Evaluation of PLGA microspheres as delivery system for antitumor agent-camptothecin

Exploring the Potential of Natural Product-Based Nanomedicine for Maintaining Oral Health

Oral diseases pose a major threat to public health across the globe. Diseases such as dental caries, periodontitis, gingivitis, halitosis, and oral cancer affect people of all age groups. Moreover, unhealthy diet practices and the presence of comorbidities aggravate the problem even further. Traditional practices such as the use of miswak for oral hygiene and cloves for toothache have been used for a long time. The present review exhaustively explains the potential of natural products obtained from different sources for the prevention and treatment of dental diseases. Additionally, natural medicine has shown activity in preventing bacterial biofilm resistance and can be one of the major forerunners in the treatment of oral infections. However, in spite of the enormous potential, it is a less explored area due to many setbacks, such as unfavorable physicochemical and pharmacokinetic properties. Nanotechnology has led to many advances in the dental industry, with various applications ranging from maintenance to restoration. However, can nanotechnology help in enhancing the safety and efficacy of natural products? The present review discusses these issues in detail.

Formulation, Characterisation and In vitro Cytotoxic Effect of Lens culinaris Medikus Seeds Extract Loaded Chitosan Microspheres

OBJECTIVE

The aim of present study was to formulate chitosan microspheres loaded with ethanolic extract of Lens culinaris Medikus (L.culinaris) seeds (ME) and to explore its anticancer potential against lung cancer (A549) cell line.

METHODS

Central composite design was applied to prepare and optimise the chitosan microspheres. The prepared microspheres were evaluated for its physicochemical characterisation, in vitro drug release and anti-cancer potential in vitro.

RESULTS

L.culinaris loaded chitosan microspheres were prepared successfully with suitable particle size, entrapment efficiency and drug release. The developed ME were spherical shaped with the particle size of 2.08 μm. The drug entrapment efficiency and cumulative drug release was found 1.58±0.02% and 81.95±0.35%, respectively. Differential scanning calorimetry studies revealed no interaction between drugs and polymers used. The cytotoxic effect of the optimised formulation revealed a significant response as compared to the ethanolic extract of L.culinaris seeds (IC₅₀: 22.56 μg/ml vs. 63.58 μg/ml), which was comparable to that of reference drug, doxorubicin (22 μg/ml). These observations demonstrate that the optimised microspheres are effective against lung cancer (A549) cells.

CONCLUSION

The significant cytotoxic response of the developed microspheres may be attributed due to its low particle size, high entrapment efficiency and prolonged drug release profile.

Bioresorbable Depot for Sustained Release of Immunostimulatory Resiquimod in Suppressing Both Primary Triple-Negative Breast Tumors and Metastatic Occurrence

In light of immune facilities trafficking toward the pathological sites along upward gradient of immunostimulatory cytokines, a localized resiquimod (Toll-like receptor 7/8 agonist) release depot was manufactured for pursuit of precision immunostimulation toward intractable triple-negative breast carcinoma. In principle, resiquimod/poly(lactic-co-glycolic acid) microspheres were fabricated and embedded into injectable and biodegradable poly(ethylene glycol) (PEG)-based hydrogel. The subsequent investigations approved persistent retention of immunostimulatory resiquimod in tumors upon peritumoral administration, which consequently led to localized and consistent secretion of immunostimulatory cytokines. Initially, not only innate tumor phagocytosis but also adaptive antitumor immunities were successfully cultivated for in situ suppression of the growth of primary solid tumors, more importantly, capable of inhibiting distant pulmonary metastasis, as evidenced by observation of enormous lymphocytes selectively gathering in the pulmonary artery. Hence, our presented study provided an important clinical indication of using immunostimulatory drugs to activate potent innate and adaptive antitumor immunities for precision antitumor therapy. Further immunomodulatory strategies, such as checkpoint blockage and tumor immunogenicity, could also be complementary for development of advanced antitumor immunotherapeutics in treatment of a number of intractable tumors.

