From tusks to teeth, plants can step in where animals break down.
For all the abuse that humans heap upon the plant kingdom, it’s a wonder that they feel inclined to help us at all. But, they do, and this item contains several examples of the true selflessness and generosity of spirit of our vegetable neighbours. For many of us trips to the dentist are not only potentially painful affairs, they can also be expensive. Anything that might minimise the number of such visits, and any attendant discomfort, is therefore to be welcomed (by patients, if not by dentists with expensive lifestyles to maintain…). Research by Joo-Won Nam et al. might therefore be just what the dentist didn’t order. They’ve characterised a proanthocyanidin extract from the bark of Chinese red pine (Pinus massoniana)* that binds to dentin(e) (collagen-containing material beneath the tooth’s hard enamel exterior.
This property not only helps strengthen the tooth (and may therefore prevent further decay, etc.), but also improves the bond between the tooth and resin fillings that are used to replace damaged and excavated tooth material. Traditionally, this filling-tooth interface is a weak spot that reduces the longevity of fillings and thereby increases the – expensive! – frequency with which they need to be replaced.
In another supporting role (which begins to sound a little like the ‘Oscars’ of the plant world…), Gianluca Fontana et al. have used ‘decellularised’** plant material as a scaffold for the growth of human cells. After decellularisation, the plant material was ‘biofunctionalised’ by either coating with minerals – ‘modified simulated body fluid’ – or dopamine-conjugated Arg-Gly-Asp (RGD) peptides. Plant tissues are particularly suited to this use because of their elevated hydrophilicity (water-holding properties) and excellent water transport abilities, which facilitate cell expansion during prolonged periods of culture.
Furthermore, because ‘they can be easily cut, fashioned, rolled or stacked to form a range of different sizes and shapes’, these phytoscaffolds can permit the assembly of a variety of structures that in future may be used to repair muscle, organs and bone. Plants so far examined for this capacity include Calathea zebrina, Anthurium waroquaenum, Anthurium magnificum, Solenostemon scutellarioides ‘wasabi’ (solenostemon), Vanilla planifolia (vanilla), Laelia ancepts, Petroselinum crispum (parsley), Schoenoplectus tabernaemontani … and ‘bamboo’. Which interesting catalogue probably tells us more about the vegetation to hand at the researchers’ base than any taxonomically-defensible search strategy.
Having developed plant-inspired techniques to support the development of aggregate human cell structures, plants are also under scrutiny for their capacity to provide solutions to the problem of ensuring an appropriate blood supply deep into developing human tissues. Appropriately, the same ‘decellularised plant scaffolds’ technique has been exploited by Joshua Gershlak et al. (research with includes several collaborators in common with the team behind the Fontana et al. paper) to use the vascular network of spinach leaves as a template for the blood supply to human organs and tissues.***
Finally, plant-based help for… elephants. With increasing concern over the numbers of elephants that are killed purely for their ivory, Kait Bolongaro reports on an initiative that might save the lives of some of these endangered pachyderms. Dutchman Heerma van Voss’s Quito (Ecuador, South America)-based company náya Nayón uses the endosperm of the fruits of the ivory-nut palm (Phytelephas aequatorialis to fashion objets d’art. As hard as ivory when dried, the so-called tagua represent a renewable, non-elephanticidal, more ethically-sourced alternative to the animal-derived product. However, how long this practice can continue must be debatable because the palm is classified as ‘near threatened’ by the IUCN (International Union for Conservation of Nature and Natural Resources [Ed. – which is only marginally better than the ‘vulnerable’ status accorded the African elephant by that same organization…]
** Whilst I don’t wish to be unnecessarily pedantic, it seems that the term ‘decellularised’ is used in a rather loose fashion here. Whilst the methodology apparently removes the cuticle, and cell contents such as pigments, proteins and DNA, it appears to leave the cell walls intact. Since in many respects the ‘essence’ of a plant cell is its wall, the material isn’t really decellularised as such.
*** For a video showcasing this technique – and with further explanations of the process from two of the paper’s authors, visit here.
Nam, J.-W., Phansalkar, R. S., Lankin, D. C., McAlpine, J. B., Leme-Kraus, A. A., Vidal, C. M. P., … Pauli, G. F. (2017). Absolute Configuration of Native Oligomeric Proanthocyanidins with Dentin Biomodification Potency. The Journal of Organic Chemistry, 82(3), 1316–1329. https://doi.org/10.1021/acs.joc.6b02161
Fontana, G., Gershlak, J., Adamski, M., Lee, J.-S., Matsumoto, S., Le, H. D., … Murphy, W. L. (2017). Biofunctionalized Plants as Diverse Biomaterials for Human Cell Culture. Advanced Healthcare Materials, 6(8), 1601225. https://doi.org/10.1002/adhm.201601225
Wu, D.-C., Li, S., Yang, D.-Q., & Cui, Y.-Y. (2011). Effects of Pinus massoniana bark extract on the adhesion and migration capabilities of HeLa cells. Fitoterapia, 82(8), 1202–1205. https://doi.org/10.1016/j.fitote.2011.08.008