Molecular Elucidation of Biological Response to Mesoporous Silica Nanoparticles in Vitro and in Vivo

Pyrogenic and Precipitated Amorphous Silica Nanoparticles Differentially Affect Cell Responses to LPS in Human Macrophages

Previous work has demonstrated that precipitated (NM-200) and pyrogenic (NM-203) Amorphous Silica Nanoparticles (ASNPs) elicit the inflammatory activation of murine macrophages, with more pronounced effects observed with NM-203. Here, we compare the effects of low doses of NM-200 and NM-203 on human macrophage-like THP-1 cells, assessing how the pre-exposure to these nanomaterials affects the cell response to lipopolysaccharide (LPS). Cell viability was affected by NM-203, but not by NM-200, and only in the presence of LPS. While NM-203 stimulated mTORC1, neither ASNPs activated NFκB or the transcription of its target genes PTGS2 and IL1B. NM-200 and NM-203 caused a block of the autophagic flux and inhibited the LPS-dependent increase of Glutamine Synthetase (GS) expression. Both ASNPs suppressed the activation of caspase-1, delaying the LPS-dependent secretion of IL-1β. Thus, ASNPs modulate several important pathways in human macrophages, altering their response to LPS. NM-203 had larger effects on autophagy, mTORC1 activity and GS expression than NM-200, confirming the higher biological activity of pyrogenic ASNPs when compared with precipitated ASNPs.

An integrative multi-omics approach uncovers the regulatory role of CDK7 and CDK4 in autophagy activation induced by silica nanoparticles

Dysfunction of macroautophagy/autophagy has been postulated as a major cellular toxicological response to nanomaterials. It has been reported that excessive autophagy activation, induced by silica nanoparticles (SiNPs), contributes to autophagy dysfunction, whereas little is known how SiNPs trigger autophagy activation. Here, we treated normal rat kidney (NRK) cells using 3 different sizes of SiNPs (16, 29, and 51 nm) and observed that 16-nm SiNPs, with a final concentration of 60 μg/mL, dramatically induce autophagy activation without reducing cell viability. We further conducted a transcriptomic, proteomic, and phosphoproteomic profiling, and detected 23 autophagy-related (Atg) genes and 35 autophagy regulators regulated on at least one omic layer. To identify key regulators from the multi-omics data, we developed a new algorithm of computational prediction of master autophagy-regulating kinases (cMAK) to detect 21 candidates and revealed the CDK7-CDK4 cascade to be functional. The silence or inhibition of Cdk7 or Cdk4 significantly attenuated autophagic activation but not influenced autophagic flux blockage induced by 16-nm SiNPs. Further computational modeling indicated that the CDK7-CDK4 signaling axis potentially triggers autophagy activation by phosphorylating RB1 (RB transcriptional corepressor 1), activating two critical transcription factors, E2F1 (E2F transcription factor 1) and FOXO3 (forkhead box O3), and enhancing the transcriptional levels of at least 8 Atg genes and autophagy regulators in response to SiNPs. Our studies not only established a powerful method for predicting regulatory kinases from the multi-omics data but also revealed a potential mechanism of SiNP-triggered autophagy activation through modulating the CDK7-CDK4 cascade.Abbreviations: 3-MA: 3-methyladenine; Atg: autophagy-related; BECN1: beclin 1; CCK-8: cell counting kit-8; CDK4: cyclin dependent kinase 4; CDK7: cyclin dependent kinase 7; cMAK: computational prediction of master autophagy-regulating kinases; CQ: chloroquine; DMEM: Dulbecco's modified Eagle's medium; DMSO: dimethyl sulfoxide; E-ratio: enrichment ratio; E2F1: E2F transcription factor 1; EBSS: Earle's balanced salt solution; ER: endoplasmic reticulum; FOXO3: forkhead box O3; FPKM: fragments per kilobase of exon per million fragments mapped; GO: gene ontology; H₂O₂: hydrogen peroxide; iGPS: in vivo GPS; KEGG: Kyoto Encyclopedia of Genes and Genomes; LC-MS/MS: liquid chromatography-tandem mass spectrometry; LDH: lactate dehydrogenase; MAP1LC3B/LC3: microtubule associated protein 1 light chain 3 beta; NRK: normal rat kidney; p-site: phosphorylation site; PBS: phosphate-buffered saline; PDI: polydispersity index; PTM: post-translational modification; QKS: quantitative kinase state; RB1: RB transcriptional corepressor 1; RBHs: reciprocal best hits; RNA-Seq: RNA sequencing; ROS: reactive oxygen species; rSiNPs: SiNPs fluorescently labeled with rhodamine B; SEM: scanning electronic microscopy; SiNPs: silica nanoparticles; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; ssKSR: site-specific kinase-substrate relation; TEM: transmission electron microscopy; tfLC3: mRFP-GFP tandem fluorescent-tagged LC3.

