Polymer-supported lipid shells, onions, and flowers

Lipid polymer hybrid nanoparticles against lung cancer and their application as inhalable formulation

Lung cancer is a leading cause of global cancer mortality, often treated with chemotherapeutic agents. However, conventional approaches such as oral or intravenous administration of drugs yield low bioavailability and adverse effects. Nanotechnology has unlocked new gateways for delivering medicine to their target sites. Lipid-polymer hybrid nanoparticles (LPHNPs) are one of the nano-scaled delivery platforms that have been studied to exploit advantages of liposomes and polymers, enhancing stability, drug loading, biocompatibility and controlled release. Pulmonary administration of drug-loaded LPHNPs enables direct lung deposition, rapid onset of action and heightened efficacy at low doses of drugs. In this manuscript, we will review the potential of LPHNPs in management of lung cancer through pulmonary administration.

LipoParticles: a lipid membrane coating onto polymer particles to enhance the internalization in osteoblast cells

LipoParticles, core-shell assemblies consisting of a polymer core coated by a lipid membrane, are promising carriers for drug delivery applications with intracellular targets. This is of great interest since it is actually challenging to treat infections involving intracellular bacteria such as bone and joint infections where the bacteria are hidden in osteoblast cells. The present work reports for the first time to the best of our knowledge the proof of enhanced internalization of particles in osteoblast cells thanks to a lipid coating of particles (= LipoParticles). The ca. 300 nm-sized assemblies were elaborated by reorganization of liposomes (composed of DPPC/DPTAP 10/90 mol/mol) onto the surface of poly(lactic-co-glycolic acid) (PLGA) particles, and were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), and zetametry. Optimization of these assemblies was also performed by adding poly(ethylene glycol) (PEG) chains on their surface (corresponding to a final formulation of DPPC/DPTAP/DPPE-PEG5000 8/90/2 mol/mol/mol). Interestingly, this provided them colloidal stability after their 20-fold dilution in PBS or cell culture medium, and made possible their freeze-drying without forming aggregates after their re-hydration. Their non-cytotoxicity towards a human osteoblast cell line (MG63) was also demonstrated. The enhanced internalization of LipoParticles in this MG63 cell line, in comparison with PLGA particles, was proven by observations with a confocal laser scanning microscope, as well as by flow cytometry assays. Finally, this efficient internalization of LipoParticles in MG63 cells was confirmed by TEM on ultrathin sections, which also revealed localization close to intracellular Staphylococcus aureus.

Advances in Hybrid Vesicular-based Drug Delivery Systems: Improved Biocompatibility, Targeting, Therapeutic Efficacy and Pharmacokinetics of Anticancer Drugs

Anticancer drugs and diagnostics can be transported in nanoscale vesicles that provide a flexible platform. A hybrid nanoparticle, a nano assembly made up of many types of nanostructures, has the greatest potential to perform these two activities simultaneously. Nanomedicine has shown the promise of vesicular carriers based on lipopolymersomes, lipid peptides, and metallic hybrid nano-vesicle systems. However, there are significant limitations that hinder the clinical implementation of these systems at the commercial scale, such as low productivity, high energy consumption, expensive setup, long process durations, and the current cancer therapies described in this article. Combinatorial hybrid systems can be used to reduce the above limitations. A greater therapeutic index and improved clinical results are possible with hybrid nanovesicular systems, which integrate the benefits of many carriers into a single structure. Due to their unique properties, cell-based drug delivery systems have shown tremendous benefits in the treatment of cancer. Nanoparticles (NPs) can benefit significantly from the properties of erythrocytes and platelets, which are part of the circulatory cells and circulate for a long time. Due to their unique physicochemical properties, nanomaterials play an essential role in cell-based drug delivery. Combining the advantages of different nanomaterials and cell types gives the resulting delivery systems a wide range of desirable properties. NPs are nextgeneration core-shell nanostructures that combine a lipid shell with a polymer core. The fabrication of lipid-polymer hybrid NPs has recently undergone a fundamental shift, moving from a two-step to a one-step technique based on the joint self-assembly of polymers and lipids. Oncologists are particularly interested in this method as a combinatorial drug delivery platform because of its two-in-one structure. This article addresses various preparative methods for the preparation of hybrid nano-vesicular systems. It also discusses the cellular mechanism of hybrid nano-vesicular systems and describes the thorough knowledge of various hybrid vesicular systems.

Design and Development of a New Type of Hybrid PLGA/Lipid Nanoparticle as an Ursolic Acid Delivery System against Pancreatic Ductal Adenocarcinoma Cells

Despite many attempts, trials, and treatment procedures, pancreatic ductal adenocarcinoma (PDAC) still ranks among the most deadly and treatment-resistant types of cancer. Hence, there is still an urgent need to develop new molecules, drugs, and therapeutic methods against PDAC. Naturally derived compounds, such as pentacyclic terpenoids, have gained attention because of their high cytotoxic activity toward pancreatic cancer cells. Ursolic acid (UA), as an example, possesses a wide anticancer activity spectrum and can potentially be a good candidate for anti-PDAC therapy. However, due to its minimal water solubility, it is necessary to prepare an optimal nano-sized vehicle to overcome the low bioavailability issue. Poly(lactic-co-glycolic acid) (PLGA) polymeric nanocarriers seem to be an essential tool for ursolic acid delivery and can overcome the lack of biological activity observed after being incorporated within liposomes. PLGA modification, with the addition of PEGylated phospholipids forming the lipid shell around the polymeric core, can provide additional beneficial properties to the designed nanocarrier. We prepared UA-loaded hybrid PLGA/lipid nanoparticles using a nanoprecipitation method and subsequently performed an MTT cytotoxicity assay for AsPC-1 and BxPC-3 cells and determined the hemolytic effect on human erythrocytes with transmission electron microscopic (TEM) visualization of the nanoparticles and their cellular uptake. Hybrid UA-loaded lipid nanoparticles were also examined in terms of their stability, coating dynamics, and ursolic acid loading. We established innovative and repeatable preparation procedures for novel hybrid nanoparticles and obtained biologically active nanocarriers for ursolic acid with an IC50 below 20 µM, with an appropriate size for intravenous dosage (around 150 nm), high homogeneity of the sample (below 0.2), satisfactory encapsulation efficiency (up to 70%) and excellent stability. The new type of hybrid UA-PLGA nanoparticles represents a further step in the development of potentially effective PDAC therapies based on novel, biologically active, and promising triterpenoids.

