Periodic Reporting for period 1 - BioSMaLL (Biopolymers for the Generation of 3D Tissue Engineering Scaffolds by Solution Mask Liquid Lithography)
Período documentado: 2019-07-01 hasta 2021-06-30
Musculoskeletal based conditions reduce the quality of life of many adults , with THE WHO citing that up to 1.71 billion people worldwide are affected. Lower back injury is the most prevailing issue, suffered by nearly 568 million people. As the joint cartilage breaks down, inflammation and pain cause poor mobility and dexterity for patients, in some cases requiring surgical intervention. Continued pressure on healthcare professionals is to come up with a viable treatment solution, with cartilage regeneration of particular interest to tackle this issue. The demand has prompted the investigation of medically applicable biomaterials. Biomaterials are a class of synthetically optimised polymers that are biocompatible, meaning they have compatibility with human tissues and bodily fluids and do not promote any toxicity within the individual. Hydrogels, which are three-dimensional networks that form soft materials capable of holding high concentrations of water, can be designed by synthetic modification of biomaterials. Continued worldwide research in biomaterial hydrogel development has led to many successful studies on their use as biocompatible 3D implantable or injectable augments for cartilage regeneration, albeit in purely academic settings. With these promising studies in mind, they could hold the potential to provide solutions to current healthcare issues surrounding impact or wear and tear injuries that damage cartilage, by replacing existing treatments such as mosaicplasty, an autologous transplant from a non-weight-bearing area of the articular cartilage replacement to the local deformed cartilage – which isn’t always successful in patients. Although, the number of available hydrogel materials is very limited, and there are some drawbacks associated with them such as material reproduction issues and poor mechanical strength of the hydrogels. Newer tailored made materials that could harness the potential to reproducibly make these 3D patient-specific implants in cartilage regeneration is of significant interest – with polypeptide hydrogels chosen as potential suitors due to many reports of their application within biomedical fields. Coupling tailor made polypeptide materials and cell components with a low-cost technology for fabrication of 3D objects, namely Solution Mask Liquid Lithography (SMaLL) – a digital light processing (DLP) 3D printing method, improved technologies for personalised medicine could be realised. To summarise, this project aims to provide a new hydrogel material platform for potential translation to clinical issue with 3 main overlapping objectives: 1. Development of synthetically simplified polypeptide hydrogel materials that can be reproduced on demand. 2. The use of these developed hydrogels as viable growth matrices for mammalian cells with a focus on cartilage regeneration. 3. Enabling 3D object development with this hydrogel/cell matrix using a custom-built, low-cost 3D printer.
Using traditional synthetic techniques, polypeptide (long chains of amino acids) hydrogels with the ability to change their physical state from liquid to solid following exposure to ultraviolet (UV) light were developed. This ability, known as photopatterning, was then exploited in 3D printing. A dynamic 3D printing method SMaLL, which uses a continuous light source that irradiates a resin bath forming a desired 3D object, was then trialed for the hydrogels. In SMaLL, the resin bath is formulated with the main component (polypeptide) and two side components (photoinitiator – promotes the photopatterning process and a photomasking dye – prevents scattering of the light for well-resolved 3D objects generation). Different hydrogel formulations were attempted with SMaLL, with most unsuccessful due to compatibility issues with the light wavelength intensity and the hydrogel materials. More promising results were obtained after use of a stereolithography (SLA) 3D printing system, with 3D objects formed with acceptable resolution. Another polypeptide hydrogel system was designed and synthesised, using similar synthetic concepts. These materials also had n-built UV light triggers, but had a different initial physical state. They were designed to have ‘hair-gel’ like consistency, meaning that they could be used in extrusion 3D printing. This hydrogels were optimised to be extrudable, meaning they can be pushed through a needle becoming a fluid and then returning to a solid like consistency after exiting the nozzle. While the materials are soft, after irradiation with light hydrogels can again change their physical state to a solid like consistency. The hydrogels were then used in 3D extrusion direct ink writing (DIW), a process where layers of materials are extruded onto a platform in a controlled manner to form a 3D object of interest, with self-supporting structures such as inverted pyramids and star structures capable of being printed. These materials can hold the potential for encapsulation of living cells such as patient derived cells or genetically engineered bacteria, both of which can have applications in biomedical science such as tissue engineering or wound healing.
3D printing using hydrogels as feedstocks mainly use extrusion printing, achieved using a software-controlled nozzle which deposits the material in a layer by layer fashion. Although successful, sophisticated 3D architectures are difficult to produce with it. This project aimed to utilise a method that can address the lack of sophistication in 3D object development, by using DLP SMaLL3D printing system. Although unsuccessful in developing 3D objects using this system, novel hydrogels based on polypeptides have been successfully developed. New amino acid monomers (starting materials to polypeptides) and polypeptide sequences that have not been made before, have been made on demand after extensive synthetic optimization. These material platforms could provide great additions in the field of hydrogel development, in addition to being materials that can be readily chemically modified for specific applications – both very relevant in the fields of polymer chemistry and biomedical science. Next generation materials are envisaged from now until the project end, taking inspiration and improving on the properties of the current series polypeptide hydrogels. Ongoing work could eventually lead to a hydrogel formulation that is readily 3D printable, in addition to the synthetic production of the hydrogel already being reproducible and scalable. It is expected that all new materials will be trialed for biocompatibility (bear in mind they have been designed, inspired by reports on biocompatible polypeptide sequences) so they can then be assessed for their suitability as cartilage augment scaffolds (blending with cells and growth factors, 3D object printing and then maturation of object). Liaising virtually with engineers at UCSB, we will endeavor to replicate their newly developed 2.0 SMaLL system (improving on the compatibility of the first system) in order to fabricated sophisticated 3D objects using our hydrogel system. A significant societal impact would be the identification of new implantable technologies that could have patient specific 3D structure, improving current strategies for cartilage regeneration. In the event that the materials aren’t directly translated, their impact can improve future systems, offering an adaptable platform in the field of biomedical science.