Adsorption and Recovery of Polyphenolic Flavonoids Using TiO2-Functionalized Mesoporous Silica Nanoparticles

Functionalization of niobium nitrogen-doped titanium dioxide (TiO2) nanoparticles with ethanolic extracts of Mentha arvensis

Titanium dioxide (TiO2) nanoparticles have gained significant attention due to their wide-ranging applications. This research explores an approach to functionalize Niobium Nitrogen Titanium Dioxide nanoparticles (Nb-N-TiO2 NPs) with Mentha arvensis ethanolic leaf extracts. This functionalization allows doped NPs to interact with the bioactive compounds in extracts, synergizing their antioxidant activity. While previous studies have investigated the antioxidant properties of TiO2 NPs synthesized using ethanolic extracts of Mentha arvensis, limited research has focused on evaluating the antioxidant potential of doped nanoparticles functionalized with plant extracts. The characterization analyses are employed by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Ultraviolet-visible (UV-Vis) spectroscopy to evaluate these functionalized doped nanoparticles thoroughly. Subsequently, the antioxidant capabilities through the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric-reducing antioxidant power (FRAP) assays have been assessed. Within functionalized Nb-N-TiO2, the FTIR has a distinctive peak at 2350, 2010, 1312, 1212, and 1010 cm-1 with decreased transmittance associated with vibrations linked to the Nb-N bond. SEM revealed a triangular aggregation pattern, 500 nm to 2 µm of functionalized Nb-N-TiO2 NPs. Functionalized doped Nb-N-TiO2 NPs at 500 µg mL-1 exhibited particularly robust antioxidant activity, achieving an impressive 79% efficacy at DPPH assessment; meanwhile, ferric reduction efficiency of functionalized doped Nb-N-TiO2 showed maximum 72.16%. In conclusion, doped Nb-N-TiO2 NPs exhibit significantly enhanced antioxidant properties when functionalized with Mentha arvensis ethanolic extract compared to pure Nb-N-TiO2 manifested that doped Nb-N-TiO2 have broad promising endeavors for various biomedicine applications.

Efficient and Selective Adsorption of cis-Diols via the Suzuki-Miyaura Cross-Coupling-Modified Phenylboronic-Acid Functionalized Covalent Organic Framework

In this work, a functional group (boronic acid) was modified onto a covalent organic framework (COF) using the Suzuki-Miyaura cross-coupling reaction to obtain a phenylboronic acid-functionalized covalent organic framework (BrCOF-PBA). This product was used as a selective adsorbent and largely as an efficient solid-phase extractant of flavonoids containing cis-diol structures like quercetin (QUE). Five or six-membered cyclic esters generated from the COF were characterized, and some physicochemical studies were performed, resulting in excellent chemical stability and crystallinity, high specific surface area, stable pore structure, and regular pore size. Unique selectivity of BrCOF-PBA was observed toward QUE and exhibited a huge adsorption capacity (213.96 mg g-1) in a relatively short time (90 min). In contrast, the adsorption properties of morin (MOR) and kaempferol (KAE) with a certain degree of chemical similarity to QUE were only 27.62 and 21.76 mg g-1, respectively. BrCOF-PBA also demonstrated good reusability and robustness, making it an attractive composite material for further analytical applicability.

Mesoporous silica-based nanocarriers with dual response to pH and ROS for enhanced anti-inflammation therapy of 5-demethylnobiletin against psoriasis-like lesions

Psoriasis is an inflammatory skin disease accompanied with chronic papulosquamous lesions and multiple comorbidities that considerably affect patients' quality of life. In order to develop an enhanced therapeutic strategy for psoriasis, 5-demethylnobiletin (5-DN), a kind of polymethoxyflavones (PMFs) with high anti-inflammatory activity, was delivered in vitro and in vivo by the nanocarrier of mesoporous silica nanoparticles (MSNs) both in the human keratinocytes HaCaT cell line and the mouse model with psoriasis-like lesions. The drug-loaded nanocarrier system (MSNs@5-DN) significantly improved the biocompatibility and bioavailability of 5-DN. Investigations at cell biological, histopathological, and molecular levels revealed the pharmacological mechanism of the drug delivery system, including the inhibition of inflammatory responses by downregulating the proinflammatory cytokine levels of tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6). The upregulation of anti‑inflammatory cytokine of transforming growth factor-β1 (TGF-β1) and microRNA-17-5p, a critical regulator of the PTEN/AKT pathway, was also observed. The psoriasis-like lesions were markedly ameliorated in the mouse models treated with MSNs@5-DN. The designed drug-loading system shows an enhanced therapeutic outcome for psoriasis-like lesion compared with free 5-DN. This study revealed the synergistic effect of functionalized MSNs loaded with PMFs on the clinical treatment of human psoriasis.

Silica-based nanosystems against antibiotic-resistant bacteria and pathogenic viruses

Today, with the intensity of antibiotic abuse and self-medication, the need for the use of novel systems with high efficiency and biosafety for targeted drug delivery against antibiotic-resistant bacteria and their infections should be highly considered by researchers. Silica-based nanosystems with unique physicochemical properties such as large surface area, tuneable pore diameter, drug loading capacity, controlled particle size/morphology, and good biocompatibility are attractive candidates against antibiotic-resistant bacteria and pathogenic viruses. They can be loaded with antiviral and antimicrobial drugs or molecules through their exclusive internal porous structures or different surface linkers. In this context, smart nanosystems can be produced via suitable surface functionalization/modification with a variety of functional groups to act against different clinical pathogenic microbes or viruses, offering great opportunities for controlling and treating various infections. However, important criteria such as the ability to degrade, biocompatibility, biodegradability, cytotoxicity, stability, clearance from targeted organs should be systematically analysed to develop nanosystems or nanocarriers with high efficiency and multifunctionality. Herein, recent advancements pertaining to the application of silica-based nanosystems against antibiotic-resistant bacteria and pathogenic viruses are deliberated, focussing on important challenges and future perspectives.

