Multifunctional, stimuli-sensitive nanoparticulate systems for drug delivery

A Virus-Mimicking, Endosomolytic Liposomal System for Efficient, pH-Triggered Intracellular Drug Delivery

A novel multifunctional liposomal delivery platform has been developed to resemble the structural and functional traits of an influenza virus. Novel pseudopeptides were prepared to mimic the pH-responsive endosomolytic behavior of influenza viral peptides through grafting a hydrophobic amino acid, l-phenylalanine, onto the backbone of a polyamide, poly(l-lysine isophthalamide), at various degrees of substitution. These pseudopeptidic polymers were employed to functionalize the surface of cholesterol-containing liposomes that mimic the viral envelope. By controlling the cholesterol proportion as well as the concentration and amphiphilicity of the pseudopeptides, the entire payload was rapidly released at endosomal pHs, while there was no release at pH 7.4. A pH-triggered, reversible change in liposomal size was observed, and the release mechanism was elucidated. In addition, the virus-mimicking nanostructures efficiently disrupted the erythrocyte membrane at pH 6.5 characteristic of early endosomes, while they showed negligible cytotoxic effects at physiological pH. The efficient intracellular delivery of the widely used anticancer drug doxorubicin (DOX) by the multifunctional liposomes was demonstrated, leading to significantly increased potency against HeLa cancer cells over the DOX-loaded bare liposomes. This novel virus-mimicking liposomal system, with the incorporated synergy of efficient liposomal drug release and efficient endosomal escape, is favorable for efficient intracellular drug delivery.

An amphiphilic graft copolymer-based nanoparticle platform for reduction-responsive anticancer and antimalarial drug delivery

Medical applications of anticancer and antimalarial drugs often suffer from low aqueous solubility, high systemic toxicity, and metabolic instability. Smart nanocarrier-based drug delivery systems provide means of solving these problems at once. Herein, we present such a smart nanoparticle platform based on self-assembled, reduction-responsive amphiphilic graft copolymers, which were successfully synthesized through thiol-disulfide exchange reaction between thiolated hydrophilic block and pyridyl disulfide functionalized hydrophobic block. These amphiphilic graft copolymers self-assembled into nanoparticles with mean diameters of about 30-50 nm and readily incorporated hydrophobic guest molecules. Fluorescence correlation spectroscopy (FCS) was used to study nanoparticle stability and triggered release of a model compound in detail. Long-term colloidal stability and model compound retention within the nanoparticles was found when analyzed in cell media at body temperature. In contrast, rapid, complete reduction-triggered disassembly and model compound release was achieved within a physiological reducing environment. The synthesized copolymers revealed no intrinsic cellular toxicity up to 1 mg mL(-1). Drug-loaded reduction-sensitive nanoparticles delivered a hydrophobic model anticancer drug (doxorubicin, DOX) to cancer cells (HeLa cells) and an experimental, metabolically unstable antimalarial drug (the serine hydroxymethyltransferase (SHMT) inhibitor (±)-1) to Plasmodium falciparum-infected red blood cells (iRBCs), with higher efficacy compared to similar, non-sensitive drug-loaded nanoparticles. These responsive copolymer-based nanoparticles represent a promising candidate as smart nanocarrier platform for various drugs to be applied to different diseases, due to the biocompatibility and biodegradability of the hydrophobic block, and the protein-repellent hydrophilic block.

Photosensitizer cross-linked nano-micelle platform for multimodal imaging guided synergistic photothermal/photodynamic therapy

The multifunctional nano-micelle platform holds great promise to enhance the accuracy and efficiency of cancer diagnosis and therapy. In this work, an amphiphilic poly[(poly(ethylene glycol) methyl ether methacrylate)-co-(3-aminopropyl methacrylate)]-block-poly(methyl methacrylate) (P(PEGMA-co-APMA)-b-PMMA) block copolymer was synthesized by successive RAFT polymerizations and subsequent chemical modification. Then the multifunctional micelles with high solubility in physiological environments were developed by a self-assembly and crosslinking processes. The photosensitizer segment, 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin (TCPP), serves as a tetra-functional cross-linker, photodynamic agent, fluorescence indicator, as well as magnetic resonance (MR) contrast agent after labelling with manganese ions (Mn(2+)), while IR825 simultaneously locating in the interior of the fabricated micelles contributed to the photoacoustic (PA) imaging ability and the photothermal effect. The prepared nanoparticles show great stability in a physiological environment with uniform morphology and diameters of around 80 nm as disclosed by stability investigation, TEM and DLS analysis. IR825@P(PEGMA-co-APMA)-b-PMMA@TCPP/Mn nanoparticles displayed high in vivo tumor uptake with a long blood circulation half-life (∼3.64 h) by the EPR effect after intravenous (i.v.) injection, as revealed by fluorescence, MR and PA imaging models. In vivo anti-tumor effects were achieved via a combined photothermal and photodynamic therapy without noticeable dark toxicity, and this strategy was able to induce a remarkably improved synergistic therapeutic effect to both superficial and deep regions of tumors under mild conditions compared with either single photothermal or photodynamic mechanisms.

