Confinement and Polarity Effects on the Peptide Packing Density on Mesoporous Silica Nanoparticles.

The adsorption of cationic peptide JM21 onto different mesoporous silica nanoparticles (MSNs) from an aqueous solution was studied as a function of pH. In agreement with the literature, the highest loading degrees could be achieved at pH close to the isoelectric point of the peptide where the peptide-peptide repulsion is minimum. However, mesopore size, mesopore geometry, and surface polarity all had an influence on the peptide adsorption in terms of both affinity and maximum loading at a given pH. This adsorption behavior could largely be explained by a combination of pH-dependent electrostatic interactions and confinement effects. It is demonstrated that hydrophobic interactions enhance the degree of peptide adsorption under pH conditions where the electrostatic attraction was absent in the case of mesoporous organosilica nanoparticles (MONs). The lower surface concentration of silanol groups for MON led to a lower level of peptide adsorption under optimum pH conditions compared to all-silica particles. Finally, the study confirmed the protective role of MSNs in preserving the biological activity of JM#21 against enzymatic degradation, even for large-pore MSNs, emphasizing their potential as nanocarriers for therapeutic peptides. By integrating experimental findings with theoretical modeling, this research elucidates the complex interplay of factors that influence peptide-silica interactions, providing vital insights for optimizing peptide loading and stabilization in biomedical applications.

Silica nanoparticles: A review of their safety and current strategies to overcome biological barriers.

Silica nanoparticles (SNP) have gained tremendous attention in the recent decades. They have been used in many different biomedical fields including diagnosis, biosensing and drug delivery. Medical uses of SNP for anti-cancer, anti-microbial and theranostic applications are especially prominent due to their exceptional performance to deliver many different small molecules and recently biologics (mRNA, siRNA, antigens, antibodies, proteins, and peptides) at targeted sites. The physical and chemical properties of SNP such as large specific surface area, tuneable particle size and porosity, excellent biodegradability and biocompatibility make them an ideal drug delivery and diagnostic platform. Based on the available data and the pre-clinical performance of SNP, recent interest has driven these innovative materials towards clinical application with many of the formulations already in Phase I and Phase II trials. Herein, the progress of SNP in biomedical field is reviewed, and their safety aspects are analysed. Importantly, we critically evaluate the key structural characteristics of SNP to overcome different biological barriers including the blood-brain barrier (BBB), skin, tumour barrier and mucosal barrier. Future directions, potential pathways, and target areas towards rapid clinical translation of SNP are also recommended.

Towards a simple in vitro surface chemistry pre-screening method for nanoparticles to be used for drug delivery to solid tumours.

An efficient nanoparticulate drug carrier intended for chemotherapy based on intravenous administration must exhibit a long enough blood circulation time, a good penetrability into the tumour volume, as well as an efficient uptake by cancer cells. Limiting factors for the therapeutic outcome in vivo are recognition of the nanoparticles as foreign objects, which triggers nanoparticle uptake by defence organs rich in macrophages, e.g. liver and spleen, on the time-scale of accumulation and uptake in/by the tumour. However, the development of nanomedicine towards efficient nanoparticle-based delivery to solid tumours is hampered by the lack of simple, reproducible, cheap, and predictive means for early identification of promising nanoparticle formulations. The surface chemistry of nanoparticles is known to be the most important determinant for the biological fate of nanoparticles, as it influences the extent of serum protein adsorption, and also the relative composition of the protein corona. Here we preliminarily evaluate an extremely simple screening method for nanoparticle surface chemistry pre-optimization based on nanoparticle uptake in vitro by PC-3 cancer cells and THP-1 macrophages. Only when both selectivity for the cancer cells as well as the extent of nanoparticle uptake are taken into consideration do the in vitro results mirror literature results obtained for small animal models. Furthermore, although not investigated here, the screening method does also lend itself to the study of actively targeted nanoparticles.

Virus-like silica nanoparticles enhance macromolecule permeation in vivo.

