Multifunctional Mesoporous Silica Nanocomposite Nanoparticles for Theranostic Applications

The ideal vehicle for smart delivery systems should be able to accommodate large drug loads, be traceable and feature targeting and smart release control mechanisms that allow the delivery of their cargo on-demand at the desired location. In this editorial, we will focus on hybrid mesoporous silica nanoparticles (hMSNs) that can combine therapeutic and diagnostic (theranostic) functionalities, with the ultimate goal of creating smart nanocarriers that use the diagnostic information to control their therapeutic action.

In the early 1990s the discovery of the MCM-41 and the M41S family of mesoporous materials had open new era in the chemistry and biology. They have prominent application inbiotechnological, biomedical and heterogeneous catalysts. Mesoporous silica nanoparticles (MSNs) exhibit unique structural features like as their large surface areas, tunable pore sizes in nanometer and well-defined surface properties. MSN materials which are comprised of a honeycomb-like porous structure with hundreds of empty mesoporous channel that are able to encapsulate relatively large amounts of biomolecules. They are ideal candidate for constructing multifunctional materials that encapsulate a variety of functional nanostructured materials. Multifunctional MSN materials have become one of the most attractive areas in nanobiotechnology and nanomedicine for various disease diagnosis and therapy. Multifunctional MSN have been successfully developed as a multifunctional platform to deliver therapeutic and diagnostic agents. Multifunctional MSNs are a highly promising platform for intracellular controlled release of drugs. In this review we discuss the recent developments in design and fabrication of multifunctional mesoporous silica nanoparticles in as efficient drug delivery applications such as the site-specific delivery and intracellular controlled release of drugs.Abbreviations;APTES; 3-aminopropyl triethoxy sialne, ATP; Adenosine triphospahate, CD; cyclodextrinCPT; camptothecin, CS; Chitosan,CTAB; cyltrimethylammonium bromide,DNA; Deoxyribonucleic acid,DOX; doxorubicin,EDC; 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide,FD; fluorescein disodium,FSP;Fluroscent particle ,IBU;ibuprofen,MCM; mobil composition material, MPS; 3-trimethoxylsilyl propyl methacrylate, MS; mesoporous silica,MSN; mesoporous silica nanoparticle, MSNs; mesoporous silica nanoparticles,MSNP; mesoporous silica nanoparticle,NPS; nanoparticles;PFDTES;perfluorodecyltriethoxysilane, PAA; polyacrylic acid,PR;photo responsive,PMAA; polymethyl methacrylate,SBF; simulated body fluid,TEOS;tetraethyl orthosilicate,TUNA;Thio undecyl-tetraethyleneglycoestero-nitrobenzylethyldimethyl ammonium bromide.

Silica-based materials like mesoporous silica nanoparticles have been in research practice for almost three decades now. Its artistic properties such as tuneable pore size, pore volume, surface area, colloidal stability, and ease of functionalization on inner and outer surfaces make it a potent and suitable choice for biomedical applications. Surface functionalization on mesoporous silica nanoparticles has been carried out in order to achieve active targeting to cancer cells for detection and therapeutic purposes. The mesoporous silica nanoparticles provide a significant property of enhanced adsorption owing to its mesoporous nature, thereby making it an adequate vehicle for drug delivery applications. Mesoporous silica nanoparticle-based drug delivery systems may be controlled and manipulated through specific stimuli to generate precise responses in pathological conditions across biological cells. The fabrication of mesoporous silica nanoparticles with advanced drug delivery strategies are driven by ultrasounds, magnetic fields, and electric fields in response to change in pH, temperature, and enzymatic activity across the microenvironment of targeted pathological conditions. In order to impart suitability and to offer multifunctionality, the mesoporous silica nanoparticle-based drug delivery systems are functionalized with multiple moieties simultaneously. Various functionalities like pH, magnetic, ultrasound, biomolecule and light-responsive mesoporous silica nanoparticles are fabricated and transformed into multi-responsive mesoporous silica nanoparticles. In this report, diverse strategies to functionalize mesoporous silica nanoparticles along with their mechanism of action are critically reviewed and discussed. Insight into recent advances in stimuli-responsive approaches of mesoporous silica nanoparticle-based drug delivery systems is conferred that associates the progress of mesoporous silica nanoparticles in the field of drug delivery and imaging.

