Design and Characterization of Novel Peptide-Coated Lipid Nanoparticles for Targeting Anti-HIV Drug to CD4 Expressing Cells

Human immunodeficiency virus (HIV) persists in lymph nodes and lymphoid tissues even during aggressive drug treatment, likely due to insufficient drug concentrations at this site. Therefore, to eliminate this residual virus, methods that enhance lymph node drug concentrations are currently being evaluated. Although enhanced drug concentrations in tissue have been achieved with drug-associated lipid nanoparticles, targeting these particles to CD4(+) cells may provide specific delivery of drug to HIV target cells and further enhance drug efficacy. We have evaluated four candidate peptides with reported binding specificity to CD4 for anchoring on lipid nanoparticle preparations previously shown to localize in lymph nodes. Terminal cysteine containing candidate peptides were conjugated to lipid nanoparticles through maleimide-linked phopholipids for targeting to CD4 cells. Using fluorescently labeled lipid nanoparticle binding to cells with varying degree of CD4 expression (CEMx174, Molt-4, Jurkat, and Ramos), we indentified two peptide sequences that provided CD4 selectivity to nanoparticles. These two peptide candidates on lipid nanoparticles bound to cells corresponding to the degree of CD4 expression and in a peptide dose dependent manner. Further, binding of these targeted lipid nanoparticles was CD4 specific, as pre-exposure of CD4(+) cells to anti-CD4 antibodies or free peptides inhibited the binding interactions. These results indicate targeting of lipid nanoparticles for specific binding to CD4 can be accomplished by tagging CD4 binding peptides with peptides, and these results provide a basis for further evaluation of this targeted delivery system to enhance antiviral drug delivery to CD4(+) HIV host cells, particularly those in lymph nodes and lymphoid tissues.     

Degradable and biocompatible nanoparticles decorated with cyclic RGD peptide for efficient drug delivery to hepatoma cells in vitro

Amphiphilic derivatives of poly(benzyl malate) were synthesized and characterized with the aim of being used as degradable and biocompatible building blocks for the design of functional nanoparticles (NPs). An anti-cancer model drug, doxorubicin, has been successfully encapsulated into the prepared NPs and its release profile has been evaluated in water and in culture medium. NPs bearing biotin molecules were prepared either for site-specific drug delivery via the targeting of biotin receptors overexpressed on the surface of several cancer cells, or for grafting biotinylated cyclic RGD peptide onto their surface using the strong and highly specific interactions between biotin and the streptavidin protein. We have shown that this binding did not affect dramatically the physico-chemical properties of the corresponding NPs. Cyclic RGD grafted fluorescent NPs were more efficiently uptaken by the HepaRG hepatoma cells than biotinylated fluorescent NPs. Furthermore, the targeting of HepaRG hepatoma cells with NPs bearing cyclic RGD was very efficient and much weaker for HeLa and HT29 cell lines confirming that cyclic RGD is a suitable targeting agent for liver cells. Our results also provide a new mean for rapid screening of short hepatotropic peptides in order to design NPs showing specific liver targeting properties.     

Somatostatin receptors as a new active targeting sites for nanoparticles

The delivery of nanoparticles through receptor-mediated cell interactions has nowadays a major attention in the area of drug targeting applications. This specific kind of targeting is mediated by localized receptors impeded into the target site with subsequent drugs internalization. Hence, this type of interaction would diminish side effects and enhance drug delivery efficacy to the target site. Somatostatin receptors (SSTRs) are one type of G protein-coupled receptors, which could be active targeted for various purposes. There are five SSTRs types (SSTR1-5) which are localized at various organs in the body and spread into different tissues. SSTRs could be considered as a promising target to various nanoparticles which is facilitated when nanoparticles are modified through specific ligand or coating to allow better binding. This review discusses the exploration of SSTRs for active targeting of nanoparticles with certain emphasize on their interaction at the cellular level.     

