Conjugates of poly(DL-lactic acid) with ethylenediamino or diethylenetriamino bridged bis(beta-cyclodextrin)s and their nanoparticles as protein delivery systems

An Injectable Nano-Enabled Thermogel to Attain Controlled Delivery of p11 Peptide for the Potential Treatment of Ocular Angiogenic Disorders of the Posterior Segment

This investigation focused on the design of an injectable nano-enabled thermogel (nano-thermogel) system to attain controlled delivery of p11 anti-angiogenic peptide for proposed effective prevention of neovascularisation and to overcome the drawbacks of the existing treatment approaches for ocular disorders characterised by angiogenesis, which employ multiple intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) antibodies. Synthesis of a polyethylene glycol-polycaprolactone-polyethylene glycol (PEG-PCL-PEG) triblock co-polymer was undertaken, followed by characterisation employing Fourier-transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and differential scanning calorimetry (DSC) to ascertain the chemical stability and integrity of the co-polymer instituted for nano-thermogel formulation. The p11 anti-angiogenic peptide underwent encapsulation within poly(lactic-co-glycolic acid) (PLGA) nanoparticles via a double emulsion solvent evaporation method and was incorporated into the thermogel following characterisation by scanning electron microscopy (SEM), zeta size and zeta-potential analysis. The tube inversion approach and rheological analysis were employed to ascertain the thermo-sensitive sol-gel conversion of the nano-thermogel system. Chromatographic assessment of the in vitro release of the peptide was performed, with stability confirmation via Tris-Tricine PAGE (Polyacrylamide Gel Electrophoresis). In vitro biocompatibility of the nano-thermogel system was investigated employing a retinal cell line (ARP-19). A nanoparticle size range of 100–200 nm and peptide loading efficiency of 67% was achieved. Sol-gel conversion of the nano-thermogel was observed between 32–45 °C. Release of the peptide in vitro was sustained, with maintenance of stability, for 60 days. Biocompatibility assessment highlighted 97–99% cell viability with non-haemolytic ability, which supports the potential applicability of the nano-thermogel system for extended delivery of peptide for ocular disorder treatment.

Cyclodextrins based delivery systems for macro biomolecules

Macro biomolecules are of vital importance in regulating the biofunctions in organisms, in which proteins (including peptides when mentioned below) and nucleic acids (NAs) are the most important. Therefore, these proteins and NAs can be applied as "drugs" to regulate the biofunctions from abnormal to normal. Either for proteins and NAs, the most challenging thing is to avoid the biodegradation or physicochemical degradation before they reach the targeted location, and then functions as complete functional structures. Hence, appropriate delivery systems are very important which can protect them from these degradations. Cyclodextrins (CDs) based delivery systems achieved mega successes due to their outstanding pharmaceutical properties and there have been several reviews on CDs based small molecule drug delivery systems recently. But for biomolecules, which are getting more and more important for modern therapies, however, there are very few reviews to systematically summarize and analyze the CDs-based macro biomolecules delivery systems, especially for proteins. In this review, there were some of the notable examples were summarized for the macro biomolecules (proteins and NAs) delivery based on CDs. For proteins, this review included insulin, lysozyme, bovine serum albumin (BSA), green fluorescent protein (GFP) and IgG's, etc. deliveries in slow release, stimulating responsive release or targeting release manners. For NAs, this review summarized cationic CD-polymers and CD-cluster monomers as NAs carriers, notably, including the multicomponents targeting CD-based carriers and the virus-like RNA assembly method siRNA carriers.

Biocompatible Polymers Combined with Cyclodextrins: Fascinating Materials for Drug Delivery Applications

Cyclodextrins (CD) are a group of cyclic oligosaccharides with a cavity/specific structure that enables to form inclusion complexes (IC) with a variety of molecules through non-covalent host-guest interactions. By an elegant combination of CD with biocompatible, synthetic and natural polymers, different types of universal drug delivery systems with dynamic/reversible properties have been generated. This review presents the design of nano- and micro-carriers, hydrogels, and fibres based on the polymer/CD supramolecular systems highlighting their possible biomedical applications. Application of the most prominent hydrophobic aliphatic polyesters that exhibit biodegradability, represented by polylactide and polycaprolactone, is described first. Subsequently, particular attention is focused on materials obtained from hydrophilic polyethylene oxide. Moreover, examples are also presented for grafting of CD on polysaccharides. In summary, we show the application of host-guest interactions in multi-component functional biomaterials for controlled drug delivery.