Facile and selective separation of anthraquinones by alizarin-modified iron oxide magnetic nanoparticles

Anthraquinones are widely distributed in higher plants and possess broad biological activities. The conventional separation procedures for isolating anthraquinones from the plant crude extracts require multiple extraction, concentration, and column chromatography steps. In this study, we synthesized three alizarin (AZ)-modified Fe₃O₄ nanoparticles (Fe₃O₄@AZ, Fe₃O₄@SiO₂-AZ, and Fe₃O₄@SiO₂-PEI-AZ) by thermal solubilization method. Fe₃O₄@SiO₂-PEI-AZ showed strong magnetic responsiveness, high methanol/water dispersion, good recyclability, and high loading capacity for anthraquinones. To evaluate the feasibility of using Fe₃O₄@SiO₂-PEI-AZ for separating various aromatic compounds, we employed molecular dynamics simulations to predict the adsorption/desorption effects of PEI-AZ for various aromatic compounds in different methanol concentrations. The results showed that the anthraquinones could be efficiently separated from the monocyclic and bicyclic aromatic compounds by adjusting the methanol/water ratio. The Fe₃O₄@SiO₂-PEI-AZ nanoparticles were then used to separate the anthraquinones from the rhubarb extract. At 5% methanol, all the anthraquinones were adsorbed by the nanoparticles, thus allowing their separation from other components in the crude extract. Compared with the conventional separation methods, this adsorption method has the advantages of high adsorption specificity, simple operation, and solvent saving. This method sheds light on the future application of functionalized Fe₃O₄ magnetic nanoparticles to selectively separate desired components from complex plant and microbial crude extracts.

Environmental exposure and nanotoxicity of titanium dioxide nanoparticles in irrigation water with the flavonoid luteolin

Different concentrations of titanium oxide nanoparticles (TiO2NPs) have been frequently reported in treated wastewater used for the irrigation of crops. Luteolin is a susceptive anticancer flavonoid in many crops and rare medicinal plants that can be affected by exposure to TiO2NPs. This study investigates the potential transformation of pure luteolin in exposure to TiO2NP-containing water. In an in vitro system, three replicates of 5 mg L-1 of pure luteolin were exposed to TiO2NPs (0, 25, 50, 100 ppm). After 48 h exposure, the samples were extensively analyzed by Raman spectroscopy, ultraviolet-visible (UV-vis) spectroscopy, and dynamic light scattering (DLS). A positive correlation was found between TiO2NPs concentrations and the structural alteration of luteolin content, where over 20% of luteolin structure was allegedly altered in the presence of 100 ppm TiO2NPs. The increase of NPs diameter (∼70 nm) and dominant peaks in Raman spectra revealed that luteolin was adsorbed onto the TiO2NPs surface. Further, the second-order derivative analysis confirmed the transformation of luteolin upon exposure to TiO2NPs. This study provides fundamental insight into agricultural safety measures when exposed to air or water-borne TiO2NPs.

TiO2 Nanocrystals and Annona crassiflora Polyphenols Used Alone or Mixed Impact Differently on Wound Repair

Wounds treated with TiO2 nanoparticles (TiO2-NPs) show an improvement in healing time. However, little is known about the parameters that can contribute to this result. On the other hand, the treatment of wounds with polyphenols is widely known. These compounds are found in the peel of Annona crassiflora fruit and have antioxidant, analgesic and anti-inflammatory properties. In this study, we evaluated the healing effect of TiO2 nanocrystals (TiO2-NCs), polyphenolic fractions obtained from ethanolic extract of A. crassiflora fruit peel (PFAC) and mix (PFAC + TiO2-NCs) on the parameters of wound closure, inflammation, collagen deposition, metalloproteinase activity (MMPs) and angiogenesis. TiO2-NCs and PFAC have activity for wound healing, showed anti-inflammatory action and a shorter wound closure time. These treatments also contributed to increased collagen deposition, while only treatment with TiO2-NCs increased MMP-2 activity, parameters essential for the migration of keratinocytes and for complete restoration of the injured tissue. The combination of PFAC + TiO2-NCs reduced the effectiveness of individual treatments by intensifying the inflammatory process, in addition to delaying wound closure. We conclude that the interaction between the hydroxyl groups of PFAC polyphenols with TiO2-NCs may have contributed to difference in the healing activity of skin wounds.

Synthesis, modification and application of titanium dioxide nanoparticles: a review

Titanium dioxide (TiO₂) has been heavily investigated owing to its low cost, benign nature and strong photocatalytic ability. Thus, TiO₂ has broad applications including photocatalysts, Li-ion batteries, solar cells, medical research and so on. However, the performance of TiO₂ is not satisfactory due to many factors such as the broad band gap (3.01 to 3.2 eV) and fast recombination of electron-hole pairs (10^-12 to 10^-11 s). Plenty of work has been undertaken to improve the properties, such as structural and dopant modifications, which broaden the applications of TiO₂. This review mainly discusses the aspects of TiO₂-modified nanoparticles including synthetic methods, modifications and applications.

