Modified diatomite for soil remediation and its implications for heavy metal absorption in Calendula officinalis.

BACKGROUND: Among different adsorbents, natural and inorganic compounds such as diatomite are important and advantageous in terms of high efficiency and cost-effectiveness, and function in stabilizing heavy metals in the environment. Calendula officinalis, a plant known as a high accumulator of heavy metals, was cultivated in soil treated with varying concentrations of modified diatomite to demonstrate the efficiency of modified diatomite in stabilizating of heavy metals in soils, RESULTS: The modification of diatomite aimed to enhance Calendula officinalis adsorptive properties, particularly towards heavy metals such as lead (Pb), Zinc (Zn), Chromium (Cr), Nickle (Ni), and Copper (Cu), common contaminants in industrial soils. The experimental design included both control and treated soil samples, with assessments at regular intervals. Modified diatomite significantly decreased the bioaccumulation of heavy metals in contaminated soils except Zn, evidenced by decreased DTPA extractable heavy metals in soil and also heavy metal concentrations in plant tissues. Using 10% modified diatomite decreased 91% Pb and Cu, 78% Cr, and 79% Ni concentration of plants compared to the control treatment. The highest concentration of Zn in plant tissue was observed in 2.5% modified diatomite treatment. Remarkably, the application of modified diatomite also appeared to improve the nutrient profile of the soil, leading to enhanced uptake of key nutrients like phosphorus (P) 1.18%, and potassium (K) 79.6% in shoots and 82.3% in roots in Calendula officinalis. Consequently, treated plants exhibited improved growth characteristics, including shoots and roots height of 16.98% and 12.8% respectively, and shoots fresh and dry weight of 48.5% and 50.2% respectively., compared to those in untreated, contaminated soil. CONCLUSION: The findings suggest promising implications for using such amendments in ecological restoration and sustainable agriculture, particularly in areas impacted by industrial pollution.

Obtaining New Biocompatible Composite Materials with Antibacterial Properties Based on Diatomite and Biologically Active Compounds.

This study aimed to create new composite materials based on diatomite-a non-organic porous compound-through its surface modification with bioactive organic compounds, both synthetic and natural. Chloramphenicol, tetrahydroxymethylglycoluril and betulin were used as modifying substances. Composite materials were obtained by covering the diatomite surface with bioactive substance compounds as a solution and material dispersion in it. The materials were characterized by IR spectroscopy, SEM and X-ray photoelectron spectroscopy. For the biocomposites, the hemolytic effect, plasma proteins' adsorption on the surface and the antibacterial activity of the obtained materials were studied. Results show that the obtained materials are promising for medicine and agriculture.

In-line sample trap columns with diatomite for large-volume injection in CZE-IM-MS.

The analysis of low-abundant compounds with capillary zone electrophoresis-drift-tube ion mobility spectrometry-mass spectrometry (CZE-DTIMS-MS) is compromised due to the low injectable sample volumes in CZE and low duty cycle in DTIMS. Fritless packed in-line trap columns, using solid-phase extraction sorbent particles, have been used to increase injection volumes in CZE, but these columns are difficult to prepare and exhibit rapidly increasing back pressures. To provide smooth and complete filling of trap columns as well as to ensure higher and sustained flow rates though the columns, blends of cation and anion exchange particles with diatomite were used. The application of diatomite blends ensured the use of trap columns for at least 100 injections, with maximum injection volumes over 10 µl, which corresponds to an enrichment factor of more than 1000 over conventional injections in CZE-MS, enabling the detection of low nM concentrations of N-glycans with CZE-IMS-MS.

Comparison of host cell protein removal by depth filters with diatomaceous earth and synthetic silica filter aids using model proteins.

A number of studies have demonstrated that depth filtration can provide significant adsorptive removal of host cell proteins (HCP), but there is still considerable uncertainty regarding the underlying factors controlling HCP binding. This study compared the binding characteristics of two fine grade depth filters, the X0SP (polyacrylic fiber with a synthetic silica filter aid) and X0HC (cellulose fibers with diatomaceous earth (DE) as a filter aid), using a series of model proteins with well-defined physical characteristics. Protein binding to the X0SP filter was dominated by electrostatic interactions with greatest capacity for positively-charged proteins. In contrast, the X0HC filter showed greater binding of more hydrophobic proteins although electrostatic interactions also played a role. In addition, ovotransferrin showed unusually high binding capacity to the X0HC, likely due to interactions with metals in the DE. Scanning Electron Microscopy with Energy Dispersive Spectroscopy was used to obtain additional understanding of the binding behavior. These results provide important insights into the physical phenomena governing HCP binding to both fully synthetic and natural (cellulose + DE) depth filters.