The synthesis of drug delivery systems based on surface-modified mesoporous silica hollow structures remains a huge challenge. In this paper, we have obtained hollow mesoporous silica nanoparticles (MSNs) by surfactant directed sol-gel assisted hydrothermal treatment. The MSNs have the inorganic-organic hybrid frameworks with uniform diameter distribution (260 nm), and their specific surface area, mesoporous size and pore volume are 540 m2 g−1, 3.7 nm, 0.58 cm3 g−1, respectively. It was proved that the preparation of hollow ethane-bridged nanospheres with two silicon source was due to the high crosslinking of the silicone interface and hydrothermal treatment, providing a new approach for the study of drug-loaded and controlled release behavior. Based on the synthesis of MSNs, MSNs were modified by methacryloxy propyl trimethoxyl silane (MPS) on the surface of MSNs. Then N-isopropylacryamide (NIPAM) and acrylic acid (AA) were grafted onto the surface of modified MSNs. The hollow ethane-bridged PNA–MSNs (poly (NIPAM-co-acrylic acid)-MSNs) with two silicon source were prepared successfully. Due to their distinctive hollow structure, PNA–MSNs demonstrated high drug encapsulation efficiency (70.4% ± 2.9%). The experiment results proved that the modified hollow nanoparticles not only had good biocompatibility and stability, but also possessed pH-/thermal-dual responsiveness in drug release.

Biomacromolecules, such as miRNA/siRNA and proteins, have been drawing increasing attention because of their powerful application in treating disease. These biomolecules open new treatment opportunities for diseases which were previously considered as untreatable by conventional approaches. However, the broad clinical utilization of biomacromolecules is hindered by inefficient cellular uptake. Therefore, a variety of materials have been developed as carriers for biomacromolecule delivery. These materials include gold nanoparticles, lipid-based carriers, polymer spheres and silica nanoparticles. Among these carriers, mesoporous silica nanoparticles (MSNs) are particularly attractive due to their large surface area for cargo adsorption, tuneable pore size to encapsulate large molecules, and adjustable particle size to facilitate cellular uptake. In order to efficiently load cargos, a surface functionalization of MSN is often necessary to introduce functional groups. The covalent chemical functionalization of MSN usually requires multiple complicated chemical reactions and introduces extra cytotoxicity to the carrier. In some cases, the MSN modified by this approach cannot release the cargo efficiently. To address these challenges, this PhD thesis has developed two strategies to functionalize MSN for biomacromolecule delivery. These strategies are: i) developing and optimizing covalent chemical functionalization to enable the controlled release of miRNA, and; ii) developing non-covalent biological functionalization of MSN by using binding peptides/proteins as linkers to conjugate carriers and cargos through non-covalent binding. In the first approach, a cleavable S-S linker was introduced to enable a controlled release of miRNA. The density of functional groups (amine groups) was optimized on the surface of a large pore MSN (LP-MSN) with a pore size of 17 nm and a particle size of 200 nm. Three molecular layers were covalently