Prestin binding peptides as ligands for targeted polymersome mediated drug delivery to outer hair cells in the inner ear

Targeted delivery of treatment agents to the inner ear using nanoparticles is an advanced therapeutic approach to cure or alleviate hearing loss. Designed to target the outer hair cells of the cochlea, two 12-mer peptides (A(665) and A(666)) with affinity to prestin were identified following 3 rounds of sequential phage display. Two-round display with immobilized prestin protein was used to enrich the library for full-length prestin. The last round was performed using Cos-7 cells transiently transfected with a cCFP-prestin plasmid to display phages expressing peptides restrictive to the extracellular loops of prestin. The binding properties of A(665) and A(666) shown by flow cytometry demonstrated selectivity to prestin-expressing Chinese hamster ovary cells. PEG6K-b-PCL19K polymersomes covalently labelled with these peptides demonstrated effective targeting to outer hair cells in a rat cochlear explant study.     

Visualization and analysis of superparamagnetic iron oxide nanoparticles in the inner ear by light microscopy and energy filtered TEM

Nanoparticles as potential carriers for local drug transfer are an alternative to systemic drug delivery into the inner ear. We report on the first in vitro tests of a new ferrogel consisting of superparamagnetic iron oxide nanoparticles (SPIONs) and a Pluronic(?) F127 (PF127) copolymer. Pluronic copolymers possess a unique viscosity-adjustable property that makes PF127 gels easy to handle compared to conventional cross-linked hydrogels. This ferrogel was successfully tested in cadaver human temporal bones as well as in organotypic explant cultures of mouse inner ears. SPIONs were identified by light microscopy and localized with different imaging modes in energy-filtered transmission electron microscopy. Our approach shows a promising possibility to use iron oxide nanoparticles, which are suitable for visualization and characterization at both the light- and electron-microscopic levels. FROM THE CLINICAL EDITOR: The authors report the first in vitro tests of a new ferrogel consisting of superparamagnetic iron oxide nanoparticles (SPIONs) and a Pluronic? F127 (PF127) copolymer for drug delivery in the inner ear, demonstrasting a promising possibility to use iron oxide nanoparticles, which are suitable for visualization and characterization at both the light- and electron-microscopic levels.     

Disposition of nanoparticle-based delivery system via inner ear administration

The inner ear is difficult to access by conventional systemic drug delivery due to formidable physiological and anatomic barriers. There is an increasing interest in the treatment of inner ear disorders by topical application of drugs to the inner ear. One of the most important issues to overcome before full clinical application is the development of smart delivery systems for drugs to the target sites and controlled release in the inner ear. This is an area where nanoparticles will play an extremely important role. These submicron particles have exhibited improved biocompatibility, in vivo stability, target specificity, and cell/tissue uptake and internalization of the encapsulated therapeutic agents, leading to a decrease in the dose required and a decrease in side effects. This unique combination of properties makes nanoparticles a novel delivery device, which fulfils the requirements for inner ear application. This review will summarize recent findings and applications of various nanoparticle-based systems like poly (D, L-lactic/glycolic acid) nanoparticles, magnetic nanoparticles, lipid nanoparticles, liposomes, polymersomes, hydroxyapatite nanoparticles, and silica nanoparticles in the field of inner ear drug delivery. Moreover, the review will provide an insight into the future strategies of nanoparticle-based cochlear drug delivery. In conjunction, physiological considerations related to inner ear administration will be highlighted. The routes and applications for local inner-ear drug delivery will also be mentioned. In closing, this review will give an overview of the potential future development in inner ear administration with nanoparticles.     

Highly Specific HER2-mediated Cellular Uptake of Antibody-modified Nanoparticles in Tumour Cells

Nanoparticles represent useful drug delivery systems for the specific transport of drugs to tumour cells. In the present study biodegradable nanoparticles based on gelatin and human serum albumin (HSA) were developed. The surface of the nanoparticles was modified by covalent attachment of the biotin–binding protein NeutrAvidin? enabling the binding of biotinylated drug targeting ligands by avidin–biotin-complex formation. Using the HER2 receptor specific antibody trastuzumab (Herceptin®) conjugated to the surface of these nanoparticles, a specific targeting to HER2-overexpressing cells could be shown. Attachment of the antibody-conjugated nanoparticles to the surface of HER2-overexpressing cells was time and dose dependent. Confocal laser scanning microscopy demonstrated an effective internalisation of the nanoparticles by HER2-overexpressing cells via receptor-mediated endocytosis. The results indicate that nanoparticles conjugated with an antibody against a specific tumour antigen holds promise, as selective drug delivery systems for the treatment of tumours expressing a specific tumour antigen. To our knowledge, this is the first study that demonstrates the effective and specific targeting of protein-based nanoparticles as drug delivery systems.     

