGDA) hydrogel microstructures was presented. By controlling UV projection in real-time using a DMD as digital dynamic mask instead of a physical mask, polymerization of the pre-polymer solution could be controlled to create custom-designed hydrogel microstructures. Arbitrary microstructures could also be fabricated within several seconds (<5 s) using a single-exposure, providing a much higher efficiency than existing methods, while also offering a high degree of flexibility and repeatability. Moreover, different cell chains, which can be used for straightforwardly and effectively studying the cell interaction, were formed by fabricated PEGDA microstructures