Delivery of ricin toxin a-chain by peptide-targeted mesoporous silica nanoparticle-supported lipid bilayers

Computational design of fusion proteins against ErbB2-amplified tumors inspired by ricin toxin

Although the anti-cancer activity of ricin is well-known, its non-specific targeting challenges the development of ricin-derived medicines. In the present study, novel potential ribosome-inactivating fusion proteins (RIPs) were computationally engineered by incorporation of an ErbB2-dependant penetrating peptide (KCCYSL, MARAKE, WYSWLL, MARSGL, MSRTMS, and WYAWML), a linker (either EAAAK or GGGGS) and chain A of ricin which is responsible for the ribosome inactivation. Molecular dynamics simulations assisted in making sure that the least change is made in conformation and dynamic behavior of ricin chain A in selected chimeric protein (CP). Moreover, the potential affinity of the selected CPs against the ligand-uptaking ErbB2 domain was explored by molecular docking. The results showed that two CPs (CP2 and 10) could bind the receptor with the greatest affinity.

Engineering mesoporous silica nanoparticles for drug delivery: where are we after two decades?

The present review details a chronological description of the events that took place during the development of mesoporous materials, their different synthetic routes and their use as drug delivery systems. The outstanding textural properties of these materials quickly inspired their translation to the nanoscale dimension leading to mesoporous silica nanoparticles (MSNs). The different aspects of introducing pharmaceutical agents into the pores of these nanocarriers, together with their possible biodistribution and clearance routes, would be described here. The development of smart nanocarriers that are able to release a high local concentration of the therapeutic cargo on-demand after the application of certain stimuli would be reviewed here, together with their ability to deliver the therapeutic cargo to precise locations in the body. The huge progress in the design and development of MSNs for biomedical applications, including the potential treatment of different diseases, during the last 20 years will be collated here, together with the required work that still needs to be done to achieve the clinical translation of these materials. This review was conceived to stand out from past reports since it aims to tell the story of the development of mesoporous materials and their use as drug delivery systems by some of the story makers, who could be considered to be among the pioneers in this area.

Characterizing Lipid‐Coated Mesoporous Silica Nanoparticles as CD169‐Binding Delivery System for Rilpivirine and Cabotegravir

Herein, lipid-coated mesoporous silica nanoparticles (LMSN) are investigated as biomimetic delivery vehicle for two antiretroviral compounds (ARVs), rilpivirine (RPV) and cabotegravir (CAB). Monosialodihexosylganglioside (GM3) is incorporated into the membrane to facilitate LMSN binding to CD169 (Siglec-1)-expressing myeloid cells, that are predominantly expressed in secondary lymphoid tissues in vivo. It is demonstrated that in addition to providing CD169-binding functionalities, the lipid membrane around the silica core provides stealth properties that dampen the inflammatory cytokine response to ARVs-loaded LMSN in human monocyte-derived macrophages. Quantification of RPV and CAB releases from nanoparticles, and assessment of antiviral potency to human immunodeficiency virus (HIV-1) infection in vitro reveals that RPV and CAB co-formulated into LMSN retain optimal antiviral potency for 90 days, even upon storage at room temperature, making LMSN an attractive nanoplatform, immune to cold chain requirements. These findings suggest that GM3-LMSN equip the mesoporous silica nanoparticle (MSN) core with lipid-derived properties for surface passivation and lipid-mediated binding that are of high interest for achieving an effective delivery of ARVs to tissue reservoirs of HIV-1 replication.

Targeted liposomal drug delivery: a nanoscience and biophysical perspective

Liposomes are a unique platform for drug delivery, and a number of liposomal formulations have already been commercialized. Doxil is a representative example, which uses PEGylated liposomes to load doxorubicin for cancer therapy. Its delivery relies on the enhanced permeability and retention (EPR) effect or passive targeting. Drug loading can be achieved using both standard liposomes and also those containing a solid core such as mesoporous silica and poly(lactide-co-glycolide) (PLGA). Developments have also been made on active targeted delivery using bioaffinity ligands such as small molecules, antibodies, peptides and aptamers. Compared to other types of nanoparticles, the surface of liposomes is fluid, allowing dynamic organization of targeting ligands to achieve optimal binding to cell surface receptors. This review article summarizes development of liposomal targeted drug delivery systems, with an emphasis on the biophysical properties of lipids. In both passive and active targeting, the effects of liposome size, charge, fluidity, rigidity, head-group chemistry and PEGylation are discussed along with recent examples. Most of the examples are focused on targeting tumors or cancer cells. Finally, a few examples of commercialized formulations are described, and some future research opportunities are discussed.

