Silica Phytoliths Research Articles

The effect of burning on the dissolution behaviour and silicon and oxygen isotope composition of phytolith silica

Theδ30Si andδ18O values of opal-A precipitated in plants (silica phytoliths) have been shown to be useful for paleoenvironmental reconstructions. Here, the effects of burning and partial dissolution of phytoliths on their isotopic compositions and dissolution behaviour were examined. Phytoliths were heated to 700 °C and then dissolution experiments were conducted in batch reactors under a range of pH (4–8) and temperature (4–19 °C) conditions. Heating caused a −2.6 ‰ shift in phytolithδ18O values. NMR results suggest that heating reduces the number of surface vicinal silanols, which likely results in the formation of strained SiOSi bonds which incorporate oxygen from18O-depleted hydroxyl groups. During dissolution, theδ18O of burned phytoliths increased by up to 3.5 ‰ (average 1.8 ‰) until 15–45 % saturation was reached, and then adsorption of silica on the surface of the solid began to reducethe δ18O value of solid silica despite a net dissolution. The maximum increase in δ18O during dissolution of burned phytoliths is 1.8 ‰ smaller than previously observed for unburned silica subjected to partial dissolution under the same conditions. Heating did not cause a significant change inδ30Si values, and partial dissolution of burned phytoliths caused a slight increase inδ30Si values that was smaller in magnitude than for unburned phytoliths. Dissolution of burned phytoliths progressed more slowly than dissolution of fresh phytoliths in low pH and temperature conditions, but was faster than the dissolution of fresh phytoliths when pH > 6 and temperature = 19 °C. We propose that because fewer hydrolysis sites exist on the surface of burned phytoliths that the isolated silanols that remain after heating are difficult to deprotonate at low pH resulting in slower dissolution. However, at higher pH the breakage of strained SiOSi bonds in burned phytoliths may explain their higher dissolution rate relative to fresh phytoliths. We recommend caution in using theδ18O values of soil phytoliths in paleoclimate reconstructions as they can be altered during both heating and partial dissolution. For phytolith assemblages collected from archaeological hearths or grasslands prone to wildfires, the shift towards lowerδ18O values caused by heating would result in overestimations of temperature using paleothermometer equations. Care must be taken to identify alteration by dissolution or burning, which may not always be visually evident.

Location, speciation, and quantification of carbon in silica phytoliths using synchrotron scanning transmission X-ray microspectroscopy.

Phytoliths of biogenic silica play a vital role in the silicon biogeochemical cycle and occlude a fraction of organic carbon. The location, chemical speciation, and quantification of this carbon within phytoliths have remained elusive due to limited direct experimental evidence. In this work, phytoliths (bilobate morphotype) from the sugarcane stalk epidermis are sectioned with a focused ion beam to produce lamellas (≈10 × 10 μm2 size, <500 nm thickness) and probed by synchrotron scanning transmission X-ray microspectroscopy (≈100-200 nm pixel size; energies near the silicon and carbon K-absorption edges). Analysis of the spectral image stacks reveals the complementarity of the silica and carbon spatial distributions, with carbon found at the borders of the lamellas, in islands within the silica, and dispersed in extended regions that can be described as a mixed silica-carbonaceous matrix. Carbon spectra are assigned mainly to lignin-like compounds as well as to proteins. Carbon contents of 3-14 wt.% are estimated from the spectral maps of four distinct phytolith lamellas. The results provide unprecedented spatial and chemical information on the carbon in phytoliths obtained without interference from wet-chemical digestion.

Soil surface grass phytolith morphotypes across bioclimatic gradients and biomes at about latitude 29°S in South Africa

This study examines the distribution patterns of grass subfamilies and their diagnostic silica phytoliths along a transect running approximately at latitude 28° S in South Africa. The transect encompasses 77 surface samples collected along moisture and temperature gradients, across 6 biomes and 39 ecozones, and spanning elevations between near-sea level and over 2253 m. This study tests the relation between the distribution and density of grass subfamilies and the proportions of their diagnostic grass silica short cell phytoliths (GSSCP) representing them, and how these proportions correlate with five climatic variables (mean temperature of the wettest quarter, annual precipitation, precipitation of the wettest quarter, precipitation variability, and the aridity index). The results suggest that C3-grass diagnostic GSSCP morphotypes increase with a decline in temperature in the wettest quarter, occurring in areas receiving mostly winter rain or at high elevations in areas of summer rain. Of the C4 grass subfamilies, the Panicoideae increase with summer precipitation and low precipitation variability, while the Aristidoideae-Stipagrostis the opposite. The distribution of Chloridoideae depends on complex changes in all climatic variables, suggesting aridity gradients only in the eastern half of the transect. In view of the data, this study reviews the usefulness of the phytolith humidity-aridity index (Iph) and the water stress index (Fs) and proposes the Panicoideae index (PI) and Stipagrostis index (SI) as indicator of aridity and high precipitation variability in southern Africa.

