Refine
Document Type
Language
- English (7)
Has Fulltext
- yes (7)
Is part of the Bibliography
- yes (7)
Keywords
- bioinspired adhesives (1)
- biomaterials (1)
- catechol-functionalized polymers (1)
- elastomers (1)
- extrusion printing (1)
- hydrogels (1)
- nanocomposite (1)
- optical fibers (1)
- optical waveguides (1)
- photoactivation (1)
Scientific Unit
Advances in optogenetics and the increasing use of implantable devices for therapies and health monitoring are driving demand for compliant, biocompatible optical waveguides and scalable methods for their manufacture. Molding, thermal drawing, and dip-coating are the most prevalent approaches in recent literature. Here the authors demonstrate that extrusion printing at room temperature can be used for continuous fabrication of compliant optical waveguides with polydimethylsiloxane (PDMS) core and crosslinked Pluronic F127-diacrylate (Pluronic-DA) cladding. The optical fibers are printed from fluid precursor inks and stabilized by physical interactions and photoinitiated crosslinking in the Pluronic-DA. The printed fibers show optical loss values of 0.13–0.34 dB cm–1 in air and tissue within the wavelength range of 405–520 nm. The fibers have a Young's Modulus (Pluronic cladding) of 150 kPa and can be stretched to more than 5 times their length. The optical loss of the fibers shows little variation with extension. This work demonstrates how printing can simplify the fabrication of compliant and stretchable devices from materials approved for clinical use. These can be of interest for optogenetic or photopharmacology applications in extensible tissues, like muscles or heart.
A solid-to-hollow evolution in macroscopic structure is challenging in synthetic materials. Herein we report a fundamentally new strategy for guiding macroscopic, unidirectional shape-evolution of materials without compromising the material’s integrity, based on the creation of a field with a “swelling pole” and a “shrinking pole” to drive polymers to disassemble, migrate, and resettle in the targeted region. We demonstrate this concept by using dynamic hydrogels containing anchored acrylic ligands and hydrophobic long alkyl chains. Adding water molecules and ferric ions (Fe3+) to induce a swelling-shrinking field transforms the hydrogels from solid to hollow. The strategy is versatile in the generation of various closed hollow objects including spheres, helix tubes, and cubes with different diameters, for different applications.
In this paper we explore the printability of reversible networks formed by catechol functionalized PEG solutions and metal cations (Al3+, Fe3+ or V3+). The printability and shape fidelity were dependent on the ink composition (metal ion type, pH, PEG molecular weight) and printing parameters (extrusion pressure and printing speed). The relaxation time, recovery rate and viscosity of the inks were analyzed in rheology studies and correlated with thermodynamic and ligand exchange kinetic constants of the dynamic bonds and the printing performance (i.e. shape fidelity of the printed structures). The relevance of the relaxation time and ligand exchange kinetics for printability was demonstrated. Cells seeded on the materials crosslinked with Al3+, Fe3+ ions were viable and revealed well-spread morphologies during 7 day culture, indicating the potential of the formulations to be used as inks for cell encapsulation. The proposed dynamic ink design offers significant flexibility for 3D bioprinting, and enables straightforward adjustment of the printable formulation to meet application-specific needs.
Lighting the Path: Light Delivery Strategies to Activate Photoresponsive Biomaterials In Vivo
(2021)
Photoresponsive biomaterials are experiencing a transition from in vitro models to in vivo demonstrations that point toward clinical translation. Dynamic hydrogels for cell encapsulation, light-responsive carriers for controlled drug delivery, and nanomaterials containing photosensitizers for photodynamic therapy are relevant examples. Nonetheless, the step to the clinic largely depends on their combination with technologies to bring light into the body. This review highlights the challenge of photoactivation in vivo, and presents strategies for light management that can be adopted for this purpose. The authors’ focus is on technologies that are materials-driven, particularly upconversion nanoparticles that assist in “direct path” light delivery through tissue, and optical waveguides that “clear the path” between external light source and in vivo target. The authors’ intention is to assist the photoresponsive biomaterials community transition toward medical technologies by presenting light delivery concepts that can be integrated with the photoresponsive targets. The authors also aim to stimulate further innovation in materials-based light delivery platforms by highlighting needs and opportunities for in vivo photoactivation of biomaterials.