Enhanced efficacy of propranolol therapy for infantile hemangiomas based on a mesoporous silica nanoplatform through mediating autophagy dysfunction

Infantile hemangioma is one of the most common vascular tumors, which might result in morbidity and mortality without timely intervention. Propranolol is currently the first-line therapy for hemangiomas, but its potential side effects and high frequency of administration make it urgent to develop a suitable drug delivery system for propranolol. In the present study, we formulated a propranolol delivery system based on mesoporous silica nanoparticles (PRN@MSN) and investigated the interplay between autophagic activities mediated by nanoparticles and improved therapeutic efficacy of PRN@MSN. The results showed that PRN@MSN nanoparticles exhibited higher cytotoxicity compared with free propranolol in vitro and in vivo, which could induce excessive autophagosome accumulation through increased autophagosome formation and impaired autophagic degradation. Inhibition of autophagy in the early stage could attenuate the cytotoxicity of PRN@MSN. ROS generation was essential for nanoparticle-mediated autophagy and cytotoxicity, and PRN@MSN-induced autophagy dysfunction could enhance endoplasmic reticulum (ER) stress in hemangioma stem cells. Our study revealed a promising PRN delivery system based on a mesoporous silica nanoplatform that could induce autophagy dysfunction with excessive autophagosome accumulation to promote the therapeutic efficacy of PRN therapy. PRN@MSN drug delivery system combined with autophagy modulation may act as a promising treatment pattern in the treatment of hemangiomas.

Immunomodulatory Potential of Differently-Terminated Ultra-Small Silicon Carbide Nanoparticles

Ultra-small nanoparticles with sizes comparable to those of pores in the cellular membrane possess significant potential for application in the field of biomedicine. Silicon carbide ultra-small nanoparticles with varying surface termination were tested for the biological system represented by different human cells (using a human osteoblastic cell line as the reference system and a monocyte/macrophage cell line as immune cells). The three tested nanoparticle surface terminations resulted in the observation of different effects on cell metabolic activity. These effects were mostly noticeable in cases of monocytic cells, where each type of particle caused a completely different response ('as-prepared' particles, i.e., were highly cytotoxic, -OH terminated particles slightly increased the metabolic activity, while -NH2 terminated particles caused an almost doubled metabolic activity) after 24 h of incubation. Subsequently, the release of cytokines from such treated monocytes and their differentiation into activated cells was determined. The results revealed the potential modulation of immune cell behavior following stimulation with particular ultra-small nanoparticles, thus opening up new fields for novel silicon carbide nanoparticle biomedical applications.

Efficacy of Ca2+- or PO4 3--conjugated mesoporous silica nanoparticles on dentinal tubule occlusion: an in-vitro assessment

Background

Maintaining a long-term biological effect of dental materials on dentinal tubule occlusion is one of the great technical challenges in dental clinics. In addition to physical treatment, chemical treatment to produce insoluble precipitates to seal dentinal tubules has been used. As dentin is mostly composed of calcium and phosphate complexes, in this study, we have developed a novel tubule-occluding material [Ca²⁺/PO₄³⁻@mesoporous silica nanoparticles (MSNs)] by separately conjugating either Ca²⁺ or PO₄³⁻ with MSNs.

Methods

The shape and structure of the MSNs were examined using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The surface morphology and chemical compositions of Ca²⁺@MSNs/PO₄³⁻@MSNs and Ca²⁺/PO₄³⁻@MSNs were examined using SEM and X-ray fluorescence (XRF). The element distribution of Ca²⁺/PO₄³⁻@MSNs was detected using energy dispersive spectrometer (EDS). The sustained release ability of Ca²⁺@MSNs/PO₄³⁻@MSNs was detected using inductively coupled plasma atomic emission spectrometry (ICP-AES). The efficacy of Ca²⁺/PO₄³⁻@MSNs on dentinal tubule sealing was evaluated using SEM, and the results were analyzed by Image-Pro software to determine the best water-powder ratio. We also compared the sealing efficacy between Ca²⁺/PO₄³⁻@MSNs and NovaMin, which is currently used in clinics, under the simulated conditions of oral acidic corrosion and mechanical friction.

Results

Ca²⁺/PO₄³⁻@MSNs are a new type of tubule-occluding material with sustained release properties. The ratio of Ca²⁺@MSNs: PO₄³⁻@MSNs: H₂O =0.015 g: 0.015 g: 150 µL exhibited an excellent sealing effect on dentinal tubules as well as resistance to oral acid corrosion and daily oral friction.