Drug Delivery through Epidermal Tissue Cells by Functionalized Biosilica from Diatom Microalgae.

Diatom microalgae are a natural source of fossil biosilica shells, namely the diatomaceous earth (DE), abundantly available at low cost. High surface area, mesoporosity and biocompatibility, as well as the availability of a variety of approaches for surface chemical modification, make DE highly profitable as a nanostructured material for drug delivery applications. Despite this, the studies reported so far in the literature are generally limited to the development of biohybrid systems for drug delivery by oral or parenteral administration. Here we demonstrate the suitability of diatomaceous earth properly functionalized on the surface with n-octyl chains as an efficient system for local drug delivery to skin tissues. Naproxen was selected as a non-steroidal anti-inflammatory model drug for experiments performed both in vitro by immersion of the drug-loaded DE in an artificial sweat solution and, for the first time, by trans-epidermal drug permeation through a 3D-organotypic tissue that better mimics the in vivo permeation mechanism of drugs in human skin tissues. Octyl chains were demonstrated to both favour the DE adhesion onto porcine skin tissues and to control the gradual release and the trans-epidermal permeation of Naproxen within 24 h of the beginning of experiments. The evidence of the viability of human epithelial cells after permeation of the drug released from diatomaceous earth, also confirmed the biocompatibility with human skin of both Naproxen and mesoporous biosilica from diatom microalgae, disclosing promising applications of these drug-delivery systems for therapies of skin diseases.

Diatom-Based Nanomedicine for Colorectal Cancer Treatment: New Approaches for Old Challenges.

Colorectal cancer is among the most prevalent and lethal cancers globally. To address this emergency, countries have developed diffuse screening programs and innovative surgical techniques with a consequent decrease in mortality rates in non-metastatic patients. However, five years after diagnosis, metastatic CRC is still characterized by less than 20% survival. Most patients with metastatic CRC cannot be surgically treated. For them, the only option is treatment with conventional chemotherapies, which cause harmful side effects in normal tissues. In this context, nanomedicine can help traditional medicine overcome its limits. Diatomite nanoparticles (DNPs) are innovative nano-based drug delivery systems derived from the powder of diatom shells. Diatomite is a porous biosilica largely found in many areas of the world and approved by the Food and Drug Administration (FDA) for pharmaceutical and animal feed formulations. Diatomite nanoparticles with a size between 300 and 400 nm were shown to be biocompatible nanocarriers capable of delivering chemotherapeutic agents against specific targets while reducing off-target effects. This review discusses the treatment of colorectal cancer with conventional methods, highlighting the drawbacks of standard medicine and exploring innovative options based on the use of diatomite-based drug delivery systems. Three targeted treatments are considered: anti-angiogenetic drugs, antimetastatic drugs, and immune checkpoint inhibitors.

Acclimatization of Sweet Potatoes Under in vitro Application of Diatomaceous Earth.

Diatomaceous earth is an organic naturally occurring material rich in silicon. This silicon source can be used in organic agriculture, it also has a great potential of use in the acclimatization of crops. However, there are no reports of the effects of diatomaceous earth supplementation on the micropropagation of sweet potato. Thus, the objective of this study was to evaluate the effects of different concentrations of diatomaceous earth applied in vitro on the growth, physiology and anatomy of sweet potato cv. 'Brazlândia Branca' after acclimatization. Four concentrations of diatomaceous earth. After 30 days of in vitro growth, the plants were transferred to a greenhouse for acclimatization. After 45 days, leaf number, shoot and root length, fresh and dry shoot and root mass, gas exchange, chlorophyll content, root and leaf anatomy. The experimental design was completely randomized. The supplementation of diatomaceous earth in the in vitro cultivation had beneficial effects, increasing the accumulation of mass, improving the photosynthetic apparatus and promoting favorable anatomical characteristics during the acclimatization of the sweet potato plants. In addition, the use of diatomaceous earth achieved adequate seedling development, with higher seedling quality and resistance to biotic and abiotic effects than attained with control treatment.