Amphiphilic poly-N-vynilpyrrolidone nanoparticles: Cytotoxicity and acute toxicity study

The aim of the present study was to evaluate the cytotoxicity against MCF-7 cells and acute intraperitoneal toxicity of amphiphilic poly-N-vinylpyrrolidone nanoparticles to confirm possibility of their application for creation of novel drug delivery systems. The effect of cellular uptake of polymeric nanoparticles on human cancer cell line MCF-7 cells was investigated by MTT assay. MTT analysis showed that tested amphiphilic polymers were essentially non-toxic. In acute toxicity studies, LD50 and other toxicity indexes were evaluated, under which no deaths or treatment related complications were observed even in high concentration treatment for 14 days of experiment. For histological analysis, organs of the animals were weighed and examined. No animal died during the study and no significant changes have been observed regarding body weight, feed consumption, organ weight or histological data. Obtained results show that amphiphilic poly-N-vinylpyrrolidone nanoparticles possessed no toxicity against cells and in animals after intraperitoneal administration. Thus, amphiphilic PVP nanoparticles demonstrate high potential as carriers for novel high-effective drug delivery systems.

Polymeric lipid vesicles with pH-responsive turning on-off membrane for programed delivery of insulin in GI tract

A kind of polymeric lipid vesicles (PLVs) with pH-responsive turning on-off membrane for programed delivery of insulin in gastrointestinal (GI) tract was developed, which was self-assembled from the grafted amphipathic polymer of N-tocopheryl-N'-succinyl-ɛ-poly-l-lysine (TP/SC-g-PLL). By controlling the grafting ratio of hydrophobic alkane and ionizable carboxyl branches, the permeability of membrane was adjustable and thus allowing insulin release in a GI-pH dependent manner. The effects of grafting degree of substitution (DS) on the pH-responsive behavior of the formed vesicles were confirmed by critical aggregation concentration determination, morphology and size characterization. Their transepithelial permeability across the GI tract was proved by both confocal visualization in vitro model of Caco-2 cellular monolayer and in vivo hypoglycemic study in diabetic rats. Accordingly, the work described here indicated that the self-assembled PLVs could be a promising candidate for improving the GI delivery of hydrophilic biomacromolecule agents.

Development of a bone-targeted pH-sensitive liposomal formulation containing doxorubicin: physicochemical characterization, cytotoxicity, and biodistribution evaluation in a mouse model of bone metastasis

BACKGROUND

Despite recent advances in cancer therapy, the treatment of bone tumors remains a major challenge. A possible underlying hypothesis, limitation, and unmet need may be the inability of therapeutics to penetrate into dense bone mineral, which can lead to poor efficacy and high toxicity, due to drug uptake in healthy organs. The development of nanostructured formulations with high affinity for bone could be an interesting approach to overcome these challenges.

PURPOSE

To develop a liposomal formulation with high affinity for hydroxyapatite and the ability to release doxorubicin (DOX) in an acidic environment for future application as a tool for treatment of bone metastases.

MATERIALS AND METHODS

Liposomes were prepared by thin-film lipid hydration, followed by extrusion and the sulfate gradient-encapsulation method. Liposomes were characterized by average diameter, ζ-potential, encapsulation percentage, X-ray diffraction, and differential scanning calorimetry. Release studies in buffer (pH 7.4 or 5), plasma, and serum, as well as hydroxyapatite-affinity in vitro analysis were performed. Cytotoxicity was evaluated by MTT assay against the MDA-MB-231 cell line, and biodistribution was assessed in bone metastasis-bearing animals.

RESULTS

Liposomes presented suitable diameter (~170 nm), DOX encapsulation (~2 mg/mL), controlled release, and good plasma and serum stability. The existence of interactions between DOX and the lipid bilayer was proved through differential scanning calorimetry and small-angle X-ray scattering. DOX release was faster when the pH was in the range of a tumor than at physiological pH. The bone-targeted formulation showed a strong affinity for hydroxyapatite. The encapsulation of DOX did not interfere in its intrinsic cytotoxicity against the MDA-MB-231 cell line. Biodistribution studies demonstrated high affinity of this formulation for tumors and reduction of uptake in the heart.

CONCLUSION

These results suggest that bone-targeted pH-sensitive liposomes containing DOX can be an interesting strategy for selectively delivering this drug into bone-tumor sites, increasing its activity, and reducing DOX-related toxicity.

Design of smart GE11-PLGA/PEG-PLGA blend nanoparticulate platforms for parenteral administration of hydrophilic macromolecular drugs: synthesis, preparation and in vitro/ex vivo characterization

Active drug targeting and controlled release of hydrophilic macromolecular drugs represent crucial points in designing efficient polymeric drug delivery nanoplatforms. In the present work EGFR-targeted polylactide-co-glycolide (PLGA) nanoparticles were made by a blend of two different PLGA-based polymers. The first, GE11-PLGA, in which PLGA was functionalized with GE11, a small peptide and EGFR allosteric ligand, able to give nanoparticles selective targeting features. The second polymer was a PEGylated PLGA (PEG-PLGA) aimed at improving nanoparticles hydrophilicity and stealth features. GE11 and GE11-PLGA were custom synthetized through a simple and inexpensive method. The nanoprecipitation technique was exploited for the preparation of polymeric nanoparticles composed by a 1:1weight ratio between GE11-PLGA and PEG-PLGA, obtaining smart nanoplatforms with proper size for parenteral administration (143.9±5.0nm). In vitro cellular uptake in EGFR-overexpressing cell line (A549) demonstrated an active internalization of GE11-functionalized nanoparticles. GE11-PLGA/PEG-PLGA blend nanoparticles were loaded with Myoglobin, a model hydrophilic macromolecule, reaching a good loading (2.42% respect to the theoretical 4.00% w/w) and a prolonged release over 60days. GE11-PLGA/PEG-PLGA blend nanoparticles showed good in vitro stability for 30days in physiological saline solution at 4°C and for 24h in pH 7.4 or pH 5.0 buffer at 37°C respectively, giving indications about potential storage and administration conditions. Furthermore ex vivo stability study in human plasma using fluorescence Single Particle Tracking (fSPT) assessed good GE11-PLGA/PEG-PLGA nanoparticles dimensional stability after 1 and 4h. Thanks to the versatility in polymeric composition and relative tunable nanoparticles features in terms of drug incorporation and release, GE11-PLGA/PEG-PLGA blend NPs can be considered highly promising as smart nanoparticulate platforms for the treatment of diseases characterized by EGFR overexpression by parenteral administration .

