Scientists at Nanyang Technological University (NTU Singapore) in Singapore have discovered how to use sunflower pollen to develop 3D printing ink materials that can be used in tissue engineering, toxicity testing, and the manufacture of parts useful for drug delivery. bottom.
This pollen-derived ink retains its shape when attached to the surface, making it a viable alternative to current inks used in 3D printing (also known as bioprinting) in the biomedical field. Become. These inks are usually soft and delicate, making it difficult for bioprinters to maintain the desired 3D shape and structure of the final product as they deposit the ink layer by layer.
To illustrate the capabilities of pollen-based 3D printing inks, NTU Singapore scientists have printed a “scaffold” of biological tissue. Laboratory research Showed to be suitable for Cell adhesion Growth essential for tissue regeneration.
This new use of pollen, described in a scientific treatise that is characteristic of the cover of a scientific journal Advanced functional materials, The research team emphasizes the potential of today’s bioprinting inks as a sustainable alternative.
Professor Cho Nam-Joon of the Faculty of Materials Science and Engineering, NTU, co-author of this study, said: By adjusting the mechanical properties of sunflower pollen, we have developed a pollen-based hybrid ink that can be used to print structures with excellent structural integrity. The use of pollen for 3D printing is a major achievement in the process of producing pollen-based inks. Sustainable and affordable. Given the large number of pollen species that differ in size, shape, and surface properties, pollen microgel suspensions have the potential to create a new class of environmentally friendly 3D printing materials. “
Assistant Professor Song Juha of the NTU School of Chemistry and Biomedical Engineering, co-author of the study, said: Flexible membranes are usually manufactured on the basis of a flat shape, so when applied to large surface areas of the skin, such as areas of frequent movement such as the face and joints, problems such as layer breakage and poor fit can occur. Occurs. Pollen-based 3D printing inks are biocompatible, flexible, and low-cost, allowing them to produce films that can bend unbroken to the contours of human skin. “
The research team also includes Assistant Professor Chang Tae-sik of Korea University in South Korea.
Professor Paul S. Weiss, a prominent professor of chemistry and biochemistry, biotechnology, and materials science and engineering at the University of California, Los Angeles, who was not involved in the study, said: Countless uses. Song, Cho, and their team have added it to the arsenal of what can be structured on a larger scale through additive manufacturing and 3D printing by incorporating it into ink. “
Dr. Jeffrey S. Glen, director of the Center for Hepatitis and Liver Tissue Engineering at Stanford University and not involved in the study, added: Drug delivery We use sustainable, inexpensive and non-toxic materials. “
How to develop pollen-based hybrid inks
The most widely used bioprinting method today is extrusion-based bioprinting. With this method, ink is continuously dispensed from the nozzles and deposited along a digitally defined path, creating a 3D structure layer by layer.
One of the challenges of this method is that it is difficult to retain the 3D structure and shape of soft and delicate materials such as hydrogels, cells and biopolymers without additional support. A structure called a support matrix is typically used in which soft ink is deposited during the printing process. However, this is wasteful because the support matrix becomes unusable after printing.
Assistant Professor Song said: “Previous research has focused on the development of specialized bio-inks that mix hydrogels with fibers and particles for efficient deposition and printability. The main focus of such hydrogel composite inks. The downside is clogging of the nozzles. In contrast, the pollen-based hybrid inks we have developed have sufficient mechanical strength to maintain their structure without clogging the printer. “
The process of developing a pollen-based hybrid ink begins with incubating tough sunflower pollen in an alkaline solution for 6 hours. This is an environmentally friendly process similar to soap making, forming pollen microgel particles.
The pollen microgel is then mixed with a hydrogel such as alginate, a natural polymer normally obtained from brown algae, or hyaluronic acid, a clear, sticky substance naturally produced by the body to complete the pollen-hydrogel. Form hybrid ink.
Pollen-based scaffolding for cell culture and drug delivery
As a proof of concept, scientists printed a five-layer tissue engineering scaffold to help culture cells in 12 minutes. Next, collagen was added to the scaffold to provide an anchor point where cells could attach and grow.
Scientists then seeded the scaffold with human cells and found that they had a high cell seeding efficiency of 96% to 97%. It is widely used as a 3D cell culture platform, but has performance comparable to reverse colloidal crystal (ICC) hydrogel, which requires time and effort to manufacture.
Given that pollen responds to changes in pH (when the environment becomes acidic or alkaline), the NTU team has also tested the feasibility of 3D scaffolding as a stimulus-responsive drug delivery system. Scientists have discovered that pollen microgel particles gradually release the dye onto the scaffold when the fluorescent red dye is dropped onto the scaffold. The addition of acid increased the amount and rate of release. This indicates that pollen scaffolding could be used as a sustained release drug delivery system, scientists said. Professor Cho said: “Because pollen microgel particles have a hollow shell structure, they could be used to carry drugs, cells, and biomolecules in a customized 3D structure drug delivery platform. Currently, the use of these pollen microgels We are exploring methods. Scaffolds for 3D cell culture platforms in a variety of biomedical applications.
“Given the stimulatory responsiveness of pollen, pollen-based scaffolds may also be used as smart drug carriers. For example, coating pollen-based scaffolds with a thin layer further slows drug release. It can stimulate the release of arginates, and by introducing acids. “
Pollen-based support structure for soft 3D printing inks
Scientists have also shown that soft, flexible pollen microgel particles derived from tough pollen grains can serve as a recyclable support matrix for use in free-form 3D printing where soft inks are deposited. discovered. The support matrix prevents the print structure from collapsing as the ink cures.
To test the feasibility of their approach, scientists used pollen microgels as a support to retain the shape of the elbow mesh during printing to produce a 3D-printed silicone rubber mesh for the elbow.
After curing the printed matter at 75 ° C (167 ° F) for 24 hours in pollen microgels, scientists discovered that the printed 3D silicone rubber mesh could adapt to the curvature of the human elbow. They also found that the mechanical properties of silicone rubber samples printed and cured with a pollen microgel support matrix were similar to those of samples produced by conventional casting methods.
The use of pollen in the field of biomedicine is based on a series of work by the NTU research team on diversion. pollen Grain is a natural renewable resource and is a component of a variety of environmentally friendly alternatives, from environmentally friendly paper to biodegradable sponges that can absorb petroleum pollutants.
This research is consistent with NTU’s research ambitions in the 2025 Strategic Plan to transform invention and creativity into results that improve economic benefits and quality of life.
The team is currently working with the industry to improve 3D printing innovation and promote its commercial adoption.
Shengyang Chen et al, Engineering of Natural Pollen Grains as a Multifunctional 3D Printing Material, Advanced functional materials (2021). DOI: 10.1002 / adfm.202106276
Nanyang Technological University
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Turn pollen into 3D printing ink for biomedical applications
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