Antioxidant Capacity of Chitosan on Sorghum Plants under Salinity Stress

Salinity stress is one of the major environmental constraints responsible for the reductions in agricultural productivity. Salinity affects crop growth, by causing osmotic and ionic stresses, which induce oxidative damage due to increased reactive oxygen species (ROS). Exogenous application of natural compounds can reduce the negative impacts of salinity stress on plants. This study evaluated the antioxidant capacity of chitosan, a biopolymer to reduce the salt-induced oxidative damage on sorghum plants. Morpho-physiological and biochemical attributes of sorghum plants stressed with 300 mM NaCl, in combination with chitosan (0.25 and 0.5 mg/mL), were assayed. Salt stress decreased growth, fresh (66.92%) and dry (48.26%) weights, affected the shape and size of the stomata, caused deformation of the xylem and phloem layers, and increased the Na+/K+ (1.3) and Na+/Si+ (5.4) ratios. However, chitosan effectively reversed these negative effects, as supported by decreased Na+/Si+ ratio (~0.9) and formed silica phytoliths. Oxidative stress was exerted as observed by increased H2O2 (44%) and malondialdehyde (125%) contents under salt stress, followed by their reduction in chitosan-treated sorghum plants. Salt increased proline (318.67%), total soluble sugars (44.69%), and activities of SOD (36.04%) and APX (131.58%), indicating sorghum’s ROS scavenging capacity. The antioxidant capacity of chitosan was measured by determining its ability to reduce oxidative damage and minimizing the induction of the antioxidant defense system. Chitosan reduced oxidative stress markers, proline, total soluble sugars, and the antioxidant enzyme activities by more than 50%. Fourier Transform Infrared Spectra of chitosan-treated samples confirmed a reduction in the degradation of biomolecules, and this correlated with reduced oxidative stress. The results suggest that chitosan’s antioxidant capacity to alleviate the effects of salt stress is related to its role in improving silicon accumulation in sorghum plants.

Fate of silica phytoliths in the industrial crushing of sugarcane stalks

Biomass from grasses such as sugarcane contains bodies of biogenic silica, the phytoliths. In industrial biomass processing, phytoliths can be harmful to equipment causing wear and ash deposits. However, phytoliths can also be beneficial if they are valorized into silica-based products. This work investigates the fate of phytolith in the industrial crushing of sugarcane stalks using biomass fractionation, ashing, and imaging techniques. Phytoliths can be traced by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS) due to their proximity to the outer surface and fingerprint size, shape, and chemistry. In native sugarcane stalks, phytoliths are concentrated in the epidermal region. Industrial crushing promotes tissue ruptures that transform stalks into bagasse, where the epidermal tissues and phytoliths are found with preserved integrity, fractured, or even detached from the native tissue structures. The observations presented in this work suggest novel strategies for the isolation of phytoliths in biorefinery designs integrable to the well-established industrial crushing of sugarcane stalks.

Modern Analog Assemblages of Phytoliths Under Various Plant Communities of the Middle Volga and their Applicability for Archaeological Reconstructions

The article describes the results of investigations of the sub-recent assemblages of silica phytoliths in top soils of various modern plant communities of the Middle Volga region in Tatarstan, Samarskaya and Ulyanovskaya oblasts conducted in 2017–2020. Counts of various phytolith morphotypes from 40 samples suggest a relatively low level of vegetation community specificity as revealed by multivariate statistical analyses. Nevertheless, coniferous and mixed forests can be distinguished based on the presence of a suite of conifer phytoliths, while steppes can be identified based on high proportion of rondels. Deciduous forests of the region can be detected based on high proportion of straight elongates and acutous bulbosus (trichome) type. Some matchings are made to 10 archaeological samples from various strata and ages across the region. Such samples reveal high proportion of cultured grass phytoliths and are most similar to steppes or agricultural assemblages in the modern dataset.

The mechanisms of silicon on maintaining water balance under water deficit stress.