attached on the surface of LP-MSN sequentially, including: i) a layer of oligo-lysine that controls the density of amine groups; ii) a layer containing the S-S linker that enables the release of miRNA, and; iii) a final polylysine layer that can efficiently bind miRNAs. From 5 different surface structures, LP-MSN-Epoxy-Trilysine-DSP-PLL has been identified as the optimal carrier that shows minimum cytotoxicity to normal rat kidney (NRK) cells while possessing a relatively high loading capacity and a controlled release for miRNA delivery. In the second approach, a non-covalent biological functionalization of MSN was developed based on self-assembly of the silica binding peptides/protein. Both the bi-functional peptides and the silica binding protein (the L2 protein) have been evaluated for functionalization of LP-MSN as delivery vehicles of biomacromolecules. Three bi-functional peptides that can bind both silica and nucleic acids have been designed, and it was found that the LP-MSN-RGRRRRLSCRLLK₈ complex is most effective in delivering a Cy3 labelled miRNA into NRK cells, while no cytotoxicity was observed at the working concentration. The function of miR-29B delivered by LP-MSN-RGRRRRLSCRLLK₈ was demonstrated by determining the down-regulated protein genes using a quantitative polymerase chain reaction (qPCR). The potential of the silica binding protein, the L2 protein, for functionalization of silica particles, was confirmed by the successful uptake of the LP-MSN-L2 complex into NRK cells. To further explore the influence of MSN properties on the delivery system, a dendritic mesoporous silica nanosphere (DMSN) modified by bi-functional peptides was evaluated for miRNA delivery. Although the fabricated DMSN-peptide complex shows relatively higher cytotoxicity to NRK cells compared with the LP-MSN-peptide complex, Alexa647-labelled miRNA was successfully delivered by DMSN-RGRRRRLSCRLLK₈ into NRK cells. Fundamental studies were carried out on the non-covalent biological functionalization system. Quartz crystal microbalance (QCM) results have quantified the binding amounts of bi-functional peptides on silica surfaces and confirmed rapid adsorption of these peptides. Small angel neutron scattering characterization of the L2 protein on a silica nanoparticle has shown that the affinity of L2 with silica is not affected by a high ionic strength up to 2 M MgCl₂, suggesting that the interaction between the L2 protein and silica particle is not just a charge interaction. Live cell imaging on the cellular uptake of DMSNS-RGRRRRLSCRLLK₈-Alexa647 labelled miRNA into NRK cells was performed, and the results suggest a phagocytotic pathway for the cluster of carrier-cargo complexes entering NRK cells. In summary, this PhD research has demonstrated two complementary approaches for functionalization of MSN as advanced delivery vehicles of macromolecules. The non-covalent biological functionalization approach, in particular, can serve as a powerful tool to modify silica surfaces by the self-assembly of designed bi-functional peptides. The method offers a simple fabrication process while decreasing cytotoxicity. The evaluation and fundamental study of these delivery systems provides valuable information to guide the functionalization of MSN as next generation of delivery vehicles for biomacromolecules (e.g. miRNA and proteins).