A glutathione-responsive silica-based nanosystem capped with in-situ polymerized cell-penetrating poly(disulfide)s for precisely modulating immuno-inflammatory responses

HYPOTHESIS

Precise modulation of immuno-inflammatory response is crucial to control periodontal diseases and related systemic comorbidities. The present nanosystem with the controlled-release and cell-penetrating manner enhances the inflammation modulation effects of baicalein in human gingival epithelial cells (hGECs) for better oral healthcare.

EXPERIMENTS

We constructed a red-emissive mesoporous silica nanoparticle-based nanosystem with cell-penetrating poly(disulfide) (CPD) capping, through a facile in-situ polymerization approach. It was featured with a glutathione-responsive manner and instant cellular internalization capacity for precisely delivering baicalein intracellularly. Laboratory experiments assessed whether and how the nanosystem per se with the delivered baicalein could modulate immuno-inflammatory responses in hGECs.

FINDINGS

The in-situ polymerized CPD layer capped the nanoparticles and yet controlled the release of baicalein in a glutathione-responsive manner. The CPD coating could facilitate cellular internalization of the nanosystem via endocytosis and thiol-mediated approaches. Notably, the intracellularly released baicalein effectively downregulated the expression of pro-inflammatory cytokines through inhibiting the NF-κB signaling pathway. The nanosystem per se could modulate immuno-inflammatory responses by passivating the cellular response to interlukin-1β. This study highlights that the as-synthesized nanosystem may serve as a novel multi-functional vehicle to modulate innate host response via targeting the NF-κB pathway for precision healthcare.

Nanomaterials: The New Antimicrobial Magic Bullet

Bacterial infections are a significant cause of mortality and morbidity worldwide, despite decades of use of numerous existing antibiotics and constant efforts by researchers to discover new antibiotics. The emergence of infections associated with antibiotic-resistant bacterial strains, has amplified the pressure to develop additional bactericidal therapies or new unorthodox approaches that can deal with antimicrobial resistance. Nanomaterial-based strategies, particularly those that do not rely on conventional small-molecule antibiotics, offer promise in part due to their ability to dodge existing mechanisms used by drug-resistant bacteria. Therefore, the use of nanomaterial-based formulations has attracted attention in the field of antibiotic therapy. In this Review, we highlight novel and emerging nanomaterial-based formulations along with details about the mechanisms by which nanoparticles can target bacterial infections and antimicrobial resistance. A detailed discussion about types and the activities of nanoparticles is presented, along with how they can be used as either delivery systems or as inherent antimicrobials, or a combination of both. Lastly, we highlight some toxicological concerns for the use of nanoparticles in antibiotic therapies.

TiO2 nanoparticles negatively impact the bioavailability and antioxidant activity of tea polyphenols

This study was to investigate the influence of TiO₂ nanoparticles (NPs) on the stability, bioavailability, and antioxidant activity of co-ingested tea polyphenols extract using an in vitro digestion model. The tea polyphenol contents decreased significantly after addition of 0.5 % (w/w) TiO₂ NPs. The gallocatechin gallate level decreased the most, changing from 101.9 to 27.2 µg/mL (about 73.3%). The TiO₂ NPs also reduced the bioavailability of the tea polyphenols in a dose-dependent manner, which was ascribed to the formation of large polyphenol-TiO₂ NP complex aggregates that could not pass through the pores in the dialysis tube used to simulate the gut wall. Additionally, the TiO₂ NPs decreased the antioxidant activity of the tea polyphenols within the simulated gastrointestinal tract. In summary, our results show that high levels of TiO₂ NPs (but within the current legal limits in many countries) may negatively impact the bioavailability and bioactivity of polyphenols in foods.

Strategy for Conjugating Oligopeptides to Mesoporous Silica Nanoparticles Using Diazirine-Based Heterobifunctional Linkers

Successful strategies for the attachment of oligopeptides to mesoporous silica with pores large enough to load biomolecules should utilize the high surface area of pores to provide an accessible, protective environment. A two-step oligopeptide functionalization strategy is examined here using diazirine-based heterobifunctional linkers. Mesoporous silica nanoparticles (MSNPs) with average pore diameter of ~8 nm and surface area of ~730 m²/g were synthesized and amine-functionalized. Tetrapeptides Gly-Gly-Gly-Gly (GGGG) and Arg-Ser-Ser-Val (RSSV), and a peptide comprised of four copies of RSSV (4RSSV), were covalently attached via their N-terminus to the amine groups on the particle surface by a heterobifunctional linker, sulfo-succinimidyl 6-(4,4′-azipentanamido)hexanoate (sulfo-NHS-LC-diazirine, or SNLD). SNLD consists of an amine-reactive NHS ester group and UV-activable diazirine group, providing precise control over the sequence of attachment steps. Attachment efficiency of RSSV was measured using fluorescein isothiocyanate (FITC)-tagged RSSV (RSSV-FITC). TGA analysis shows similar efficiency (0.29, 0.31 and 0.26 mol peptide/mol amine, respectively) for 4G, RSSV and 4RSSV, suggesting a generalizable method of peptide conjugation. The technique developed here for the conjugation of peptides to MSNPs provides for their attachment in pores and can be translated to selective peptide-based separation and concentration of therapeutics from aqueous process and waste streams.