An engineered TIMP2-based and enediyne-integrated fusion protein for targeting MMP-14 shows potent antitumor efficacy

Recent studies have shown that MMP-14 is highly expressed in a panel of human solid tumors and poses as a potential molecular target for anticancer drugs. Currently, major strategies for targeted therapeutics have mainly focused on the use of antibody or ligand-based agents. For seeking an alternative approach, it is of interest to employ endogenous proteins as drug delivery carriers. Considering the facts that TIMP2, the tissue inhibitor of metalloproteinase 2, shows specific interaction with MMP-14 and that Lidamycin (LDM), an extremely potent cytotoxic antitumor antibiotic, consists of an apoprotein (LDP) and a highly active enediyne (AE); we designed and prepared a TIMP2-based and enediyne-integrated fusion protein LDP(AE)-TIMP2 by DNA recombination and molecular reconstitution consecutively. Furthermore, the MMP-14 binding attributes of the active fusion protein were determined and its therapeutic efficacy against human esophageal carcinoma KYSE150 xenograft and human fibrosarcoma HT1080 xenograft models in nude mice was investigated. It is suggested that TIMP2, the endogenous and MMP-14 binding protein, might serve as a guided carrier for targeted therapeutics.

3D Imaging of Nanoparticle Distribution in Biological Tissue by Laser-Induced Breakdown Spectroscopy

Nanomaterials represent a rapidly expanding area of research with huge potential for future medical applications. Nanotechnology indeed promises to revolutionize diagnostics, drug delivery, gene therapy, and many other areas of research. For any biological investigation involving nanomaterials, it is crucial to study the behavior of such nano-objects within tissues to evaluate both their efficacy and their toxicity. Here, we provide the first account of 3D label-free nanoparticle imaging at the entire-organ scale. The technology used is known as laser-induced breakdown spectroscopy (LIBS) and possesses several advantages such as speed of operation, ease of use and full compatibility with optical microscopy. We then used two different but complementary approaches to achieve 3D elemental imaging with LIBS: a volume reconstruction of a sliced organ and in-depth analysis. This proof-of-concept study demonstrates the quantitative imaging of both endogenous and exogenous elements within entire organs and paves the way for innumerable applications.

Lipid Nanovectors to Deliver RNA Oligonucleotides in Cancer

The growing knowledge on the mechanisms of gene silencing and gene regulation by non-coding RNAs (ncRNA), mainly small interfering RNA (siRNA) and microRNA (miRNA), is providing a significant boost to the development of new therapeutic strategies for the treatment of cancer. However, the design of RNA-based therapeutics is hampered by biopharmaceutical issues, thus requiring the use of suitable delivery strategies. In this regards, lipid nanovectors have been successfully investigated to deliver RNA in different forms of cancer. Compared to other biomaterials, lipids offer advantages such as biocompatibility, biodegradability, easy production, low cost, limited toxicity and immunogenicity. The possibility to formulate these materials in the form of nanovectors allows overcoming biopharmaceutical issues associated to the therapeutic use of RNA, with the possibility to target tumors. This review takes stock of the main lipid nanovectors proposed to deliver ncRNA. For each considered delivery strategy, the rational design and the most meaningful in vitro and in vivo results are reported and discussed.

Stimuli-free programmable drug release for combination chemo-therapy

Combinational chemotherapy capable of targeted delivery and programmable multi-drug release leads to enhanced drug efficacy, and is highly desired for cancer treatment. However, effective approaches for achieving both features in a single treatment are limited. In the present work, we demonstrated programmed delivery of both chemotherapeutic and immunotherapeutic agents with tumor cell targeting capability by using SiO2 based self-decomposable nanoparticulate systems. The programmable drug delivery is realized by manipulating drug loading configurations instead of relying on external stimuli. Both in vitro and in vivo results showed specific drug binding to FAT1-expressing colon cancer cells. The loaded dual drugs were demonstrated to be delivered in a sequential manner with specific time intervals between their peak releases, which maximize the synergistic effect of the chemotherapeutics. These features led to significantly enhanced drug efficacy and reduced system toxicity. The tumor weight decreased by 1/350, together with a moderate increase in rats' body weight, which were observed when adopting the dual drug loaded nanoparticles, as compared to those of the control groups. The present system provides a simple and feasible method for the design of targeting and combination chemotherapy with programmed drug release.