Nanoparticle based permeation enhancers have the potential to improve the oral delivery of biologics. Recently, solid silica nanoparticles were discovered to improve the intestinal permeability of peptides and proteins via transient opening of the gut epithelium. In this study, we have developed small-sized (∼60 nm) virus-like silica nanoparticles (VSNP) as a reversible and next generation non-toxic permeation enhancer for oral delivery of biologics. Our results show that the anionic VSNP showed a better permeation-enhancing effect than the same sized spherical Stöber silica nanoparticles (∼60 nm) by enhancing the apparent insulin permeability by 1.3-fold in the Caco-2 monolayer model and by 1.2-fold in the Caco-2/MTX-HT-29 co-culture model. In vivo experiments in healthy mice demonstrated that anionic VSNP significantly enhanced the permeation of fluorescently labelled 4 kDa dextran after oral administration compared to Stöber nanoparticles and positively charged VSNP. The results indicated that the nanoscale surface roughness is an important consideration when designing nanoparticle-based permeation enhancers. Overall, our study shows for the first time that small-sized (∼60 nm) VSNP with nanoscale surface roughness can be used as a non-toxic permeation enhancer for oral delivery of therapeutic peptides and proteins.

Investigation of the Mechanism of SiO2 Particle and Capsule Formation at the Oil-Water Interface of Dye-Stabilized Emulsions.

In a previous contribution we described the formation of silica nanostructures in dye-stabilized nanoemulsions from tetraethyl orthosilicate droplets in water. Depending on the type of dye, either capsules (crystal violet, CV) or nanoparticles (congo red, CR) are formed. The thorough study of the sol-gel process uses a combination of time- and/or temperature-resolved small-angle X-ray scattering, transmission electron microscopy, and 1H NMR spectroscopy to elucidate the detailed kinetics and mechanism of structure formation. In both cases, small nuclei of 1.5-2 nm are formed, followed by either a fast cluster-cluster (CV) or a much slower monomer-cluster aggregation (CR). The former leads to a cross-linked network and finally to patchy capsules, while the latter leads to individual nanoparticles (SNPs). From an Avrami plot it can be deduced that the SNPs are formed by an interface-controlled one-dimensional growth process. The mechanisms are based on the different local environments at the oil-water interface, which is either slightly acidic (CV) or fairly basic (CR). The kinetics differ by a factor between 3 and 20 and are presumably caused by the different mobility of the catalyzing species H+ or OH-.

Enhanced Electrochemical Capacity of Spherical Co-Free Li1.2 Mn0.6 Ni0.2 O2 Particles after a Water and Acid Treatment and its Influence on the Initial Gas Evolution Behavior.

Li-rich layered oxides (LRLO) with specific energies beyond 900 Wh kg-1 are one promising class of high-energy cathode materials. Their high Mn-content allows reducing both costs and the environmental footprint. In this work, Co-free Li1.2 Mn0.6 Ni0.2 O2 was investigated. A simple water and acid treatment step followed by a thermal treatment was applied to the LRLO to reduce surface impurities and to establish an artificial cathode electrolyte interface. Samples treated at 300 °C show an improved cycling behavior with specific first cycle capacities of up to 272 mAh g-1 , whereas powders treated at 900 °C were electrochemically deactivated due to major structural changes of the active compounds. Surface sensitive analytical methods were used to characterize the structural and chemical changes compared to the bulk material. Online DEMS measurements were conducted to get a deeper understanding of the effect of the treatment strategy on O2 and CO2 evolution during electrochemical cycling.

Delivery by Dendritic Mesoporous Silica Nanoparticles Enhances the Antimicrobial Activity of a Napsin-Derived Peptide Against Intracellular Mycobacterium tuberculosis.