Mesoporous polystyrene-based microspheres with polar functional surface groups synthesized from double emulsion for selective isolation of acetoside

In this study, a series of the functionalized mesoporous polystyrene-based microspheres (FMPMs) with different functional comonomers (acrylamide, AM; ethyleneglycol dimethacrylate, EGDMA; hydroxyethyl methacrylate, HEMA) and ratios of styrene (St) to divinylbenzene (DVB) were designed and synthesized by a double emulsion interface polymerization method. Among them, St and DVB existed in the oil phase, forming the skeleton structure of FMPMs. AM, EGDMA or HEMA in the water phase formed functional layers on the inner and outer surfaces of FMPMs. The experimental results indicated that the optimal functional comonomers and the ratio of St to DVB were AM (provided the hydrophilic -CONH₂ groups) and 1:1, respectively. Thus, A-FMPMs-2 exhibited the highest adsorption capacity of 108.95 ± 8.13 mg/g and the selectivity of 5.14 ± 0.17. These results were attributed to the hydrophilic -CONH₂ groups on A-FMPMs-2, and these groups were beneficial to ACT molecules diffusion driven by concentration gradient, improving the adsorption performance. Furthermore, hydrophilic -CONH₂ groups on the inner and outer surfaces of A-FMPMs-2 acted as hydrophilic sites that had a high-affinity interaction with ACT molecules, thus increasing the adsorption selectivity. In addition, A-FMPMs-2 had the highest specific surface area and largest pore volume, resulting in the highest adsorption capacity and adsorption selectivity. Therefore, the development of adsorbents with adjustable pore structure and a large number of hydrophilic sites will provide a new strategy for selective separation of bioactive components from natural products.

Functionalized silica nanoparticles: classification, synthetic approaches and recent advances in adsorption applications

Nanotechnology is rapidly sweeping through all the vital fields of science and technology such as electronics, aerospace, defense, medicine, and catalysis. It involves the design, synthesis, characterization, and applications of materials and devices on the nanometer scale. At the nanoscale, physical and chemical properties differ from the properties of the individual atoms and molecules of bulk matter. In particular, the design and development of silica nanomaterials have captivated the attention of several researchers worldwide. The applications of hybrid silicas are still limited by the lack of control on the morphology and particle size. The ability to control both the size and morphology of the materials and to obtain nano-sized silica particles has broadened the spectrum of applications of mesoporous organosilicas and/or has improved their performances. On the other hand, adsorption is a widely used technique for the separation and removal of pollutants (metal ions, dyes, organics,...) from wastewater. Silica nanoparticles have specific advantages over other materials for adsorption applications due to their unique structural characteristics: a stable structure, a high specific surface area, an adjustable pore structure, the presence of silanol groups on the surface which allow easy modification, less environmental harm, simple synthesis, low cost, etc. Silica nanoparticles are potential adsorbents for pollutants. We present herein an overview of the different types of silica nanoparticles going from the definitions to properties, synthetic approaches and the mention of potential applications. We focus mainly on the recent advances in the adsorption of different target substances (metal ions, dyes and other organics).

Impact of Polyphenol Interactions with Titanium Dioxide Nanoparticles on Their Bioavailability and Antioxidant Activity

Titanium dioxide is widely utilized as a pigment in the food industry to enhance the whiteness or brightness of foods and beverages. The powdered forms of titanium dioxide used as food ingredients contain a substantial fraction of nanoparticles (d < 100 nm), which may have adverse effects on human health. This is a model study that investigated the molecular interactions between TiO₂ nanoparticles and selected polyphenols, as well as their influence on the in vitro bioavailability and antioxidant activity of the polyphenols. Our results showed that the chemical structure of polyphenols significantly influenced their binding affinity to TiO₂ nanoparticle surfaces, with those possessing vicinal trihydroxy groups having the highest binding affinities. The presence of TiO₂ nanoparticles was shown to reduce the bioavailability of polyphenols using an in vitro digestion model. This effect was mainly ascribed to the formation of large TiO₂ nanoparticle-polyphenol complex agglomerates that could not pass through the pores in the dialysis tube used to simulate the epithelium layer. Additionally, the binding of polyphenols to the surfaces of TiO₂ nanoparticles reduced their antioxidant activity. This study provides valuable insights into the impact of inorganic nanoparticles on the bioavailability and bioactivity of polyphenols.

Mechanism of Mesoporous Silica Nanoparticle Interaction with Hairy Root Cultures during Nanoharvesting of Biomolecules

Cellular uptake and expulsion mechanisms of engineered mesoporous silica nanoparticles (MSNPs) are important in their design for novel biomolecule isolation and delivery applications such as nanoharvesting, defined as using nanocarriers to transport and isolate valuable therapeutics (secondary metabolites) out of living plant organ cultures (e.g., hairy roots). Here, temperature-dependent MSNP uptake and recovery processes in hairy roots are examined as a function of surface chemistry. MSNP uptake into hairy roots and time-dependent expulsion are quantified using Ti content (present for biomolecule binding) and fluorescence spectroscopy of fluorescently tagged MSNPs, respectively. The results suggest that functionalization and surface charge (regulated by amine group attachment) play the biggest role in the effectiveness of uptake and recovery. Comparison of MSNP interactions with hairy roots at 4 and 23 °C shows that weakly charged MSNPs functionalized only with Ti are taken up and expelled by thermally activated mechanisms, while amine-modified positively charged particles are taken up and expelled mainly by direct penetration of cell walls. Amine-functionalized MSNPs move spontaneously in and out of plant cells by dynamic exchange with a residence time of 20 ± 5 min, suggesting promise as a biomolecule nanoharvesting platform for plant organ cultures.