Water deficit stress severely threatens crop yield and numerous reports have shown silicon could enhance plants resistance to water deficit. One of the most important mechanisms is that silicon maintains the water balance. In this review, we summarized advanced research to elucidate the effect of silicon on plant water transport processes, including leaf water loss, vessel water transport, and root water uptake. In leaves, the deposition of silica phytolith on cuticle and stomata decreases transpirational water loss under water deficit stress. However, accumulating evidence suggest that silicon maintaining leaf water content is not through reducing water loss, but through osmotic adjustments, enhancing water transport and uptake. Enhancement of stem water transport efficiency by silicon is due to silica phytolith depositing in the cell wall of vessel tubes and pits, which support it avoiding to collapse and embolism, respectively. The improvement of root water uptake capacity by silicon acts as a key role in maintaining water balance. The underlying mechanisms include (i) enlargement of the root water uptake area, (ii) improvement of the water driving force, (iii) the prevention of water loss from root to soil, and (iv) the up-regulation of aquaporin activity. This review provides three simple models to understand the mechanism of silicon on water balance and highlights the future research area.

Multiproxy analysis of omnivore and herbivore coprolites: Inferences on Mid-Holocene dietary habits in Argentine Patagonia

Learning about past biological interactions is possible thanks to the study of trace fossils, such as coprolites found in archaeological sites. The multiproxy analysis of coprolites may provide evidence of direct and indirect consumption of diet items and thus reconstructing the ecological dynamics of past ecosystems. In this study, we performed a comparative analysis of the content of plant fragments, pollen and silica phytoliths in coprolites found in the archaeological site Cerro Casa de Piedra 5 (47°57′S; 72°05′W), located in the Perito Moreno National Park, Santa Cruz, Argentina, in an archaeological layer dated to 6540 ± 110 years 14C BP (7402 cal years BP), with the aim to recognize dietary habits in those times. According to their morphological features and content, the coprolites were assigned to omnivores (humans/canids) and herbivores (camelids). The multiproxy analysis of these coprolites allowed us to reach a higher taxonomic resolution in the identification of some plant items in the diet, to make inferences on the indirect consumption of vegetation through the consumption of stomachs and other viscera of camelids by omnivores, and to observe similarities and complementarities in terms of the presence and abundance of taxa. The limitations and potentialities of multiproxy analysis to infer past dietary habits are discussed. The information obtained provides greater knowledge about the predator-prey interactions of the Middle Holocene in south-western Patagonia.

High silicon concentrations in grasses are linked to environmental conditions and not associated with C4 photosynthesis.

The uptake and deposition of silicon (Si) as silica phytoliths is common among land plants and is associated with a variety of functions. Among these, herbivore defense has received significant attention, particularly with regard to grasses and grasslands. Grasses are well known for their high silica content, a trait which has important implications ranging from defense to global Si cycling. Here, we test the classic hypothesis that C4 grasses evolved stronger mechanical defenses than C3 grasses through increased phytolith deposition, in response to extensive ungulate herbivory ("C4 -grazer hypothesis"). Despite mixed support, this hypothesis has received broad attention, even outside the realm of plant biology. Because C3 and C4 grasses typically dominate in different climates, with the latter more abundant in hot, dry regions, we also investigated the effects of water availability and temperature on Si deposition. We compiled a large dataset of grasses grown under controlled environmental conditions. Using phylogenetically informed generalized linear mixed models and character evolution models, we evaluated whether photosynthetic pathway or growth condition influenced Si concentration. We found that C4 grasses did not show consistently elevated Si concentrations compared with C3 grasses. High temperature treatments were associated with increased concentration, especially in taxa adapted to warm regions. Although the effect was less pronounced, reduced water treatment also promoted silica deposition, with slightly stronger response in dry habitat species. The evidence presented here rejects the "C4 -grazer hypothesis." Instead, we propose that the tendency for C4 grasses to outcompete C3 species under hot, dry conditions explains previous observations supporting this hypothesis. These findings also suggest a mechanism via which anthropogenic climate change may influence silica deposition in grasses and, by extension, alter the important ecological and geochemical processes it affects.

FTIR Nanospectroscopy Shows Molecular Structures of Plant Biominerals and Cell Walls.