Tuberculosis remains a serious global health problem causing 1.3 million deaths annually. The causative pathogen Mycobacterium tuberculosis (Mtb) has developed several mechanisms to evade the immune system and resistances to many conventional antibiotics, so that alternative treatment strategies are urgently needed. By isolation from bronchoalveolar lavage and peptide optimization, a new antimicrobial peptide named NapFab is discovered. While showing robust activity against extracellular Mtb, the activity of NapFab against intracellular bacteria is limited due to low intracellular availability. By loading NapFab onto dendritic mesoporous silica nanoparticles (DMSN) as a carrier system, cellular uptake, and consequently antimycobacterial activity against intracellular Mtb is significantly enhanced. Furthermore, using lattice light-sheet fluorescence microscopy, it can be shown that the peptide is gradually released from the DMSN inside living macrophages over time. By electron microscopy and tomography, it is demonstrated that peptide loaded DMSN are stored in vesicular structures in proximity to mycobacterial phagosomes inside the cells, but the nanoparticles are typically not in direct contact with the bacteria. Based on the combination of functional and live-cell imaging analyses, it is hypothesized that after being released from the DMSN NapFab is able to enter the bacterial phagosome and gain access to the bacilli.

Multi-Modal PET and MR Imaging in the Hen's Egg Test-Chorioallantoic Membrane (HET-CAM) Model for Initial in Vivo Testing of Target-Specific Radioligands.

The validation of novel target-specific radioligands requires animal experiments mostly using mice with xenografts. A pre-selection based on a simpler in vivo model would allow to reduce the number of animal experiments, in accordance with the 3Rs principles (reduction, replacement, refinement). In this respect, the chick embryo or hen's egg test-chorioallantoic membrane (HET-CAM) model is of special interest, as it is not considered an animal until day 17. Thus, we evaluated the feasibility of quantitative analysis of target-specific radiotracer accumulation in xenografts using the HET-CAM model and combined positron emission tomography (PET) and magnetic resonance imaging (MRI). For proof-of-principle we used established prostate-specific membrane antigen (PSMA)-positive and PSMA-negative prostate cancer xenografts and the clinically widely used PSMA-specific PET-tracer [68Ga]Ga-PSMA-11. Tracer accumulation was quantified by PET and tumor volumes measured with MRI (n = 42). Moreover, gamma-counter analysis of radiotracer accumulation was done ex-vivo. A three- to five-fold higher ligand accumulation in the PSMA-positive tumors compared to the PSMA-negative tumors was demonstrated. This proof-of-principle study shows the general feasibility of the HET-CAM xenograft model for target-specific imaging with PET and MRI. The ultimate value for characterization of novel target-specific radioligands now has to be validated in comparison to mouse xenograft experiments.

Quantitative 19F MRI of perfluoro-15-crown-5-ether using uniformity correction of the spin excitation and signal reception.

OBJECTIVES: A common limitation of all 1H contrast agents is that they only allow indirect visualization through modification of the intrinsic properties of the tissue, making quantification of this effect challenging. 19F compounds, on the contrary, are measured directly, without any background signal. There is a linear relationship between the amount of 19F spins and the intensity of the signal. However, non-uniformity of the radiofrequency field may lead to errors in the quantified 19F signal and should be carefully addressed for any quantitative imaging. MATERIALS AND METHODS: Adaptation of the previously introduced [Formula: see text] mapping technique to the problem of quantifying the 19F signal from perfluoro-15-crown-5-ether (PFCE) is proposed in this work. Initial evaluation of the proposed technique simultaneously accounting for transmit [Formula: see text] and receive [Formula: see text] field inhomogeneities is performed in a PFCE phantom. As a proof of concept, in vivo quantification of the 19F signal is performed in a murine model after application of custom-designed hollow mesoporous silica spheres (HMSS) loaded with PFCE. RESULTS: A phantom experiment clearly shows that only compensation for both transmit and receive characteristics outperforms inaccurate quantification based on the non- or partly-corrected signal intensities. Furthermore, an optimized protocol is proposed for in vivo application. CONCLUSION: The proposed [Formula: see text]/[Formula: see text] mapping technique represents a simple to implement and easy-to-use solution for quantification of the 19F signal from PFCE in the presence of B1-field inhomogeneities.

Comparison of different cytotoxicity assays for in vitro evaluation of mesoporous silica nanoparticles.