As a drug delivery system (DDS), traditional mesoporous silica nanoparticles (MSNs) suffer from bioaccumulation in vivo and premature drug release in systemic circulation due to low degradation rate and lack of protective gatekeeper. Herein, we developed a safe and intelligent DDS with characteristics of pH-responsive biodegradation and controlled drug release based on mesoporous silica composite nanoparticles (MSCNs) capped with ZnO quantum dots (ZnO QDs). Acidic degradable MSCNs were successfully synthesized by doping Ca2+ and PO43− into the MSNs’ framework. The in vitro doxorubicin hydrochloride (DOX) release was inhibited at neutral pH 7.4 but triggered significantly at pH 5.0 due to the dissociation of ZnO caps. The internalization behavior and cytotoxicity of 4T1 cells indicated MSCNs-ZnO could efficiently deliver DOX into the cells with significant antitumor activity. Such a DDS with pH-responsive biodegradation and controlled drug release has promising potential for cancer therapy.

Purpose: Modern methods of pancreatic cancer diagnosis and treatment are severely lacking and have failed to provide effectual treatment options for patients. The root cause of this inadequacy stems from the hypovascularized nature of pancreatic cancer, making traditional chemotherapeutics and cancer detecting contrast agents nearly obsolete. A potential solution for tumor-targeting difficulties is through the implementation of nanotechnology, specifically targeting ligand capped, theranostic nanoparticles. We hypothesize that silica based, mesoporous nanoparticles capped with the targeting ligand, urokinase plasminogen activator (UPA) will serve as theranostic agents for treatment and diagnosis of pancreatic cancer. Methods: Mesoporous, silica nanoparticles (MSNs) were synthesized through the covering of acetyl trimethylammonium bromide (CTAB) scaffolding with tetraethyl orthosilicate (TEOS) in an aqueous environment. Refluxing was later used to remove the CTAB scaffolding and construct the desired mesoporous structure of the nanoparticles. MSNs were chemically engineered to be sensitive to acidic pH, contain fluorescent dye, and utilize a protein targeting ligand UPA. Multiple characterization techniques were employed to analyze the synthesized MSNs including UV-Vis spectroscopy, Zeta Potential, and Transmission Electron Microscopy (TEM). Pancreatic cancer tumor cells, S2CP9 and S2VP10, were treated with UPA-targeted or no-ligand encapsulated MSNs at pH 7.4 and 6.5. Following treatment, cells were washed to remove unbound particles followed by particle visualization based upon fluorescent dyes rhodamine or indocyanine green. Alternatively, cells treated with indocyanine green (ICG) loaded MSNs were placed into a tissue phantom and viewed using the Multispectral Optoacoustic Tomography system (MSOT). Mice with S2CP9 orthotopic pancreatic tumors were i.v. injected with 100 μL of UPA-ICG loaded MSNs. Particle localization was conducted using MSOT after 4h post injection. Results: Zeta potential and UV-Vis analysis confirmed the MSNs chemical conjugation, attributing the MSNs properties of pH sensitivity and fluorescence. pH sensitivity tests on the MSNs displayed drug release quantities at pH 6.5 to be ∼x2 the quantities of pH 6.8 and 7.4. Fluorescence microscopy showed the MSN uptake into S2VP10 and S2CP9 cell lines, while NIH3T3 cells (negative control) showed less binding. Use of UPAR antibody on S2VP10 and S2CP9 cell lines (positive control) blocked cellular binding. In tissue phantoms, UPA-ICG loaded MSNs at pH 6.5 demonstrated 20X and 7X more cell signal than without ligand or at pH 7.4, respectively. In-vivo, UPA-ICG loaded MSNs were detected within the orthotopic pancreatic tumor. Conclusion: UPA targeted, pH sensitive MSNs were found to possess substantial tumor cell binding against multiple cell lines and demonstrate potential as a theranostic nanoparticle for pancreatic cancer. Citation Format: Dillon S. Pender, Anil Khanal, Michael E. Egger, Lacey R. McNally. Development of theranostic mesoporous silica nanoparticles for pancreatic cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1481. doi:10.1158/1538-7445.AM2015-1481

Mesoporous silica nanoparticles (MSNs) have been proposed as DNA and drug delivery carriers, as well as efficient tools for fluorescent cell tracking. The major limitation is that MSNs enter cells regardless of a target-specific functionalization. Here we show that non functionalized MSNs, synthesized using a PEG surfactant-based interfacial synthesis procedure, do not enter cells, while a highly specific, receptor mediated, cellular internalization of folic acid (FOL) grafted MSNs (MSN-FOL), occurs exclusively in folate receptor (FR) expressing cells. Neither the classical clathrin pathway nor macropinocytosis is involved in the MSN endocytic process, while fluorescent MSNs (MSN-FITC) enter cells through aspecific, caveolae-mediated, endocytosis. Moreover, internalized particles seem to be mostly exocytosed from cells within 96 h. Finally, cisplatin (Cp) loaded MSN-FOL were tested on cancerous FR-positive (HeLa) or normal FR-negative (HEK293) cells. A strong growth arrest was observed only in HeLa cells treated with MSN-FOL-Cp. The results presented here show that our mesoporous nanoparticles do not enter cells unless opportunely functionalized, suggesting that they could represent a promising vehicle for drug targeting applications.

Evaluating the inherent osteogenic and angiogenic potential of mesoporous silica nanoparticles to augment vascularized bone tissue formation