Siderophore purification with titanium dioxide nanoparticle solid phase extraction

Siderophores are metal chelators produced by microorganisms to facilitate binding and uptake of iron. The isolation and characterization of siderophores are impeded by typically low siderophore yields and the complexity of siderophore-containing extracts generated with traditional purification methods. We investigated titanium dioxide nanoparticle solid-phase extraction (TiO2 NP SPE) as a technique to selectively concentrate and purify siderophores from complex matrices for subsequent LC-MS detection and identification. TiO2 NP SPE showed a high binding capacity (15.7 ± 0.2 μmol mg-1 TiO2) for the model siderophore desferrioxamine B (DFOB) and proved robust to pH changes and the presence of EDTA. These are significant advances in comparison to immobilized metal affinity chromatography (IMAC). The TiO2 NP SPE was highly selective and recovered 77.6 ± 6.2% of DFOB spiked to a compositionally complex bacterial culture supernatant. The simple clean-up procedure removed the majority of contaminants and allowed direct detection of siderophores from the LC-MS base peak chromatogram. The 'untargeted' purification and analysis of an untreated supernatant of iron-deprived bacterial culture allowed for the direct identification of two known and three novel ferrioxamines. Thus, TiO2 NP SPE in combination with LC-MS offers great potential as a discovery platform for the purification and subsequent quantification or identification of novel siderophores of microbial origin.

Application of micro/nanomaterials in adsorption and sensing of active ingredients in traditional Chinese medicine

Traditional Chinese medicine (TCM) has been widely applied for the prevention and cure of various diseases for centuries. Ingredient with pharmacological activity is the key to the application of TCM. Hence, it is of significance to separate and detect active ingredients in TCM effectively. Micro/nanomaterial is the promising candidate for adsorption and sensing due to its unique physical and chemical properties. For years, many efforts have been made to develop functional micro/nanomaterials to realize the effective adsorption or sensing of bioactive compounds in TCM. In this review, we discussed recent progresses in the application of various functional micro/nanomaterials for adsorption or detection (electrochemical detection, fluorescent detection, and colorimetric detection) of active ingredients. Based on the kind of matrix materials, micro/nano-adsorbents or sensors can be classified into following categories: metal-based micro/nanomaterials, porous materials, carbon-based materials, graphene/graphite-liked micro/nanomaterials and hybrid micro/nanomaterials.

Effect of Confinement in Nanopores on RNA Interactions with Functionalized Mesoporous Silica Nanoparticles

Amine-functionalized mesoporous silica nanoparticles (MSNPAs) are ideal carriers for oligonucleotides for gene delivery and RNA interference. This investigation examines the thermodynamic driving force of interactions of double-stranded (ds) RNA with MSNPAs as a function of RNA length (84 and 282 base pair) and particle pore diameter (nonporous, 2.7, 4.3, and 8.1 nm) using isothermal titration calorimetry, extending knowledge of solution-based nucleic acid-polycation interactions to RNA confined in nanopores. Adsorption of RNA follows a two-step process: endothermic interactions driven by entropic contribution from counterion (and water) release and an exothermic regime dominated by short-range interactions within the pores. Evidence of hindered pore loading of the longer RNA and pore size-dependent confinement of RNA in the MSPAs is provided from the relative contributions of the endothermic and exothermic regimes. Reduction of endothermic and exothermic enthalpies in both regimes in the presence of salt for both lengths of RNA indicates the significant contribution of short-range electrostatic interactions, whereas ΔH and ΔG values are consistent with conformation changes and desolvation of nucleic acids upon binding with polycations. Knowledge of the interactions between RNA and functionalized porous nanoparticles will aid in porous nanocarrier design suitable for functional RNA delivery.

Ultrafast and simultaneous removal of anionic and cationic dyes by nanodiamond/UiO-66 hybrid nanocomposite

In this research, UiO-66 and its composite nanoparticles with thermally oxidized nanodiamond (OND) were synthesized via a simple solvothermal method and utilized as solid adsorbent for the removal of anionic methyl red (MR) dye and cationic malachite green (MG) dye from contaminated water. The synthesized adsorbents were analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), N₂ adsorption-desorption, and zeta potential analyzer. The influences of various factors such as initial concentrations of the dyes, adsorption process time, solution pH, solution temperature and ionic strength on adsorption behavior of MR dye onto OND-UiO hybrid nanoparticle were investigated. The adsorption of MR onto OND-UiO hybrid nanoparticle could be well described by Langmuir isotherm model. Meanwhile, pseudo-second order kinetic model was found to be suitable for illustration of adsorption kinetics of MR onto OND-UiO. Thermodynamic investigation suggested that the adsorption process was spontaneous and endothermic, and controlled by an entropy change instead of enthalpy effect. The experimental adsorption results indicated that OND-UiO hybrid nanoparticle could simultaneously adsorb 59% of MR and 43% of MG from the mixture of both dyes in only 2 min showing synergistic effect compared with single UiO-66 and OND nanoparticles in terms of adsorption rate and removal capacity of anionic dyes. The appropriate removal efficiency, rapid adsorption kinetic, high water stability, and good reusability make OND-UiO hybrid nanoparticle attractive candidate for simultaneously removal of both anionic MR and cationic MG dyes from wastewater.