Colorimetric or luminogenic cytotoxicity assays are typically applied for in vitro cytotoxicity evaluations due to their easy handling and low cost. However, the results may be strongly assay-dependent. Furthermore, when applied to nanoparticle toxicity screening, nanoparticle-specific interferences can occur. Therefore, it is important to evaluate the assays for different classes of nanoparticles. Mesoporous silica nanoparticles (MSNs) have emerged as a promising platform for both diagnostic and therapeutic applications but a comparison between the commonly employed colorimetric formazan-dependent MTT and WST-1 and luminescent ATP-dependent cytotoxicity assays is still missing. In this work, we evaluated the applicability of four different in vitro cell viability assays for the cytotoxicity analysis of three differently functionalized mesoporous silica nanoparticles towards TZM-bl indicator cells. The results derived from the colorimetric measurements of cell-viability were compared with results obtained by cell count experiments, flow cytometry, and optical microscopy. The correlation between the viability assay results and the viable cell count was observed to be both assay and particle dependent. The MTT assay generally overestimated the cytotoxicity of the mesoporous silica particles, while the WST-1 assay sometimes clearly underestimated their cytotoxicity and even suggested a viability exceeding 100%. Of the two ATP-based assays, the CellTiterGlo assay gave the best correlation with cell count data, although some particle-dependent effects were observed. In conclusion, ATP-based assays seem most suitable for in vitro cytotoxicity evaluation of MSNs.

Targeting murine leukemic stem cells by antibody functionalized mesoporous silica nanoparticles.

Acute leukemia is initiated and maintained by leukemia stem cells (LSCs) and therefore there is great interest to develop innovative therapeutic approaches which target LSCs. Here we show that mesoporous silica nanoparticles (MSNs) functionalized with succinic anhydride, tagged with an anti-B220 antibody and loaded with the anthracycline daunorubicin are efficiently incorporated into murine B220-positive AML LSCs and preferentially kill these cells in comparison to B220-negative AML LSCs in vitro. Furthermore, short - term treatment of the AML LSCs with these MSNs before transplant significantly delayed leukemia development in recipient mice. These data demonstrate that targeting of AML LSCs can be improved by using functionalized and antigen directed MSNs as carriers for anti-leukemic drugs.

Quantitative and correlative biodistribution analysis of 89Zr-labeled mesoporous silica nanoparticles intravenously injected into tumor-bearing mice.

The biodistribution of 89Zr-labeled mesoporous silica nanoparticles (MSNs) was evaluated in detail using a prostate cancer mouse model bearing LNCaP C4-2 and PC-3 tumor xenografts with focus on passive targeting. PEGylation of radiolabeled MSNs significantly improved the blood circulation times and radically enhanced the accumulation in tumors comparable to the accumulation levels previously reported for similar but actively targeted particles. The distribution of the passively targeted MSNs was related to the degree of vascularization of the tumors and did not follow the trends observed in vitro. Correlative analyses of organ-to-blood ratios revealed that little or no accumulation of the particles is observed in the lungs, heart, and brain, and that the particles detected were present in the blood pool. On the other hand, clear accumulation was observed in the liver and spleen, in addition to the uptake in the tumors. The accumulation of particles in the kidney did not correlate with the MSN concentration in the blood, but indicated a rather steady level of particles in the kidney. The results, which partly contradict previous studies, highlight the importance of correlative analyses in order to evaluate the organ accumulation of particles.

Mesoporous silica nanoparticles in injectable hydrogels: factors influencing cellular uptake and viability.

The incorporation of nanoparticles as drug vectors into 3D scaffolds has attracted a lot of recent interest. In particular, tissue engineering applications would benefit from a spatially and temporally regulated release of biological cues, which act on precursor/stem cells in a three-dimensional growth environment. Injectable cell- and nanoparticle-containing scaffolds are especially interesting in this respect, but require matrix self-assembly and coordinated interactions between cells, matrices, and nanoparticles, which are largely uncharacterized yet. In this proof of concept study we combined the matrix-forming self-assembling peptide RADA16-I, different mesoporous silica nanoparticles (MSN) as potential drug carriers, and MC3T3-E1 osteoblast precursor cells. When injected to physiological media, the mixtures rapidly formed hybrid peptide-silica hydrogels containing RADA16-I nanofiber scaffolds with uniform spatial distribution of viable cells and MSN. MSN surface chemistry was critical for interactions within the hydrogel and for RADA16-I adsorption, thereby dominantly influencing cellular uptake and cell viability, whereas the impact of serum protein was minor. Thus, important parameters which allow tuning of nanoparticulate drug vector interactions with cells in injectable 3D scaffolds are identified, which are of importance for the future design of smart scaffolds for advanced tissue engineering in vivo.

