Researchers Turn Apple Waste into Biomaterials to Make 3D Matrices for Tissue Regeneration

Nearly every day, 3D printing technology is helping to advance the medical field in leaps and bounds, from 3D printed medical implements and medical models, to 3D printed prosthetics and even 3D printed organs. But 3D printing is also having a positive effect on another area of the medical field: tissue and bone regeneration. Researchers in Ireland created a new bioprinting method for regenerating bone in vivo, and the University of Pittsburgh’s Swanson School of Engineering used 3D printing technology to produce microscopic manganese and iron scaffolds to foster tissue and bone growth. Now, a team of researchers from the Centre for Biomedical Technology at Universidad Politécnica de Madrid (CTB-UPM) is working with the Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC) and the Institute of Catalysis and Petrochemistry (ICP-CSIC), from the Spanish Council for Scientific Research (CSIC), to use waste from the agri-food industry (apple pomace from juice production, to be precise) to make biomaterials for regenerating bone and cartilage tissues.

The biomaterials act as 3D matrices for tissue regeneration, which are useful for aging-related diseases that require regenerative medicine, like arthritis, osteoporosis, or osteoarthritis. The average age of our population is slowly increasing – on a personal note, both of my father’s parents are 91, and my grandpa still heads out on the golf course whenever he can! But with this average advanced age, the economical impact of these diseases is staggering, so it goes without saying that 3D printing technology, which is known to cut production costs, could help lower that amount, and even some of the pain of the diseases, if tissue regeneration methods are successful.

So, why apple pomace? This raw material, which is the solid remains of fruit after it’s pressed for oil or juice and contains stems, seeds, pulp, and skins, is readily available – in 2015, world production of apples was over 70 million tons. Roughly 75% of apples are converted into juice, and the pomace that’s left contains about 20-30% of dried matter, which is mostly used for compost or animal feed. However, due to the large amounts of water-heavy apple pomace generated each year, storage problems abound, and to prevent putrefaction, the pomace itself needs to be treated immediately. So if the pomace can be turned into biomaterials for research like this, the volume of waste goes way down.

“With this approach we achieve a double goal, firstly using waste as a renewable raw material of high value and chemical diversity, and secondly, to reduce the impact of such waste accumulation on the environment,” said Milagros Ramos Gomez, one of the researchers for this study.

The researchers published a paper in the Journal of Cleaner Production, titled “Multivalorization of apple pomace towards materials and chemicals. Waste to wealth.” In addition to Ramos, co-authors include Malcolm Yates, Maria A. Martin-Luengo, Violeta Zurdo Ibañez, and Ana Maria Martinez Serrano.

The paper’s abstract reads, “The work presented here uses apple pomace (AP), an industrial waste from apple juice and cider production as a renewable raw material (RRM), to obtain materials that can be utilized as biocompatible scaffolds for osteoblasts and chondrocytes, employed in tissue engineering, valuable extracts that can be used as nutraceuticals and pectin. All of these have much higher values than the original raw material, pectin can be priced up to 1 euro/g, chlorogenic acid is ca. 120 euros/g, caffeic acid 3–5 euros/g and especially the scaffolds that are usually made by synthetic methods using non-renewable raw materials with high fabrication costs and sold at prices higher than 100 euros/g, while the residues used here have prices lower than 100 euros per ton. Thus, there are clear environmental and financial incentives in transforming this waste material into valuable substances and materials.

As indicated in the Graphical Abstract, the procedure followed consists in sequential extractions of antioxidants, pectin and finally the preparation of a biocompatible material, giving priority to the latter due to its importance as a renewable scaffold for tissue engineering. From a literature search, to date, although separate ways of valorization have been applied to this kind of waste, the sequential multivalorization adopted here, has not been previously attempted. Furthermore, biocompatible scaffolds from AP have not been described.”

Graphical Abstract

According to the paper, this is the first report of materials derived from apple waste to be used in hard and soft tissue engineering applications. The team’s apple pomace multivalorization procedure is based on the “sequential extractions” of bioactive molecules such as pectin and antioxidants. Once they had the waste material, the team prepared a biomaterial with the appropriate texture and porosity for tissue engineering.

When compared with commercial products, the chemicals and materials obtained from apple pomace are not only environmentally sound, but also competitive. The extraction of the carbohydrates and antioxidants makes up 2% of the pomace’s dry weight, and these cells, once removed, are valued nutraceuticals. The pectin extracted constitutes 10%, and it is highly biocompatible, especially in terms of treating coetaneous wounds and making anti-tumor drugs.

In addition, the materials that remain in the apple pomace, once the pectin and antioxidants are extracted, can still be designed with the proper amount of texture, composition, and structure that’s needed to grow diverse types of cells. In this case of the biomaterials being used for regenerating bone and cartilage tissues, chondrocyte cells and osteoblast cells were used, both of which are related to cartilage and bone tissue regeneration due to their applications in regenerative medicine in the aging-related diseases mentioned previously.

In order to give sequential multivalorization more versatility, more research is being carried out. Additionally, as new materials have been obtained in this work, researchers are working to develop new technological applications, where 3D printing techniques can be used to structure customized biomaterials. There are obvious financial incentives in continuing this research, and converting this type of waste into valuable final products: for example, the biomaterial waste in this research costs less than €100 per ton, while other products currently on the market, with similar applications, can cost over €100 per gram. Discuss in the Apple Waste forum at 3DPB.com.