SP94 peptide mediating highly specific and efficacious delivery of polymersomal doxorubicin hydrochloride to hepatocellular carcinoma in vivo

The effective treatment of hepatocellular carcinoma (HCC) requires development of novel drug formulations that selectively kill HCC cells while sparing healthy liver cells. Here, we designed and investigated HCC-specific peptide, SP94 (SFSIIHTPILPLGGC), decorated smart polymersomal doxorubicin hydrochloride (SP94-PS-DOX) for potent treatment of orthotopic human SMMC-7721 HCC xenografts. SP94-PS-DOX was fabricated by post ligand-modification, affording robust nano-formulations with a diameter of ∼ 76 nm and DOX content of 9.9 wt.%. The internalization of SP94-PS-DOX by SMMC-7721 cells showed a clear dependence on SP94 surface densities, in which 30 % SP94 resulted in ca. 3-fold better cellular uptake over non-targeted control (PS-DOX). In accordance, SP94-PS-DOX exhibited superior inhibition of SMMC-7721 cells to PS-DOX and clinical liposome injections (Lipo-DOX). Notably, a remarkable tumor deposition of 14.9 %ID/g and tumor-to-normal liver ratio of ca. 6.9 was observed for SP94-PS-DOX in subcutaneous SMMC-7721 HCC xenografts. More interestingly, SP94-PS-DOX under 10 mg DOX/kg induced far better therapeutic efficacy toward orthotopic SMMC-7721 HCC models than PS-DOX and Lipo-DOX controls giving substantial survival benefits and little adverse effects. The remarkable specificity and therapeutic outcomes lend SP94-PS-DOX promising for targeted HCC therapy.

Biodegradable nanofibrous temperature-responsive gelling microspheres for heart regeneration

Myocardial infarction (heart attack) is the number one killer of heart patients. Existing treatments for heart attack do not address the underlying problem of cardiomyocyte (CM) loss and cannot regenerate the myocardium. Introducing exogenous cardiac cells is required for heart regeneration due to the lack of resident progenitor cells and very limited proliferative potential of adult CMs. Poor retention of transplanted cells is the critical bottleneck of heart regeneration. Here, we report the invention of a poly(l-lactic acid)-b-poly(ethylene glycol)-b-poly(N-Isopropylacrylamide) copolymer and its self-assembly into nanofibrous gelling microspheres (NF-GMS). The NF-GMS undergo thermally responsive transition to form not only a 3D hydrogel after injection in vivo, but also exhibit architectural and structural characteristics mimicking the native extracellular matrix (ECM) of nanofibrous proteins and gelling proteoglycans or polysaccharides. By integrating the ECM-mimicking features, injectable form, and the capability of maintaining 3D geometry after injection, the transplantation of hESC-derived CMs carried by NF-GMS led to a striking 10-fold graft size increase over direct CM injection in an infarcted rat model, which is the highest reported engraftment to date. Furthermore, NF-GMS carried CM transplantation dramatically reduced infarct size, enhanced integration of transplanted CMs, stimulated vascularization in the infarct zone, and led to a substantial recovery of cardiac function. The NF-GMS may also serve as advanced injectable and integrative biomaterials for cell/biomolecule delivery in a variety of biomedical applications.

Emerging and Innovative Theranostic Approaches for Mesoporous Silica Nanoparticles in Hepatocellular Carcinoma: Current Status and Advances

Hepatocellular carcinoma (HCC) is one of the most prevalent and lethal solid cancers globally. To improve diagnosis sensitivities and treatment efficacies, the development of new theranostic nanoplatforms for efficient HCC management is urgently needed. In the past decade, mesoporous silica nanoparticles (MSNs) with tailored structure, large surface area, high agents loading volume, abundant chemistry functionality, acceptable biocompatibility have received more and more attention in HCC theranostic. This review outlines the recent advances in MSNs-based systems for HCC therapy and diagnosis. The multifunctional hybrid nanostructures that have both of therapy and diagnosis abilities are highlighted. And the precision delivery strategies of MSNs in HCC are also discussed. Final, we conclude with our personal perspectives on the future development and challenges of MSNs.