Novel multifunctional pH-sensitive nanoparticles loaded into microbubbles as drug delivery vehicles for enhanced tumor targeting

This study fabricated novel multifunctional pH-sensitive nanoparticles loaded into microbubbles (PNP-MB) with the combined advantages of two excellent drug delivery vehicles, namely, pH-sensitive nanoparticles and microbubbles. As an antitumor drug, resveratrol (RES) was loaded into acetylated β-cyclodextrin nanoparticles (RES-PNP). The drug-loaded nanoparticles were then encapsulated into the internal space of the microbubbles. The characterization and morphology of this vehicle were investigated through dynamic light scattering and confocal laser scanning microscopy, respectively. In vitro drug release was performed to investigate the pH sensitivity of RES-PNP. The antitumor property of RES-loaded PNP-MB (RES-PNP-MB) was also analyzed in vivo to evaluate the antitumor effect of RES-PNP-MB. Results suggested that PNP exhibited pH sensitivity, and was successfully encapsulated into the microbubbles. RES-PNP-MB exhibit effective tumor growth suppressing in vivo. Therefore, such drug delivery vehicle should be of great attention in tumor therapy.

Silicon Dioxide Impedes Antiviral Response and Causes Genotoxic Insult During Calicivirus Replication

Noroviruses (NoV) are the leading cause of nonbacterial gastroenteritis in humans, and replicate extensively in the human gastrointestinal (GI) tract. Silica (also known as silicon dioxide, SiO2) nanoparticles (NPs) used in processed foods, dairy products, and beverages also accumulate in the GI tract. We investigated the effect of silica NPs on NoV replication and host cell response during virus infection, using murine norovirus (MNV-1) infection of RAW 264.7 murine macrophages. Pretreatment with 10 μg/ml silica significantly reduced the viability of macrophages, but no cumulative effects on viability of macrophages were observed with MNV-1 infection. No difference was observed between exposure to control or silica NPs on either the quantity of viral genome copies or the production of infectious virus in macrophages infected with MNV-1. Silica NPs reduced the ability of macrophages to upregulate genes encoding bone morphogenic proteins (BMPs), chemokine ligands and cytokines for which expression levels were otherwise found to be upregulated in response to MNV-1 infection. Furthermore, silica NPs reduced the levels of proinflammatory cytokines secreted by macrophages in response to MNV infection. Finally, silica NPs with MNV-1 infection produced a genotoxic insult to macrophages. Strikingly, this genotoxic insult was also found to occur as a synergistic effect of silica NPs and feline calicivirus infection in feline kidney epithelial cells. Taken together, our study suggests important safety considerations related to reducing exposure to silica NPs affecting the GI tract in individuals infected with NoVs and possibly other foodborne viruses.

Physical, Chemical, and Biological Structures based on ROS-Sensitive Moieties that are Able to Respond to Oxidative Microenvironments

Reactive oxygen species (ROS) (H2 O2 , OCl(-) , (•) OH, O2 (-) ) are a family of reactive molecules that are generated intracellularly and are engaged in many biological processes. In physiological concentrations, ROS act as signaling molecules to a number of metabolic pathways; however, in excess they can be harmful to living organisms. Overproduction of ROS has been related to many pathophysiological conditions and a number of studies have been reported in elucidating their mechanism in these conditions. With the aim of harnessing this role, a number of imaging tools and therapeutic compounds have been developed. Here these imaging and therapeutic tools are reviewed and particularly those structures with ROS-sensitivity based on their biomedical applications and their functional groups. There is also a brief discussion about the method of preparation as well as the mechanism of action.

Plasmonic, Targeted, and Dual Drugs-Loaded Polypeptide Composite Nanoparticles for Synergistic Cocktail Chemotherapy with Photothermal Therapy

To integrate cocktail chemotherapy with photothermal therapy into one biocompatible and biodegradable nanocarrier, the plasmonic, lactose-targeted, and dual anticancer drugs-loaded polypeptide composite nanoparticles were for the first time fabricated under mild conditions. The glyco-PEGylated polypeptide micelles that self-assembled from the lactose (LAC) and PEG grafted polycysteine terpolymer were used as templates to generate the plasmonic composite nanoparticles, as mainly characterized by DLS, TEM, SEM, and XPS. These composite nanoparticles showed a broad and strong near-infrared (NIR) absorption at 650-1100 nm and increased the temperature of phosphate buffer solution by 30.1 °C upon a continuous-wave laser irradiation (808 nm, 5 min, 2 W·cm(-2)), while the same dose of NIR-mediated heating completely killed HepG2 cancer cells in vitro, presenting excellent photothermal properties. Two anticancer drugs, doxorubicin (DOX) and 6-mercaptopurine (6-MP), were loaded into the composite nanoparticles through physical interactions and Au-S bond, respectively. The dual drugs-loaded composite nanoparticles exhibited reduction-sensitive and NIR-triggered cocktail drugs release profiles and trigger-enhanced cytotoxicity. As evidenced by flow cytometry, fluorescence microscopy, and MTT assay, the LAC-coated composite nanoparticles were more internalized by the HepG2 than the HeLa cell line, demonstrating a LAC-targeting enhanced cytotoxicity toward HepG2. The combination cocktail chemo-photothermal therapy produced a lower half maximal inhibitory concentration than cocktail chemotherapy or photothermal therapy alone, displaying a good synergistic antitumor effect.