TPGS/hyaluronic acid dual-functionalized PLGA nanoparticles delivered through dissolving microneedles for markedly improved chemo-photothermal combined therapy of superficial tumor

Nanoparticles (NPs) have shown potential in cancer therapy, while a single administration conferring a satisfactory outcome is still unavailable. To address this issue, the dissolving microneedles (DMNs) were developed to locally deliver functionalized NPs with combined chemotherapy and photothermal therapy (PTT). α-Tocopheryl polyethylene glycol succinate (TPGS)/hyaluronic acid (HA) dual-functionalized PLGA NPs (HD10 NPs) were fabricated to co-load paclitaxel and indocyanine green. HD10 NPs significantly enhanced the cytotoxicity of low-dose paclitaxel because of active and mitochondrial targeting by HA and TPGS, respectively. PTT could further sensitize tumor cells toward chemotherapy by promoting apoptosis into the advanced period, highly activating caspase 3 enzyme, and significantly reducing the expression of survivin and MMP-9 proteins. Further, the anti-tumor effects of HD10 NPs delivered through different administration routes were conducted on the 4T1 tumor-bearing mice. After a single administration, HD10 NPs delivered with DMNs showed the best anti-tumor effect when giving chemotherapy alone. As expected, the anti-tumor effect was profoundly enhanced after combined therapy, and complete tumor ablation was achieved in the mice treated with DMNs and intra-tumor injection. Moreover, DMNs showed better safety due to moderate hyperthermia. Therefore, the DMNs along with combined chemo-photothermal therapy provide a viable treatment option for superficial tumors.

Role of stealth lipids in nanomedicine-based drug carriers

The domain of nanomedicine owns a wide-ranging variety of lipid-based drug carriers, and novel nanostructured drug carriersthat are further added to this range every year. The primary goal behind the exploration of any new lipid-based nanoformulation is the improvement of the therapeutic index of the concerned drug molecule along with minimization in the associated side-effects. However, for maintaining a sustained delivery of these intravenously injected lipoidal nanomedicines to the targeted tissues and organ systems in the body, longer circulation in the bloodstream, as well as their stability, are important. After administration, upon recognition as foreign entities in the body, these systems are rapidly cleared by the cells associated with the mononuclear phagocyte system. In order to provide these lipid-based systems with long circulation characteristics, techniques such as coating of the lipoidal surface with an inert polymeric material like polyethylene glycol (PEG) assists in imparting 'stealth properties' to these nanoformulations for avoiding recognition by the macrophages of the immune system. In this review, detailed importance is given to the hydrophilic PEG polymer and the role played by PEG-linked lipid polymers in the field of nanomedicine-based drug carriers. The typical structure and classification of stealth lipids, clinical utility, assemblage techniques, physicochemical characterization, and factors governing the in-vivo performance of the PEG-linked lipids containing formulations will be discussed. Eventually, the novel concept of accelerated blood clearance (ABC) phenomenon associated with the use of PEGylated therapeutics will be deliberated.

Co-adsorption of synthetic Mincle agonists and antigen to silica nanoparticles for enhanced vaccine activity: A formulation approach to co-delivery

To date there is no clinically approved adjuvant to drive a protective T-helper cell 17 (Th17) immune response against Mycobacterium tuberculosis (Mtb). Trehalose Dimycolate (TDM) is a glycolipid molecule found in the cell wall of Mtb and similar species. Our team has discovered novel synthetic TDM derivatives that target Mincle receptors and when presented on the surface of amine functionalized silica nanoparticles (A-SNPs) adopt the requisite supramolecular structure for Mincle receptor agonism. Here we describe the preparation and characterization methods for these critical silica nanoparticles (SNPs) co-loaded with Mincle agonists (MAs) and a model antigen. In this work, A-SNPs with a particle diameter of 246 ± 11 nm were prepared and examined for co-adsorption of two synthetic MAs along with ovalbumin (OVA). Due to the insolubility of the studied MAs in aqueous environment, aggregation of the MAs made separation of the adjuvant-loaded A-SNPs from the free-form MAs via centrifugation very challenging. To facilitate separation, we synthesized modified SNPs with comparable amine surface functionalization to the original A-SNPs, but with a superparamagnetic iron oxide core (M-A-SNPs), to allow for magnetic separation. We also substituted Alexa Fluor 488-labeled ovalbumin (AF 488 OVA) for the un-tagged OVA to improve the sensitivity of our quantitation method. A RP-HPLC method was developed to simultaneously determine the amount of adsorption of both the Mincle adjuvant and the model antigen to the A-SNPs. AF488 OVA demonstrated higher than 90% adsorption, with or without the co-adsorption of MAs. Likewise, MAs exhibited higher than 80% adsorption in the presence or absence of antigen. The developed formulations were tested in vitro using murine RAW cells and human peripheral blood mononuclear cells, exhibiting good cytokine induction in both cell lines. Results from these studies indicate that A-SNPs could be used as a customizable presentation platform to co-deliver antigens along with different MAs of varying structural features and biophysical properties.