Ricin and Ricinus communis in pharmacology and toxicology-from ancient use and "Papyrus Ebers" to modern perspectives and "poisonous plant of the year 2018"

While probably originating from Africa, the plant Ricinus communis is found nowadays around the world, grown for industrial use as a source of castor oil production, wildly sprouting in many regions, or used as ornamental plant. As regards its pharmacological utility, a variety of medical purposes of selected parts of the plant, e.g., as a laxative, an anti-infective, or an anti-inflammatory drug, have been described already in the sixteenth century BC in the famous Papyrus Ebers (treasured in the Library of the University of Leipzig). Quite in contrast, on the toxicological side, the native plant has become the "poisonous plant 2018" in Germany. As of today, a number of isolated components of the plant/seeds have been characterized, including, e.g., castor oil, ricin, Ricinus communis agglutinin, ricinin, nudiflorin, and several allergenic compounds. This review mainly focuses on the most toxic protein, ricin D, classified as a type 2 ribosome-inactivating protein (RIP2). Ricin is one of the most potent and lethal substances known. It has been considered as an important bioweapon (categorized as a Category B agent (second-highest priority)) and an attractive agent for bioterroristic activities. On the other hand, ricin presents great potential, e.g., as an anti-cancer agent or in cell-based research, and is even explored in the context of nanoparticle formulations in tumor therapy. This review provides a comprehensive overview of the pharmacology and toxicology-related body of knowledge on ricin. Toxicokinetic/toxicodynamic aspects of ricin poisoning and possibilities for analytical detection and therapeutic use are summarized as well.

Anticancer Activities of Ricin-Liposome Complexes on SKMEL-28 Cells

Background: Ricin has been reported as a potential chemical for cancer treatment. However, so far, the application of ricin in cancer treatment is very limited because of its non-specificity. Methods: In this study, ricin were conjugated/ encapsulated with DOTAP/DOPE liposome to form ricin-liposome complexes (ricin-lipososme1, ricin-liposome2, ricin-liposome3 and ricin-liposome4). Characteristics of ricin-liposome complexes were analyzed and their effects on survival, apoptosis, migration, invasion and tumor formation of SKMEL-28 melanoma cells were examined by carrying out the MTT assay, apoptosis assay, scratch wound healing assay, invasion assay and soft-agar colony formation assay, respectively. Results: Ricin-liposome complexes had even size-distribution with average size of around 340 nm. These ricin-liposome complexes were able to penetrate into the cells via endocytosis with the highest ability of the ricinliposome3. It also showed that ricin-liposome3 expressed very high toxicity with the IC50 of 62.4 ng/mL and followed by ricin-liposome4 (286.4 mg/mL), ricin-liposome2 (417.5 ng/mL), and ricin-liposome1 (604.3 ng/mL) to SKMEL-28 cells at 36 hours post treatment. At the concentrations of IC10 (10.1 ng/mL), ricin-liposome3 strongly induced necrosis and apoptosis of SKMEL-28 cells up to 25.6% and 11.4%, respectively. Moreover, ricin-liposome3 expressed great anticancer properties by decreasing the migration, invasion and tumor formation abilities of SKMEL-28 cells of 7.5 folds, 4.3 folds and 5.9 folds, respectively, compared with those of control SKMEL-28 cells. Conclusion: The obtained results from our study suggest that although ricin is listed as one of the most poisonous substances in nature, it can be used in the complex forms with liposome to increase its specificity to apply in treatment of melanoma and other cancers.

Charge-Selective Delivery of Proteins Using Mesoporous Silica Nanoparticles Fused with Lipid Bilayers

Efficient and safe intracellular delivery of proteins is highly desired in the development of protein therapeutics. Current methods of protein delivery commonly suffer from low loading efficiency, low stability in serum, and lack of versatility for different proteins. Here, we developed a platform for efficient protein delivery using mesoporous silica nanoparticles (MSN) with lipid fusion. By different surface modifications on MSN, the positively charged MSN (MSN⁺) and the negatively charged MSN (MSN^-), were generated for loading different proteins. The cargo proteins, based on the surface charges, can be selectively loaded in very high efficiency. The protein-loaded MSNs were fused with liposomes to form a protocell-like delivery system (MSN-LP) in order to prevent burst release of proteins. The lipid fusion significantly increases the stability of the nanosystem in physiological conditions, and the MSN-LP protocell can efficiently deliver proteins into cells. The cargo proteins can be released in cells in a sustained manner. Fifteen different proteins, including two protein complexes, were tested using this delivery system. Further analyses indicate that the proteins can maintain their functions after delivery into cells. Fluorescent proteins, GFP, and KillerRed show fluorescence in cells, indicating the correct folding of proteins during encapsulation and delivery. Protein activity analysis shows that KillerRed protein can generate ROS in cells, while SOD can eliminate ROS in cells. Hence, the proteins delivered by this system remain their structure and function in cells. This work provides a versatile strategy for charge-selective delivery of proteins with high loading efficiency and high stability.

Lipid surface modifications increase mesoporous silica nanoparticle labeling properties in mesenchymal stem cells

BACKGROUND

Nanoparticles have emerged as promising cell-labeling tools, as they can be precisely tailored in terms of chemical and physical properties. Mesoporous silica nanoparticles (MSNs), in particular, are easily tunable with regard to surface and core chemistry, and are able to confine dyes and drug molecules efficiently.