Conclusions

The novel dental material Ca²⁺/PO₄³⁻@MSNs demonstrates potential long-term effectiveness in sealing dentinal tubules and reducing dentin sensitivity, which is one of the most important problems in dental clinics.

Magnetically Stimulated Drug Release Using Nanoparticles Capped by Self-Assembling Peptides

A novel self-assembling peptide-functionalized core-shell mesoporous silica nanoparticle was developed as a drug carrier. Superparamagnetic manganese- and cobalt-doped iron oxide nanoparticles formed the core for the mesoporous silica shell coating. On the silica outer shell, the peptide Boc-Phe-Phe-Gly-Gly-COOH was covalently conjugated by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysulfosuccinimide sodium salt coupling. The self-assembling property of the peptide at physiological temperature was utilized to block the pore openings, while the disassembly at elevated local particle temperature released cargo molecules without bulk heating that would cause cell damage. Both conventional heating and heating in an alternating magnetic field were tested for the release of fluorescein and daunorubicin. In vitro experiments showed high cytotoxicity on pancreatic carcinoma cells (PANC-1) when this delivery system was activated by an alternating magnetic field, while control particles without drugs showed no obvious cytotoxicity.

A Dynamic 3D Tumor Spheroid Chip Enables More Accurate Nanomedicine Uptake Evaluation

Nanomedicine has brought great advances for drug delivery by improving the safety and efficacy of pharmaceuticals. However, many nanomaterials showing good distribution property in vitro often display poor cellular uptake during in vivo administration. Current cellular uptake research models are mainly based on the traditional 2D culture system, which is a single layer and static system, thus the results cannot accurately reflect the distribution of nanoparticles (NPs) in vivo. In the present study, a multiple tumor culture chip (MTC-chip) is constructed to mimic solid tumor and dynamic fluid transport, in order to better study NPs penetration in vitro. Cellular uptake of mesoporous silica particles (MSNs) is evaluated using the 3D tumor spheroids on chip, and it is found that: 1) continuous administration results in larger MSNs penetration than transient administration at the same dose; 2) the size effect on cellular uptake is less significant than reported by previous in vitro studies; and 3) pretreatment with hyaluronidase (HAase) enhances the tumor penetration of large-size MSNs.

A Responsive Mesoporous Silica Nanoparticle Platform for Magnetic Resonance Imaging-Guided High-Intensity Focused Ultrasound-Stimulated Cargo Delivery with Controllable Location, Time, and Dose

Magnetic resonance imaging (MRI) is an essential modality for clinical diagnosis, and MRI-guided high-intensity focused ultrasound (MRgHIFU) is a powerful technology for targeted therapy. Clinical applications of MRgHIFU primarily utilize hyperthermia and ablation to treat cancerous tissue, but for drug delivery applications thermal damage is undesirable. A biofriendly MRgHIFU-responsive mesoporous silica nanoparticle (MSN) platform that is stimulated within a physiological safe temperature range has been developed, reducing the possibility of thermal damage to the surrounding healthy tissues. Biocompatible polyethylene glycol (PEG) was employed to cap the pores of MSNs, and the release of cargo molecules by HIFU occurs without substantial temperature increase (∼4 °C). To visualize by MRI and measure the stimulated delivery in situ, a U.S. Food and Drug Administration (FDA)-approved gadolinium-based contrast agent, gadopentetate dimeglumine (Gd(DTPA)^2-), was used as the imageable cargo. Taking advantage of the three-dimensional (3-D) imaging and targeting capabilities of MRgHIFU, the release of Gd(DTPA)^2- stimulated by HIFU was pinpointed at the HIFU focal point in 3-D space in a tissue-mimicking gel phantom. The amount of Gd(DTPA)^2- released was controlled by HIFU stimulation times and power levels. A positive correlation between the amount of Gd(DTPA)^2- released and T₁ was found. The MRgHIFU-stimulated cargo release was further imaged in a sample of ex vivo animal tissue. With this technology, the biodistribution of the nanocarriers can be tracked and the MRgHIFU-stimulated cargo release can be pinpointed, opening up an opportunity for future image-guided theranostic applications.