Natural deep eutectic solvent (fructose-glycine) functionalized-celite/ polyethylene glycol hydrogel nanocomposite for phosphate adsorption: Statistical analysis.

The increasing usage of phosphate fertilizers for agricultural purposes has led to an augmented level of phosphorus in watercourses negatively impacting the ecosystems and water quality warranting its amputation from polluted water. This article describes the preparation of a novel natural deep eutectic solvent (NADES) functionalized-celite/polyethylene glycol hydrogel nanocomposite (NADES-Cel/PEG HNC) for adsorptive phosphate removal from water. The XRD, FTIR, SEM coupled with EDX spectroscopy, TEM, BET analysis, and pHpzc measurement were used to characterise the prepared material. Central composite design (CCD) in response surface methodology (RSM) was used for experimental design to analyse the individual and combined impact of five operational parameters on equilibrium adsorption capacity (Qe), and evaluate the optimal operating conditions by numerical optimization, which were obtained as: contact time (60 min), adsorbent dosage (1.0 g/L), initial [PO43-] (80 mg/L), initial solution pH (3.5), and temperature (304 K). The adsorption process was best explicated via Langmuir adsorption isotherm with a noteworthy saturation capacity, Qm of 111.80 mg PO43-/g at 298 K, and was favourable (S* = 0.99), feasible (ΔG° = -7.02 kJ/mol), exothermic (ΔH° = -8.39 kJ/mol) and physical in nature. The uptake mechanism largely involved H-bonding, electrostatic interaction, n-π interaction and pore-filling. Uptake kinetics of PO43- was best explicated by pseudo-second order model, and the rate-determining step involved both intraparticle and liquid film diffusion mechanisms. The admirable performance of NADES-Cel/PEG HNC was signified by its competent adsorption efficacy and effectual reusability. The pertinence of the hydrogel nanocomposite for treatment of real wastewater was tested. Hence, NADES-Cel/PEG HNC might prove to be a pragmatic adsorbent for decontamination of PO43- from an aqueous environment.

Modified Diatomaceous Earth in Heparin Recovery from Porcine Intestinal Mucosa.

Heparin, a highly sulfated glycosaminoglycan, is a naturally occurring anticoagulant that plays a vital role in various physiological processes. The remarkable structural complexity of heparin, consisting of repeating disaccharide units, makes it a crucial molecule for the development of commercial drugs in the pharmaceutical industry. Over the past few decades, significant progress has been made in the development of cost-effective adsorbents specifically designed for the adsorption of heparin from porcine intestinal mucosa. This advancement has been driven by the need for efficient and scalable methods to extract heparin from natural sources. In this study, we investigated the use of cationic ammonium-functionalized diatomaceous earth, featuring enhanced porosity, larger surface area, and higher thermal stability, to maximize the isolated heparin recovery. Our results showed that the higher cationic density and less bulky quaternary modified diatomaceous earth (QDADE) could adsorb up to 16.3 mg·g-1 (31%) of heparin from the real mucosa samples. Additionally, we explored the conditions of the adsorbent surface for recovery of the heparin molecule and optimized various factors, such as temperature and pH, to optimize the heparin uptake. This is the introductory account of the implementation of modified diatomaceous earth with quaternary amines for heparin capture.

Insecticidal effects of two Tunisian diatomaceous earth loaded with Thymus capitatus (L.) Hoffmans and Links as an ecofriendly approach for stored coleopteran pest control.

This study investigated composition and toxicity of Thyme EOs against two main stored grain insect pests. Carvacrol was distinguished as a major compound (78.34%). In laboratory tests, EOs applied by both direct contact and fumigant tests was more toxic to L. serricorne than T. castaneum. The EOs were also tested combined with two Tunisian Diatomaceous earths (DEs) against T. castaneum. The LC50 was 6.28 µL/L air for natural preparation EO/R1, 5.90 µL/L air for EO/R2 and 121.17 for crude EOs by fumigant test, respectively. While, contact test revealed that natural DEs; dust act as an insecticide with 'LC50' values of 3.22 and 0.29 µL/cm2f or R1 and R2, respectively. Moreover, a significant difference was noted between crude EO, EO/R1 and EO/R2. Overall, the enhancement of the Tunisian DEs' insecticidal activity by its mix with EOs may be a promising active substance as a stored grain protectant.