Nanoparticle encapsulation increases the brain penetrance and duration of action of intranasal oxytocin

The blood-brain barrier (BBB) limits the therapeutic use of large molecules as it prevents them from passively entering the brain following administration by conventional routes. It also limits the capacity of researchers to study the role of large molecules in behavior, as it often necessitates intracerebroventricular administration. Oxytocin is a large-molecule neuropeptide with pro-social behavioral effects and therapeutic promise for social-deficit disorders. Although preclinical and clinical studies are using intranasal delivery of oxytocin to improve brain bioavailability, it remains of interest to further improve the brain penetrance and duration of action of oxytocin, even with intranasal administration. In this study, we evaluated a nanoparticle drug-delivery system for oxytocin, designed to increase its brain bioavailability through active transport and increase its duration of action through encapsulation and sustained release. We first evaluated transport of oxytocin-like large molecules in a cell-culture model of the BBB. We then determined in vivo brain transport using bioimaging and cerebrospinal fluid analysis in mice. Finally, we determined the pro-social effects of oxytocin (50 μg, intranasal) in two different brain targeting and sustained-release formulations. We found that nanoparticle formulation increased BBB transport both in vitro and in vivo. Moreover, nanoparticle-encapsulated oxytocin administered intranasally exhibited greater pro-social effects both acutely and 3 days after administration, in comparison to oxytocin alone, in mouse social-interaction experiments. These multimodal data validate this brain targeting and sustained-release formulation of oxytocin, which can now be used in animal models of social-deficit disorders as well as to enhance the brain delivery of other neuropeptides.

Nanoparticle formulations that allow for sustained delivery and brain targeting of the neuropeptide oxytocin

Oxytocin is a promising candidate for the treatment of social-deficit disorders such as Autism Spectrum Disorder, but oxytocin cannot readily pass the blood-brain barrier. Moreover, oxytocin requires frequent dosing as it is rapidly metabolized in blood. We fabricated four polymeric nanoparticle formulations using poly(lactic-co-glycolic acid) (PLGA) or bovine serum albumin (BSA) as the base material. In order to target them to the brain, we then conjugated the materials to either transferrin or rabies virus glycoprotein (RVG) as targeting ligands. The formulations were characterized in vitro for size, zeta potential, encapsulation efficiency, and release profiles. All formulations showed slightly negative charges and sizes ranging from 100 to 278 nm in diameter, with RVG-conjugated BSA nanoparticles exhibiting the smallest sizes. No formulation was found to be immunogenic or cytotoxic. The encapsulation efficiency was ≥75% for all nanoparticle formulations. Release studies demonstrated that BSA nanoparticle formulation exhibited a faster initial burst of release compared to PLGA particles, in addition to later sustained release. This initial burst release would be favorable for clinical dosing as therapeutic effects could be quickly established, especially in combination with additional sustained release to maintain the therapeutic effects. Our size and release profile data indicate that RVG-conjugated BSA nanoparticles are the most favorable formulation for brain delivery of oxytocin.

Lipid‐enveloped PLGA as a hybrid carrier for sustained delivering camptothecin in ovarian cancer

Camptothecin (CPT) is plant alkaloid exhibiting in a wide range of solid tumours. However, CPT was instability at physiological pH conditions, the lactone moieties easily hydrolysed makes systemic toxicity risky. Moreover, the water insolubility of CPT was obstructed in clinical development. The aim of the study was to utilise nontoxic and biodegradable poly(D,L‐lactic‐co‐glycolic acid) (PLGA) incorporated lipid as a hybrid nanoparticle (lipid‐PLGA NPs) for delivery of CPT. Lipid‐PLGA NPs were produced by a nano‐precipitation technique. The optimal formulation was presented that particles of which were 43 nm in diameter, with a polydispersity index of 0.3 which indicated a smaller and well‐distributed pattern. Moreover, a high capacity of ∼95% entrapment efficiency was achieved. An in vitro release study showed that non‐formulated CPT with a lag time of ∼0 h, demonstrated an obvious burst effect; in contrast, sustained released and a lag time delay were clearly observed in lipid‐PLGA NPs. The cytotoxicity study confirmed that human ovarian cancer cells (ES‐2) were inhibited by lipid‐PLGA NPs. CPT was successful entrapped in lipid‐PLGA NPs which achieved smaller size and well distribution. Lipid‐PLGA NPs resolve the water insolubility and produced a sustained, slow‐release pattern of CPT and controlled the cytotoxicity toward ES‐2.