Nanoparticle tumor localization, disruption of autophagosomal trafficking, and prolonged drug delivery improve survival in peritoneal mesothelioma

The treatment outcomes for malignant peritoneal mesothelioma are poor and associated with high co-morbidities due to suboptimal drug delivery. Thus, there is an unmet need for new approaches that concentrate drug at the tumor for a prolonged period of time yielding enhanced antitumor efficacy and improved metrics of treatment success. A paclitaxel-loaded pH-responsive expansile nanoparticle (PTX-eNP) system is described that addresses two unique challenges to improve the outcomes for peritoneal mesothelioma. First, following intraperitoneal administration, eNPs rapidly and specifically localize to tumors. The rate of eNP uptake by tumors is an order of magnitude faster than the rate of uptake in non-malignant cells; and, subsequent accumulation in autophagosomes and disruption of autophagosomal trafficking leads to prolonged intracellular retention of eNPs. The net effect of these combined mechanisms manifests as rapid localization to intraperitoneal tumors within 4 h of injection and persistent intratumoral retention for >14 days. Second, the high tumor-specificity of PTX-eNPs leads to delivery of greater than 100 times higher concentrations of drug in tumors compared to PTX alone and this is maintained for at least seven days following administration. As a result, overall survival of animals with established mesothelioma more than doubled when animals were treated with multiple doses of PTX-eNPs compared to equivalent dosing with PTX or non-responsive PTX-loaded nanoparticles.

Extracellular control of intracellular drug release for enhanced safety of anti-cancer chemotherapy

The difficulty of controlling drug release at an intracellular level remains a key challenge for maximising drug safety and efficacy. We demonstrate herein a new, efficient and convenient approach to extracellularly control the intracellular release of doxorubicin (DOX), by designing a delivery system that harnesses the interactions between the system and a particular set of cellular machinery. By simply adding a small-molecule chemical into the cell medium, we could lower the release rate of DOX in the cytosol, and thereby increase its accumulation in the nuclei while decreasing its presence at mitochondria. Delivery of DOX with this system effectively prevented DOX-induced mitochondria damage that is the main mechanism of its toxicity, while exerting the maximum efficacy of this anti-cancer chemotherapeutic agent. The present study sheds light on the design of drug delivery systems for extracellular control of intracellular drug delivery, with immediate therapeutic implications.

Antibody drug conjugates

Antibody drug conjugates (ADCs) have emerged as a viable option in targeted delivery of highly potent cytotoxic drugs in treatment of solid tumors. At the time of writing, only two ADCs have received regulatory approval with >40 others in clinical development. The first generation ADCs suffered from a lack of specificity in amino acid site-conjugations, yielding statistically heterogeneous stoichiometric ratios of drug molecules per antibody molecule. For the second generation ADCs, however, site-specific amino acid conjugation using enzymatic ligation, introduction of unnatural amino acids, and site-specific protein engineering hold promise to alleviate some of the current technical limitations. The rapid progress in technology platforms and antibody engineering has introduced novel linkers, site-specific conjugation chemistry, and new payload candidates that could possibly be exploited in the context of ADCs. A search using the Clinical Trial Database registry ( www.clinicaltrials.gov ), using the keyword 'antibody drug conjugate', yielded ~270 hits. The main focus of this article is to present a brief overview of the recent developments and current challenges related to ADC development.

Use of a non-covalent cell-penetrating peptide strategy to enhance the nasal delivery of interferon beta and its PEGylated form

The conjugation of therapeutic proteins to polyethylene glycol (PEG) is known as PEGylation. It improves their retention in the body and reduces the frequency of injections. Development of noninvasive delivery systems for biopharmaceuticals can improve the patients' quality of life. The present study aimed to evaluate the cell-penetrating peptides (CPPs), which act as bioenhancers, for the nasal delivery of protein drug interferon beta (IFN-β) and its PEGylated form (PEG-IFN-β). The ability of CPPs to enhance the nasal mucosal absorption of unmodified IFN-β was assessed in rats. It was shown that only d-amino acid forms of amphipathic CPPs, penetratin and PenetraMax significantly enhanced the nasal absorption of IFN-β. Especially, D-penetratin (up to 2mM) enhanced the absorption of INF-β in a dose-dependent manner. The maximum absolute bioavailability reached 8.26% following in situ nasal coadministration of IFN-β with d-penetratin (2mM). Furthermore, it was found that the coadministration of d-penetratin also facilitated the nasal absorption of PEG-IFN-β, which remained in the circulation for more than 6h. Moreover, the toxicity assessments showed no damage to the epithelial membranes after nasal administration of CPPs including penetratin and PenetraMax. Altogether, this study provides the first evidence that the noncovalent coadministration of PEGylated proteins with CPPs could be a potent strategy for the noninvasive and sustained nasal delivery of therapeutic proteins.

The Smart Drug Delivery System and Its Clinical Potential

With the unprecedented progresses of biomedical nanotechnology during the past few decades, conventional drug delivery systems (DDSs) have been involved into smart DDSs with stimuli-responsive characteristics. Benefiting from the response to specific internal or external triggers, those well-defined nanoplatforms can increase the drug targeting efficacy, in the meantime, reduce side effects/toxicities of payloads, which are key factors for improving patient compliance. In academic field, variety of smart DDSs have been abundantly demonstrated for various intriguing systems, such as stimuli-responsive polymeric nanoparticles, liposomes, metals/metal oxides, and exosomes. However, these nanoplatforms are lack of standardized manufacturing method, toxicity assessment experience, and clear relevance between the pre-clinical and clinical studies, resulting in the huge difficulties to obtain regulatory and ethics approval. Therefore, such relatively complex stimulus-sensitive nano-DDSs are not currently approved for clinical use. In this review, we highlight the recent advances of smart nanoplatforms for targeting drug delivery. Furthermore, the clinical translation obstacles faced by these smart nanoplatforms have been reviewed and discussed. We also present the future directions and perspectives of stimuli-sensitive DDS in clinical applications.