Shortwave Infrared Imaging with J-Aggregates Stabilized in Hollow Mesoporous Silica Nanoparticles

Tissue is translucent to shortwave infrared (SWIR) light, rendering optical imaging superior in this region. However, the widespread use of optical SWIR imaging has been limited, in part, by the lack of bright, biocompatible contrast agents that absorb and emit light above 1000 nm. J-Aggregation offers a means to transform stable, near-infrared (NIR) fluorophores into red-shifted SWIR contrast agents. Here we demonstrate that J-aggregates of NIR fluorophore IR-140 can be prepared inside hollow mesoporous silica nanoparticles (HMSNs) to result in nanomaterials that absorb and emit SWIR light. The J-aggregates inside PEGylated HMSNs are stable for multiple weeks in buffer and enable high resolution imaging in vivo with 980 nm excitation.

Silica nanoparticles induce spermatocyte cell apoptosis through microRNA-2861 targeting death receptor pathway

Silica nanoparticles (SiNPs) are found in the environmental particulate matter and have been proved to pose an adverse effect on fertility. However, the relationship between miRNA and apoptosis induced by SiNPs in spermatogenesis and its underlying mechanism remains confusing. Therefore, the present study was designed to investigate the toxic effects of SiNPs on spermatogenic cells mediated through miRNAs. Spermatocyte cells were divided into 0 μg/mL and 5 μg/mL SiNPs groups, and the cells were collected and analyzed after passaging for 1, 10, 20, and 30 generations. miRNA profile and mRNA profile of spermatocyte cells were measured after exposure to SiNPs for 30 generations. Further, mimics and inhibitors of miRNA were used to verify the relationship between miRNA and their predicted target genes in the 30th-generation cells. The results showed that the degree of cell apoptosis in the SiNPs group significantly increased in the 30th generation. After exposure to SiNPs for 30 generations, the expression of 15 miRNAs was altered, including 5 upregulated miRNAs and 10 downregulated miRNAs. Of the 15 miRNAs, miR-138 and miR-2861 were related to the death receptor pathway. The miR-2861 mimic could target to regulate the mRNA expression of fas/fasl/ripk1 and increase the protein expression of Fas/FasL/RIPK1/FADD/caspase-8/caspase-3 of spermatogenic cells in the 30th generation, while the miR-138 inhibitor could not. In conclusion, SiNPs could cause apoptosis of spermatocyte cells by inhibiting the expression of miRNA-2861, thereby resulting in the upregulation of mRNA expression of fas/fasl/ripk1 and activating the death receptor pathway of spermatocyte cells. miRNA-2861 could be considered a biomarker of the toxic effect of SiNPs on spermatocyte cells. The main finding: Silica nanoparticles induce apoptosis in spermatocyte cells through microRNA-2861 inhibition, thereby upregulating mRNA expression of fas/fasl/ripk1 and activating the death receptor pathway of spermatocyte cells.

Iron oxide nanoparticles induce reversible endothelial-to-mesenchymal transition in vascular endothelial cells at acutely non-cytotoxic concentrations

BACKGROUND

Iron oxide nanoparticles (IONPs) have been extensively studied in different biomedical fields. Recently, the non-cytotoxic concentration of IONPs induced cell-specific response raised concern of their safety. Endothelial cell exposure was unavoidable in their applications, while whether IONPs affect the phenotype of vascular endothelial cells is largely unknown. In this work, the effect of IONPs on endothelial-to-mesenchymal transition (EndMT) was investigated in vitro and in vivo.

RESULTS

The incubation with γ-Fe₂O₃ nanoparticles modified with polyglucose sorbitol carboxymethyether (PSC-Fe₂O₃) at non-cytotoxic concentration induced morphological changes of human umbilical vein endothelial cells (HUVECs) from cobblestone-like to spindle mesenchymal-like morphology, while PSC-Fe₂O₃ mostly stay in the culture medium and intercellular space. At the same time, the endothelial marker CD31 and VE-cadherin was decreased along with the inhibitory of angiogenesis properties of HUVEC. Meanwhile, the mesenchymal marker α-smooth muscle actin (α-SMA) and fibroblast specific protein (FSP) was up regulated significantly, and the migration ability of the cells was enhanced. When ROS scavenger mannitol or AA was supplemented, the EndMT was rescued. Results from the in vivo study showed that, expression of CD31 was decreased and α-SMA increased in the liver, spleen and kidney of mice given PSC-Fe₂O₃, and the density of collagen fibers in the liver sinusoid of mice was increased. The supplementary mannitol or AA could reverse the degree of EndMT in the tissues. Mechanistic study in vitro indicated that the level of extracellular hydroxyl radicals (·OH) was up regulated significantly by PSC-Fe₂O₃, which induced the response of intracellular ROS and resulted in the EndMT effect on HUVECs.

CONCLUSION

The PSC-Fe₂O₃ was capable of inducing EndMT in the endothelial cells at acutely non-cytotoxic dose due to its intrinsic peroxidase-like activity, though they were few taken up by endothelial cell. The EndMT effect on HUVEC can be rescued by ROS scavenger in vitro and in vivo.