Cyclodextrin-Based Formulations: A Non-Invasive Platform for Targeted Drug Delivery

Cyclodextrins (CDs) are recognized as promising pharmaceutical excipients due to their unique ability to form water-soluble inclusion complexes with various poorly soluble compounds. The numerous investigations on CDs and their use in nanomedicine have received considerable attention in the last three decades, leading to the rapid development of new CD-containing formulations that significantly facilitate targeted drug delivery and controlled drug release, with consequent improvements in drug bioavailability. This MiniReview highlights the efficacy and recent uses of CDs for non-invasive drug delivery. Using ophthalmic and nasal drug delivery as examples, an overview of chemical properties, mechanisms of CDs on drug solubilization, stabilization and permeation, along with their toxicological profiles relevant to nasal and ocular administration, are provided and discussed. The recent development and application of CD-based nanocarrier systems for targeted drug delivery are summarized.

Exploiting developments in nanotechnology for the preferential delivery of platinum-based anti-cancer agents to tumours: targeting some of the hallmarks of cancer

Platinum drugs as anti-cancer therapeutics are held in extremely high regard. Despite their success, there are drawbacks associated with their use; their dose-limiting toxicity, their limited activity against an array of common cancers and patient resistance to Pt-based therapeutic regimes. Current investigations in medicinal inorganic chemistry strive to offset these shortcomings through selective targeting of Pt drugs and/or the development of Pt drugs with new or multiple modes of action. A comprehensive overview showcasing how liposomes, nanocapsules, polymers, dendrimers, nanoparticles and nanotubes may be employed as vehicles to selectively deliver cytotoxic Pt payloads to tumour cells is provided.

pH-Responsive Polyethylene Glycol Monomethyl Ether-ε-Polylysine-G-Poly (Lactic Acid)-Based Nanoparticles as Protein Delivery Systems

The application of poly(lactic acid) for sustained protein delivery is restricted by the harsh pH inside carriers. In this study, we synthesized a pH-responsive comb-shaped block copolymer, polyethylene glycol monomethyl ether-ε-polylysine-g-poly (lactic acid) (PEP)to deliver protein (bovine serum albumin (BSA)). The PEP nanoparticles could automatically adjust the internal pH to a milder level, as shown by the quantitative ratio metric results. The circular dichroism spectra showed that proteins from the PEP nanoparticles were more stable than those from poly(lactic acid) nanoparticles. PEP nanoparticles could achieve sustained BSA release in both in vitro and in vivo experiments. Cytotoxicity results in HL-7702 cells suggested good cell compatibility of PEP carriers. Acute toxicity results showed that the PEP nanoparticles induced no toxic response in Kunming mice. Thus, PEP nanoparticles hold potential as efficient carriers for sustained protein release.

Biodegradable polymeric microcapsules for sustained release of riboflavin

In the current study, a series of polylactic acid and polylactic-co-glycolic acid were prepared in an easy, simple, safe and economically feasible way with yield% greater than 90%. Studying the effect of a catalyst on polymerization process was performed. Riboflavin (RF) was chosen as a model drug and microencapsulated in different (drug: polymer) ratios to modify its performance via o/w emulsion solvent evaporation technique and characterized in terms of the morphology and entrapment efficiency (E.E.) and evaluated via in vitro RF release studies. It has been found that, the release rate consists a burst release at the first 12h, followed by a gradual release over 3days. The cumulative riboflavin release from these microcapsules formulations at the end of 3days was 70% and 80% for PDLA and PDLAGA respectively. The kinetics of release profiles were zero order. The highest (E.E.) of RF obtained among all formulations was 85%.

Reverse micelles based on biocompatible β-cyclodextrin conjugated polyethylene glycol block polylactide for protein delivery

The oil-based formulation fabricated from biodegradable PEG-b-PLA-CD copolymers with high drug loading showed great potential for protein delivery.