PURPOSE

The aim of this study was to investigate the effect of lipid and polyethylene glycol (PEG) surface modifications on MSN stem-cell-tracking abilities.

METHODS

Lipid and PEG surface functionalized MSNs were synthesized and the effect of surface functionalization on cell internalization, proliferation, differentiation and cell proteomics was investigated in patient derived mesenchymal stem cells (MSCs).

RESULTS

MSNs and lipid surface-modified MSNs were internalized by >80% of the MSC population, with the exception of nanoparticles modified with short PEG chains (molecular weight 750 [MSN-PEG750]). Lipid-modified MSNs had higher labeling efficiency with maximum uptake after 2 hours of exposure and were in addition internalized 17 times higher compared to unmodified MSNs, without negatively affecting differentiation capacity. Using a mass-spectrometry-based label-free quantitative proteomics approach, we show that MSN labeling leads to the up- and downregulation of proteins that were unique for the different surface-modified MSNs. In addition, functional enrichments were found in human MSCs labeled with MSNs, MSN-PEG750, and lipid-modified MSNs.

SUMMARY

Here we show that organic modifications with lipids and PEGylation can be used as a promising strategy to improve MSN labeling capabilities. In particular, we show that lipid modifications can optimize such probes in three distinct ways: significantly improved signal strength, a barrier for sustained release of additional probes, and improved stem-cell-labeling efficiency.

Protein Nanotherapeutics as an Emerging Modality for Cancer Therapy

Protein drugs are a unique and versatile class of biotherapeutics that have not only high biological activity but also superb specificity. This rapidly evolving biotechnology has rendered it possible to produce various proteins in a large scale and reproducible way. Many proteins have demonstrated striking anticancer activities and have emerged as advanced alternatives to cytotoxic chemotherapeutic agents for cancer therapy. The clinical translation of anticancer proteins with intracellular targets is, nevertheless, severely hindered by their fast degradation in vivo, poor cell penetration, and inefficient intracellular transportation. The past few years have witnessed tremendous effort and progress in developing polymeric protein delivery nanosystems, ranging from nanoparticles, nanocapsules, nanogels, micelles, to polymersomes, for the treatment of different tumors such as lung tumors, breast tumors, ovarian cancers, and glioblastoma. These proof-of-concept studies point out that protein nanotherapeutics, with rationally designed nanovehicles, are able to overcome the extracellular barriers, cell membrane barriers, and intracellular barriers, and systemically deliver proteins into targeted cancer cells, resulting in effective cancer protein therapy. Protein nanotherapeutics appear to be a novel modality for safe and efficient cancer treatment.

Electric double layer electrostatics of lipid-bilayer-encapsulated nanoparticles: Toward a better understanding of protocell electrostatics

Lipid-bilayer-encapsulated nanoparticles (LBLENPs) or NP-supported LBL systems, such as protocells (which are lipid bilayer encapsulated mesoporous silica nanoparticles or MSNPs) have received extensive attention for applications like targeted drug and gene deliveries, multimodal diagnostics, characterization of membrane-geometry sensitive molecules, etc. Very often electrostatic-mediated interactions have been hypothesized to play key roles in the functioning of these LBLENPs. Despite that, very little has been done to theoretically quantify the fundamental electric double layer (EDL) electrostatics of such LBLENPs. In this study, we develop an EDL theory to describe the electrostatics of such LBLENPs. We show that the electrostatics is a manifestation of the charged/dielectric nature of the NP, LBL structure and charging, and the ionic environment in which the LBLENPs are present. We also establish that for certain conditions of charging of the NP one witnesses a most remarkable charge inversion like electrostatics within the LBL membrane or the NP itself. We anticipate that our findings will provide an extremely useful platform for better understanding the fabrication and functioning of such LBLENPs and discuss examples where our theory can be useful.

Membrane Fusion Mediated Intracellular Delivery of Lipid Bilayer Coated Mesoporous Silica Nanoparticles

Protein delivery into the cytosol of cells is a challenging topic in the field of nanomedicine, because cellular uptake and endosomal escape are typically inefficient, hampering clinical applications. In this contribution cuboidal mesoporous silica nanoparticles (MSNs) containing disk-shaped cavities with a large pore diameter (10 nm) are studied as a protein delivery vehicle using cytochrome-c (cytC) as a model membrane-impermeable protein. To ensure colloidal stability, the MSNs are coated with a fusogenic lipid bilayer (LB) and cellular uptake is induced by a complementary pair of coiled-coil (CC) lipopeptides. Coiled-coil induced membrane fusion leads to the efficient cytosolic delivery of cytC and triggers apoptosis of cells. Delivery of these LB coated MSNs in the presence of various endocytosis inhibitors strongly suggests that membrane fusion is the dominant mechanism of cellular uptake. This method is potentially a universal way for the efficient delivery of any type of inorganic nanoparticle or protein into cells mediated by CC induced membrane fusion.