Bioresponsive polymer coated drug nanorods for breast cancer treatment

Ineffective drug release at the target site is among the top challenges for cancer treatment. This reflects the facts that interaction with the physiological condition can denature active ingredients of drugs, and low delivery to the disease microenvironment leads to poor therapeutic outcomes. We hypothesize that depositing a thin layer of bioresponsive polymer on the surface of drug nanoparticles would not only protect drugs from degradation but also allow the release of drugs at the target site. Here, we report a one-step process to prepare bioresponsive polymer coated drug nanorods (NRs) from liquid precursors using the solvent diffusion method. A thin layer (10.3 ± 1.4 nm) of poly(ε-caprolactone) (PCL) polymer coating was deposited on the surface of camptothecin (CPT) anti-cancer drug NRs. The mean size of PCL-coated CPT NRs was 500.9 ± 91.3 nm length × 122.7 ± 10.1 nm width. The PCL polymer coating was biodegradable at acidic pH 6 as determined by Fourier transform infrared spectroscopy. CPT drugs were released up to 51.5% when PCL coating dissolved into non-toxic carboxyl and hydroxyl groups. Trastuzumab (TTZ), a humanized IgG monoclonal antibody, was conjugated to the NR surface for breast cancer cell targeting. Combination treatments using CPT and TTZ decreased the HER-2 positive BT-474 breast cancer cell growth by 66.9 ± 5.3% in vitro. These results suggest effective combination treatments of breast cancer cells using bioresponsive polymer coated drug delivery.

Synthetic high-density lipoproteins for delivery of 10-hydroxycamptothecin

The purpose of this study was to develop a novel synthetic high-density lipoprotein (sHDL) nanoparticle delivery system for 10-hydroxycamptothecin (HCPT) for treatment of colon carcinoma. HDL is recognized by scavenger receptor B-I (SR-BI) over-expressed in colon carcinomas 5- to 35-fold relative to the human fibroblasts. The sHDL nanoparticles were composed of apolipoprotein A-I mimic peptide (5A) and contained 0.5%–1.5% (w/w) of HCPT. An optimized HCPT-sHDL formulation exhibited 0.7% HCPT loading with 70% efficiency with an average size of 10–12 nm. Partitioning of HCPT in the sHDL lipid membrane enhanced drug stability in its active lactone form, increased solubilization, and enabled slow release. Cytotoxicity studies in HT29 colon carcinoma cells revealed that the IC₅₀ of HCPT-sHDL was approximately 3-fold lower than that of free HCPT. Pharmacokinetics in rats following intravenous administration showed that the area under the serum concentration-time curve (AUC_0−t) and C_max of HCPT-HDL were 2.7- and 6.5-fold higher relative to the values for the free HCPT, respectively. These results suggest that sHDL-based formulations of hydrophobic drugs are useful for future evaluation in treatment of SR-BI-positive tumors.

Brain delivery of camptothecin by means of solid lipid nanoparticles: formulation design, in vitro and in vivo studies

For the purpose of brain delivery upon intravenous injection, formulations of camptothecin-loaded solid lipid nanoparticles (SLN), prepared by hot high pressure homogenisation, were designed. Incorporation of camptothecin in the hydrophobic and acidic environment of SLN matrix was chosen to stabilise the lactone ring, which is essential for its antitumour activity, and for avoiding premature loss of drug on the way to target camptothecin to the brain. A multivariate approach was used to assess the influence of the qualitative and quantitative composition on the physicochemical properties of camptothecin-loaded SLN in comparison to plain SLN. Mean particle sizes of ≤200 nm, homogenous size distributions and high encapsulation efficiencies (>90%) were achieved for the most suitable formulations. In vitro release studies in plasma, showed a prolonged release profile of camptothecin from SLN, confirming the physical stability of the particles under physiological pH. A higher affinity of the SLN to the porcine brain capillary endothelial cells (BCEC) was shown in comparison to macrophages. MTT studies in BCEC revealed a moderate decrease in the cell viability of camptothecin, when incorporated in SLN compared to free camptothecin in solution. In vivo studies in rats showed that fluorescently labelled SLN were detected in the brain after i.v. administration. This study indicates that the camptothecin-loaded SLN are a promising drug brain delivery system worth to explore further for brain tumour therapy.