Combating Intracellular Pathogens with Nanohybrid-Facilitated Antibiotic Delivery

BACKGROUND

Lipid polymer hybrid nanoparticles (LPHNPs) have been widely investigated in drug and gene delivery as well as in medical imaging. A knowledge of lipid-based surface engineering and its effects on how the physicochemical properties of LPHNPs affect the cell-nanoparticle interactions, and consequently how it influences the cytological response, is in high demand.

METHODS

Herein, we have engineered antibiotic-loaded (doxycycline or vancomycin) LPHNPs with cationic and zwitterionic lipids and examined the effects on their physicochemical characteristics (size and charge), antibiotic entrapment efficiency, and the in vitro intracellular bacterial killing efficiency against Mycobacterium smegmatis or Staphylococcus aureus infected macrophages.

RESULTS

The incorporation of cationic or zwitterionic lipids in the LPHNP formulation resulted in a size reduction in LPHNPs formulations and shifted the surface charge of bare NPs towards positive or neutral values. Also observed were influences on the drug incorporation efficiency and modulation of the drug release from the biodegradable polymeric core. The therapeutic efficacy of LPHNPs loaded with vancomycin was improved as its minimum inhibitory concentration (MIC) (2 µg/mL) versus free vancomycin (4 µg/mL). Importantly, our results show a direct relationship between the cationic surface nature of LPHNPs and its intracellular bacterial killing efficiency as the cationic doxycycline or vancomycin loaded LPHNPs reduced 4 or 3 log CFU respectively versus the untreated controls.

CONCLUSION

In our study, modulation of surface charge in the nanomaterial formulation increased macrophage uptake and intracellular bacterial killing efficiency of LPHNPs loaded with antibiotics, suggesting alternate way for optimizing their use in biomedical applications.

Lipid-polymer hybrid nanoparticles as a next-generation drug delivery platform: state of the art, emerging technologies, and perspectives

Lipid-polymer hybrid nanoparticles (LPHNPs) are next-generation core-shell nanostructures, conceptually derived from both liposome and polymeric nanoparticles (NPs), where a polymer core remains enveloped by a lipid layer. Although they have garnered significant interest, they remain not yet widely exploited or ubiquitous. Recently, a fundamental transformation has occurred in the preparation of LPHNPs, characterized by a transition from a two-step to a one-step strategy, involving synchronous self-assembly of polymers and lipids. Owing to its two-in-one structure, this approach is of particular interest as a combinatorial drug delivery platform in oncology. In particular, the outer surface can be decorated in multifarious ways for active targeting of anticancer therapy, delivery of DNA or RNA materials, and use as a diagnostic imaging agent. This review will provide an update on recent key advancements in design, synthesis, and bioactivity evaluation as well as discussion of future clinical possibilities of LPHNPs.

Cross-Platform Comparison of Therapeutic Delivery from Multilamellar Lipid-Coated Polymer Nanoparticles

Significant efforts have been invested in finding a delivery system that can encapsulate and deliver therapeutics. Core-shell polymer-lipid hybrid nanoparticles have been studied as a promising platform because of their mechanical stability, narrow size distribution, biocompatibility, and ability to co-deliver diverse drugs. Here, novel core-shell nanoparticles based on a poly(lactic-co-glycolic acid) (PLGA) core and multilamellar lipid shell are designed, where the lipid bilayers are crosslinked between the two adjacent bilayers (PLGA-ICMVs). The cross-platform performance of the nanoparticles to other polymer-lipid hybrid platforms is examined, including physicochemical characteristics, ability to encapsulate a variety of therapeutics, biocompatibility, and functionality as a vaccine delivery platform. Differential abilities of nanoparticle systems to encapsulate distinct pharmaceutics are observed, which suggest careful consideration of the platform chosen depending on the therapeutic agent and desired function. The novel PLGA-ICMV platform herein demonstrates great potential in stably encapsulating water-soluble agents and therefore is an attractive platform for therapeutic delivery.

Core-shell nanoparticles for targeted and combination antiretroviral activity in gut-homing T cells

A major sanctuary site for HIV infection is the gut-associated lymphoid tissue (GALT). The α4β7 integrin gut homing receptor is a promising therapeutic target for the virus reservoir because it leads to migration of infected cells to the GALT and facilitates HIV infection. Here, we developed a core-shell nanoparticle incorporating the α4β7 monoclonal antibody (mAb) as a dual-functional ligand for selectively targeting a protease inhibitor (PI) to gut-homing T cells in the GALT while simultaneously blocking HIV infection. Our nanoparticles significantly reduced cytotoxicity of the PI and enhanced its in vitro antiviral activity in combination with α4β7 mAb. We demonstrate targeting function of our nanocarriers in a human T cell line and primary cells isolated from macaque ileum, and observed higher in vivo biodistribution to the murine small intestines where they accumulate in α4β7+ cells. Our LCNP shows the potential to co-deliver ARVs and mAbs for eradicating HIV reservoirs.