Mesoporous Silica Nanoparticle-Coated Microneedle Arrays for Intradermal Antigen Delivery

PURPOSE

To develop a new intradermal antigen delivery system by coating microneedle arrays with lipid bilayer-coated, antigen-loaded mesoporous silica nanoparticles (LB-MSN-OVA).

METHODS

Synthesis of MSNs with 10-nm pores was performed and the nanoparticles were loaded with the model antigen ovalbumin (OVA), and coated with a lipid bilayer (LB-MSN-OVA). The uptake of LB-MSN-OVA by bone marrow-derived dendritic cells (BDMCs) was studied by flow cytometry. The designed LB-MSN-OVA were coated onto pH-sensitive pyridine-modified microneedle arrays and the delivery of LB-MSN-OVA into ex vivo human skin was studied.

RESULTS

The synthesized MSNs demonstrated efficient loading of OVA with a maximum loading capacity of about 34% and the lipid bilayer enhanced the colloidal stability of the MSNs. Uptake of OVA loaded in LB-MSN-OVA by BMDCs was higher than that of free OVA, suggesting effective targeting of LB-MSN-OVA to antigen-presenting cells. Microneedles were readily coated with LB-MSN-OVA at pH 5.8, yielding 1.5 μg of encapsulated OVA per microneedle array. Finally, as a result of the pyridine modification, LB-MSN-OVA were effectively released from the microneedles upon piercing the skin.

CONCLUSION

Microneedle arrays coated with LB-MSN-OVA were successfully developed and shown to be suitable for intradermal delivery of the encapsulated protein antigen.

Recent Advances in Stimuli-Responsive Release Function Drug Delivery Systems for Tumor Treatment

Benefiting from the development of nanotechnology, drug delivery systems (DDSs) with stimuli-responsive controlled release function show great potential in clinical anti-tumor applications. By using a DDS, the harsh side effects of traditional anti-cancer drug treatments and damage to normal tissues and organs can be avoided to the greatest extent. An ideal DDS must firstly meet bio-safety standards and secondarily the efficiency-related demands of a large drug payload and controlled release function. This review highlights recent research progress on DDSs with stimuli-responsive characteristics. The first section briefly reviews the nanoscale scaffolds of DDSs, including mesoporous nanoparticles, polymers, metal-organic frameworks (MOFs), quantum dots (QDs) and carbon nanotubes (CNTs). The second section presents the main types of stimuli-responsive mechanisms and classifies these into two categories: intrinsic (pH, redox state, biomolecules) and extrinsic (temperature, light irradiation, magnetic field and ultrasound) ones. Clinical applications of DDS, future challenges and perspectives are also mentioned.

Mesoporous Silica Nanoparticles with Large Pores for the Encapsulation and Release of Proteins

Mesoporous silica nanoparticles (MSNs) have been explored extensively as solid supports for proteins in biological and medical applications. Small (<200 nm) MSNs with ordered large pores (>5 nm), capable of encapsulating therapeutic small molecules suitable for delivery applications in vivo, are rare however. Here we present small, elongated, cuboidal, MSNs with average dimensions of 90 × 43 nm that possess disk-shaped cavities, stacked on top of each other, which run parallel to the short axis of the particle. Amine functionalization was achieved by modifying the MSN surface with 3-aminopropyltriethoxysilane or 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane (AP-MSNs and AEP-MSNs) and were shown to have similar dimensions to the nonfunctionalized MSNs. The dimensions of these particles, and their large surface areas as measured by nitrogen adsorption-desorption isotherms, make them ideal scaffolds for protein encapsulation and delivery. We therefore investigated the encapsulation and release behavior for seven model proteins (α-lactalbumin, ovalbumin, bovine serum albumin, catalase, hemoglobin, lysozyme, and cytochrome c). It was discovered that all types of MSNs used in this study allow rapid encapsulation, with a high loading capacity, for all proteins studied. Furthermore, the release profiles of the proteins were tunable. The variation in both rate and amount of protein uptake and release was found to be determined by the surface chemistry of the MSNs, together with the isoelectric point (pI), and molecular weight of the proteins, as well as by the ionic strength of the buffer. These MSNs with their large surface area and optimal dimensions provide a scaffold with a high encapsulation efficiency and controllable release profiles for a variety of proteins, enabling potential applications in fields such as drug delivery and protein therapy.