Current Highlights About the Safety of Inorganic Nanomaterials in Healthcare

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In recent years inorganic materials are largely present in products intended for health care. Literature gives many examples of inorganic materials used in many healthcare products, mainly in pharmaceutical field.

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Silver, zinc oxide, titanium oxide, iron oxide, gold, mesoporous silica, hydrotalcite-like compound and nanoclays are the most common inorganic materials used in nanosized form for different applications in the health field. Generally, these materials are employed to realize formulations for systemic use, often with the aim to perform a specific targeting to the pathological site. The nanometric dimensions are often preferred to obtain the cellular internalization when the target is localized in the intracellular space.

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Some materials are frequently used in topical formulations as rheological agents, adsorbents, mattifying agents, physical sunscreen (e.g. zinc oxide, titanium dioxide), and others.

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Recent studies highlighted that the use of nanosized inorganic materials can represent a risk for health. The very small dimension (nanometric) until a few years ago represented a fundamental requirement; however, it is currently held responsible for the inorganic material toxicity. This aspect is very important to be considered as actually numerous inorganic materials can be found in many products available in the market, often dedicated to infants and children. These materials are used without taking into account their dimensional properties with increased risk for the user/patient.

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This review deals with a deep analysis of current researches documenting the toxicity of nanometric inorganic materials especially those largely used in products available in the market.

Hyaluronidase-Responsive Mesoporous Silica Nanoparticles with Dual-Imaging and Dual-Target Function

Nanoparticle-based drug delivery systems are among the most popular research topics in recent years. Compared with traditional drug carriers, mesoporous silica nanoparticles (MSN) offer modifiable surfaces, adjustable pore sizes and good biocompatibility. Nanoparticle-based drug delivery systems have become a research direction for many scientists. With the active target factionalized, scientists could deliver drug carriers into cancer cells successfully. However, drugs in cancer cells could elicit drug resistance and induce cell exocytosis. Thus, the drug cannot be delivered to its pharmacological location, such as the nucleus. Therefore, binding the cell membrane and the nuclear target on the nanomaterial so that the anticancer drug can be delivered to its pharmacological action site is our goal. In this study, MSN-EuGd was synthesized by doping Eu3+ and Gd3+ during the synthesis of MSN. The surface of the material was then connected to the TAT peptide as the nucleus target for targeting the cancer nucleus and then loaded with the anticancer drug camptothecin (CPT). Then, the surface of MSN-EuGd was bonded to the hyaluronic acid as an active target and gatekeeper. With this system, it is possible and desirable to achieve dual imaging and dual targeting, as well as to deliver drugs to the cell nucleus under a hyaluronidase-controlled release. The experimental approach is divided into three parts. First, we conferred the material with fluorescent and magnetic dual-imaging property by doping Eu3+ and Gd3+ into the MSN. Second, modification of the cell membrane target molecule and the nucleus target molecule occurred on the surface of the nanoparticle, making the nanoparticle a target drug carrier. Third, the loading of drug molecules into the carrier gave the entire carrier a specific target profile and enabled the ability to treat cancer. In this study, we investigated the basic properties of the drug carrier, including physical properties, chemical properties, and in vitro tests. The result showed that we have successfully designed a drug delivery system that recognizes normal cells and cancer cells and has good anticancer effects.

Propranolol-Loaded Mesoporous Silica Nanoparticles for Treatment of Infantile Hemangiomas

Infantile hemangioma (IH) is one of the most common neoplasm of infancy. Although with the potential to involute slowly after proliferation, IH has several subsets that could develop severe complications and lead to functional impairment or permanent disfigurement. In the present study, a novel propranolol (PRN) delivery system is developed that encapsulated in mesoporous silica nanoparticles (MSN). The primary nanoparticles are further treated with polyvinyl alcohol (PVA) to form PVA-MSN-PRN nanoparticles. The encapsulation efficiency is 58.8% ± 7.2%, and nanoparticles could release PRN in a controlled-release way. It is discovered that PVA-MSN-PRN could significantly suppress hemangioma stem cell (Hemsc) proliferation, promote Hemsc apoptosis in vitro, and inhibit the growth of hemangiomain xenografts in vivo. A conclusion could be made that this novel nanodrug delivery system has high therapeutic efficacy, low cytotoxicity, low administration frequency, and provides an attractive strategy for efficient IH therapy.