Targeting properties of peptide-modified radiolabeled liposomal nanoparticles

Radiolabeled PEGylated liposomal nanoparticles (NPs) open new possibilities for a variety of applications including diagnosis, drug delivery, targeted therapy, and monitoring treatment effects. Here we describe the characterization of liposomal NPs (liposomes and micelles) derivatized with the somatostatin analogue tyrosine-3-octreotide as a proof of concept for tumor targeting. NPs were radiolabeled with indium-111, and targeting properties were evaluated in vitro on rat pancreatic tumor cells (AR42J), demonstrating specific binding and IC(50) values in the low nanomolar range. Biodistribution studies were performed in Lewis rats and compared to single-photon emission computed tomography images. Moderate tumor uptake was found in xenografted nude mice (<2.5% ID/g tissue) as compared to control. Micelles and liposomes revealed comparable pharmacokinetics and targeting properties. This study provides insight into tumor-targeting characteristics of peptide-derivatized liposomal NPs and can serve as a basis for further improvement of these constructs. FROM THE CLINICAL EDITOR: The authors investigated tumor-targeting characteristics of peptide-derivatized liposomal NPs. Similar radiolabeled PEGylated liposomal NPs open new possibilities for a variety of applications including diagnosis, drug delivery, targeted therapy, and treatment monitoring.     

Highly specific HER2-mediated cellular uptake of antibody-modified nanoparticles in tumour cells

Nanoparticles represent useful drug delivery systems for the specific transport of drugs to tumour cells. In the present study biodegradable nanoparticles based on gelatin and human serum albumin (HSA) were developed. The surface of the nanoparticles was modified by covalent attachment of the biotin-binding protein NeutrAvidin enabling the binding of biotinylated drug targeting ligands by avidin-biotin-complex formation. Using the HER2 receptor specific antibody trastuzumab (Herceptin) conjugated to the surface of these nanoparticles, a specific targeting to HER2-overexpressing cells could be shown. Attachment of the antibody-conjugated nanoparticles to the surface of HER2-overexpressing cells was time and dose dependent. Confocal laser scanning microscopy demonstrated an effective internalisation of the nanoparticles by HER2-overexpressing cells via receptor-mediated endocytosis. The results indicate that nanoparticles conjugated with an antibody against a specific tumour antigen holds promise, as selective drug delivery systems for the treatment of tumours expressing a specific tumour antigen. To our knowledge, this is the first study that demonstrates the effective and specific targeting of protein-based nanoparticles as drug delivery systems.     

A comparison of peptide and folate receptor targeting of cancer cells: from single agent to nanoparticle

INTRODUCTION: There is broad interest in a targeted strategy that delivers a concentrated therapeutic payload to tumor cells, because of the significant potential for improvements in therapeutic outcomes and reduction of side effects if therapeutics can be delivered only to diseased tissue. AREAS COVERED: This review describes how the coupling chemistry and surface charge effects of peptide labeling in nanoparticle drug delivery strategies have proved difficult to control, resulting in many studies that use folate instead. However, the successful peptide targeting of structural, hormonal, cytokine and endocrine receptors in the delivery of therapeutic and diagnostic radionuclides provides a strong indication that it is worth finding methods to synthesize peptide-targeted nanoparticles. EXPERT OPINION: Chemical conjugation to peptides reduces colloidal stability, which is a limiting factor in the development of targeting nanoparticles. Mechanistic studies are needed in order to develop peptide targeting for nanoparticles to rival the selectivity that has been achieved with the small molecule folate. Although most of the work so far has been done using gold nanoparticles, biological and polymer nanoparticles are more colloidally stable and present enormous opportunities for coupling to peptides.     