Anisotropic biodegradable lipid coated particles for spatially dynamic protein presentation

There has been growing interest in the use of particles coated with lipids for applications ranging from drug delivery, gene delivery, and diagnostic imaging to immunoengineering. To date, almost all particles with lipid coatings have been spherical despite emerging evidence that non-spherical shapes can provide important advantages including reduced non-specific elimination and increased target-specific binding. We combine control of core particle geometry with control of particle surface functionality by developing anisotropic, biodegradable ellipsoidal particles with lipid coatings. We demonstrate that these lipid coated ellipsoidal particles maintain advantageous properties of lipid polymer hybrid particles, such as the ability for modular protein conjugation to the particle surface using versatile bioorthogonal ligation reactions. In addition, they exhibit biomimetic membrane fluidity and demonstrate lateral diffusive properties characteristic of natural membrane proteins. These ellipsoidal particles simultaneously provide benefits of non-spherical particles in terms of stability and resistance to non-specific phagocytosis by macrophages as well as enhanced targeted binding. These biomaterials provide a novel and flexible platform for numerous biomedical applications.

STATEMENT OF SIGNIFICANCE

The research reported here documents the ability of non-spherical polymeric particles to be coated with lipids to form anisotropic biomimetic particles. In addition, we demonstrate that these lipid-coated biodegradable polymeric particles can be conjugated to a wide variety of biological molecules in a "click-like" fashion. This is of interest due to the multiple types of cellular mimicry enabled by this biomaterial based technology. These features include mimicry of the highly anisotropic shape exhibited by cells, surface presentation of membrane bound protein mimetics, and lateral diffusivity of membrane bound substrates comparable to that of a plasma membrane. This platform is demonstrated to facilitate targeted cell binding while being resistant to non-specific cellular uptake. Such a platform could allow for investigations into how physical parameters of a particle and its surface affect the interface between biomaterials and cells, as well as provide biomimetic technology platforms for drug delivery and cellular engineering.

Lipid-polymer hybrid nanocarriers for delivering cancer therapeutics

Cancer remained a major cause of death providing diversified challenges in terms of treatment including non-specific toxicity, chemoresistance and relapse. Nanotechnology- based delivery systems grabbed tremendous attention for delivering cancer therapeutics as they provide benefits including controlled drug release, improved biological half-life, reduced toxicity and targeted delivery. Majority of the nanocarriers consists of either a polymer or a lipid component along with other excipients to stabilize the colloidal system. Lipid-based systems provide advantages like better entrapment efficiency, scalability and low- cost raw materials, however, suffer from limitations including instability, a burst release of the drug, and limited surface functionalization. On the other hand, polymeric systems provide an excellent diversity of chemical modifications, stability, controlled release, however limited drug loading capacities and scale up limit their use. Hybrid nanocarriers consisting of lipid and polymer were able to overcome some of these disadvantages while retaining the advantages of both the systems. Designing a stable lipid-polymer hybrid system requires a thorough understanding of the material properties and their behavior in in vitro and in vivo environments. This review highlights the current status and future prospects of lipid-polymer hybrid systems with a particular focus on cancer nanotherapeutics.

Preparation of particulate polymeric therapeutics for medical applications

Particulate therapeutics fabricated from polymeric materials have become increasingly popular over the past several decades. Generally, polymeric systems are easy to synthesize and have tunable parameters, giving them significant potential for wide use in the clinic. They come in many different forms, including as nanoparticles, microparticles, and colloidal gels. In this review, we discuss the current preparation methods for each type of platform, as well as some representative applications. To achieve enhanced performance, lipid coatings and other surface modification techniques for introducing additional functionality are also mentioned. We hope that, by outlining the various methods and techniques for their preparation, it will be possible to provide insights into the utility of these polymeric platforms and further encourage their development for biomedical applications.

Gelatin modified lipid nanoparticles for anti- viral drug delivery

The major challenges to clinical application of zidovudine are its moderate aqueous solubility and relative short half-life and serious side effects due to frequent administrations. We investigated the preparation of zidovudine-loaded nanoparticles based on lipids which were further modified with the polymer gelatin. Formulation and stability of the modified nanoparticles were analysed from the physico-chemical characterizations. The interactions of nanoparticles with blood components were tested by haemolysis and aggregation studies. The drug content and entrapment efficiencies were assessed by UV analysis. The effect of nanoparticles on protein adsorption was assessed by native polyacrylamide gel electrophoresis (PAGE). In vitro release studies showed a sustained release profile of zidovudine. In vitro cytotoxicity and cellular uptake of the zidovudine-loaded nanoparticles were performed in MCF-7 and neuro 2a brain cells. The enhanced cellular internalization of drug loaded modified nanoparticles in both the cell lines were revealed by fluorescence microscopy. Hence the present study focuses on the feasibility of zidovudine-loaded polymer modified lipid nanoparticles as carriers for safe and efficient HIV/AIDS therapy.

Lipid-Based Drug Delivery Systems in Cancer Therapy: What Is Available and What Is Yet to Come

Cancer is a leading cause of death in many countries around the world. However, the efficacy of current standard treatments for a variety of cancers is suboptimal. First, most cancer treatments lack specificity, meaning that these treatments affect both cancer cells and their normal counterparts. Second, many anticancer agents are highly toxic, and thus, limit their use in treatment. Third, a number of cytotoxic chemotherapeutics are highly hydrophobic, which limits their utility in cancer therapy. Finally, many chemotherapeutic agents exhibit short half-lives that curtail their efficacy. As a result of these deficiencies, many current treatments lead to side effects, noncompliance, and patient inconvenience due to difficulties in administration. However, the application of nanotechnology has led to the development of effective nanosized drug delivery systems known commonly as nanoparticles. Among these delivery systems, lipid-based nanoparticles, particularly liposomes, have shown to be quite effective at exhibiting the ability to: 1) improve the selectivity of cancer chemotherapeutic agents; 2) lower the cytotoxicity of anticancer drugs to normal tissues, and thus, reduce their toxic side effects; 3) increase the solubility of hydrophobic drugs; and 4) offer a prolonged and controlled release of agents. This review will discuss the current state of lipid-based nanoparticle research, including the development of liposomes for cancer therapy, different strategies for tumor targeting, liposomal formulation of various anticancer drugs that are commercially available, recent progress in liposome technology for the treatment of cancer, and the next generation of lipid-based nanoparticles.