Spatial, Temporal, and Dose Control of Drug Delivery using Noninvasive Magnetic Stimulation

Noninvasive stimuli-responsive drug delivery using magnetic fields in conjunction with superparamagnetic nanoparticles offers the potential for the spatial and temporal control of drug release. When hyperthermia is not desired and control of the dosage is required, it is necessary to design a platform in which local heating on the nanoscale releases the therapeutic cargo without the bulk heating of the surrounding medium. In this paper, we report a design using a stimuli-responsive nanoparticle platform to control the dosage of the cargo released by an alternating magnetic field (AMF) actuation. A core@shell structure with a superparamagnetic doped iron oxide (MnFe₂O₄@CoFe₂O₄) nanoparticle core in a mesoporous silica shell was synthesized. The core used here has a high saturation magnetization value and a high specific loss power for heat generation under an AMF. The mesoporous shell has a high cargo-carrying capacity. A thermoresponsive molecular-based gatekeeper containing an aliphatic azo group was modified on the core@shell nanoparticles to regulate the cargo release. The mesoporous structure of the silica shell remained intact after exposure to an AMF, showing that the release of cargo is due to the removal of the gatekeepers instead of the destruction of the structure. Most importantly, we demonstrated that the amount of cargo released could be adjusted by the AMF exposure time. By applying multiple sequential exposures of AMF, we were able to release the cargo step-wise and increase the total amount of released cargo. In vitro studies showed that the death of pancreatic cancer cells treated by drug-loaded nanoparticles was controlled by different lengths of AMF exposure time due to different amount of drugs released from the carriers. The strategy developed here holds great promise for achieving the dosage, temporal, and spatial control of therapeutics delivery without the risk of overheating the particles' surroundings.

Surface Charge-Dependent Cellular Uptake of Polystyrene Nanoparticles

The evaluation of the role of physicochemical properties in the toxicity of nanoparticles is important for the understanding of toxicity mechanisms and for controlling the behavior of nanoparticles. The surface charge of nanoparticles is suggested as one of the key parameters which decide their biological impact. In this study, we synthesized fluorophore-conjugated polystyrene nanoparticles (F-PLNPs), with seven different types of surface functional groups that were all based on an identical core, to evaluate the role of surface charge in the cellular uptake of nanoparticles. Phagocytic differentiated THP-1 cells or non-phagocytic A549 cells were incubated with F-PLNP for 4 h, and their cellular uptake was quantified by fluorescence intensity and confocal microscopy. The amount of internalized F-PLNPs showed a good positive correlation with the zeta potential of F-PLNPs in both cell lines (Pearson’s r = 0.7021 and 0.7852 for zeta potential vs. cellular uptake in THP-1 cells and nonphagocytic A549 cells, respectively). This result implies that surface charge is the major parameter determining cellular uptake efficiency, although other factors such as aggregation/agglomeration, protein corona formation, and compositional elements can also influence the cellular uptake partly or indirectly.

Silica-gentamicin nanohybrids: combating antibiotic resistance, bacterial biofilms, and in vivo toxicity

INTRODUCTION

Antibiotic resistance is a growing concern in health care. Methicillin-resistant Staphylococcus aureus (MRSA), forming biofilms, is a common cause of resistant orthopedic implant infections. Gentamicin is a crucial antibiotic preventing orthopedic infections. Silica-gentamicin (SiO2-G) delivery systems have attracted significant interest in preventing the formation of biofilms. However, compelling scientific evidence addressing their efficacy against planktonic MRSA and MRSA biofilms is still lacking, and their safety has not extensively been studied.

MATERIALS AND METHODS

In this work, we have investigated the effects of SiO2-G nanohybrids against planktonic MRSA as well as MRSA and Escherichia coli biofilms and then evaluated their toxicity in zebrafish embryos, which are an excellent model for assessing the toxicity of nanotherapeutics.

RESULTS

SiO2-G nanohybrids inhibited the growth and killed planktonic MRSA at a minimum concentration of 500 µg/mL. SiO2-G nanohybrids entirely eradicated E. coli cells in biofilms at a minimum concentration of 250 µg/mL and utterly deformed their ultrastructure through the deterioration of bacterial shapes and wrinkling of their cell walls. Zebrafish embryos exposed to SiO2-G nanohybrids (500 and 1,000 µg/mL) showed a nonsignificant increase in mortality rates, 13.4±9.4 and 15%±7.1%, respectively, mainly detected 24 hours post fertilization (hpf). Frequencies of malformations were significantly different from the control group only 24 hpf at the higher exposure concentration.

CONCLUSION

Collectively, this work provides the first comprehensive in vivo assessment of SiO2-G nanohybrids as a biocompatible drug delivery system and describes the efficacy of SiO2-G nanohybrids in combating planktonic MRSA cells and eradicating E. coli biofilms.