Local drug delivery using poly(lactic-co-glycolic acid) nanoparticles in thermosensitive gels for inner ear disease treatment

Intratympanic (IT) therapies have been explored to address several side effects that could be caused by systemic administration of steroids to treat inner ear diseases. For effective drug delivery to the inner ear, an IT delivery system was developed using poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) and thermosensitive gels to maintain sustained release. Dexamethasone (DEX) was used as a model drug. The size and zeta potential of PLGA NPs and the gelation time of the thermosensitive gel were measured. In vitro drug release was studied using a Franz diffusion cell. Cytotoxicity of the formulations was investigated using SK-MEL-31 cells. Inflammatory responses were evaluated by histological observation of spiral ganglion cells and stria vascularis in the mouse cochlea 24 h after IT administration. In addition, the biodistribution of the formulations in mouse ears was observed by fluorescence imaging using coumarin-6. DEX-NPs showed a particle size of 150.0 ± 3.2 nm in diameter and a zeta potential of −18.7 ± 0.6. The DEX-NP-gel showed a gelation time of approximately 64 s at 37 °C and presented a similar release profile and cytotoxicity as that for DEX-NP. Furthermore, no significant inflammatory response was observed after IT administration. Fluorescence imaging results suggested that DEX-NP-gel sustained release compared to the other formulations. In conclusion, the PLGA NP-loaded thermosensitive gel may be a potential drug delivery system for the inner ear.     

SS-31 peptide enables mitochondrial targeting drug delivery: a promising therapeutic alteration to prevent hair cell damage from aminoglycosides

Aminoglycoside-induced hearing loss stems from damage or loss of mechanosensory hair cells in the inner ear. Intrinsic mitochondrial cell death pathway plays a key role in that cellular dysfunction for which no proven effective therapies against oto-toxicities exist. Therefore, the aim of the present study was to develop a new mitochondrial targeting drug delivery system (DDS) that provided improved protection from gentamicin. Particularly, SS-31 peptide-conjugated geranylgeranylacetone (GGA) loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles were constructed successfully via emulsion-solvent evaporation method. The zebrafish lateral line sensory system was used as an in vivo evaluating platform to investigate the protective efficiency against gentamicin. SS-31 modification significantly reduced the activity of mechanoelectrical transduction (MET) channel and gentamicin uptake in zebrafish lateral line hair cells. As expected, SS-31 conjugated nanoparticles showed mitochondrial specific accumulation in hair cells when compared with unconjugated formulations. Furthermore, intracellular SS-31 modified PLGA NPs slightly enhanced mitochondrial membrane potential (MMP, ΔΨ_m) and then returned to a steady-state, indicating their effect on the respiratory chain complexes in mitochondria. GGA loaded SS-31 conjugated nanoparticles demonstrated the most favorable hair cells survivals against gentamicin when compared with unconjugated groups whereas blank formulations failed to exhibit potency, indicating that the efficiency was attributed to drug delivery of GGA. These results suggest that our constructed mitochondria-targeting PLGA based DDS have potential application in protecting hair cells from ototoxic agents.     

Concanavalin A-conjugated poly(ethylene glycol)–poly(lactic acid) nanoparticles for intranasal drug delivery to the cervical lymph nodes

Abstract

Concanavalin A (ConA)-conjugated poly(ethylene glycol)–poly(lactic acid) nanoparticles (ConA-NPs) were prepared for targeted drug delivery to the cervical lymph nodes after intranasal administration. ConA, a lectin specifically binding to α-mannose and α-glucose, was covalently conjugated on NPs without loss of its carbohydrates binding bioactivity. In vitro cellular uptake experiment demonstrated that NPs could be uptaken by Calu-3 cells in a time- and concentration-dependent manner, and conjugation of ConA on NPs could significantly increase the rate and amount of cellular uptake. ConA-NP showed no obvious toxicity to Calu-3 cells in vitro or to the nasal cilia of rats in vivo. Compared with NPs without ConA, ConA-NP is more effective in targeting drugs to the deep cervical lymph nodes, as evidenced by 1.36–2.52 times increase of targeting efficiency, demonstrating that ConA-NP is a potential carrier for targeted drug delivery to the cervical lymph nodes via nasal route.     