Carboxylate microsphere-induced cellular toxicity in human lung fibroblasts

Carboxylate microspheres (CMs) are mainly used in industrial, biomedical and various household products. In this study, we assessed the cytotoxic effects of CMs on human MRC-5 lung fibroblasts by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Oxidative stress was determined by measurements of reactive oxygen species and antioxidant (superoxide dismutase and catalase) levels and proinflammatory cytokines quantified by enzyme-linked immunosorbent assay. Morphological changes were examined by light microscopy, confocal microscopy and transmission electron microscopy. The lung fibroblasts were exposed to increasing concentrations of CMs (0.1–1000 μmol/L) for 24 h. The results showed significant changes in cell morphology with induction of cytotoxicity and oxidative stress observed in 10–1000 μmol/L concentrations of CM-treated fibroblasts. Ultrastructural examination revealed the presence of CMs inside the cytoplasm of treated lung fibroblasts. CMs also induced elevated interleukin (IL)-1, IL-6, IL-8, IL-10 and tumor necrosis factor α levels at higher concentrations. We have demonstrated that CMs significantly reduce cell viability in a dose-dependant manner in lung fibroblasts at 0.1–1000 μmol/L doses. The findings suggest that high doses of CMs have the potential to induce cellular toxicity to the lung in vitro.

Camptothecin nanocolloids based on N,N,N-trimethyl chitosan: efficient suppression of growth of multiple myeloma in a murine model

Camptothecin (CPT) exhibits very strong antitumor effects by inhibiting the activity of DNA topoisomerase I, but its application is greatly limited due to its low solubility and the instability of the active lactone form. To overcome these shortcomings, in the present study, we prepared novel camptothecin nanocolloids based on N,N,N-trimethyl chitosan (CPT-TMC) to efficiently and safely administer CPT systemically. Herein, we investigated the antitumor activity of CPT-TMC against a murine Balb/c myeloma model. Our results showed that CPT-TMC more effectively inhibited tumor growth and prolonged survival time than CPT in vivo, but no statistical difference was observed in vitro between CPT-TMC and CPT. These findings suggest that N,N,N-trimethyl chitosan could increase the stability and the antitumor effect of CPT and CPT-TMC is a potential approach for the effective treatment of multiple myeloma.

Pharmacokinetic analysis and optimization of hydroxycamptothecin-loaded nanoparticles for liver targeting

In this paper, a pharmacokinetic model to describe the tissue distribution process of nanoparticles was established. To test the possibility of the model, nanoparticles composed of poly(butylcyanoacrylate) and hydroxypropyl-β-cyclodextrins (HP-β-CD) was prepared with a poorly soluble anticancer drug, hydroxycamptothecin (HCPT). Characteristics were determined including particle's size, morphology and in vitro release. The tissue distribution of nanoparticles was also studied. Further, mathematical equation was fitted to the curve of drug concentration-time in liver of hydroxycamptothecin-loaded nanoparticles and the pharmacokinetic parameters of liver were obtained. The effectiveness of hydroxycamptothecin-loaded nanoparticles for liver targeting was evaluated. The results showed that nanoparticles composed of poly(butylcyanoacrylate) and hydroxypropyl-β-cyclodextrins (HP-β-CD) exhibited enhanced liver targeting in rats after i.v. injection. More importantly, the pharmacokinetic parameters (transport constant from blood to target organ KT, drug release rate from nanoparticles Kr and drug elimination constant in target organ Ke) provided some quantitative measure of liver distribution and were useful guidelines for development of targeted drug delivery systems.

Functionalized nanoscale oil bodies for targeted delivery of a hydrophobic drug

Effective formulations of hydrophobic drugs for cancer therapies are challenging. To address this issue, we have sought to nanoscale artificial oil bodies (NOBs) as an alternative. NOBs are lipid-based particles which consist of a central oil space surrounded by a monolayer of oleosin (Ole)-embedded phospholipids (PLs). Ole was first fused with the anti-HER2/neu affibody (Ole-ZH2), and the resulting hybrid protein was overproduced in Escherichia coli. ZH2-displayed NOBs were then assembled by sonicating the mixture containing plant oil, PLs, and isolated Ole-ZH2 in one step. To illustrate their usefulness, functionalized NOBs were employed to encapsulate a hydrophobic anticancer drug, Camptothecin (CPT). As a result, these CPT-loaded NOBs remained stable in serum and the release of CPT at the non-permissive condition exhibited a sustained and prolonged profile. Moreover, plain NOBs were biocompatible whereas CPT-loaded NOBs exerted a strong cytotoxic effect on HER2/neu-positive cells in vitro. Administration of xenograft nude mice with CPT-loaded NOBs also led to the regression of solid tumors in an effective way. Overall, the result indicates the potential of NOBs for targeted delivery of hydrophobic drugs.