Facile Strategy Enabling Both High Loading and High Release Amounts of the Water-Insoluble Drug Clofazimine Using Mesoporous Silica Nanoparticles

The use of nanocarriers to deliver poorly soluble drugs to the sites of diseases is an attractive and general method, and mesoporous silica nanoparticles (MSNs) are increasingly being used as carriers. However, both loading a large amount of drugs into the pores and still being able to release the drug is a challenge. In this paper, we demonstrate a general strategy based on a companion molecule that chaperones the drug into the pores and also aids it in escaping. A common related strategy is to use a miscible co-solvent dimethyl sulfoxide (DMSO), but although loading may be efficient in DMSO, this co-solvent frequently diffuses into an aqueous environment, leaving the drug behind. We demonstrate the method by using acetophenone (AP), an FDA-approved food additive as the chaperone for clofazimine (CFZ), a water-insoluble antibiotic used to treat leprosy and multidrug-resistant tuberculosis. AP enables a high amount of CFZ cargo into the MSNs and also carries CFZ cargo out from the MSNs effectively when they are in an aqueous biorelevant environment. The amount of loading and the CFZ release efficiency from MSNs were optimized; 4.5 times more CFZ was loaded in MSNs with AP than that with DMSO and 2300 times more CFZ was released than that without the assistance of the AP. In vitro treatment of macrophages infected by Mycobacterium tuberculosis with the optimized CFZ-loaded MSNs killed the bacteria in the cells in a dose-dependent manner. These studies demonstrate a highly efficient method for loading nanoparticles with water-insoluble drug molecules and the efficacy of the nanoparticles in delivering drugs into eukaryotic cells in aqueous media.

The Bioimaging Applications of Mesoporous Silica Nanoparticles

The unique features of Mesoporous Silica Nanoparticles (MSNs) provide a suitable platform to carry fluorescence dyes for various bioimaging applications. Several strategies have been developed to conjugate a variety of dyes either in the pores or on the surfaces of MSNs to form the fluorescence MSNs (FMSNs). In this chapter, we will discuss recent research progress and future development of FMSNs for living system imaging. We will first describe different strategies for the fabrications of FMSNs. Then, we will discuss the recent developments of cellular and intracellular imaging including self-probe for the interactions of FMSNs with the cells, receptor and organelle labeling, sensing and tracking of biological system, and monitoring the drug delivery and release processes. Moreover, we will include the applications of FMSNs as contrast agents for in vivo imaging. Finally, we will conclude and highlight the challenges and opportunities for MSNs in medical applications.

The toxicity of silica nanoparticles to the immune system

Silicon-based materials and their oxides are widely used in drug delivery, dietary supplements, implants and dental fillers. Silica nanoparticles (SiNPs) interact with immunocompetent cells and induce immunotoxicity. However, the toxic effects of SiNPs on the immune system have been inadequately reviewed. The toxicity of SiNPs to the immune system depends on their physicochemical properties and the cell type. Assessments of immunotoxicity include determining cell dysfunctions, cytotoxicity and genotoxicity. This review focuses on the immunotoxicity of SiNPs and investigates the underlying mechanisms. The main mechanisms were proinflammatory responses, oxidative stress and autophagy. Considering the toxicity of SiNPs, surface and shape modifications may mitigate the toxic effects of SiNPs, providing a new way to produce these nanomaterials with less toxic impaction.

Risk assessment of silica nanoparticles on liver injury in metabolic syndrome mice induced by fructose

This study aims to assess the effects and the mechanisms of silica nanoparticles (SiNPs) on hepatotoxicity in both normal and metabolic syndrome mouse models induced by fructose. Here, we found that SiNPs exposure lead to improved insulin resistance in metabolic syndrome mice, but markedly worsened hepatic ballooning, inflammation infiltration, and fibrosis. Moreover, SiNPs exposure aggravated liver injury in metabolic syndrome mice by causing serious DNA damage. Following SiNPs exposure, liver superoxide dismutase and catalase activities in metabolic syndrome mice were stimulated, which is accompanied by significantly increased malondialdehyde and 8-hydroxy-2-deoxyguanosine levels as compared to normal mice. Scanning electron microscope (SEM) revealed that SiNPs were more readily deposited in the liver mitochondria of metabolic syndrome mice, resulting in more severe mitochondrial injury as compared to normal mice. We speculated that SiNPs-induced mitochondrial injury might be the cause of hepatic oxidative stress, which further lead to a series of liver lesions as observed in mice following SiNPs exposure. Based on these results, it is likely that SiNPs will increase the risk and severity of liver disease in individuals with metabolic syndrome. Therefore, SiNPs should be used cautiously in food additives and clinical settings.