Biodegradable, Tethered Lipid Bilayer-Microsphere Systems with Membrane-Integrated α-Helical Peptide Anchors

Supported lipid bilayers (SLBs) are ideally suited for the study of biomembrane-biomembrane interactions and for the biomimicry of cell-to-cell communication, allowing for surface ligand displays that contain laterally mobile elements. However, the SLB paradigm does not include three-dimensionality and biocompatibility. As a way to bypass these limitations, we have developed a biodegradable form of microsphere SLBs, also known as proteolipobeads (PLBs), using PLGA microspheres. Microspheres were synthesized using solvent evaporation and size selected with fluorescence activated cell sorting (FACS). Biomembranes were covalently tethered upon fusion to microsphere supports via short-chain PEG spacers connecting membrane-integrated α-helical peptides and the microsphere surface, affecting membrane diffusivity and mobility as indicated by confocal FRAP analysis. Membrane heterogeneities, which are attributed to PLGA hydrophobicity and rough surface topography, are curtailed by the addition of PEG tethers. This method allows for the presentation of tethered, laterally mobile biomembranes in three dimensions with functionally embedded attachment peptides for mobile ligand displays.

Exploiting Conjugated Polyelectrolyte Photophysics toward Monitoring Real-Time Lipid Membrane-Surface Interaction Dynamics at the Single-Particle Level

Herein we report the real-time observation of the interaction dynamics between cationic liposomes flowing in solution and a surface-immobilized charged scaffolding formed by the deposition of conjugated polyanion poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylenevinylene (MPS-PPV) onto 100-nm-diameter SiO2 nanoparticles (NPs). Contact of the freely floating liposomes with the polymer-coated surfaces led to the formation of supported lipid bilayers (SLBs). The interaction of the incoming liposomes with MPS-PPV adsorbed on individual SiO2 nanoparticles promoted the deaggregation of the polymer conformation and led to large emission intensity enhancements. Single-particle total internal reflection fluorescence microscopy studies exploited this phenomenon as a way to monitor the deformation dynamics of liposomes on surface-immobilized NPs. The MPS-PPV emission enhancement (up to 25-fold) reflected on the extent of membrane contact with the surface of the NP and was correlated with the size of the incoming liposome. The time required for the MPS-PPV emission to reach a maximum (ranging from 400 to 1000 ms) revealed the dynamics of membrane deformation and was also correlated with the liposome size. Cryo-TEM experiments complemented these results by yielding a structural view of the process. Immediately following the mixing of liposomes and NPs the majority of NPs had one or more adsorbed liposomes, yet the presence of a fully formed SLB was rare. Prolonged incubation of liposomes and NPs showed completely formed SLBs on all of the NPs, confirming that the liposomes eventually ruptured to form SLBs. We foresee that the single-particle studies we report herein may be readily extended to study membrane dynamics of other lipids including cellular membranes in live cell studies and to monitor the formation of polymer-cushioned SLBs.

Nanoengineered drug delivery systems for enhancing antibiotic therapy

Formulation scientists are recognizing nanoengineered drug delivery systems as an effective strategy to overcome limitations associated with antibiotic drug therapy. Antibiotics encapsulated into nanodelivery systems will contribute to improved management of patients with various infectious diseases and to overcoming the serious global burden of antibiotic resistance. An extensive review of several antibiotic-loaded nanocarriers that have been formulated to target drugs to infectious sites, achieve controlled drug release profiles, and address formulation challenges, such as low-drug entrapment efficiencies, poor solubility and stability is presented in this paper. The physicochemical properties and the in vitro/in vivo performances of various antibiotic-loaded delivery systems, such as polymeric nanoparticles, micelles, dendrimers, liposomes, solid lipid nanoparticles, lipid-polymer hybrid nanoparticles, nanohybirds, nanofibers/scaffolds, nanosheets, nanoplexes, and nanotubes/horn/rods and nanoemulsions, are highlighted and evaluated. Future studies that will be essential to optimize formulation and commercialization of these antibiotic-loaded nanosystems are also identified. The review presented emphasizes the significant formulation progress achieved and potential that novel nanoengineered antibiotic drug delivery systems have for enhancing the treatment of patients with a range of infections.

Lipid polymer hybrid as emerging tool in nanocarriers for oral drug delivery

The oral route for drug delivery is a widely accepted route. For that reason, many researchers are currently working to develop efficient oral drug delivery systems. Use of polymeric nanoparticles (NPs) and lipid carrier systems, including liposomes, solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLC), has limitations such as drug leakage and high water content of dispersions. Thus, lipid polymer hybrid nanoparticles (LPNs) have been explored by the researchers to provide a better effect using properties of both polymers and lipids. The present review is focused on the challenges, possibilities, and future perspectives of LPNs for oral delivery.

Antigen delivery by lipid-enveloped PLGA microparticle vaccines mediated by in situ vesicle shedding

Lipid-coated poly(lactide-co-glycolide) microparticles (LCMPs) consist of a solid polymer core wrapped by a surface lipid bilayer. Previous studies demonstrated that immunization with LCMPs surface-decorated with nanograms of antigen elicit potent humoral immune responses in mice. However, the mechanism of action for these vaccines remained unclear, as LCMPs are too large to drain efficiently to lymph nodes from the vaccination site. Here, we characterized the stability of the lipid envelope of LCMPs and discovered that in the presence of serum the lipid coating of the particles spontaneously delaminates, shedding antigen-displaying vesicles. Lipid delamination generated 180 nm liposomes in a temperature- and lipid/serum-dependent manner. Vesicle shedding was restricted by inclusion of high-T_M lipids or cholesterol in the LCMP coating. Administration of LCMPs bearing stabilized lipid envelopes generated weaker antibody responses than those of shedding-competent LCMPs, suggesting that in situ release of antigen-loaded vesicles plays a key role in the remarkable potency of LCMPs as vaccine adjuvants.