Nanoparticles in the clinic

Nanoparticle/microparticle-based drug delivery systems for systemic (i.e., intravenous) applications have significant advantages over their nonformulated and free drug counterparts. For example, nanoparticle systems are capable of delivering therapeutics and treating areas of the body that other delivery systems cannot reach. As such, nanoparticle drug delivery and imaging systems are one of the most investigated systems in preclinical and clinical settings. Here, we will highlight the diversity of nanoparticle types, the key advantages these systems have over their free drug counterparts, and discuss their overall potential in influencing clinical care. In particular, we will focus on current clinical trials for nanoparticle formulations that have yet to be clinically approved. Additional emphasis will be on clinically approved nanoparticle systems, both for their currently approved indications and their use in active clinical trials. Finally, we will discuss many of the often overlooked biological, technological, and study design challenges that impact the clinical success of nanoparticle delivery systems.

Carrier-Free, Chemophotodynamic Dual Nanodrugs via Self-Assembly for Synergistic Antitumor Therapy

There are tremendous challenges from both tumor and its therapeutic formulations affecting the effective treatment of tumor, including tumor recurrence, and complex multistep preparations of formulation. To address these issues, herein a simple and green approach based on the self-assembly of therapeutic agents including a photosensitizer (chlorine e6, Ce6) and a chemotherapeutic agent (doxorubicin, DOX) was developed to prepare carrier-free nanoparticles (NPs) with the ability to inhibit tumor recurrence. The designed NPs were formed by self-assembly of Ce6 and DOX associated with electrostatic, π-π stacking and hydrophobic interactions. They have a relatively uniform size of average 70 nm, surface charge of -20 mV and high drug encapsulation efficiency, which benefits the favorable accumulation of drugs at the tumor region through a potential enhanced permeability and retention (EPR) effect as compared to their counterpart of free Ce6 solution. In addition, they could eradiate tumors without recurrence in a synergistic way following one treatment cycle. Furthermore, the NPs are safe without any activation of inflammation or immune response in separated organs. Taken together, the rationale of these pure nanodrugs via the self-assembly approach might open an alternative avenue and give inspiration to fabricate new carrier-free nanodrugs for tumor theranostics, especially for two small molecular antitumor drugs with the aim of combinational antitumor therapy in a synergistic way.

Incorporation of VSV-G produces fusogenic plasma membrane vesicles capable of efficient transfer of bioactive macromolecules and mitochondria

The objective of this study was to determine if plasma membrane vesicles (PMVs) could be exploited for efficient transfer of macro-biomolecules and mitochondria. PMVs were derived from mechanical extrusion, and made fusogenic (fPMVs) by incorporating the glycoprotein G of vesicular stomatitis virus (VSV-G). Confocal microscopy examination revealed that cytoplasmic proteins and mitochondria were enclosed in PMVs as evidenced by tracing with cytoplasmically localized and mitochondria-targeted EGFP, respectively. However, no fluorescence signal was detected in PMVs from cells whose nucleus was labeled with an EGFP-tagged histone H2B. Consistently, qRT-PCR measurement showed that mRNA, miRNA and mitochondrial DNA decreased slightly; while nuclear DNA was not measureable. Further, Western blot analysis revealed that cytoplasmic and membrane-bound proteins fell inconspicuously while nuclear proteins were barely detecsle. In addition, fPMVs carrying cytoplamic DsRed proteins transduced about ~40 % of recipient cells. The transfer of protein was further confirmed by using the inducible Cre/loxP system. Mitochondria transfer was found in about 20 % recipient cells after incubation with fPMVs for 5 h. To verify the functionalities of transferred mitochondria, mitochodria-deficient HeLa cells (Rho0) were generated and cultivated with fPMVs. Cell enumeration demonstrated that adding fPMVs into culture media stimulated Rho0 cell growth by 100 % as compared to the control. Lastly, MitoTracker and JC-1 staining showed that transferred mitochondria maintained normal shape and membrane potential in Rho0 cells. This study established a time-saving and efficient approach to delivering proteins and mitochondria by using fPMVs, which would be helpful for finding a cure to mitochondria-associated diseases. Graphical abstract Schematic of the delivery of macro-biomolecules and organelles by fPMVs. VSV-G-expressing cells were extruded through a 3 μm polycarbonate membrane filter to generate fusogenic plasma membrane vesicles (fPMVs), which contain bioactive molecules and organelles but not the nucleus. fPMVs can be endocytosed by target cells, while the cargo is released due to low-pH induced membrane fusion. These nucleus-free fPMVs are efficient at delivery of cytoplasmic proteins and mitochondria, leading to recovery of mitochondrial biogenesis and proliferative ability in mitochondria-deficient cells.

An injectable drug-loaded hydrogel based on a supramolecular polymeric prodrug

We reported a novel injectable doxorubicin-loaded hydrogel based on host-guest interaction and Schiff's base reaction. A supramolecular polymeric prodrug was prepared through the inclusion of adamantane-modified doxorubicin into the β-cyclodextrin cavity on the polyaldehyde dextran chain, which was in situ crosslinked by carboxymethyl chitosan.