HER2-Targeted Multifunctional Silica Nanoparticles Specifically Enhance the Radiosensitivity of HER2-Overexpressing Breast Cancer Cells

We investigated the effects of targeted functionalized silica nanoparticles on the radiosensitivity of cancer cells. Better control of the local concentration of silica nanoparticles may facilitate their use as an adjuvant in conjunction with ionizing radiation to target cancer cells while preventing damage to normal cells. Hyperbranched polyamidoamine (PAMAM) was grafted onto the surface of amorphous silica nanoparticles to functionalize them. The PAMAM-coated silica nanoparticles (PCSNs) were then conjugated with fluorescent dyes. Anti-HER2 antibodies were covalently attached to the labeled PCSNs. The HER2-overexpressing SK-BR3 breast cancer cell line was incubated in medium containing the PCSN probes. After incubation; the cells were exposed to X-ray radiation. Cells were counted in all samples using cell proliferation assays; and apoptotic cells were detected. The cell survival results showed that the combination of the targeted PCSN probes and radiation reduced the survival rate of SK-BR3 cells to a greater extent than when either PCSN probes, PCSNs or radiation were applied individually. The results also showed an increase in apoptosis in the SK-BR3 cells that internalized the PCSN probes and were then irradiated. Based on these data, PCSN probes act as specific radiosensitizing agents for HER2-overexpressing cells.

Novel Schiff base (DBDDP) selective detection of Fe (III): Dispersed in aqueous solution and encapsulated in silica cross-linked micellar nanoparticles in living cell

This work demonstrated the synthesis of (4E)-4-(4-(diphenylamino)benzylideneamino)-1,2-dihydro-1,5- dimethyl-2-phenylpyrazol-3-one (DBDDP) for Fe (III) detection in aqueous media and in the core of silica cross-linked micellar nanoparticles in living cells. The free DBDDP performed fluorescence enhancement due to Fe (III)-promoted hydrolysis in a mixed aqueous solution, while the DBDDP-doped silica cross-linked micellar nanoparticles (DBDDP-SCMNPs) performed an electron-transfer based fluorescence quenching of Fe (III) in living cells. The quenching fluorescence of DBDDP-SCMNPs and the concentration of Fe (III) exhibited a linear correlation, which was in accordance with the Stern-Volmer equation. Moreover, DBDDP-SCMNPs showed a low limit of detection (LOD) of 0.1 ppm and an excellent selectivity against other metal ions. Due to the good solubility and biocompatibility, DBDDP-SCMNPs could be applied as fluorescence quenching nanosensors in living cells.

Global gene expression analysis of macrophage response induced by nonporous and porous silica nanoparticles

Little is known about the global gene expression profile of macrophages in response to changes in size and porosity of silica nanoparticles (SNPs). Spherical nonporous SNPs of two different diameters, and mesoporous spherical SNPs with comparable size were characterized. Reactive oxygen species, mitochondrial membrane potential, lysosome degradation capacity, and lysosome pH were measured to evaluate the influence of nonporous and mesoporous SNPs on mitochondrial and lysosomal function. RNA-sequencing was utilized to generate transcriptional profiles of RAW264.7 macrophages exposed to non-toxic SNP doses. DESeq2, limma, and BinReg2 software were used to analyze the data based on both unsupervised and supervised strategies to identify genes with greatest differences among NP treatments. Utilizing GATHER and DAVID software, possible induced pathways were studied. We found that mesoporous silica nanoparticles are capable of altering gene expression in macrophages at doses that do not elicit acute cytotoxicity, while gene transcription was minimally affected by nonporous SNPs.

Inorganic Nanocrystals Functionalized Mesoporous Silica Nanoparticles: Fabrication and Enhanced Bio-applications

Mesoporous SiO2 nanoparticles (MSNs) are one of the most promising materials for bio-related applications due to advantages such as good biocompatibility, tunable mesopores, and large pore volume. However, unlike the inorganic nanocrystals with abundant physical properties, MSNs alone lack functional features. Thus, they are not sufficiently suitable for bio-applications that require special functions. Consequently, MSNs are often functionalized by incorporating inorganic nanocrystals, which provide a wide range of intriguing properties. This review focuses on inorganic nanocrystals functionalized MSNs, both their fabrication and bio-applications. Some of the most utilized methods for coating mesoporous silica (mSiO2) on nanoparticles were summarized. Magnetic, fluorescence and photothermal inorganic nanocrystals functionalized MSNs were taken as examples to demonstrate the bio-applications. Furthermore, asymmetry of MSNs and their effects on functions were also highlighted.