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Engineering responsive and biomimetic hydrogels for biomedical therapeutic and diagnostic applications

Periodic Reporting for period 2 - BIOGEL (Engineering responsive and biomimetic hydrogels for biomedical therapeutic and diagnostic applications)

Reporting period: 2017-01-01 to 2018-12-31

A large library of building blocks was established, ranging from the molecular level, such as bicyclic peptides, engineered elastin-like recombinamers (ELRs), and modified polymers, to microscale elements, such as microgels. A combination of these biological and synthetic building blocks were applied to construct hybrid macroscopic biointegrative coatings, tissue engineering constructs, and diagnostic devices. The bottom-up synthetic approach to create these novel materials enables easy adjustment for a wide range of applications. Within the project, we discovered new types of highly selective bicyclic peptides for cell adhesion, which were incorporated in 3 different types of three-dimensional (3D) hydrogels, leading to improved cell spreading and growth. Regenerative materials are important to heal damaged or injured tissues in the body. One example is articular cartilage injury, which is a serious clinical problem as it can lead to disabilities and high health care costs when untreated. Within Biogel, different injectable gels were designed to fill irregular cavities and support cell growth and regeneration. However, many hydrogels for 3D cell culture do not efficiently mimic the biological environment of a cell, including the open porous architecture and the mechanical properties. Here, we developed dynamic hydrogels, which can adjust to the needs of the cells and growing tissues, and were employed to study the mechanobiology involved in the interaction between cells and their substrates. In addition to larger hydrogels, small cell-loaden micron-scale microgels were produced, which can be injected as cell transplant. The microgels protect the cells and reduce their migration away from the injury site. In addition to 3D regenerative materials, medical polymer coatings were tested to improve the efficiency of glucose sensors. Moreover, new types of hydrogel-based biosensors were developed that comprise metallic nanostructures and responsive hydrogel architectures to target analytes present in complex biological fluids.
(i) Different coating systems were developed that do not alter the function of the sensor They retain glucose sensitivity, while allowing the introduction of non-fouling behavior (doi: 10.1021/acs.biomac.7b00516 10.1073/pnas.1720055115 10.1021/acs.biomac.8b01405). Stable cholesteryl modified ELR-based nano-carriers were produced with superior cell-membrane interaction and cell-type specificity for potential cell coatings or drug delivery systems.
(ii) More efficient cell adhesive bicyclic peptides were synthesized (doi: 10.1021/acscombsci.8b00144) with a newly developed technique to measure binding efficiency (doi: 10.1021/acs.analchem.7b00554). For the purpose of cartilage repair, two injectable hydrogels were developed: One is a hybrid Silk Elastin-Like co-Recombinamer hydrogel (doi: 10.1021/acs.biomac.8b01211) which can be post-modified with the bicyclic peptides yielding in enhanced cell adhesion (doi: 10.1088/1748-605X/aafd83). The second gel is an injectable hyaluronic acid-based hydrogel with tunable biochemical and mechanical properties (doi: 10.1016/j.eurpolymj.2019.02.024). In addition to these biological gels, synthetic gels were developed to better mimic the non-linear mechanics of the natural ECM. Fibrous, macroporous polyisocyanides (PIC) hydrogels were synthesized with stress-stiffening behavior, regulating cell behavior (doi: 10.1021/acs.biomac.8b01445). A combination of PIC with the bicyclic peptides accelerates stem cell spreading (doi: 10.1038/s41467-019-08569-4). The mechanical properties and gelation temperature can be tailored by copolymerization (doi: 10.1016/j.cclet.2017.11.002). Another method to obtain macropores in an injectable material is by crosslinking micron-scale microgels together after injection. Novel microfluidic techniques were established to produce hollow and rod-shaped microgels that enable drug and cell encapsulation directly on chip (doi: 10.1039/c7bm00322f). In order to mimic the tissue architecture, bioactive domains are patterned into 3D poly(ethylene glycol) hydrogels using light-sensitive chemistry. To test the efficiency of the novel Biogel hydrogels ex vivo, a new bioreactor platform was created. Nanocellulose-based hydrogels were successfully employed to culture and differentiate human liver organoids. In addition, an isolated perfused porcine liver platform was realized.
(iii) Poly (N-isopropylacrylamide) (pNIPAM)-based thermosensitive hydrogels, embedded with gold nanoparticles, were prepared as hydrogel films that can locally actuate upon irradiation to study mechanobiology. Nanopatterned pNIPAM microgel surfaces leads to controlled bending of microgels upon actuation. The same pNIPAM/gold material was employed to design new diagnostic devices with improved sensitivity (doi: 10.1039/C7NR08905H). In parallel, a portable optical biosensor platform was established for label-free detection of proteins. Additionally, ELRs with both a lower and upper critical solution temperature were produced with potential use as responsive temperature sensors. A last sensing approach targeted the degradability of specific peptide patterns incorporated into the ELR backbone to detect different proteases.
To improve biointegration of medical devices and sensors inside the body and increase their life-time, Biogel developed new hydrogel coatings. As tissue engineering application, cartilage repair was a main focus to reduce disability and high costs of treatment. The newly developed injectable cell-laden hydrogels can be administrated via a minimally invasive procedure and fill irregularly-shaped cartilage defects, combined with bioactive molecules and anti-inflammatory drugs. Besides cartilage repair, many other damaged or diseased tissues could greatly benefit from efficient regeneration therapies. The challenge is to design materials that provide the right signals to form functional tissue. The artificial synthetic polymeric hydrogels developed in Biogel better mimic the extracellular matrix, have tunable properties to direct cellular responses, and can be mixed with other gels to to obtain properties that cannot be achieved using single component gels. A novel microfluidic technique was developed to also encapsulate drugs and cells inside microgels to combine cell transplantations with material-based therapies to increase their efficiency. As testing platform, a new bioreactor was developed that allows for long-term flow cultures of cells within hydrogel constructs with online analysis methods. With this technology, tissues can be constructed that mimic the in vivo situation to gain relevant insights into the mechanisms of the cells or pathologies thereof. Besides the bioreactor, an ex vivo perfusion system was established to keep pig livers alive and develop a damage model of a fatty liver to explore the mechanisms involved in this illness and test possible cures. For diagnostic purposes, tailored hydrogel materials are deployed at the interface between the biological sample and technical transducer to open new ways for a sensitive analysis of trace amounts of biomarkers in new settings that are closer to the patient and do not require centralized laboratories. These advances allow for portable devices and the detection of lower target concentrations, which will in the future pave the way to detect earlier stages of diseases.