Serum Protein Adsorption Enhances Active Leukemia Stem Cell Targeting of Mesoporous Silica Nanoparticles.

The functionalization of nanoparticles with a ligand targeting receptors overexpressed by the target cells is a commonly used strategy when aiming at nanoparticle-based, cell type-specific drug delivery.1-4 However, the influence of particle surface chemistry on the targetability has received much less attention. The surface charge is known to directly or indirectly affect the nanoparticle cellular uptake kinetics by influencing serum protein adsorption.5-7 Thus, it is fair to assume that both the specificity and cellular uptake kinetics of targeted nanoparticles are influenced by the nanoparticle charge, both of which are important parameters for controlling cell-specific drug delivery efficiency. We therefore studied the influence of the surface chemistry of mesoporous silica nanoparticles (MSNs) carrying identical amounts of a specific antibody (anti-B220) on the selectivity toward B220-positive leukemia stem cells. The uptake by these cells was higher compared to the nanoparticle uptake by B220-negative leukemia stem cells, demonstrating uptake specificity. In addition, the adsorption of serum proteins onto the differently charged MSNs was studied by SDS-PAGE. Interestingly, the highest selectivity was not observed for the MSNs with the lowest level of serum protein adsorption, which suggests that proteins present in the protein corona of the MSNs may positively influence the selective uptake of targeted nanoparticles. For the particles exhibiting the highest selectivity, successful selective delivery of cargo to the B220-positive cells was demonstrated. Taken together, our results indicate that nanoparticle surface charge and adsorption of serum proteins is an important factor for enhancing selectivity in targeted delivery of drugs using nanoparticulate vectors, an observation tentatively attributed to enhanced cellular internalization kinetics in the presence of adsorbed serum proteins on the nanoparticles.

Inhibiting Notch Activity in Breast Cancer Stem Cells by Glucose Functionalized Nanoparticles Carrying γ-secretase Inhibitors.

Cancer stem cells (CSCs) are a challenge in cancer treatment due to their therapy resistance. We demonstrated that enhanced Notch signaling in breast cancer promotes self-renewal of CSCs that display high glycolytic activity and aggressive hormone-independent tumor growth in vivo. We took advantage of the glycolytic phenotype and the dependence on Notch activity of the CSCs and designed nanoparticles to target the CSCs. Mesoporous silica nanoparticles were functionalized with glucose moieties and loaded with a γ-secretase inhibitor, a potent interceptor of Notch signaling. Cancer cells and CSCs in vitro and in vivo efficiently internalized these particles, and particle uptake correlated with the glycolytic profile of the cells. Nanoparticle treatment of breast cancer transplants on chick embryo chorioallantoic membranes efficiently reduced the cancer stem cell population of the tumor. Our data reveal that specific CSC characteristics can be utilized in nanoparticle design to improve CSC-targeted drug delivery and therapy.

Mesoporous silica particle-PLA-PANI hybrid scaffolds for cell-directed intracellular drug delivery and tissue vascularization.

Instructive materials are expected to revolutionize stem cell based tissue engineering. As many stem cell cues have adverse effects on normal tissue homeostasis, there is a need to develop bioactive scaffolds which offer locally retained and cell-targeted drug delivery for intracellular release in targeted cell populations. Further, the scaffolds need to support vascularization to promote tissue growth and function. We have developed an electrospun PLA-PANI fiber scaffold, and incorporated mesoporous silica nanoparticles within the scaffold matrix to obtain cell-targeted and localized drug delivery. The isotropy of the scaffold can be tuned to find the optimal morphology for a given application and the scaffold is electroactive to support differentiation of contractile tissues. We demonstrate that there is no premature drug release from particles under physiological conditions over a period of one week and that the drug is released upon internalization of particles by cells within the scaffold. The scaffold is biocompatible, supports muscle stem cell differentiation and cell-seeded scaffolds are vascularized in vivo upon transplantation on the chorioallantoic membrane of chicken embryos. The scaffold is a step towards instructive biomaterials for local control of stem cell differentiation, and tissue formation supported by vascularization and without adverse effects on the homeostasis of adjacent tissues due to diffusion of biological cues.