Construction of micelles based on biocompatible pseudo-graft polymers via β-cyclodextrin/cholesterol interaction for protein delivery

A pseudo-graft copolymer micelle was constructed from the self-assembly of (6-(2-aminoethyl)-amino-6-deoxy)-cyclodextrin (β-CDen)-modified poly(aspartic acid) (PASP-CD) with cholesterol-modified poly(d,l-lactide) (PLA-Chol) using host–guest inclusion complexation in water.

Construction of reverse vesicles from pseudo-graft poly(glycerol methacrylate)s via cyclodextrin–cholesterol interactions

Reverse vesicles were constructed from pseudo-graft amphiphilic copolymers by dint of the host–guest inclusion complexation between β-cyclodextrins and cholesterols, and transformed into organogels by adding trace amounts of water.

Nanocarriers for delivery of platinum anticancer drugs

Platinum based anticancer drugs have revolutionized cancer chemotherapy, and continue to be in widespread clinical use especially for management of tumors of the ovary, testes, and the head and neck. However, several dose limiting toxicities associated with platinum drug use, partial anti-tumor response in most patients, development of drug resistance, tumor relapse, and many other challenges have severely limited the patient quality of life. These limitations have motivated an extensive research effort towards development of new strategies for improving platinum therapy. Nanocarrier-based delivery of platinum compounds is one such area of intense research effort beginning to provide encouraging preclinical and clinical results and may allow the development of the next generation of platinum chemotherapy. This review highlights current understanding on the pharmacology and limitations of platinum compounds in clinical use, and provides a comprehensive analysis of various platinum-polymer complexes, micelles, dendrimers, liposomes and other nanoparticles currently under investigation for delivery of platinum drugs.

Amphiphilic polylactic acid-hyperbranched polyglycerol nanoparticles as a controlled release system for poorly water-soluble drugs: physicochemical characterization

Objectives

Quercetin was applied as a model drug to evaluate the potential application of amphiphilic polylactic acid-hyperbranched polyglycerol (HPG-PLA) nanoparticles as carriers for poorly water-soluble drugs.

Methods

The drug delivery systems were characterized by dynamic light scattering, powder X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) and so forth.

Key findings

The results showed the particle sizes ranged from 205.3 to 433.3 nm with low polydispersity index. XRD and FTIR demonstrated that the crystal of the drug was converted to an amorphous state in the matrices and formed intermolecular interaction with carriers. The drug encapsulation efficiency and drug loading could reach 91.8% and 21.0%, respectively. Cell viability assay suggested the nanoparticles had good cytocompatibility. The in-vitro drug release profiles showed a sustained quercetin release up to 192 h, indicating the suitability of nanoparticles in sustained drug release. Furthermore, the influence of many factors on release profiles could also be evaluated for the potential of using nanoparticles as controlled release systems.

Conclusions

This system may be of clinical importance in both stabilizing and delivering hydrophobic drugs for the treatment of many diseases.

A hydrotropic β-cyclodextrin grafted hyperbranched polyglycerol co-polymer for hydrophobic drug delivery

The development of successful formulations for poorly water soluble drugs remains a longstanding, critical, and challenging issue in cancer therapy. A β-cyclodextrin (CD) functionalized hyperbranched polyglycerol (HPG) has been prepared as a potential water insoluble drug carrier. The HPG-g-CD molecules could self-assemble into multimolecular spherical micelles in water, the size of which ranged from 200 to 300 nm, with good dispersity. A high loading capacity and high encapsulation efficiency of paclitaxel, as a model, were obtained. The release profiles of different co-polymer compositions showed a burst release followed by continuous extended release. Furthermore, MTT analysis showed that HPG-g-CD had good biocompatibility, indicating that HPG-g-CD may be considered a promising hydrophobic drug delivery system.

Development of peptide and protein nanotherapeutics by nanoencapsulation and nanobioconjugation

The targeted delivery of therapeutic peptide by nanocarriers systems requires the knowledge of interactions of nanomaterials with the biological environment, peptide release, and stability of therapeutic peptides. Therapeutic application of nanoencapsulated peptides are increasing exponentially and >1000 peptides in nanoencapsulated form are in different clinical/trial phase. This review covers current scenario of therapeutic protein and peptides encapsulation on polymer to metallic nanocarriers including methods of protein encapsulation, peptide bioconjugation on nanoparticles, stability enhancement of encapsulated proteins and its biomedical applications.