Ligand-targeted theranostic nanomedicines against cancer

Nanomedicines have significant potential for cancer treatment. Although the majority of nanomedicines currently tested in clinical trials utilize simple, biocompatible liposome-based nanocarriers, their widespread use is limited by non-specificity and low target site concentration and thus, do not provide a substantial clinical advantage over conventional, systemic chemotherapy. In the past 20years, we have identified specific receptors expressed on the surfaces of tumor endothelial and perivascular cells, tumor cells, the extracellular matrix and stromal cells using combinatorial peptide libraries displayed on bacteriophage. These studies corroborate the notion that unique receptor proteins such as IL-11Rα, GRP78, EphA5, among others, are differentially overexpressed in tumors and present opportunities to deliver tumor-specific therapeutic drugs. By using peptides that bind to tumor-specific cell-surface receptors, therapeutic agents such as apoptotic peptides, suicide genes, imaging dyes or chemotherapeutics can be precisely and systemically delivered to reduce tumor growth in vivo, without harming healthy cells. Given the clinical applicability of peptide-based therapeutics, targeted delivery of nanocarriers loaded with therapeutic cargos seems plausible. We propose a modular design of a functionalized protocell in which a tumor-targeting moiety, such as a peptide or recombinant human antibody single chain variable fragment (scFv), is conjugated to a lipid bilayer surrounding a silica-based nanocarrier core containing a protected therapeutic cargo. The functionalized protocell can be tailored to a specific cancer subtype and treatment regimen by exchanging the tumor-targeting moiety and/or therapeutic cargo or used in combination to create unique, theranostic agents. In this review, we summarize the identification of tumor-specific receptors through combinatorial phage display technology and the use of antibody display selection to identify recombinant human scFvs against these tumor-specific receptors. We compare the characteristics of different types of simple and complex nanocarriers, and discuss potential types of therapeutic cargos and conjugation strategies. The modular design of functionalized protocells may improve the efficacy and safety of nanomedicines for future cancer therapy.

Mesoporous Silica Nanoparticle-Supported Lipid Bilayers (Protocells) for Active Targeting and Delivery to Individual Leukemia Cells

Many nanocarrier cancer therapeutics currently under development, as well as those used in the clinical setting, rely upon the enhanced permeability and retention (EPR) effect to passively accumulate in the tumor microenvironment and kill cancer cells. In leukemia, where leukemogenic stem cells and their progeny circulate within the peripheral blood or bone marrow, the EPR effect may not be operative. Thus, for leukemia therapeutics, it is essential to target and bind individual circulating cells. Here, we investigate mesoporous silica nanoparticle (MSN)-supported lipid bilayers (protocells), an emerging class of nanocarriers, and establish the synthesis conditions and lipid bilayer composition needed to achieve highly monodisperse protocells that remain stable in complex media as assessed in vitro by dynamic light scattering and cryo-electron microscopy and ex ovo by direct imaging within a chick chorioallantoic membrane (CAM) model. We show that for vesicle fusion conditions where the lipid surface area exceeds the external surface area of the MSN and the ionic strength exceeds 20 mM, we form monosized protocells (polydispersity index <0.1) on MSN cores with varying size, shape, and pore size, whose conformal zwitterionic supported lipid bilayer confers excellent stability as judged by circulation in the CAM and minimal opsonization in vivo in a mouse model. Having established protocell formulations that are stable colloids, we further modified them with anti-EGFR antibodies as targeting agents and reverified their monodispersity and stability. Then, using intravital imaging in the CAM, we directly observed in real time the progression of selective targeting of individual leukemia cells (using the established REH leukemia cell line transduced with EGFR) and delivery of a model cargo. Overall, we have established the effectiveness of the protocell platform for individual cell targeting and delivery needed for leukemia and other disseminated disease.

Protocells: Modular Mesoporous Silica Nanoparticle-Supported Lipid Bilayers for Drug Delivery

Mesoporous silica nanoparticle-supported lipid bilayers, termed 'protocells,' represent a potentially transformative class of therapeutic and theranostic delivery vehicle. The field of targeted drug delivery poses considerable challenges that cannot be addressed with a single 'magic bullet'. Consequently, the protocell has been designed as a modular platform composed of interchangeable biocompatible components. The mesoporous silica core has variable size and shape to direct biodistribution and a controlled pore size and surface chemistry to accommodate diverse cargo. The encapsulating supported lipid bilayer can be modified with targeting and trafficking ligands as well as polyethylene glycol (PEG) to effect selective binding, endosomal escape of cargo, drug efflux prevention, and potent therapeutic delivery, while maintaining in vivo colloidal stability. This review describes the individual components of the platform, including the mesoporous silica nanoparticle core and supported lipid bilayer, their assembly (by multiple techniques) into a protocell, and the combined, often synergistic, performance of the protocell based on in vitro and in vivo studies, including the assessment of biocompatibility and toxicity. In closing, the many emerging variations of the protocell theme and the future directions for protocell research are commented on.