Preparation of camptothecin-loaded PCEC microspheres for the treatment of colorectal peritoneal carcinomatosis and tumor growth in mice

The aim of this study was to prepare PCL-PEG-PCL (PCEC) microspheres to protect camptothecin from hydrolysis, to extend its release time and to enhance its treatment efficacy on colorectal peritoneal carcinomatosis and tumor growth in mice. Camptothecin (CPT)-loaded PCL-PEG-PCL (PCEC) microspheres were prepared by oil-in-water emulsion solvent evaporation method. The particle size, morphological characteristics, encapsulation efficiency, in vitro drug release studies and in vitro cytotoxicity of CPT-loaded PCEC microspheres have been investigated. In vivo studies were carried out on Balb/c male mice bearing colorectal peritoneal carcinomatosis. CPT-loaded PCEC microspheres were applied to abdominal cavity of mice once a week. Free CPT was used as a positive control. On 14th day of treatment, mice were sacrificed and antitumor activities of CPT-loaded PCEC microspheres were evaluated. Compared with control group, a significant decrease in the number of tumor nodes was observed in group treated with CPT-loaded PCEC microspheres. Immunohistochemistry staining of tumor tissues with CD34 revealed that MVD positive cells were significantly reduced in CPT-loaded PCEC microspheres treated group in contrast to other groups (P<0.05). The CPT-loaded PCEC microspheres were considered potentially useful to treat the abdominal metastases of colon carcinoma.

PLGA nanoparticles containing various anticancer agents and tumour delivery by EPR effect

As mortality due to cancer continues to rise, advances in nanotechnology have significantly become an effective approach for achieving efficient drug targeting to tumour tissues by circumventing all the shortcomings of conventional chemotherapy. During the past decade, the importance of polymeric drug-delivery systems in oncology has grown exponentially. In this context, poly(lactic-co-glycolic acid) (PLGA) is a widely used polymer for fabricating 'nanoparticles' because of biocompatibility, long-standing track record in biomedical applications and well-documented utility for sustained drug release, and hence has been the centre of focus for developing drug-loaded nanoparticles for cancer therapy. Such PLGA nanoparticles have also been used to develop proteins and peptides for nanomedicine, and nanovaccines, as well as a nanoparticle-based drug- and gene-delivery system for cancer therapy, and nanoantigens and growth factors. These drug-loaded nanoparticles extravasate through the tumour vasculature, delivering their payload into the cells by the enhanced permeability and retention (EPR) effect, thereby increasing their therapeutic effect. Ongoing research about drug-loaded nanoparticles and their delivery by the EPR effect to the tumour tissues has been elucidated in this review with clarity.

Absorption of 10-hydroxycamptothecin on Fe3O4 magnetite nanoparticles with layer-by-layer self-assembly and drug release response

In this paper, the structural and zeta potential properties of 10-hydroxycamptothecin (HCPT) were investigated by FT-IR and zeta potential analyzer under different pH. The anticancer drug HCPT as a model drug was used to prepare a high-performance and relatively easy-to-fabricate system on Fe(3)O(4) magnetite nanoparticles by using a polystyrene sulfonate (PSS) and HCPT interlayer self-assembly method. The results obtained from FT-IR and XRD confirmed that HCPT was molecularly dispersed into the nanoparticles. The method holds not only environment-friendly characteristics and the ability to mimic the self-organization process in biological systems but also greatly decreases adjuvant polymers. In addition, the system has an ideal drug payload for the delivery of insoluble HCPTs.

Treatment of rat brain tumors using sustained-release of camptothecin from poly(lactic-co-glycolic acid) microspheres in a thermoreversible hydrogel

A thermoreversible gelation polymer consisting of an aqueous solution in the sol state at room temperature and in the gel state near body temperature was examined for its use in the retention of microspheres and sustained, long-term delivery of anti-cancer drugs using a rat model of malignant glioma. The poly(lactic-co-glycolic acid) (PLGA) microspheres containing camptothecin at ratios of 1 : 33 or 1 : 50 mediated sustained release, with approximate 80% of camptothecin released after 28 d. Rats were inoculated in the brain with C6 glioma cells, followed 7 d later by injection in the tumor site with 1 : 33 and 1 : 50 PLGA microspheres dispersed in a thermoreversible gelation polymer (TGP) solution. Kaplan-Meier analysis showed that the mean survival period of the untreated group was 16 d, with a slight increase in rats treated with TGP-only solution, empty or 1 : 50 microspheres in phosphate-buffered saline. The mean survival period of rats treated with the camptothecin powder in TGP was 21 d, while that of rats treated with 1 : 33 and 1 : 50 microspheres in TGP was significantly longer than the untreated group; long-term survival rats were observed. These results suggest that the anti-tumor effect of camptothecin can be enhanced by long-term sustained release from microspheres retained in the rat brain by TGP gel.