Properties of Salvia officinalis L. and Thymus serpyllum L. Extracts Free and Embedded into Mesopores of Silica and Titania Nanomaterials

This study evidenced the nanoconfinement effect on polyphenolic extracts prepared from Salvia officinalis L. and Thymus serpyllum L. into the mesopores of silica and titania nanomaterials on their radical scavenging capacity and antimicrobial potential. The ethanolic and hydroalcoholic extracts obtained either by conventional or microwave-assisted extraction were characterized in terms of total polyphenols, total flavonoids, and chlorophyll content, as well as radical scavenging activity by consecrated spectrometric determinations. The phytochemical fingerprint of extracts was analyzed by high-performance liquid chromatography-photodiode array detector. Salvia officinalis extracts exhibited better radical scavenging capacity and antimicrobial potential than Thymus serpyllum extracts. The mesoporous MCM-41 silica and titania nanomaterials, prepared by the sol-gel method, were characterized by small- and wide-angle powder diffraction, FTIR spectroscopy, nitrogen adsorption-desorption isotherms, scanning electron microscopy and transmission electron microscopy, while the materials containing embedded extracts were analyzed through Fourier-transform infrared spectroscopy, N₂ sorption measurements, and thermal analysis. All extracts free and embedded in mesoporous matrix exhibited high radical scavenger properties and good bactericidal activity against several reference strains. It was proved that by embedding the polyphenolic extracts into mesopores of silica or titania nanoparticles, the phytochemicals stability was enhanced as the materials containing extract exhibited higher radical scavenger activity after 3-6 months storage than that of the free extracts. Additionally, the extract-loaded material showed mild improved antimicrobial activity in comparison with the corresponding free extract.

Interaction of lignin-derived dimer and eugenol-functionalized silica nanoparticles with supported lipid bilayers

The potential to impart surfaces with specific lignin-like properties (i.e. resistance to microbes) remains relatively unexplored due to the lack of well-defined lignin-derived small molecules and corresponding surface functionalization strategies. Here, allyl-modified guaiacyl β-O-4 eugenol (G-eug) lignin-derived dimer is synthesized and attached to mesoporous silica nanoparticles (MSNPs) via click chemistry. The ability of G-eug lignin-dimer functionalized particles to interact with and disrupt synthetic lipid bilayers is compared to that of eugenol, a known natural antimicrobial. Spherical MSNPs (∼150 nm diameter with 4.5 nm pores) were synthesized using surfactant templating. Post-synthesis thiol (SH) attachment was performed using (3-mercaptopropyl) trimethoxysilane and quantified by Ellman's test. The resultant SH-MSNPs were conjugated with the G-eug dimers or eugenol by a thiol-ene reaction under ultraviolet light in the presence of a photo initiator. From thermogravimetric analysis (TGA), attachment densities of approximately 0.22 mmol eugenol/g particle and 0.13 mmol G-eug dimer/g particle were achieved. The interaction of the functionalized MSNPs with a phospholipid bilayers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (representing model cell membranes) supported on gold surface was measured using Quartz Crystal Microbalance with Dissipation monitoring (QCM-D). Eugenol-grafted MSNPs in PBS (up to 1 mg/mL) associated with the bilayer and increased the mass adsorbed on the QCM-D sensor. In contrast, MSNPs functionalized with G-eug dimer show qualitatively different behavior, with more uptake and evidence of bilayer disruption at and above a particle concentration of 0.5 mg/mL. These results suggest that bio-inspired materials with conjugated lignin-derived small molecules can serve as a platform for novel antimicrobial coatings and therapeutic carriers.

Efficient Selective Removal of Pb(II) by Using 6-Aminothiouracil-Modified Zr-Based Organic Frameworks: From Experiments to Mechanisms

We report an efficient, reusable, and selective 6-aminothiouracil (ATA)-modified Zr(IV)-based adsorbent (defined as UiO-66-ATA(Zr)) for lead ion removal in water. The adsorption equilibrium time and the maximum sorption capacity of UiO-66-ATA(Zr) for Pb(II) are, respectively, 120 min and 386.98 mg/g at pH 4 and 298 K. The Pb(II) removal rate reaches 96% at 60 min and exceeds 99% at the equilibrium state in the pH range of 2.0-5.8. Hill and pseudo-second-order models can well describe the sorption process. Pb(II) adsorbing onto UiO-66-ATA(Zr) is an irreversible, favorable chemisorption process with multimolecule participation and film diffusion control. The calculations of density functional theory, the experimental results, and the characterization analyses suggest that the binding mechanisms are the chelation and ion-exchange/electrostatic interactions between hydroxyl/amino/sulfhydryl groups of UiO-66-ATA(Zr) and Pb(II). Besides, UiO-66-ATA(Zr) has a better affinity to Pb(II) than the coexisting ions in water and an excellent repeatability at eight cycles of adsorption. Moreover, the thermodynamic study shows that UiO-66-ATA(Zr) adsorbing Pb(II) is an endothermic reaction. Thus, UiO-66-ATA(Zr) is a prospective sorbent for Pb(II) removal under the initiative of environmental protection and water purification, and this work may also provide an idea for industrial catalysis.