Nanoparticles as drug delivery agents specific for CNS: in vivo biodistribution

The pharmacological treatment of neurological disorders is often complicated by the inability of drugs to pass the blood-brain barrier. Recently we discovered that polymeric nanoparticles (NPs) made of poly(d,l-lactide-co-glycolide), surface-decorated with the peptide Gly-l-Phe-d-Thr-Gly-l-Phe-l-Leu-l-Ser(O-β-d-glucose)-CONH₂ are able to deliver, after intravenous administration, the model drug loperamide into the central nervous system (CNS). This new drug delivery agent is able to ensure a strong and long-lasting pharmacological effect, far greater than that previously observed with other nanoparticulate carriers. Here we confirmed the effectiveness of this carrier for brain targeting, comparing the effect obtained by the administration of loperamide-loaded NPs with the effect of an intracerebroventricular administration of the drug; moreover, the biodistribution of these NPs showed a localization into the CNS in a quantity about two orders of magnitude greater than that found with the other known NP drug carriers. Thus, a new kind of NPs that target the CNS with very high specificity was discovered.From the Clinical EditorThis paper discusses a nanoparticle-based technique of targeted drug delivery through the blood-brain barrier. The biodistribution of these novel nanoparticles showed two orders of magnitude greater efficiency compared to other known NP drug carriers.     

Synthetic enzyme inhibitor: a novel targeting ligand for nanotherapeutic drug delivery inhibiting tumor growth without systemic toxicity

Unresolved problems associated with ligand-targeting of liposomal nanoparticles (NPs) to solid tumors include variable target receptor expression due to genetic heterogeneity and insufficient target specificity, leading to systemic toxicities. This study addresses these issues by developing a novel ligand-targeting strategy for liposomal NPs using RR-11a, a synthetic enzyme inhibitor of Legumain, an asparaginyl endopeptidase. Cell-surface expression of Legumain is driven by hypoxic stress, a hallmark of solid tumors. Legumain-targeted RR-11a-coupled NPs revealed high ligand-receptor affinity, enhanced solid-tumor penetration and uptake by tumor cells. Treatment of tumor-bearing mice with RR-11a-coupled NPs encapsulating doxorubicin resulted in improved tumor selectivity and drug sensitivity, leading to complete inhibition of tumor growth. These antitumor effects were achieved while eliminating systemic drug toxicity. Therefore, synthetic enzyme inhibitors, such as RR-11a, represent a new class of compounds that can be used for highly specific ligand-targeting of NPs to solid tumors. FROM THE CLINICAL EDITOR: This study addresses the problems associated with ligand-targeting of liposomal nanoparticles to solid tumors with variable target receptor expression. A novel and efficacious targeting strategy has been developed towards a synthetic enzyme inhibitor of Legumain. The authors demonstrate successful tumor growth inhibiting effect while eliminating systemic drug toxicity in an animal model using this strategy.     

Transferrin-appended PEGylated nanoparticles for temozolomide delivery to brain: in vitro characterisation

Polymer-based nanotechnologies are proposed to be an alternative for drug administration, delivery and targeting to those of conventional formulations. The blood brain barrier is frequently a rate-limiting factor in determining permeation of a drug into brain. In this study, the surface-engineered long-circulating PLGA nanoparticles (NPs) were assessed for brain-specific delivery. Long circulating NPs of PLGA- and PEG-synthesised copolymer were prepared by emulsification solvent evaporation method. Further, the surface of PEGylated NPs was modified by anchoring transferrin (Tf) ligand for receptor-mediated targeting to brain. NPs were characterised for shape and size, zeta potential, entrapment efficiency and in?vitro drug release. In?vitro cytotoxicity studies were performed on human cancer cell lines. Confocal Laser Scanning Microscopy studies show the enhanced uptake of Tf-appended PEGylated NPs and their localisation in the brain tissues. Hence, the specific role of Tf ligand on PEGylated NPs for brain delivery was confirmed.     