Core-shell nanosized assemblies mediated by the alpha-beta cyclodextrin dimer with a tumor-triggered targeting property

In this paper, the alpha-beta cyclodextrin dimer is designed via "click" chemistry to connect the hydrophilic and hydrophobic segments to form self-assembled noncovalently connected micelles (NCCMs) through host-guest interactions. A peptide containing the Arg-Gly-Asp (RGD) sequence was introduced to NCCMs as a target ligand to improve the cell uptake efficacy, while PEGylated technology was employed via benzoic-imine bonds to protect the ligands in normal tissues and body fluid. In addition, two fluorescent dyes were conjugated to different segments to track the formation of the micelles as well as the assemblies. It was found that the targeting property of NCCMs was switched off before reaching the tumor sites and switched on after removing the poly(ethylene glycol) (PEG) segment in the tumor sites, which was called "tumor-triggered targeting". With deshielding of the PEG segment, the drugs loaded in NCCMs could be released rapidly due to the thermoinduced phase transition. The new concept of "tumor-triggered targeting" proposed here has great potential for cancer treatment.

Cyclodextrin-based polymeric materials: synthesis, properties, and pharmaceutical/biomedical applications

This review describes the synthesis, properties, and, in particular, biomedical and pharmaceutical applications of an upcoming class of polymeric networks and assemblies based on cyclodextrins (CDs). CDs are cyclic oligosaccharides composed of alpha-1,4-coupled d-glucose units, which contain a hydrophobic internal cavity that can act as a host for various, generally lipophilic, guest molecules. Because of this unique physicochemical property, commonly referred to as inclusion complex formation, CDs have often been used to design polymeric materials, such as hydrogels and nanoparticles. Polymeric systems based on CDs exhibit unique characteristics in terms of mechanical properties, stimuli-responsiveness, and drug release characteristics. In this contribution, first, an outline is given of covalently cross-linked polymeric networks in which CD moieties were structurally incorporated to modulate the network strength as well as the complexation and release of low molecular weight drugs. Second, physically assembled polymeric systems are discussed, of which the formation is accomplished by inclusion complexes between polymer-conjugated CDs and various guest molecule-derivatized polymers. Due to their physical nature, these polymeric systems are sensitive to external stimuli, such as temperature changes, shear forces and the presence of competing CD-binding molecules, which can be exploited to use these systems as injectable, in situ gelling devices. In recent years, many interesting CD-containing polymeric systems have been described in literature. These systems have to be optimized and extensively evaluated in preclinical studies concerning their safety and efficacy, making future clinical applications of these materials in the biomedical and pharmaceutical field feasible.

Recent developments in nanoparticle-based drug delivery and targeting systems with emphasis on protein-based nanoparticles

BACKGROUND

Drug delivery systems with nm dimensions (nanoparticles [NPs]) are attracting increasing attention because they can sequester drugs in systemic circulation, prevent non-specific biodistribution, and target to specific tissues.

OBJECTIVE

We reviewed the recent literature pertinent to NP-based drug delivery, primarily emphasizing NPs fabricated from proteins.

METHODS

A summary of common NP fabrication techniques is provided along with the range of sizes and functional properties obtained. The NP properties critical for injectable drug delivery are reviewed, as well as the attempts to design 'tissue-specific' NPs.

RESULTS/CONCLUSIONS

It has been possible to design > 100 nm NPs from different biomaterials, and further understanding of in vivo stability and interactions with physiologic systems will lead to improved drug delivery systems.

High-loading nanosized micelles of copoly(styrene–maleic acid)–zinc protoporphyrin for targeted delivery of a potent heme oxygenase inhibitor