Recycling of used vegetable oils by powder adsorption.

The treatment of used vegetable oil (UVO) with seven different adsorbents and through two different procedures (stirring and gravity filtration) was explored. Important differences in terms of density, turbidity, electrical resistance, free fatty acids (FFAs) content and relative fatty acid distribution were observed. Different outcomes were shown depending both on the adsorbent and on the procedure. Lower values of density and FFAs were registered for oils treated by gravity filtration with portland (respectively 0.6% and 0.81 g/ml) and celite (respectively 0.7% and 0.72 g/ml). Considering the undesired leaching from the powder to the oil, related to the turbidity, the celite resulted more suitable for the oil recycling (241 Nephelometric Turbidity Unit (NTU) for portland vs 184 NTU for celite). In addition, Fourier-transform infrared spectroscopy combined with multivariate analysis allowed to determine a chemical fingerprint relative characteristic of vegetable oils recycled by gravity or by adsorption by stirring.

Development of Surface Chemical Strategies for Synthesizing Redox-Responsive Diatomite Nanoparticles as a Green Platform for On-Demand Intracellular Release of an Antisense Peptide Nucleic Acid Anticancer Agent.

Redox-responsive silica drug delivery systems are synthesized by aeco-friendly diatomite source to achieve on-demand release of peptide nucleic acid (PNA) in tumor reducing microenvironment, aiming to inhibit the immune checkpoint programmed cell death 1 receptor/programmed cell death receptor ligand 1 (PD-1/PD-L1) in cancer cells. The nanoparticles (NPs) are coated with polyethylene glycol chains as gatekeepers to improve their physicochemical properties and control drug release through the cleavable disulfide bonds (S-S) in a reductive environment. This study describes different chemical conditions to achieve the highest NPs' surface functionalization yield, exploring both multistep and one-pot chemical functionalization strategies. The best formulation is used for covalent PNA conjugation via the S-S bond reaching a loading degree of 306 ± 25 µg PNA mg-1 DNPs . These systems are used for in vitro studies to evaluate the kinetic release, biocompatibility, cellular uptake, and activity on different cancer cells expressing high levels of PD-L1. The obtained results prove the safety of the NPs up to 200 µg mL-1 and their advantage for controlling and enhancing the PNA intracellular release as well as antitumor activity. Moreover, the downregulation of PD-L1 observed only with MDA-MB-231 cancer cells paves the way for targeted immunotherapy.

Enantiodivergent Chemoenzymatic Dynamic Kinetic Resolution: Conversion of Racemic Propargyl Alcohols into Both Enantiomers.

Natural lipases typically recognize enantiomers of alcohols based on the size differences of substituents near the carbinol moiety and selectively react with the R enantiomers of secondary alcohols. Therefore, lipase-catalyzed dynamic kinetic resolution (DKR) of racemic secondary alcohols produces only R enantiomers. We report herein a method for obtaining S enantiomers by DKR of secondary 3-(trialkylsilyl)propargyl alcohols by using a well-known R-selective Pseudomonas fluorescens lipase in combination with a racemization catalyst VMPS4, in which the silyl group reverses the size relationship of substituents near the carbinol moiety. We have already reported R-selective DKR of the corresponding propargyl alcohols without substituents on the ethynyl terminal carbon, and the presence of an easily removable silyl group has enabled us to produce both enantiomers of propargyl alcohols in high chemical yields and with high enantiomeric excess. In addition, immobilization of the lipase on Celite was found to be important for achieving a high efficiency of the DKR.

A SERS platform based on diatomite modified by gold nanoparticles using a combination of layer-by-layer assembly and a freezing-induced loading method.