Nanoparticle Targeting of Neutrophils for Improved Cancer Immunotherapy

Cancer immunotherapy using tumor-specific monoclonal antibodies presents a novel approach for cancer treatment. A monoclonal antibody TA99 specific for gp75 antigen of melanoma initiates neutrophil recruitment in tumor responsible for cancer therapy. Here, a strategy is reported for hijacking neutrophils in vivo using nanoparticles (NPs) to deliver therapeutics into tumor. In a mouse model of melanoma, it is shown that systemically delivered albumin NPs increase in tumor when TA99 antibody is injected; and the NP tumor accumulation is mediated by neutrophils. After the administration of pyropheophorbide-a loaded albumin NPs and TA99, photodynamic therapy significantly suppresses the tumor growth and increases mouse survival compared with treatment with the NPs or TA99. The study reveals a new avenue to treat cancer by NP hitchhiking of immune systems to enhance delivery of therapeutics into tumor sites.

Near-infrared light-triggered thermochemotherapy of cancer using a polymer-gold nanorod conjugate

A biocompatible polymer-gold nanorod (P-AuNR) conjugate was developed as a thermo-chemotherapeutic nano-sized drug carrier for cancer therapy using near-infrared (NIR) light as an external trigger. The amphiphilic polymer, poly(ethylene glycol)-block-poly(caprolactone) (PEG-b-PCL) bearing a disulfide bond, was prepared using a facile synthetic route via copper(I)-free click chemistry and covalently linked to AuNR. The chemical structures and successful conjugation of PEG-b-PCL were analyzed using (1)H NMR and FT-IR. Doxorubicin (DOX), a hydrophobic anticancer drug, was effectively loaded into the hydrophobic PCL domain of P-AuNR through a simple dialysis method. P-AuNR showed longitudinal plasmon resonance absorption at the NIR region, thus generating heat under irradiation at 808 nm. Interestingly, exposure of P-AuNRs to NIR induced a structural change in the PCL block from a crystalline to an amorphous state, leading to the temporally controlled release of DOX. No significant release of DOX was observed from P-AuNRs under physiological conditions (pH 7.4), whereas the release rate of DOX was remarkably enhanced in response to NIR irradiation. In vitro cellular experiments to assess cytotoxicity and intracellular drug release behavior of DOX-P-AuNRs demonstrated that the release of DOX could be selectively regulated by NIR irradiation. Overall, DOX-P-AuNRs might have the potential to overcome the indiscriminate toxicity of free DOX.

Augmenting drug-carrier compatibility improves tumour nanotherapy efficacy

A major goal of cancer nanotherapy is to use nanoparticles as carriers for targeted delivery of anti-tumour agents. The drug-carrier association after intravenous administration is essential for efficient drug delivery to the tumour. However, a large number of currently available nanocarriers are self-assembled nanoparticles whose drug-loading stability is critically affected by the in vivo environment. Here we used in vivo FRET imaging to systematically investigate how drug-carrier compatibility affects drug release in a tumour mouse model. We found the drug's hydrophobicity and miscibility with the nanoparticles are two independent key parameters that determine its accumulation in the tumour. Next, we applied these findings to improve chemotherapeutic delivery by augmenting the parent drug's compatibility; as a result, we achieved better antitumour efficacy. Our results help elucidate nanomedicines' in vivo fate and provide guidelines for efficient drug delivery.

Strategies for improving the intratumoral distribution of liposomal drugs in cancer therapy

INTRODUCTION

A major limitation of current liposomal cancer therapies is the inability of liposome therapeutics to penetrate throughout the entire tumor mass. This inhomogeneous distribution of liposome therapeutics within the tumor has been linked to treatment failure and drug resistance. Both liposome particle transport properties and tumor microenvironment characteristics contribute to this challenge in cancer therapy. This limitation is relevant to both intravenously and intratumorally administered liposome therapeutics.

AREAS COVERED

Strategies to improve the intratumoral distribution of liposome therapeutics are described. Combination therapies of intravenous liposome therapeutics with pharmacologic agents modulating abnormal tumor vasculature, interstitial fluid pressure, extracellular matrix components, and tumor associated macrophages are discussed. Combination therapies using external stimuli (hyperthermia, radiofrequency ablation, magnetic field, radiation, and ultrasound) with intravenous liposome therapeutics are discussed. Intratumoral convection-enhanced delivery (CED) of liposomal therapeutics is reviewed.

EXPERT OPINION

Optimization of the combination therapies and drug delivery protocols are necessary. Further research should be conducted in appropriate cancer types with consideration of physiochemical features of liposomes and their timing sequence. More investigation of the role of tumor associated macrophages in intratumoral distribution is warranted. Intratumoral infusion of liposomes using CED is a promising approach to improve their distribution within the tumor mass.

Compound high-quality criteria: a new vision to guide the development of drugs, current situation

For several decades, the pharmaceutical industry has suffered due to major issues such as reductions of the number of FDA approved drugs and biologics. Several analyses have been highlighted that the 'druglikeness' is one of the strategies to improve succeed rates of screening such as, for instance, high-throughput screening (HTS), and then hits (as starting point), leads and clinical candidates. It is clear that the improvement of compound quality accelerates the drug discovery projects. The monitoring of several indices to avoid 'molecular obesity' (ADMET problems) of final drugs from good-quality 'low-fat' starting points represents today a powerful strategy of optimization process. The development of the new guides to find drugs highlighting attempts at improving the attrition rate from hits to final medicines by focusing on how to improve the druggability of hits, leads and drugs during the drug discovery process represents a key approach to design next better generation of medicines.