To implement light-based diagnosis and therapies in the clinic, implantable patient-friendly devices that can deliver light inside the body while being compatible with soft tissues are needed. This Thesis presents the development of optical waveguides for guiding light into tissue, obtained by printing technologies from three different polymer combinations. Firstly, D,L-dithiothreitol (DTT) bridged PEG diacrylate were synthesized and printed into waveguides, which exhibited tunable mechanical properties and degradability, and low optical losses (as low as 0.1 dB cm-1 in visible range). Secondly, degradable waveguides from amorphous poly(D,L-lactide) and derived copolymers were developed by printing, which showed elasticity at body temperature and could guide VIS to NIR light in tissue for tens of centimeters. At last, soft and stretchable optical waveguides consisting of polydimethylsiloxane (PDMS) core and acrylated Pluronic F127 cladding were fabricated by coaxial extrusion printing, which could be stretched to 4 times of their length and showed optical loss values in tissue as low as 0.13 -0.34 dB cm-1 in the range of 405-520 nm. For proof-of-concept, above printed optical waveguides were used to deliver light across 5-8 cm tissue to remotely activate photochemical processes in in vitro cell cultures. The presented work exemplifies how rational study of medically approved biomaterials can lead to useful and cost-effective optical components for light applications.
Mechanically Reinforced Catechol-Containing Hydrogels with Improved Tissue Gluing Performance
(2017)
In situ forming hydrogels with catechol groups as tissue reactive functionalities are interesting bioinspired materials for tissue adhesion. Poly(ethylene glycol) (PEG)–catechol tissue glues have been intensively investigated for this purpose. Different cross-linking mechanisms (oxidative or metal complexation) and cross-linking conditions (pH, oxidant concentration, etc.) have been studied in order to optimize the curing kinetics and final cross-linking degree of the system. However, reported systems still show limited mechanical stability, as expected from a PEG network, and this fact limits their potential application to load bearing tissues. Here, we describe mechanically reinforced PEG–catechol adhesives showing excellent and tunable cohesive properties and adhesive performance to tissue in the presence of blood. We used collagen/PEG mixtures, eventually filled with hydroxyapatite nanoparticles. The composite hydrogels show far better mechanical performance than the individual components. It is noteworthy that the adhesion strength measured on skin covered with blood was >40 kPa, largely surpassing (>6 fold) the performance of cyanoacrylate, fibrin, and PEG–catechol systems. Moreover, the mechanical and interfacial properties could be easily tuned by slight changes in the composition of the glue to adapt them to the particular properties of the tissue. The reported adhesive compositions can tune and improve cohesive and adhesive properties of PEG–catechol-based tissue glues for load-bearing surgery applications
Abstract Optogenetics and photonic technologies are changing the future of medicine. To implement light-based therapies in the clinic, patient-friendly devices that can deliver light inside the body while offering tunable properties and compatibility with soft tissues are needed. Here extrusion printing of degradable, hydrogel-based optical waveguides with optical losses as low as 0.1 dB cm−1 at visible wavelengths is described. Core-only and core-cladding fibers are printed at room temperature from polyethylene glycol (PEG)-based and PEG/Pluronic precursors, and cured by in situ photopolymerization. The obtained waveguides are flexible, with mechanical properties tunable within a tissue-compatible range. Degradation times are also tunable by adjusting the molar mass of the diacrylate gel precursors, which are synthesized by linking PEG diacrylate (PEGDA) with varying proportions of DL-dithiothreitol (DTT). The printed waveguides are used to activate photochemical and optogenetic processes in close-to-physiological environments. Light-triggered migration of cells in a photoresponsive 3D hydrogel and drug release from an optogenetically-engineered living material by delivering light across >5 cm of muscle tissue are demonstrated. These results quantify the in vitro performance, and reflect the potential of the printed degradable fibers for in vivo and clinical applications.