Nanoharvesting of bioactive materials from living plant cultures using engineered silica nanoparticles

Plant secondary metabolites are valuable therapeutics not readily synthesized by traditional chemistry techniques. Although their enrichment in plant cell cultures is possible following advances in biotechnology, conventional methods of recovery are destructive to the tissues. Nanoharvesting, in which nanoparticles are designed to bind and carry biomolecules out of living cells, offers continuous production of metabolites from plant cultures. Here, nanoharvesting of polyphenolic flavonoids, model plant-derived therapeutics, enriched in Solidago nemoralis hairy root cultures, is performed using engineered mesoporous silica nanoparticles (MSNPs, 165 nm diameter and 950 m2/g surface area) functionalized with both titanium dioxide (TiO2, 425 mg/g particles) for coordination binding sites, and amines (NH2, 145 mg/g particles) to promote cellular internalization. Intracellular uptake and localization of the nanoparticles (in Murashige and Skoog media) in hairy roots were confirmed by tagging the particles with rhodamine B isothiocyanate, incubating the particles with hairy roots, and quenching bulk fluorescence using trypan blue. Nanoharvesting of biologically active flavonoids was demonstrated by observing increased antiradical activity (using 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay) by nanoparticles after exposure to hairy roots (indicating general antioxidant activity), and by the displacement of the radio-ligand [3H]-methyllycaconitine from rat hippocampal nicotinic receptors by solutes recovered from nanoharvested particles (indicating pharmacological activity specific to S. nemoralis flavonoids). Post-nanoharvesting growth suggests that the roots are viable after nanoharvesting, and capable of continued flavonoid synthesis. These observations demonstrate the potential for using engineered nanostructured particles to facilitate continuous isolation of a broad range of biomolecules from living and functioning plant cultures.

Recovery of Polyphenols from Grape Pomace Using Polyethylene Glycol (PEG)-Grafted Silica Particles and PEG-Assisted Cosolvent Elution

Adsorption on a functionalized surface can be an effective way of purifying polyphenols from complex plant extracts. Polymeric resins that rely on hydrophobic interactions suffer from low selectivity, weak affinity towards polyphenols, and lack tunability therefore making the purification of polyphenols less efficient. In this study, a purification process for the recovery of polyphenols from grape pomace extract was successfully developed using hydrogen bonding affinity ligands grafted on silica particles and PEG-assisted elution solvents. Bare silica (SiO₂) and polyethylene glycol (mPEG)-grafted silica microparticles with molecular weights of 2000 and 5000 were tested to determine their polyphenol binding and release characteristics. Functionalizing the surface of bare silica with mPEG ligands increased the adsorption capacity by 7.1- and 11.4-fold for mPEG-2000 and mPEG-5000 compared to bare silica particles, respectively. This was likely due to the introduction of more polyphenol binding sites with mPEG functionalization. Altering the molecular weight (MW) of mPEG grafted on silica surfaces provided tunability in the adsorption capacity. A complete recovery of polyphenols (~99.9%) from mPEG-grafted silica particles was achieved by utilizing PEG–ethanol or PEG–water cosolvent systems. Recovered polyphenols showed up to ~12-fold antioxidant activity compared to grape pomace extract. This study demonstrates that mPEG-grafted silica particles and elution of polyphenols with PEG cosolvents can potentially be used for large-scale purification of polyphenols from complex plant extracts and simplify the use of polyphenols, as PEG facilitates remarkable solvation and is an ideal medium for the final formulation of polyphenols.

Post-functionalization of UiO-66-NH2 by 2,5-Dimercapto-1,3,4-thiadiazole for the high efficient removal of Hg(II) in water

A new MOFs adsorbent was prepared by post-functionalization of UiO-66-NH₂ with 2,5-Dimercapto-1,3,4-thiadiazole and utilized to remove the Hg(II) in water selectively. The UiO-66-types were detected by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), Brunauer-Emmett-Teller (BET) and zeta potential instruments. The adsorption properties of the new MOFs adsorbent were investigated by batch experiments. The actual maximum adsorption amount was 670.5 mg/g at the optimal pH of 3. Adsorption kinetic and isotherm models were exceedingly fitted to pseudo-second-order and Langmuir/Dubinin-Radushkevich, respectively. The adsorption process and mode were geared to monolayer and chemisorption, the removal rate was directly proportional to the square of mercury ions concentration. The UiO-66-DMTD adsorbent was easy to be regenerated and the removal rate decreased by only 13.5% after ten consecutive cycles. The results of FTIR, XRD and XPS suggested that the adsorption mechanism lay on the complexation reaction between Hg(II) and thiol/nitrogen-containing groups. Moreover, compared with other competitive metal ions, viz., Zn(II), Co(IV), Ni(II), Cd(II), Mg(II), Fe(III), Ca(II) and Cu(II), the UiO-66-DMTD demonstrated an outstanding selective adsorption for Hg(II). These results manifested that the UiO-66-DMTD was a latent adsorbent for the efficient and selective removal of Hg(II) in wastewater.