Active targeting of mesoporous silica drug carriers enhances γ-secretase inhibitor efficacy in an in vivo model for breast cancer.

AIM: In this article, we use an alternative cancer model for the evaluation of nanotherapy, and assess the impact of surface functionalization and active targeting of mesoporous silica nanoparticles (MSNPs) on therapeutic efficacy in vivo. MATERIALS & METHODS: We used the chorioallantoic membrane xenograft assay to investigate the biodistribution and therapeutic efficacy of folate versus polyethyleneimine-functionalized γ-secretase inhibitor-loaded MSNPs in breast and prostate tumor models. RESULTS: γ-secretase inhibitor-loaded MSNPs inhibited tumor growth in breast and prostate cancer xenografts. Folate conjugation improved the therapeutic outcome in folic acid receptor-positive breast cancer, but not in prostate cancer lacking the receptor. CONCLUSION: The results demonstrate that therapeutic efficacy is linked to cellular uptake of MSNPs as opposed to tumor accumulation, and show that MSNP-based delivery of γ-secretase inhibitors is therapeutically effective in both breast and prostate cancer. In this article, we present a model system for a medium-to-high throughput, cost-effective, quantitative evaluation of nanoparticulate drug carriers.

Intracellular degradation of multilabeled poly(ethylene imine)-mesoporous silica-silica nanoparticles: implications for drug release.

Mesoporous silica nanoparticles, MSNs, have emerged as an interesting carrier for drugs in vitro and in vivo. The particles are typically used in a surface functionalized form, where functional silanes or other covalently linked surface functions are used to provide anchoring sites for additional functionalities like targeting groups, imaging agents, and drugs. Here, we report results related to extra- and intracellular degradation of silica nanoparticles using multilabeled nonporous silica core-mesoporous silica shell-surface hyperbranched poly(ethylene imine) shell nanoparticles as model particles. Different fluorophores have been selectively covalently linked to different regions of the particles in order to study the particle degradation in detail under in vitro conditions in human SAOS-2 cells. A novel, quantitative method for nanoparticle degradation evaluation based on confocal fluorescence microscopy is applied. Our results suggest that the core-shell-shell MSNs degrade at a higher rate inside cells as compared to outside cells, which is of high importance for further application of this class of drug carriers.

Mesoporous silica nanoparticles in medicine--recent advances.

MSNs have attracted increasing interest as drug carriers due to promising in vivo results in small-animal disease models, especially related to cancer therapy. In most cases small hydrophobic drugs have been used, but recent in vitro studies demonstrate that MSNs are highly interesting for gene delivery applications. This review covers recent advances related to the therapeutic use of mesoporous silica nanoparticles (MSNs) administered intravenously, intraperitoneally or locally. We also cover the use of MSNs in alternative modes of therapy such as photodynamic therapy and multidrug therapy. We further discuss the current understanding about the biodistribution and safety of MSNs. Finally, we critically discuss burning questions especially related to experimental design of in vivo studies in order to enable a fast transition to clinical trials of this promising drug delivery platform.

Effect of a large hole reservoir on the charge transport in TiO2/organic hybrid devices.

We have fabricated hybrid devices in the form of indium tin oxide/titanium dioxide/poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester/copper (ITO/TiO(2)/P3HT:PCBM/Cu) to clarify the impact of the TiO(2)/P3HT:PCBM interface on the charge transport using the charge extraction by linearly increasing voltage (CELIV) technique. We found that a large equilibrium charge reservoir is accumulated at negative offsets at the TiO(2)/P3HT:PCBM interface leading to space charge limited extraction current (SCLC) transients. We show analytically the SCLC transient response and compare the experimental data to calculated SCLC at a linearly increasing voltage. The theoretical calculations indicate that the large charge reservoir at negative offset voltages is due to thermally generated charges combined with poor hole extraction at the ITO/TiO(2) contact, due to the hole blocking character of TiO(2).