Integrated nanotechnology platform for tumor-targeted multimodal imaging and therapeutic cargo release

A major challenge of targeted molecular imaging and drug delivery in cancer is establishing a functional combination of ligand-directed cargo with a triggered release system. Here we develop a hydrogel-based nanotechnology platform that integrates tumor targeting, photon-to-heat conversion, and triggered drug delivery within a single nanostructure to enable multimodal imaging and controlled release of therapeutic cargo. In proof-of-concept experiments, we show a broad range of ligand peptide-based applications with phage particles, heat-sensitive liposomes, or mesoporous silica nanoparticles that self-assemble into a hydrogel for tumor-targeted drug delivery. Because nanoparticles pack densely within the nanocarrier, their surface plasmon resonance shifts to near-infrared, thereby enabling a laser-mediated photothermal mechanism of cargo release. We demonstrate both noninvasive imaging and targeted drug delivery in preclinical mouse models of breast and prostate cancer. Finally, we applied mathematical modeling to predict and confirm tumor targeting and drug delivery. These results are meaningful steps toward the design and initial translation of an enabling nanotechnology platform with potential for broad clinical applications.

Efficacious delivery of protein drugs to prostate cancer cells by PSMA-targeted pH-responsive chimaeric polymersomes

Protein drugs as one of the most potent biotherapeutics have a tremendous potential in cancer therapy. Their application is, nevertheless, restricted by absence of efficacious, biocompatible, and cancer-targeting nanosystems. In this paper, we report that 2-[3-[5-amino-1-carboxypentyl]-ureido]-pentanedioic acid (Acupa)-decorated pH-responsive chimaeric polymersomes (Acupa-CPs) efficiently deliver therapeutic proteins into prostate cancer cells. Acupa-CPs had a unimodal distribution with average sizes ranging from 157-175 nm depending on amounts of Acupa. They displayed highly efficient loading of both model proteins, bovine serum albumin (BSA) and cytochrome C (CC), affording high protein loading contents of 9.1-24.5 wt.%. The in vitro release results showed that protein release was markedly accelerated at mildly acidic pH due to the hydrolysis of acetal bonds in the vesicular membrane. CLSM and MTT studies demonstrated that CC-loaded Acupa10-CPs mediated efficient delivery of protein drugs into PSMA positive LNCaP cells leading to pronounced antitumor effect, in contrast to their non-targeting counterparts and free CC. Remarkably, granzyme B (GrB)-loaded Acupa10-CPs caused effective apoptosis of LNCaP cells with a low half-maximal inhibitory concentration (IC50) of 1.6 nM. Flow cytometry and CLSM studies using MitoCapture™ revealed obvious depletion of mitochondria membrane potential in LNCaP cells treated with GrB-loaded Acupa10-CPs. The preliminary in vivo experiments showed that Acupa-CPs had a long circulation time with an elimination phase half-life of 3.3h in nude mice. PSMA-targeted, pH-responsive, and chimaeric polymersomes have appeared as efficient protein nanocarriers for targeted prostate cancer therapy.

Mesoporous-Silica-Functionalized Nanoparticles for Drug Delivery

The ever-growing interest for finding efficient and reliable methods for treatment of diseases has set a precedent for the design and synthesis of new functional hybrid materials, namely porous nanoparticles, for controlled drug delivery. Mesoporous silica nanoparticles (MSNPs) represent one of the most promising nanocarriers for drug delivery as they possess interesting chemical and physical properties, thermal and mechanical stabilities, and are biocompatibile. In particular, their easily functionalizable surface allows a large number of property modifications further improving their efficiency in this field. This Concept article deals with the advances on the novel methods of functionalizing MSNPs, inside or outside the pores, as well as within the walls, to produce efficient and smart drug carriers for therapy.

Ligand-directed profiling of organelles with internalizing phage libraries

Phage display is a resourceful tool to, in an unbiased manner, discover and characterize functional protein-protein interactions, create vaccines, and engineer peptides, antibodies, and other proteins as targeted diagnostic and/or therapeutic agents. Recently, our group has developed a new class of internalizing phage (iPhage) for ligand-directed targeting of organelles and to identify molecular pathways within live cells. This unique technology is suitable for applications ranging from fundamental cell biology to drug development. This unit describes the methods for generating and screening the iPhage display system, and explains how to select and validate candidate internalizing homing peptide.