Plant tissues are complex composite structures of organic and inorganic components whose function relies on molecular heterogeneity at the nanometer scale. Scattering-type near-field optical microscopy (s-SNOM) in the mid-infrared (IR) region is used here to collect IR nanospectra from both fixed and native plant samples. We compared structures of chemically extracted silica bodies (phytoliths) to silicified and nonsilicified cell walls prepared as a flat block of epoxy-embedded awns of wheat (Triticum turgidum), thin sections of native epidermis cells from sorghum (Sorghum bicolor) comprising silica phytoliths, and isolated cells from awns of oats (Avena sterilis). The correlation of the scanning-probe IR images and the mechanical phase image enables a combined probing of mechanical material properties together with the chemical composition and structure of both the cell walls and the phytolith structures. The data reveal a structural heterogeneity of the different silica bodies in situ, as well as different compositions and crystallinities of cell wall components. In conclusion, IR nanospectroscopy is suggested as an ideal tool for studies of native plant materials of varied origins and preparations and could be applied to other inorganic-organic hybrid materials.

Shape, size, and quantity of ingested external abrasives influence dental microwear texture formation in guinea pigs

Food processing wears down teeth, thus affecting tooth functionality and evolutionary success. Other than intrinsic silica phytoliths, extrinsic mineral dust/grit adhering to plants causes tooth wear in mammalian herbivores. Dental microwear texture analysis (DMTA) is widely applied to infer diet from microscopic dental wear traces. The relationship between external abrasives and dental microwear texture (DMT) formation remains elusive. Feeding experiments with sheep have shown negligible effects of dust-laden grass and browse, suggesting that intrinsic properties of plants are more important. Here, we explore the effect of clay- to sand-sized mineral abrasives (quartz, volcanic ash, loess, kaolin) on DMT in a controlled feeding experiment with guinea pigs. By adding 1, 4, 5, or 8% mineral abrasives to a pelleted base diet, we test for the effect of particle size, shape, and amount on DMT. Wear by fine-grained quartz (>5/<50 µm), loess, and kaolin is not significantly different from the abrasive-free control diet. Fine silt-sized quartz (∼5 µm) results in higher surface anisotropy and lower roughness (polishing effect). Coarse-grained volcanic ash leads to significantly higher complexity, while fine sands (130 to 166 µm) result in significantly higher roughness. Complexity and roughness values exceed those from feeding experiments with guinea pigs who received plants with different phytolith content. Our results highlight that large (>95-µm) external silicate abrasives lead to distinct microscopic wear with higher roughness and complexity than caused by mineral abrasive-free herbivorous diets. Hence, high loads of mineral dust and grit in natural diets might be identified by DMTA, also in the fossil record.

Microscopic Investigationsof Silicification and Lignification Suggest Their Coexistence in Tracheary Phytoliths in Date Fruits (Phoenix dactylifera L.).

Date fruits are special representative of hard fruits and one of the richest sources of dietary silica and edible lignin, which are believed to have several health benefits. In this study, we used optical and scanning electron microscopy (SEM) to investigate the presence of associations between silicification and lignification in date fruits (Phoenix dactylifera, L.). Phloroglucinol staining was employed to observe lignification in date fruits, while silicification was studied by SEM of whole fruits and their acid digesta. This work revealed the presence of heterogeneity and complexity in the silica phytoliths and the lignified structures in date fruits. It was found that lignin exists independently of silica in the secondary cell walls of parenchymal and sclereid cells and that silica exists independently of lignin in the spheroid phytoliths that surround the sclereid cells. Interestingly, a small proportion of lignin and silica seemed to co-exist as partners in the spiral coils of the tracheid phytoliths.

Morphological characterization of biominerals from five multicellular marine algae species

Silica biominerals are deposited as amorphous solid structures in plant cells and tissues, providing rigidity to different plant parts and assisting in defence. The shape and size of phytoliths are well established and serve as a useful tool in taxonomic analyses. For the first time we extracted and studied silica biominerals of five marine macroalgae, which we observed by light microscopy, scanning electron microscopy, and X-ray diffraction analysis (XRD). More than nine different morphotypes of phytoliths ranging from ≥ 10 to ≥ 350 μm in size were found. Some of them were phytoliths made of silica while others showed characteristics of different minerals of calcium. In our study, the “honeycomb” formations were only recorded in Laurencia tropica Yamada and pyramid tabular ones were found only in Tichocarpus crinitus (S.G. Gmelin) Ruprecht. The XRD analysis showed that they consisted of virgilite and gypsum substance, respectively. Silica phytoliths are intrinsic parts of the algae and their morphological characterization can provide the basis for palaeo-reconstruction and taxonomic investigation of brown and red algae in palaeontological studies of fossils where all organic matter has decayed.