In this work, the synthesis of organic–inorganic hybrids based on pH-responsive, poly(acrylic acid) (PAA) and thermoresponsive, poly(N-isopropyl acrylamide) (PNIPAM), grafted from RAFT agent-primed mesoporous silica nanoparticles (MSNs), has been studied. The confirmation of polymer grafting was obtained through several techniques, for example, FTIR spectroscopy, NMR spectroscopy, etc. The presence of C–H stretching vibrations from FTIR confirmed the presence of organic network in the inorganic MSNs. Further support appeared as notable resonances in 13C solid-state NMR. The resonance at 175 ppm from C=O group for PAA-grafted MSNs, and at 170–172 ppm from C=O group for PNIPAM-grafted MSNs confirmed the grafting of polymer from the RAFT agent-primed MSNs. Morphological analysis for PAA- and PNIPAM-grafted MSNs was performed using FESEM and TEM. The images manifested spherical shape for isobutyric acid group, and short rod shape for phenyl ethyl group-containing RAFT agent-primed MSNs. Subsequently, for assessing their effectiveness as drug delivery vehicle, the anti-cancerous drug doxorubicin hydrochloride (Dox) was loaded into the MSNs. An effective loading in the range of 50–55% in case of PAA-grafted and 49–61% in case of PNIPAM-grafted MSNs (at pH 7.4, 25 °C) was observed. Subsequently release efficiencies for these Dox-encapsulated MSNs were studied at varying pH, temperature and time. The treatment of cultured MCF-7 cell lines by the control MSNs and polymer-grafted MSNs revealed that they are non-toxic. However, when the MSNs were Dox-loaded, the PAA-grafted ones demonstrated higher cytotoxicity than the PNIPAM-grafted MSNs at equivalent dose at pH 7.4 and 37°C. Together with other established features, we show that the polymer-grafted MSNs studied in this work can be utilized as an efficient drug delivery system for different therapeutic applications.

Stimuli-responsive controlled drug delivery systems have attracted the attention of researchers in recent decades due to their potential application in developing efficient drug carriers that are responsive to applied stimuli triggers. In this work, we present the synthesis of L-lysine (an amino acid that combines both amine and carboxylic acid groups in a single unit) modified mesoporous silica nanoparticles (MS@Lys NPs) for the delivery of the anticancer bioactive agent (curcumin, Cur) to cancer cells. To begin, mesoporous silica hybrid nanoparticles (MS@GPTS NPs) with 3-glycidoxypropyl trimethoxy silane (GPTS) were synthesized. The L-lysine groups were then functionalized onto the mesopore channel surfaces of the MS@GPTS NPs through a ring-opening reaction between the epoxy groups of the GPTS and the amine groups of the L-lysine units. Several instrumental techniques were used to examine the structural properties of the prepared L-lysine-modified mesoporous silica nanoparticles (MS@Lys NPs). The drug loading and pH-responsive drug delivery behavior of MS@Lys NPs were studied at different pH levels (pH 7.4, 6.5, and 4.0) using curcumin (Cur) as a model anticancer bioactive agent. The MS@Lys NPs' in vitro cytocompatibility and cell uptake behavior were also examined using MDA-MB-231 cells. The experimental results imply that MS@Lys NPs might be used in cancer therapy as pH-responsive drug delivery applications.

Mesoporous silica nanoparticles (MSNs) are promising drug carriers for use in cancer treatment owing to their excellent biocompatibility and drug-loading capacity. However, MSN's incomplete drug release and toxic bioaccumulation phenomena limit their clinical application. Recently, researchers have presented redox responsive mesoporous organosilica nanoparticles containing disulfide (S-S) bridges (ss-MONs). These nanoparticles retained their ability to undergo structural degradation and increased their local release activity when exposed to reducing agents. Disulfide-based mesoporous organosilica nanoparticles offer researchers a better option for loading chemotherapeutic drugs due to their effective biodegradability through the reduction of glutathione. Although the potential of ss-MONs in cancer theranostics has been studied, few researchers have systematically compared ss-MONs with MSNs with regard to endocytosis, drug release, cytotoxicity, and therapeutic effect. In this work, ss-MONs and MSNs with equal morphology and size were designed and used to payload doxorubicin hydrochloride (DOX) for liver cancer chemotherapy. The ss-MONs showed considerable degradability in the presence of glutathione and performed comparably to MSNs on biocompatibility measures, including cytotoxicity and endocytosis, as well as in drug-loading capacity. Notably, DOX-loaded ss-MONs exhibited higher intracellular drug release in cancer cells and better anticancer effects in comparison with DOX-loaded MSNs. Hence, the ss-MONs may be more desirable carriers for a highly efficient and safe treatment of cancer.