Advances in mesoporous silica nanoparticles for targeted stimuli-responsive drug delivery

INTRODUCTION

Mesoporous silica nanoparticles (MSNPs) are one of the most promising inorganic drug delivery systems (DDSs). The design and development of tumour-targeted MSNPs with stimuli-responsive drug release capability aim at enhancing the efficiency and minimising the side effects of anti-tumour drugs for cancer therapy.

AREAS COVERED

This review provides an overview of the scientific advances in MSNPs for tumour-targeted stimuli-responsive drug delivery. The key factors that govern the passive accumulation of MSNPs within solid tumours such as size, shape and surface functionalisation are roughly described. The different active targeting strategies for the specific retention and uptake of MSNPs by tumour cells are also outlined. The approaches developed so far for the synthesis of smart MSNPs capable of releasing the trapped drugs in response to internal or external stimuli and their applications are reviewed. Critical considerations in the use of MSNPs for the treatment of cancer treatment are discussed. The future prospects and key factors concerning the clinical application of MSNPs are considered throughout the manuscript.

EXPERT OPINION

MSNPs are promising nanocarriers to efficiently transport and site-specifically deliver highly toxic drugs, such as chemotherapeutic agents for cancer treatment. However, there are certain issues that should be overcome to improve the suitability of MSNPs for clinical applications. Increasing the penetration capability of MSNPs within tumour tissues, providing them of appropriate colloidal stability in physiological fluids and ensuring that their active targeting capability and stimuli-responsive performance are preserved in complex biological media are of foremost significance. Few in vivo evaluation tests of MSNPs have been reported and much research effort into this field is mandatory to be able to move from bench to bedside.

Noncovalent functionalization of mesoporous silica nanoparticles with amphiphilic peptides

The surface of mesoporous silica nanoparticles (MSNs) has been modified for enhancing their cellular uptake, cell targeting, bioimaging, and controlled drug release. For this purpose, covalent anchorage on the silica surface was predominantly exploited with a wide range of bioactive molecules. Here, we describe a facile self-assembly method to prepare a hybrid peptide silica system composed of octyl-modified mesoporous silica nanoparticles (MSNs) and peptide amphiphiles (PAs). The hydrophobic organosilane surface of mesoporous silica was coated with amphiphilic peptide molecules. The peptide functionalized particles exhibited good cyto-compatibility with vascular smooth muscle and vascular endothelial cells. The peptide coating also improved the cellular uptake of particles up to 6.3 fold, which is promising for the development of highly efficient MSN based theranostic agents.

Merging the best of both worlds: hybrid lipid-enveloped matrix nanocomposites in drug delivery

The advent of nanotechnology has revolutionized drug delivery in terms of improving drug efficacy and safety. Both polymer-based and lipid-based drug-loaded nanocarriers have demonstrated clinical benefit to date. However, to address the multifaceted drug delivery challenges ahead and further expand the spectrum of therapeutic applications, hybrid lipid-polymer nanocomposites have been designed to merge the beneficial features of both polymeric drug delivery systems and liposomes in a single nanocarrier. This review focuses on different classes of nanohybrids characterized by a drug-loaded polymeric matrix core enclosed in a lipid shell. Various nanoengineering approaches to obtain lipid-polymer nanocomposites with a core-shell nanoarchitecture will be discussed as well as their predominant applications in drug delivery.

Membrane mimetic surface functionalization of nanoparticles: methods and applications

Nanoparticles (NPs), due to their size-dependent physical and chemical properties, have shown remarkable potential for a wide range of applications over the past decades. Particularly, the biological compatibilities and functions of NPs have been extensively studied for expanding their potential in areas of biomedical application such as bioimaging, biosensing, and drug delivery. In doing so, surface functionalization of NPs by introducing synthetic ligands and/or natural biomolecules has become a critical component in regard to the overall performance of the NP system for its intended use. Among known examples of surface functionalization, the construction of an artificial cell membrane structure, based on phospholipids, has proven effective in enhancing biocompatibility and has become a viable alternative to more traditional modifications, such as direct polymer conjugation. Furthermore, certain bioactive molecules can be immobilized onto the surface of phospholipid platforms to generate displays more reminiscent of cellular surface components. Thus, NPs with membrane-mimetic displays have found use in a range of bioimaging, biosensing, and drug delivery applications. This review herein describes recent advances in the preparations and characterization of integrated functional NPs covered by artificial cell membrane structures and their use in various biomedical applications.