Biomaterials for nanoparticle vaccine delivery systems

Subunit vaccination benefits from improved safety over attenuated or inactivated vaccines, but their limited capability to elicit long-lasting, concerted cellular and humoral immune responses is a major challenge. Recent studies have demonstrated that antigen delivery via nanoparticle formulations can significantly improve immunogenicity of vaccines due to either intrinsic immunostimulatory properties of the materials or by co-entrapment of molecular adjuvants such as Toll-like receptor agonists. These studies have collectively shown that nanoparticles designed to mimic biophysical and biochemical cues of pathogens offer new exciting opportunities to enhance activation of innate immunity and elicit potent cellular and humoral immune responses with minimal cytotoxicity. In this review, we present key research advances that were made within the last 5 years in the field of nanoparticle vaccine delivery systems. In particular, we focus on the impact of biomaterials composition, size, and surface charge of nanoparticles on modulation of particle biodistribution, delivery of antigens and immunostimulatory molecules, trafficking and targeting of antigen presenting cells, and overall immune responses in systemic and mucosal tissues. This review describes recent progresses in the design of nanoparticle vaccine delivery carriers, including liposomes, lipid-based particles, micelles and nanostructures composed of natural or synthetic polymers, and lipid-polymer hybrid nanoparticles.

Intra-lymph node injection of biodegradable polymer particles

Generation of adaptive immune response relies on efficient drainage or trafficking of antigen to lymph nodes for processing and presentation of these foreign molecules to T and B lymphocytes. Lymph nodes have thus become critical targets for new vaccines and immunotherapies. A recent strategy for targeting these tissues is direct lymph node injection of soluble vaccine components, and clinical trials involving this technique have been promising. Several biomaterial strategies have also been investigated to improve lymph node targeting, for example, tuning particle size for optimal drainage of biomaterial vaccine particles. In this paper we present a new method that combines direct lymph node injection with biodegradable polymer particles that can be laden with antigen, adjuvant, or other vaccine components. In this method polymeric microparticles or nanoparticles are synthesized by a modified double emulsion protocol incorporating lipid stabilizers. Particle properties (e.g. size, cargo loading) are confirmed by laser diffraction and fluorescent microscopy, respectively. Mouse lymph nodes are then identified by peripheral injection of a nontoxic tracer dye that allows visualization of the target injection site and subsequent deposition of polymer particles in lymph nodes. This technique allows direct control over the doses and combinations of biomaterials and vaccine components delivered to lymph nodes and could be harnessed in the development of new biomaterial-based vaccines.

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.

Immunogenicity of membrane-bound HIV-1 gp41 membrane-proximal external region (MPER) segments is dominated by residue accessibility and modulated by stereochemistry

Structural characterization of epitope-paratope pairs has contributed to the understanding of antigenicity. By contrast, few structural studies relate to immunogenicity, the process of antigen-induced immune responses in vivo. Using a lipid-arrayed membrane-proximal external region (MPER) of HIV-1 glycoprotein 41 as a model antigen, we investigated the influence of physicochemical properties on immunogenicity in relation to structural modifications of MPER/liposome vaccines. Anchoring the MPER to the membrane via an alkyl tail or transmembrane domain retained the MPER on liposomes in vivo, while preserving MPER secondary structure. However, structural modifications that affected MPER membrane orientation and antigenic residue accessibility strongly impacted induced antibody responses. The solvent-exposed MPER tryptophan residue (Trp-680) was immunodominant, focusing immune responses, despite sequence variability elsewhere. Nonetheless, immunogenicity could be readily manipulated using site-directed mutagenesis or structural constraints to modulate amino acid surface display. These studies provide fundamental insights for immunogen design aimed at targeting B cell antibody responses.

How nanotechnology can enhance docetaxel therapy

Docetaxel has been recognized as one of the most efficient anticancer drugs over the past decade; however, its poor water solubility and systemic toxicity have greatly limited its clinical application. In recent decades, the emergence of nanotechnology has provided new drug delivery systems for docetaxel, which can improve its water solubility, minimize the side effects and increase the tumor-targeting distribution by passive or active targeting. This review focuses on the research progress in nanoformulations related to docetaxel delivery – such as polymer-based, lipid-based, and lipid-polymer hybrid nanocarriers, as well as inorganic nanoparticles – addressing their structures, characteristics, preparation, physicochemical properties, methods by which drugs are loaded into them, and their in vitro and in vivo efficacies. Further, the targeted ligands used in the docetaxel nanoformulations, such as monoclonal antibodies, peptides, folic acid, transferrin, aptamers and hyaluronic acid, are described. The issues to overcome before docetaxel nanoformulations can be used in clinical and commercial applications are also discussed.

Combinational delivery of lipid-enveloped polymeric nanoparticles carrying different peptides for anti-tumor immunotherapy

AIM

The authors aimed to investigate whether nanotechnology-based delivery of antigenic peptides is feasible for efficiently inducing anti-tumor cytotoxic T lymphocyte responses through vaccination.

MATERIALS & METHODS

Three different murine melanoma antigens were entrapped in lipid-coated poly(D,L-lactide-co-glycolide) nanoparticles (NPs) by the double emulsion method.