Pen management and livestock activities based on phytoliths, dung spherulites, and minerals from Cova Gran de Santa Linya (Southeastern pre-Pyrenees)

The archaeological evidence from Cova Gran de Santa Linya suggests that during the Late Neolithic and Early Bronze Age, the site was used as a livestock enclosure where the accumulated excrements were burned, generating a sequence known by the term fumier. Here we present the results of an integrated study of silica phytoliths, dung spherulites, and mineral composition of sedimentary matrix from the remaining Holocene sequence. The use of fire to sanitize the space had important consequences for the preservation of dung spherulites and the accumulation of phytoliths. Phytolith assemblages indicate that the animals enclosed in the cave were mostly sheep that exploited the pastures nearby the site during the year. In this sense, the results from our modern plant reference collection challenge the assumption that grass inflorescence phytolith can be used as a seasonality indicator.

Plant and soil phytolith analysis of a relictual community of Butia yatay in temperate-humid savannas (Entre Ríos, Argentina)

Although palms are recognized as a plant group of tropical and sub-tropical ecosystems, in South America they can also be found in temperate savannas under certain conditions. Therefore, since these plants have been widely used as palaeoindicators in warm and humid climates, it is important to know what phytolith contribution these plants have made in temperate environments. El Palmar National Park (Argentina) protects the largest remnant of savanna palm, Butia yatay (Mart.) Becc., one of the southernmost palm communities in the continent. This modern analogue study assessed the variability of silica phytoliths in 15 selected species of plants, 20 mulch samples (organic horizon) and 60 soil samples that were collected in all the plant communities selected for this study: dense palm trees (DPT), shrubbery with isolated tall palms (SIP), psammophile steppe (PS) and humid psammophile steppe (HPS). Our results show that grasses exhibit the most diverse forms. Palms, sedges and dicots can be distinguished by the different proportions of several diagnostic morphotypes. Palm tree communities can be characterized based on a presence a high proportion of globular echinate and trapeziform sinuate/oblong phytoliths. Psammophile steppes have a high proportion of bilobate, polylobate and cross phytoliths and a low presence of globular echinate. Humid psammophile steppes show a high presence of bilobate, cross and dicot phytoliths with a low proportion of trapeziform sinuate/oblong phytoliths and an absence of globular echinate morphotypes. The ratio of palm to grass phytoliths allowed us to obtain differences between the palm groves, psammophile steppe and humid psammophile steppe ecosystems. These analyses can then be used to determine this type of ecosystem in temperate humid savannas. Phytolith assemblages provide an important record for the characterization of the plant-soil system and production-incorporation system in mixed communities as a tool in the construction of palm trees paleoenvironments.

A possible role of biogenic silica in esophageal cancer in North China?

Certain areas in North China have the highest incidence of esophageal squamous cell carcinoma (ESCC) in the world, which has not seen convincing explanation by any risk factor yet. Biogenic silica in millet bran was linked to ESCC in the early 1980s but the hypothesis was largely dismissed because of the lack of geographic correlation between millet consumption and ESCC. Later epidemiological studies disclosed the linkage of wheat consumption in North China to ESCC instead. Now, we hypothesize silica phytoliths (silicified bodies that have definite shapes) from wheat chaff are a major etiologic factor of ESCC in this region. This hypothesis is supported by the potentially high abundance of silica phytoliths on the bracts of wheat (Triticum aestivum) in North China due to favorable Si-accumulation genotype, arid climate, and siallitic soil with bioavailable Si. These silica phytoliths can contaminate wheat flour and cause repeated local injuries in the esophagus and stimulate proliferation by providing anchorage.

Observation of the transformation of silica phytoliths into SiC and SiO2 particles in biomass-derived carbons by using SEM/EDS, Raman spectroscopy, and XRD

Scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy, Raman spectroscopy, and X-ray diffraction were successfully used to observe the location and morphology of the silica phytoliths in biomass-derived carbons and their transformation into SiC and SiO2 particles at high heat treatment temperatures (HTT). The analyses were conducted in chars derived from the endocarp of babassu coconut (EBC), which naturally contains 1.6 wt% of silica in its mineral matter. It was observed that EBC chars with 500–1200 °C HTT present globular echinate SiO2 phytoliths with sizes of 12–16 μm; these phytoliths are mostly concentrated around the surface of the submillimeter char fibers and also in the carbonaceous char matrix. No phytoliths are found in the interior of the char fibers. At 1200 °C HTT, the phytoliths begin to be rounded, and above 1300 °C HTT, most phytoliths decompose and silicon reacts with carbon-forming nanocrystalline β-SiC particles (~ 35 nm crystallite size). Numerous (tens to hundreds) micro- and sub-micro-amorphous or nanostructured SiO2 particles (with sizes predominantly below 2 µm) are then observed at the sites previously occupied by the phytoliths. Few rounded phytoliths survive at 1400 °C HTT, but disappear at higher HTTs (1600–2000 °C). It is likely that the ensembles of micro- and sub-micro-SiO2 particles observed in many sites correspond to the inner remaining part of the original phytoliths, whose most external SiO2 structures (at and near the surface) decompose and take part in the carbothermal reaction for the formation of SiC.