Antioxidant Nanomaterial Based on Core⁻Shell Silica Nanospheres with Surface-Bound Caffeic Acid: A Promising Vehicle for Oxidation-Sensitive Drugs

The design of efficient, biocompatible, and easily prepared vehicles for drug delivery is a subject of great interest for medicine and pharmaceutical sciences. To achieve the above goals, surface functionalization is critical. Here, we report a hybrid nanocarrier consisting of core⁻shell silica nanospheres and the antioxidant caffeic acid linked to the surface, to evaluate their in vitro antioxidant capacity, their capability to protect oxidation-sensitive compounds incorporated in nanoparticles, and to study the interaction with bovine serum albumin protein. The results show that the radical-scavenging activity of immobilized caffeic acid is attenuated in the silica nanospheres; however, other antioxidant properties such as Fe2+-chelating activity and singlet oxygen quenching are enhanced. In addition, caffeic acid is protected from binding to proteins by the nanoparticle, suggesting that this nanosystem is more likely to maintain the antioxidant activity of caffeic acid in biological media. Finally, the natural antioxidant barrier on the nanocarrier is able to delay the degradation of a compound incorporated into this nanovehicle. Considering all findings, this work proposes a suitable tool for pharmaceutical and cosmetic industries as an antioxidant nanocarrier for oxidation-sensitive drugs.

A neutral Cu-based MOF for effective quercetin extraction and conversion from natural onion juice

A new neutral metal–organic framework can efficiently extract natural product quercetin (QT) from fresh QT-rich onion juice and rapidly convert it into Cu–QT with a relatively high conversion rate.

Kinetic, Isotherm, and Thermodynamic Studies for Ag(I) Adsorption Using Carboxymethyl Functionalized Poly(glycidyl methacrylate)

Industrial wastewater contains large amounts of silver ions. Here, a new adsorbent was synthesized by functionalizing poly(glycidyl methacrylate) with carboxymethyl groups. The adsorbent was used to recover Ag(I) in wastewater. Fourier transform infrared spectroscopy, zeta potential, scanning electron microscopy, and X-ray photoelectron spectroscopy were used to characterize the adsorbent. The experimental parameters affecting the adsorption are solution pH, contact time, and initial silver ion concentration. The optimum pH for adsorption of Ag(I) is pH 4. The maximum adsorption capacity at pH 4 is 157.05 mg/g, and the adsorption reaches equilibrium at 300 min. The kinetics and isotherms of the adsorption process were described by pseudo second-order, Langmuir and D-R models, respectively. The adsorption process was a single layer chemical adsorption, exothermic, feasible, and spontaneous. The adsorption mechanism is electrostatic or chelation. The adsorbent selectively absorbed Ag(I) from coexisting ions (Cu²⁺, Ni²⁺, Co²⁺, Zn²⁺). Finally, the removal rate of silver ions decreased from 79.29% to 65.01% after four repetitive experiments, which proved that the adsorbent had good reusability. The adsorbent has great potential benefit in removing Ag(I).

In Situ Liquid-Phase-Adsorption Measurement System Based on Fiber-Optic Sensing with the Aid of Membranes

At present, liquid phase adsorption (LPA) is still being quantitatively characterized in the way of manual sampling and off-line determination because of the complexity of the system comparing to gas adsorption. This paper describes a novel method for in situ, real-time measurement of LPA in general based on fiber-optic sensing (FOS) with the aid of membranes for the first time. A self-made measurement vessel was assembled from an adsorption bag, thermostatic devices with a stirrer, and a fiber-optic dipping probe. Also, macroporous adsorption resins (MARs) and rutin were chosen as model adsorbent and adsorbate to establish the FOS system. Here, in situ light absorption measurement was achieved by eliminating interference of adsorbent particles via encapsulating them with a membrane into the adsorption bag. In situ LPA measurement of rutin solution on MARs was obtained by detecting light absorption at 353 nm using dipping probe, in the broad concentration range from 0.3 to 60 mg/L with excellent linearity (R ² = 0.9996). In situ measurements of adsorption and desorption kinetics on five kinds of MARs with different polarities were systematically carried out, showing that the adsorption process obeyed the pseudo-second-model. As well as, the system was proved to be highly accurate and reproducible. More importantly, this method enabled to study the initial stage of the adsorption process, starting from the time of the first second, which is the most important part in the adsorption kinetics, and this is impossible for traditional sampling methods. The successful application of FOS to in situ measurement of LPA not only contributes to fast, automatic, and real-time monitoring of LPA process but also enriches the research connotation of adsorption.

Secondary Metabolites in the Green Synthesis of Metallic Nanoparticles

The ability of organisms and organic compounds to reduce metal ions and stabilize them into nanoparticles (NPs) forms the basis of green synthesis. To date, synthesis of NPs from various metal ions using a diverse array of plant extracts has been reported. However, a clear understanding of the mechanism of green synthesis of NPs is lacking. Although most studies have neglected to analyze the green-synthesized NPs (GNPs) for the presence of compounds derived from the extract, several studies have demonstrated the conjugation of sugars, secondary metabolites, and proteins in these biogenic NPs. Despite several reports on the bioactivities (antimicrobial, antioxidant, cytotoxic, catalytic, etc.) of GNPs, only a handful of studies have compared these activities with their chemically synthesized counterparts. These comparisons have demonstrated that GNPs possess better bioactivities than NPs synthesized by other methods, which might be attributed to the presence of plant-derived compounds in these NPs. The ability of NPs to bind with organic compounds to form a stable complex has huge potential in the harvesting of precious molecules and for drug discovery, if harnessed meticulously. A thorough understanding of the mechanisms of green synthesis and high-throughput screening of stabilizing/capping agents on the physico-chemical properties of GNPs is warranted to realize the full potential of green nanotechnology.