RESULTS

The loading efficiency of hydrophilic peptides was greatly improved when lipids were introduced to formulate lipid-coated NPs. The lipid-coated NPs carrying a single peptide and/or combinations of multiple lipid-coated NPs carrying antigenic peptides were characterized in vitro and in vivo in a C57/BL6 (B6) mouse model. Both the single melanoma antigen peptide-loaded NPs and combinational delivery of lipid-coated NPs carrying different peptides could induce antigen-specific T-cell responses. However, single peptide-loaded NPs failed to significantly delay the growth of subcutaneously inoculated B16 melanoma cells in a prophylactic setting. By contrast, the combinational delivery of lipid-coated NPs carrying different peptides significantly suppressed growth of inoculated B16 melanoma cells.

Targeted delivery of 10-hydroxycamptothecin to human breast cancers by cyclic RGD-modified lipid-polymer hybrid nanoparticles

Lipid-polymer hybrid nanoparticles (NPs) combining the positive attributes of both liposomes and polymeric NPs are increasingly being considered as promising candidates to carry therapeutic agents safely and efficiently into targeted sites. Herein, a modified emulsification technique was developed and optimized for the targeting lipid-polymer hybrid NPs fabrication; the surface properties and stability of the hybrid NPs were systematically investigated, which confirmed that the hybrid NPs consisted of a poly (lactide-co-glycolide) core with ∼90% surface coverage of the lipid monolayer and a ∼4.4 nm hydrated polyethylene glycol (PEG) shell. Optimization results showed that the lipid:polymer mass ratio and the lipid-PEG:lipid molar ratio could affect the size, lipid association efficiency and stability of hybrid NPs. Furthermore, a model chemotherapy drug, 10-hydroxycamptothecin, was encapsulated into hybrid NPs with a higher drug loading compared to PLGA NPs. Surface modification of the lipid layer and the PEG conjugated targeting ligand did not affect their drug release kinetics. Finally, the cytotoxicity and cellular uptake studies indicated that the lipid coverage and the c(RGDyk) conjugation of the hybrid NPs gained a significantly enhanced ability of cell killing and endocytosis. Our results suggested that lipid-polymer hybrid NPs prepared by the modified emulsion technique have great potential to be utilized as an engineered drug delivery system with precise control ability of surface targeting modification.

Lipid-enveloped hybrid nanoparticles for drug delivery

Recent advances in nanotechnology and material sciences have promoted the development of nanomedicine. Among the formulations developed, novel lipid-enveloped hybrid nanoparticles have attracted more attention because of their special structure, properties and clinical applicability. The hybrid nanoparticles are composed of a hydrophilic PEG shell, a nano-sized polymeric or inorganic core and a lipid mono- or bi-layer between the core and PEG shell. This kind of nanoparticle possesses both the characteristics of liposomes and nanoparticles which endows it with many advantages like long circulation, high drug loading efficiency, high stability and biocompatibility, controlled release properties, and drug cocktail delivery. This review describes the recent developments of lipid-enveloped hybrid nanoparticles in cancer treatment, including the fabrication methods, formulations and applications of these hybrid nanoparticles. We expect that the continuing development of lipid-based nanomedicine will greatly improve cancer treatment.

Engineering nano- and microparticles to tune immunity

The immune system can be a cure or cause of disease, fulfilling a protective role in attacking cancer or pathogenic microbes but also causing tissue destruction in autoimmune disorders. Thus, therapies aimed to amplify or suppress immune reactions are of great interest. However, the complex regulation of the immune system, coupled with the potential systemic side effects associated with traditional systemic drug therapies, has presented a major hurdle for the development of successful immunotherapies. Recent progress in the design of synthetic micro- and nano-particles that can target drugs, deliver imaging agents, or stimulate immune cells directly through their physical and chemical properties is leading to new approaches to deliver vaccines, promote immune responses against tumors, and suppress autoimmunity. In addition, novel strategies, such as the use of particle-laden immune cells as living targeting agents for drugs, are providing exciting new approaches for immunotherapy. This progress report describes recent advances in the design of micro- and nano-particles for immunotherapies and diagnostics.

LIPID–POLYMER HYBRID NANOPARTICLES: SYNTHESIS, CHARACTERIZATION AND APPLICATIONS

Nanotechnology has been extensively explored in the past decade to develop a myriad of functional nanostructures to facilitate the delivery of therapeutic and imaging agents for various medical applications. Liposomes and polymeric nanoparticles represent two primary delivery vehicles that are currently under investigation. While many advantages of these two particle platforms have been disclosed, some intrinsic limitations remain to limit their applications at certain extent. Recently, a new type of nanoparticle platform, named lipid–polymer hybrid nanoparticle, has been developed that combines the positive attributes of both liposomes and polymeric nanoparticles while excluding some of their shortages. This new nanoparticle consists of a hydrophobic polymeric core, a lipid shell surrounding the polymeric core, and a hydrophilic polymer stealth layer outside the lipid shell. In this review, we first introduce the synthesis and surface functionalization techniques of the lipid–polymer hybrid nanoparticle, followed by a review of typical characterization of the particles. We then summarize the current and potential medical applications of this new nanoparticle as a delivery vehicle of therapeutic and imaging agents. Finally we highlight some challenges faced in further developing this robust delivery platform.