Amphiphilic styrene-maleic acid (SMA) copolymer efficiently formed micelles with a potent heme oxygenase inhibitor-zinc protoporphyrin (ZnPP). The micelles were constructed by subtle pH adjustments to form non-covalent interaction between the hydrophobic ZnPP and amphiphilic SMA. The micelles (SMA-ZnPP) thus formed were nanoparticles with narrow size distribution in water (mean diameter 176.5nm), having tunable loading (from 15% to 60% w/w of ZnPP) with remarkable aqueous solubility. SMA-ZnPP had an average molecular size of 144kDa as determined by size-exclusion chromatography (SEC), this size is a marked increase from the molecular weight of free ZnPP (626.03Da), suggesting the formation of micellar structure. The micelles showed a constant ZnPP release rate of about 0.5%/day in vitro at neutral pH. SMA-ZnPP micelles inhibited splenic microsomal HO-1 activity, in a competitive and dose-dependent manner, with an apparent inhibitory constant (K(i)) of 0.12mum, comparable to free ZnPP and also exhibited marked cytotoxic effect on KYSE-510 human esophageal cancer cells. The unique features of SMA-ZnPP micelles are that they are nanoparticles in aqueous solution having high water solubility and loading, yet macromolecular in nature, which can be beneficial in targeted release of a potent HO-1 inhibitor.

Conjugates of poly(DL-lactide-co-glycolide) on amino cyclodextrins and their nanoparticles as protein delivery system

Poly(DL-lactide-co-glycolide) (PLG) was chemically conjugated on two amino cyclodextrins, mono(6-(2-aminoethyl)amino-6-deoxy)-beta-cyclodextrin and ethylenediamino bridged bis(beta-cyclodextrin), to afford novel amphiphilic conjugates. Those conjugates were then characterized with infrared spectrometry (IR), proton nuclear magnetic resonance ((1)H NMR) and gel permeation chromatography (GPC). A repeat-nanoprecipitation (RP-NP) method was also developed to fabricate the nanoparticles of the conjugates with a water-soluble model protein, bovine serum albumin (BSA). At the end of RP-NP process, the availability of BSA was over 80% while the entrapment efficiency was 40-50% for each nanoprecipitation. The nanoparticles were rigid and spherical with diameters of 110-180 nm determined by transmission electron microscope (TEM), atomic force microscopy (AFM) and particle size analyzer. Nanoparticles possessed good steric stability during freeze-drying and resuspensions due to the existence of cyclodextrins corona. Interactions between BSA and the conjugates in the nanoparticles were then elucidated with IR experiments. About 25% BSA adsorbed on the surface of nanoparticles due to the interaction and was easy to release in the first day. The release of BSA from the nanoparticles was in three phases: a burst effect in the first day, a followed plateau in about a week, and a sustained release of the protein over 14 days. By changing the lactide/glycolide ratio, the degradation time of the conjugates and the release rate of BSA could be controlled. The loss of CDs content was faster than that of overall Mw during degradation since CDs formed outer corona of the nanoparticles. Both the novel biomaterials and the nanosphere fabrication technique contributed to the maintenance of protein structure.

Micellar nanocarriers: pharmaceutical perspectives

Micelles, self-assembling nanosized colloidal particles with a hydrophobic core and hydrophilic shell are currently successfully used as pharmaceutical carriers for water-insoluble drugs and demonstrate a series of attractive properties as drug carriers. Among the micelle-forming compounds, amphiphilic copolymers, i.e., polymers consisting of hydrophobic block and hydrophilic block, are gaining an increasing attention. Polymeric micelles possess high stability both in vitro and in vivo and good biocompatibility, and can solubilize a broad variety of poorly soluble pharmaceuticals many of these drug-loaded micelles are currently at different stages of preclinical and clinical trials. Among polymeric micelles, a special group is formed by lipid-core micelles, i.e., micelles formed by conjugates of soluble copolymers with lipids (such as polyethylene glycol-phosphatidyl ethanolamine conjugate, PEG-PE). Polymeric micelles, including lipid-core micelles, carrying various reporter (contrast) groups may become the imaging agents of choice in different imaging modalities. All these micelles can also be used as targeted drug delivery systems. The targeting can be achieved via the enhanced permeability and retention (EPR) effect (into the areas with the compromised vasculature), by making micelles of stimuli-responsive amphiphilic block-copolymers, or by attaching specific targeting ligand molecules to the micelle surface. Immunomicelles prepared by coupling monoclonal antibody molecules to p-nitrophenylcarbonyl groups on the water-exposed termini of the micelle corona-forming blocks demonstrate high binding specificity and targetability. This review will discuss some recent trends in using micelles as pharmaceutical carriers.