MCM-41, a type ofmesoporous silica nanoparticle, has garneredwidespread interests as a useful carrier for drug delivery whereinthe drug gets adsorbed into the pores of the carrier. To understandthe adsorption mechanism and release of the drug at the molecularlevel, in the current study, it was attempted to generate a computationalmodel for the loading of 5-fluorouracil (5-FU), a chemotherapeuticagent into surface-modified MCM-41. The molecular surface models ofthe mesoporous silica (MCM-41) nanoparticle with different surfacesubstitutions were created. In the first stage, molecular mechanics(MM) simulations were carried out to obtain the optimized surfacestructures. Subsequently, a 5-FU drug molecule in its different formswas docked on top of different MCM-41 surfaces to understand the adsorptionorientation and energetics. To further validate the results, moreaccurate quantum mechanical (QM) calculations were also carried out,and the energetics between the QM and MM calculations are found tobe similar. All the substitutions (−NH2, −CN,−COOH) except the methyl substitution exhibited favorable interactionscompared to the unsubstituted MCM-41 surface which was in accordancewith the experimental observations. The release rate of 5-FU fromMCM-41 and aminopropyl-substituted MCM-41 (MCM-NH2) wasstudied using molecular dynamics simulations which revealed that therelease rate of 5-FU from the MCM-NH2 surface was slowercompared to that of plain MCM-41. The detailed surface characteristicsand the adsorption energies from the molecular simulations correlatingthe loading capacity and release are reported in here.

A novel theranostic molecule, derived from curcumin (Cur) and naphthoquinone (NQ), allowing for cancer targeting, detection and treatment was previously described and termed CurNQ. To allow for enhanced theranostic capabilities, advanced drug delivery techniques are required. To this end, mesoporous silica nanoparticles (MSN) were synthesized and CurNQ was loaded into its pores to form the novel nanosystem MSN_CurNQ. The formation of the nanosystem aimed to augment the drug delivery of CurNQ through the EPR effect and sustained release. Moreover, the loading of CurNQ into its pores, formed a fluorescent nanoparticle that can be tracked, detected and visualized. Herein, the synthesis of a novel nanosystem is described and its theranostic potential are explored in vitro. MSN with an average size of 108 d.nm, a zeta potential of −42 mV and a PDI of 0.150 were synthesized and were impregnated with CurNQ to form the novel nanosystem MSN_CurNQ. MSN_CurNQ was demonstrated to have pH-responsivity whereby after 96 h, at pH 7.4, 31.5% of CurNQ was released from the MSN compared to 57% release at pH 6.8, corresponding to an increase of 25.5% in release with a 0.6 pH drop. The innate fluorescence was then characterized through confocal and fluorescence microscopy. Microscopy images illustrated the distinct, high intensity innate fluorescence with a high background to target ratio, thus confirming detection capabilities and potentially extending MSN_CurNQ’s application to molecular imaging purposes. Moreover, the chemotherapeutic potential of MSN_CurNQ was demonstrated as cell viability was reduced to below 50% in OVCAR-5, CACO-2, CHLA, and MCF-7 cell lines. Furthermore, MSN_CurNQ displayed tumor specific toxicity whereby the cell viability was reduced to a far greater extent in the cancer cell lines compared to a healthy fibroblast cell line (p = 0.000). Indeed, the novel MSN_CurNQ nanosystem has potential for applications in cancer targeting, detection and treatment.

Transparent inorganic-polymer nanocomposite films are of tremendous current interest inemerging solar coverings including photovoltaic encapsulants and commercial greenhouse plastics, but suffer from significant radiative heat loss. This work provides a new and simple approach for controlling this heat loss by using mesoporous silica/quantum dot nanoparticles in poly(ethylene-co-vinyl acetate) (EVA) films. Mesoporous silica shells were grown on CdS-ZnS quantum dot (QDs) cores using a reverse microemulsion technique, controlling the shell thickness. These mesoporous silica nanoparticles (MSNs) were then melt-mixed with EVA pellets using a mini twin-screw extruder and pressed into thin films of concentration variable controlled thickness. The results demonstrate that the experimental MSNs showed improved infrared and thermal wavebands retention in the EVA transparent films compared to commercial silica additives, even at lower concentrations. It was also found MSNs enhanced the quantum yield and photostability of the QDs, providing high visible light transmission and blocking of UV transmission of interest for next generation solar coatings. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 851–859