Antigen-displaying lipid-enveloped PLGA nanoparticles as delivery agents for a Plasmodium vivax malaria vaccine

The parasite Plasmodium vivax is the most frequent cause of malaria outside of sub-Saharan Africa, but efforts to develop viable vaccines against P. vivax so far have been inadequate. We recently developed pathogen-mimicking polymeric vaccine nanoparticles composed of the FDA-approved biodegradable polymer poly(lactide-co-glycolide) acid (PLGA) “enveloped” by a lipid membrane. In this study, we sought to determine whether this vaccine delivery platform could be applied to enhance the immune response against P. vivax sporozoites. A candidate malaria antigen, VMP001, was conjugated to the lipid membrane of the particles, and an immunostimulatory molecule, monophosphoryl lipid A (MPLA), was incorporated into the lipid membranes, creating pathogen-mimicking nanoparticle vaccines (VMP001-NPs). Vaccination with VMP001-NPs promoted germinal center formation and elicited durable antigen-specific antibodies with significantly higher titers and more balanced Th1/Th2 responses in vivo, compared with vaccines composed of soluble protein mixed with MPLA. Antibodies raised by NP vaccinations also exhibited enhanced avidity and affinity toward the domains within the circumsporozoite protein implicated in protection and were able to agglutinate live P. vivax sporozoites. These results demonstrate that these VMP001-NPs are promising vaccines candidates that may elicit protective immunity against P. vivax sporozoites.

A comparison between spray drying and spray freeze drying for dry powder inhaler formulation of drug-loaded lipid-polymer hybrid nanoparticles

Lipid-polymer hybrid nanoparticles - polymeric nanoparticles enveloped by lipid layers - have emerged as a potent therapeutic nano-carrier alternative to liposomes and polymeric nanoparticles. Herein we perform comparative studies of employing spray drying (SD) and spray freeze drying (SFD) to produce inhalable dry-powder form of drug-loaded lipid-polymer hybrid nanoparticles. Poly(lactic-co-glycolic acid), lecithin, and levofloxacin are employed as the polymer, lipid, and drug models, respectively. The hybrid nanoparticles are transformed into micro-scale nanoparticle aggregates (or nano-aggregates) via SD and SFD, where the effects of (1) different excipients (i.e. mannitol, polyvinyl alcohol (PVA), and leucine), and (2) nanoparticle to excipient ratio on nano-aggregate characteristics (e.g. size, flowability, aqueous reconstitution, aerosolization efficiency) are examined. In both methods, PVA is found more effective than mannitol for aqueous reconstitution, whereas hydrophobic leucineis needed to achieve effective aerosolization as it reduces nano-aggregate agglomeration. Using PVA, both methods are equally capable of producing nano-aggregates having size, density, flowability, yield and reconstitutibility in the range ideal for inhaled delivery. Nevertheless, nano-aggregates produced by SFD are superior to SD in terms of their aerosolization efficiency manifested in the higher emitted dose and fine particle fraction with lower mass median aerodynamic diameter.

In situ engineering of the lymph node microenvironment via intranodal injection of adjuvant-releasing polymer particles

Recent studies have demonstrated a simple, potentially universal strategy to enhance vaccine potency, via intralymph node (i.LN) injection. To date, intranodal immunization studies have focused on the delivery of unadjuvanted vaccines (e.g., naked DNA, peptide, or protein). We hypothesized that combining i.LN vaccination with controlled release biomaterials permitting sustained dosing of molecular adjuvants to the local tissue microenvironment would further enhance this promising vaccination strategy. To test this idea, we encapsulated the Toll-like receptor-3 ligand poly(inosinic:cytidylic acid) (polyIC) in biodegradable poly(lactide-co-glycolide) microparticles (MPs) designed to remain extracellular and release polyIC in the LN over several days. Intranodal injection of MPs increased persistence of polyIC in LNs compared to the same dose of soluble polyIC or polyIC formulated in nanoparticles, leading to increased accumulation of Toll-like receptor agonist in LN-resident antigen presenting cells and more enduring dendritic cell activation. Intralymph node injection of ovalbumin mixed with polyIC-releasing MPs enhanced the humoral response and expanded ovalbumin-specific T cells to frequencies as high as 18% among all CD8(+) cells following a single injection (8.2-fold greater than the same vaccine given i.m.), a response that could not be matched by antigen mixed with polyIC-loaded nanoparticles or a 10-fold greater dose of soluble polyIC. Thus, i.LN immunization with slow release-formulated adjuvants may be a broadly applicable strategy to enhance therapeutic or prophylactic vaccines.

Robust IgG responses to nanograms of antigen using a biomimetic lipid-coated particle vaccine

New subunit vaccine formulations with increased potency are of interest to improve immune responses against poorly immunogenic antigens, to avoid vaccine shortages in pandemic situations, and to promote dose-sparing of potent adjuvant molecules that can cause unacceptable side effects in prophylactic vaccination. Here we report strong class-switched, high avidity humoral immune responses elicited by a vaccine system based on poly(lactide-co-glycolide) micro- or nano-particles enveloped by PEGylated phospholipid bilayers, with protein antigens covalently anchored to the lipid surface and lipophilic adjuvants inserted in the bilayer coating. Strikingly, these particles elicited high endpoint antigen-specific IgG titers (>10(6)) sustained for over 100 days after two immunizations with as little as 2.5 ng of antigen. At such low doses, the conventional adjuvant alum or the molecular adjuvants monophosphoryl lipid A (MPLA) or α-galactosylceramide (αGC) failed to elicit responses. Co-delivery of antigen with MPLA or αGC incorporated into the particle bilayers in a pathogen-mimetic fashion further enhanced antibody titers by ~12-fold. MPLA provided the highest sustained IgG titers at these ultra-low antigen doses, while αGC promoted a rapid rise in serum IgG after one immunization, which may be valuable in emergencies such as disease pandemics. The dose of αGC required to boost the antibody response was also spared by particulate delivery. Lipid-enveloped biodegradable micro- and nano-particles thus provide a potent dose-sparing platform for vaccine delivery.