Influence of Calcium Silicate Application on the Population of Sucking Pests of Groundnut (Arachis hypogaea L.)

Field experiments with foliar application of calcium silicate @ 2.0, 3.5 and 5.0%, soil drenching of calcium silicate @ 10.0, 15.0 and 20.0% and combination of foliar and soil drenching @ 2.0% + 20.0%, 3.5% + 15.0% and 5.0% + 10.0% were evaluated on 20 days old groundnut plant and compared with untreated check with average weather condition of 30 ± 2 ∘C and 79 ± 5 % RH at farmers’ holdings, Azhagarkovil, Madurai District, Tamil Nadu, India. Application of calcium silicate via foliage and soil simultaneously @ 5 and 10% on 20 days after dibbling of groundnut was effective to reduce the population of Empoasca kerri, Aphis craccivora and Scirtothrips dorsalis throughout the crop period, resulting mean population of 17.52 numbers/10 plants, 18.64 numbers/2.5 cm shoot and 11.06 numbers/5 leaflets, respectively while they were 35.57 numbers/10 plants, 36.08 numbers/2.5 cm shoot and 20.28 numbers/5 leaflets in untreated control. Reduction in population of sucking pests in groundnut might be due to silica induced plant defensive enzymes, however, the moderate reduction in population of sucking pests in groundnut can be well explained due to the impression of less accumulation of silica phytoliths in shoot tips and vascular bundle of groundnut plants where sucking pests feed.

Nano-indentation of native phytoliths and dental tissues: implications for herbivore-plant combat and dental wear proxies

Tooth wear induced by abrasive particles is a key process affecting dental function and life expectancy in mammals. Abrasive particles may be plant endogenous opal phytoliths, exogene wind-blown quartz dust or rain borne mineral particles ingested by mammals. Nano-indentation hardness of abrasive particles and dental tissues is a significant yet not fully established parameter of this tribological system. We provide consistent nano-indentation hardness data for some of the major antagonists in the dental tribosystem (tooth enamel, tooth dentine and opaline phytoliths from silica controlled cultivation). All indentation data were gathered from native tissues under stable and controlled conditions and thus maximize comparability to natural systems. Here we show that native (hydrated) wild boar enamel exceeds any hardness measures known for dry herbivore tooth enamel by at least 3 GPa. The native tooth enamel is not necessarily softer then environmental quartz grit, although there is little overlap. The native hardness of the tooth enamel exceeds that of any silica phytolith hardness recently published. Further, we find that native reed phytoliths equal native suine dentine in hardness, but does not exceed native suine enamel. We also find that native suine enamel is significantly harder than dry enamel and dry phytoliths are harder than native phytoliths. Our data challenge the claim that the culprit of tooth wear may be the food we chew, but suggest instead that wear may relates more to exogenous than endogenous abrasives.

Extraction and biocompatibility analysis of silica phytoliths from sorghum husk for three-dimensional cell culture

Abstract Nowadays, scientists lay greater emphasis on bio-prospecting of new materials from biological resources. We isolated biogenic micro-silica phytolith from husk of red sorghum with rigid morphologies, to develop biocompatible scaffolds for use in 3D cultures. Spherical, dumbbell, and saddle-shaped silica phytoliths were extracted by a calcination processes and silica phytoliths with different morphologies were isolated by density gradient centrifugation. The XRD patterns confirmed that silica phytoliths were amorphous. The microscopic images suggested the presence of spherical, saddle, and dumbbell-shaped silica bodies with dimensions of 10–300 μm. The functional integrity of each spherical-, saddle-, and dumbbell-shaped three-dimensional (3D) silica phytoliths was analyzed on human mesenchymal stem cells. Our results outlined that various forms of silica phytoliths in the form of 3D scaffolds can be used in 3D cell culture models for tissue engineering applications. The results highlighted that these agricultural wastes containing silica phytoliths could be exploited for tissue engineering applications.