Siliceous diatom frustules represent an up-and-coming platform for a range of bio-assisted nanofabrication processes able to overcome the complexity and high cost of current engineering technology solutions in terms of negligibly small power consumption and environmentally friendly processing combined with unique highly porous structures and properties. Herein, the modification of diatomite - a soft, loose, and fine-grained siliceous sedimentary rock composed of the remains of fossilized diatoms - with gold nanoparticles using layer-by-layer technology in combination with a freezing-induced loading approach is demonstrated. The obtained composite structures are characterized by dynamic light scattering, extinction spectroscopy, scanning (SEM) and transmission electron microscopy (TEM), and photoacoustic imaging techniques, and tested as a platform for surface-enhanced Raman scattering (SERS) using Rhodamine 6G. SEM, TEM, and energy dispersive X-ray spectroscopy (EDX) confirmed a dense coating of gold nanoparticles with an average size of 19 nm on the surface of the diatomite and within the pores. The photoacoustic signal excited at a wavelength of 532 nm increases with increasing loading cycles of up to three polyelectrolyte-gold nanoparticle bilayers. The hybrid materials based on diatomite modified with gold nanoparticles can be used as SERS substrates, but also as biosensors, catalysts, and platforms for advanced bioimaging.

Microwave Absorption of α-Fe2O3@diatomite Composites.

A neoteric round sieve diatomite (De) decorated with sea-urchin-like alpha-type iron trioxide (α-Fe2O3) synthetics was prepared by the hydrothermal method and further calcination. The results of the electromagnetic (EM) parameters of α-Fe2O3-decorated De (α-Fe2O3@D) showed that the minimum reflection loss (RLmin) of α-Fe2O3@D could reach -54.2 dB at 11.52 GHz and the matched absorber thickness was 3 mm. The frequency bandwidth corresponding to the microwave RL value below -20 dB was up to 8.24 GHz (9.76-18 GHz). This indicates that α-Fe2O3@D composite can be a lightweight and stable material; because of the low density of De (1.9-2.3 g/cm3), the density of α-Fe2O3@D composite material is lower than that of α-Fe2O3 (5.18 g/cm3). We found that the combination of the magnetic loss of sea-urchin-like α-Fe2O3 and the dielectric loss of De has the most dominant role in electromagnetic wave absorption and loss. We focused on comparing the absorbing properties before and after the formation of sea-urchin-like α-Fe2O3 and explain in detail the effects of the structure and crystal shape of this novel composite on the absorbing properties.

The catalytic aerial oxidation of As(III) in alkaline solution by Mn-loaded diatomite.

The oxidization of As(III) to As(V) is necessary for both the detoxification of arsenic and the removal of arsenic by solidification. In order to achieve high efficiency and low cost As(III) oxidation, a novel process of catalytic aerial oxidation of As(III) is proposed, using air as oxidant and Mn-loaded diatomite as a catalyst. Through systematic characterization of the reaction products, the catalytic oxidation reaction law of Mn-loaded diatomite for As(III) was found out, and its reaction mechanism was revealed. Results show that Mn-loaded diatomite achieved a good catalytic effect for aerial oxidation of As(III) and maintained high performance over multiple cycles of reuse, which was directly related to the structure of diatomite and the behavior of manganese. Under the conditions of a catalyst concentration of 20 g/L, an air flow rate of 0.3 m3/h, a reaction temperature of 50 °C and an initial pH of 12.6, 96.04% As(III) oxidation was achieved after 3 h. Furthermore, the efficiency of As(III) oxidation did not change significantly after ten cycles of reuse. XPS analysis of the reaction products confirmed that the surface of the catalyst was rich in Mn(III), Mn(IV) and adsorbed oxygen(O-H), which was the fundamental reason for the excellent performance of Mn-loaded diatomite in the catalytic oxidation of As(III).

Enrichment of Quercetin from Winemaking Residual Diatomaceous Earth via a Tailor-Made Imprinted Adsorbent.

Residual diatomaceous earth (RDE) from winemaking activities is a rich and currently underexploited source of phenolic compounds which ought to be recycled from the perspective of circular bioeconomy. In this work, we demonstrate the feasibility of molecularly imprinted polymers (MIPs) for the enrichment of quercetin, a flavonoid at a fairly high content in residual diatomaceous earth. These MIPs were synthesized through free radical polymerization. FTIR confirmed the integration of the functional monomers into the polymeric chains. Batch adsorption experiments were used to assess the retention and selectivity of those MIPs towards quercetin. Commercial resins were compared with the synthesized materials using the same procedures. These adsorption experiments allowed the selection of the best performing MIP for the valorization of RDE extract. This treatment consisted of saturating the selected MIP with the extract and then desorbing the retained compounds using solvents of selected compositions. The desorbed fractions were analyzed using liquid chromatography, and the results demonstrated an increase in quercetin's fractional area from 5% in the RDE extract to more than 40% in some fractions, which is roughly an eightfold enrichment of quercetin. Moreover, other flavonoids of close chemical structure to quercetin have been rather retained and enriched by the MIP.