"Eat me" imaging and therapy

Clearance of apoptotic debris is a vital role of the innate immune system. Drawing upon principles of apoptotic clearance, convenient delivery vehicles including intrinsic anti-inflammatory characteristics and specificity to immune cells can be engineered to aid in drug delivery. In this article, we examine the use of phosphatidylserine (PtdSer), the well-known "eat-me" signal, in nanoparticle-based therapeutics making them highly desirable "meals" for phagocytic immune cells. Use of PtdSer facilitates engulfment of nanoparticles allowing for imaging and therapy in various pathologies and may result in immunomodulation. Furthermore, we discuss the targeting of the macrophages and other cells at sites of inflammation in disease. A thorough understanding of the immunobiology of "eat-me" signals is requisite for the successful application of "eat-me"-bearing materials in biomedical applications.

Particle-based technologies for osteoarthritis detection and therapy

Osteoarthritis (OA) is a disease characterized by degradation of joints with the development of painful osteophytes in the surrounding tissues. Currently, there are a limited number of treatments for this disease, and many of these only provide temporary, palliative relief. In this review, we discuss particle-based drug delivery systems that can provide targeted and sustained delivery of imaging and therapeutic agents to OA-affected sites. We focus on technologies such as polymeric micelles and nano-/microparticles, liposomes, and dendrimers for their potential treatment and/or diagnosis of OA. Several promising studies are highlighted, motivating the continued development of delivery technologies to improve treatments for OA.

Role of Aromatic Interactions in Temperature-Sensitive Amphiphilic Supramolecular Assemblies

Aromatic interactions were found to greatly influence the temperature-dependent dynamic behavior within supramolecular assemblies. Using an amphiphilic dendron, we systematically changed the hydrophobic groups introducing increasing levels of aromaticity while keeping the hydrophilic part constant. We show that the supramolecular assemblies become less sensitive to temperature changes when aromatic interactions in the aggregate are increased. Conversely, the absence of aromaticity in the hydrophobic moieties produces temperature-sensitive aggregates. These results show that subtle molecular-level interactions can be utilized to control temperature-sensitive behavior in the nanoscale. These findings open up new design strategies to rationally tune the behavior of stimuli-responsive supramolecular assemblies on multiple spatiotemporal scales.

Stimuli-responsive clustered nanoparticles for improved tumor penetration and therapeutic efficacy

A principal goal of cancer nanomedicine is to deliver therapeutics effectively to cancer cells within solid tumors. However, there are a series of biological barriers that impede nanomedicine from reaching target cells. Here, we report a stimuli-responsive clustered nanoparticle to systematically overcome these multiple barriers by sequentially responding to the endogenous attributes of the tumor microenvironment. The smart polymeric clustered nanoparticle (iCluster) has an initial size of ∼100 nm, which is favorable for long blood circulation and high propensity of extravasation through tumor vascular fenestrations. Once iCluster accumulates at tumor sites, the intrinsic tumor extracellular acidity would trigger the discharge of platinum prodrug-conjugated poly(amidoamine) dendrimers (diameter ∼5 nm). Such a structural alteration greatly facilitates tumor penetration and cell internalization of the therapeutics. The internalized dendrimer prodrugs are further reduced intracellularly to release cisplatin to kill cancer cells. The superior in vivo antitumor activities of iCluster are validated in varying intractable tumor models including poorly permeable pancreatic cancer, drug-resistant cancer, and metastatic cancer, demonstrating its versatility and broad applicability.

The effect of nanoparticle size on in vivo pharmacokinetics and cellular interaction

Nanoparticle-based technologies offer exciting new approaches to disease diagnostics and therapeutics. To take advantage of unique properties of nanoscale materials and structures, the size, shape and/or surface chemistry of nanoparticles need to be optimized, allowing their functionalities to be tailored for different biomedical applications. Here we review the effects of nanoparticle size on cellular interaction and in vivo pharmacokinetics, including cellular uptake, biodistribution and circulation half-life of nanoparticles. Important features of nanoparticle probes for molecular imaging and modeling of nanoparticle size effects are also discussed.

Synthesis of linear and cyclic peptide-PEG-lipids for stabilization and targeting of cationic liposome-DNA complexes

Because nucleic acids (NAs) have immense potential value as therapeutics, the development of safe and effective synthetic NA vectors continues to attract much attention. In vivo applications of NA vectors require stabilized, nanometer-scale particles, but the commonly used approaches of steric stabilization with a polymer coat (e.g., PEGylation; PEG=poly(ethylene glycol)) interfere with attachment to cells, uptake, and endosomal escape. Conjugation of peptides to PEG-lipids can improve cell attachment and uptake for cationic liposome-DNA (CL-DNA) complexes. We present several synthetic approaches to peptide-PEG-lipids and discuss their merits and drawbacks. A lipid-PEG-amine building block served as the common key intermediate in all synthetic routes. Assembling the entire peptide-PEG-lipid by manual solid phase peptide synthesis (employing a lipid-PEG-carboxylic acid) allowed gram-scale synthesis but is mostly applicable to linear peptides connected via their N-terminus. Conjugation via thiol-maleimide or strain-promoted (copper-free) azide-alkyne cycloaddition chemistry is highly amenable to on-demand preparation of peptide-PEG-lipids, and the appropriate PEG-lipid precursors are available in a single chemical step from the lipid-PEG-amine building block. Azide-alkyne cycloaddition is especially suitable for disulfide-bridged peptides such as iRGD (cyclic CRGDKGPDC). Added at 10 mol% of a cationic/neutral lipid mixture, the peptide-PEG-lipids stabilize the size of CL-DNA complexes. They also affect cell attachment and uptake of nanoparticles in a peptide-dependent manner, thereby providing a platform for preparing stabilized, affinity-targeted CL-DNA nanoparticles.