Targeted paclitaxel nanoparticles modified with follicle-stimulating hormone β 81–95 peptide show effective antitumor activity against ovarian carcinoma

The majority of patients with advanced ovarian cancer will experience a relapse and ultimately die from refractory diseases. Targeted therapy shows promise for these patients. Novel therapeutic strategies should be developed on the basis of the molecular mechanisms involved in ovarian cancer and the steroid hormone environment of ovaries. The ovary is the main target organ of follicle-stimulating hormone (FSH), which bind to its receptor with high affinity. In this study a FSH receptor-targeting ligand, FSH β 81–95 peptide, was used as a targeting moiety to synthesize an FSH receptor-mediated drug delivery system. FSH β 81–95 peptide-conjugated nanoparticles (FSH81-NPs) and paclitaxel-loaded FSH81-NPs (FSH81-NP-PTXs) were synthesized. In vitro studies showed that FSH β 81–95 peptide enabled the specific uptake of cytotoxic drugs and increased the intracellular paclitaxel concentration in FSH receptor-expressing cancer cells, resulting in enhanced cytotoxic effects. In vivo studies showed that FSH81-NP-PTXs possessed higher antitumor efficacy against FSH receptor-expressing tumors without any clinical signs of adverse side effects or body weight loss due to modification with FSH β 81–95 peptide. Therefore, FSH binding peptide-targeted drug delivery system exhibited high potential in the treatment of ovarian cancer, and tumor targeting via reproductive hormone receptors might improve the outcome of diseases.     

In situ apolipoprotein E-enriched corona guides dihydroartemisinin-decorating nanoparticles towards LDLr-mediated tumor-homing chemotherapy

The therapeutic efficiency of active targeting nanoparticulate drug delivery systems (nano-DDS) is highly compromised by the plasma proteins adsorption on nanoparticles (NPs) surface, which significantly hinders cell membrane receptors to recognize the designed ligands, and provokes the off-target toxicity and rapid clearance of NPs in vivo. Herein, we report a novel dihydroartemisinin (DHA)-decorating nano-DDS that in situ specifically recruits endogenous apolipoprotein E (apoE) on the NPs surface. The apoE-anchored corona is able to prolong PLGA-PEG2000-DHA (PPD) NPs circulation capability in blood, facilitate NPs accumulating in tumor cells by the passive enhanced permeability and retention (EPR) effect and low-density lipoprotein receptor (LDLr)-mediated target transport, and ultimately improve the in vivo antitumor activity. Our findings demonstrate that the strategy of in situ regulated apoE-enriched corona ensures NPs an efficient LDLr-mediated tumor-homing chemotherapy.     

Surface modification of doxorubicin-loaded nanoparticles based on polydopamine with pH-sensitive property for tumor targeting therapy

One major challenge of current surface modification of nanoparticles is the demand for chemical reactive polymeric layers, such modification is always complicated, inefficient, and may lead the polymer lose the ability to encapsulate drug. To overcome this limitation, we adopted a pH-sensitive platform using polydopamine (PDA) as a way of functionalizing nanoparticles (NPs) surfaces. All this method needed to be just a brief incubation in weak alkaline solution of dopamine, which was simple and applicable to a variety of polymer carriers regardless of their chemical reactivity. We successfully conjugated the doxorubicin (DOX)-PDA-poly (lactic-co-glycolic acid) (PLGA) NPs with two typical surface modifiers: folate (FA) and a peptide (Arg-Gly-Asp, RGD). The DOX-PDA-FA-NPs and DOX-PDA-RGD-NPs (targeting nanoparticles) were characterized by particle size, zeta potential, and surface morphology. They were quite stable in various physiological solutions and exhibited pH-sensitive property in drug release. Compared to DOX-NPs, the targeting nanoparticles possessed an excellent targeting ability against HeLa cells. In addition, the in vivo study demonstrated that targeting nanoparticles achieved a tumor inhibition rate over 70%, meanwhile prominently decreased the side effects of DOX and improve drug distribution in tumors. Our studies indicated that the DOX-PLGA-NPs modified with PDA and various functional ligands are promising nanocarriers for targeting tumor therapy.