SERS Quantification of Galunisertib Delivery in Colorectal Cancer Cells by Plasmonic-Assisted Diatomite Nanoparticles.

The small molecule Galunisertib (LY2157299, LY) shows multiple anticancer activities blocking the transforming growth factor-ß1 receptor, responsible for the epithelial-to-mesenchymal transition (EMT) by which colorectal cancer (CRC) cells acquire migratory and metastatic capacities. However, frequent dosing of LY can produce highly toxic metabolites. Alternative strategies to reduce drug side effects can rely on nanoscale drug delivery systems that have led to a medical revolution in the treatment of cancer, improving drug efficacy and lowering drug toxicity. Here, a hybrid nanosystem (DNP-AuNPs-LY@Gel) made of a porous diatomite nanoparticle decorated with plasmonic gold nanoparticles, in which LY is retained by a gelatin shell, is proposed. The multifunctional capability of the nanosystem is demonstrated by investigating the efficient LY delivery, the enhanced EMT reversion in CRCs and the intracellular quantification of drug release with a sub-femtogram resolution by surface-enhanced Raman spectroscopy (SERS). The LY release trigger is the pH sensitivity of the gelatin shell to the CRC acidic microenvironment. The drug release is real-time monitored at single-cell level by analyzing the SERS signals of LY in CRC cells. The higher efficiency of LY delivered by the DNP-AuNPs-LY@Gel complex paves the way to an alternative strategy for lowering drug dosing and consequent side effects.

Porous chitosan/partially reduced graphene oxide/diatomite composite as an efficient adsorbent for quantitative colorimetric detection of pesticides in a complex matrix.

On-site, instrument free quantitative analysis of pesticides is of significant importance for food safety control. However, it is still a great challenge for pesticide detection in food via the current visual detection methods due to the presence of interferents in a complex matrix. In this study, a complex tea matrix had a strong effect on a gold nanoparticles (Au NPs) based colorimetric sensor for the detection of pesticides. Here, a porous chitosan/partially reduced graphene oxide/diatomite (CS/prGO/DM) composite was successfully synthesized via a facile hydrothermal treatment. It could act as an efficient adsorbent for removing different types of tea interferents. A colorimetric sensing platform for the quantitative detection of pesticides in a complex matrix was successfully established. The color changes of the aggregation of Au NPs induced by pesticides were captured using the camera of a smartphone and the images were processed with average RGB (red, green, and blue) values obtained using self-developed software. The G/R values and A700/525 values obtained from UV-vis spectra could be used for quantitative analysis of pesticides. The limits of detection of phosalone and thiram in tea were 90 nM and 13.8 nM, respectively. It is expected that graphene-based materials are attractive for wide application of on-site colorimetric quantitative detection in a variety of fields like environmental protection, food safety and bioanalysis.

A case of oral foreign-body granuloma due to diatoms.

Diatoms are photosynthetic algae with a siliceous exoskeleton. Diatoms are utilized by a wide array of industries for applications such as filtration and pest control. Unsubstantiated claims have also propelled their societal reach to trendy oral and topical uses. This case highlights a rare case of an oral granuloma secondary to diatoms. An 80-year-old woman presented with a mobile, firm, asymptomatic submucosal mass on her lower left mandibular vestibular mucosa. Histopathology showed a non-caseating granulomatous reaction to diatoms. Her only verified contact with a diatomaceous earth product was a dental impression using alginate after upper front teeth trauma 5 months before. Although there have been several cases of allergic contact dermatitis attributed to diatoms, there are no reported cases of diatom-induced granuloma formation found in the literature. There are, however, ample data on granulomas initiated by silica. Given the silica-based composition of diatoms, and the broad use of diatoms in industry and alternative medicine, it is unclear why diatom-induced granulomas are not more widely described. This report may alert clinicians to the existence of diatom granulomas and incline them to tailor their history to cover questions about possible exposure when evaluating patients presenting with a localized oral lesion.