Nanomicelle with long-term circulation and enhanced stability of camptothecin based on mPEGylated alpha,beta-poly (L-aspartic acid)-camptothecin conjugate

To enhance the stability and long-term circulation of camptothecin (CPT), mPEGylated alpha,beta-poly (L-aspartic acid)-CPT conjugates were synthesized, and used to fabricate nanomicelle. Firstly, alpha,beta-poly (L-aspartic acid) derivative (PAA-der) containing alkyne groups was synthesized via the ring-opening of PSI with propargyl amine. And then, azide-functionalized CPT derivatives (CPT-N(3)) and azide-terminated poly (ethylene glycol) methyl ether (mPEG-N(3)) were conjugated with PAA-der by click cycloaddition to give mPEG-graft-PAA-CPT conjugates. The formation of mPEG-graft-PAA-CPT nanomicelles was confirmed by fluorescence spectrophotoscopy and particle size measurements. It was found that all the nanomicelles showed spherical shapes with size about 178 nm. MPEG-graft-PAA-CPT nanomicelles showed good storage stability, even incubation at 37 degrees C for 60 days, and improved the stability of CPT lactone form in aqueous media. A steady release rate of CPT was kept for 72h, suggested the great potential of mPEG-graft-PAA-CPT nanomicelles as polymer prodrug of CPT.

Incorporation methods for cholic acid chitosan-g-mPEG self-assembly micellar system containing camptothecin

A water-insoluble anticancer agent, camptothecin (CPT) was incorporated to a polymeric micelle carrier system preparing from cholic acid chitosan-grafted poly (ethylene glycol) methyl ether (CS-mPEG-CA). CS-mPEG-CA formed a core-shell micellar structure with a critical micelle concentration (CMC) of 7.08 microg/ml. Incorporation efficiency was investigated by varying physical incorporation method and initial drug loading. Among three incorporation methods (dialysis, emulsion and evaporation methods), an emulsion method showed the highest CPT incorporation efficiency. Increasing the initial CPT loading from 5 to 40%, the incorporation efficiency decreased. In all examined CPT-loaded CS-mPEG-CA micelles, 5% initial drug loading showed the highest drug incorporation efficiency. Release of CPT from the micelles was sustained when increasing the initial CPT loading. This indicates the importance of incorporation method and the initial drug loading to obtain the optimum particle size with high drug loading and sustained drug release. When compared to the unprotected CPT, CPT-loaded CS-mPEG-CA micelles were able to prevent the hydrolysis of the lactone group of the drug. This novel CS-mPEG-CA polymer presents considerable potential interest in the further development of CPT carrier.

Comparative evaluation of polymeric and amphiphilic cyclodextrin nanoparticles for effective camptothecin delivery

Camptothecin (CPT) is a potent anticancer agent. The clinical application of CPT is restricted by poor water solubility and instability under physiological conditions. Solubilization and stabilization of CPT were realized through nanoparticulate systems of amphiphilic cyclodextrins, poly(lactide-co-glycolide) (PLGA) or poly-epsilon-caprolactone (PCL). Nanoparticles were prepared with nanoprecipitation technique, whereas cyclodextrin nanoparticles were prepared from preformed inclusion complexes of CPT with amphiphilic cyclodextrins. Polymeric nanoparticles, on the other hand, were loaded with CPT:HP-beta-CD inclusion complex to solubilize and stabilize the drug. Mean particle sizes were under 275 nm, and polydispersity indices were lower than 0.2 for all formulations. Drug-loading values were significantly higher for amphiphilic cyclodextrin nanoparticles when compared with those for PLGA and PCL nanoparticles. Nanoparticle formulations showed a significant controlled release profile extended up to 12 days for amphiphilic cyclodextrin nanoparticles and 48h for polymeric nanoparticles. Anticancer efficacy of the nanoparticles was evaluated in comparison with CPT solution in dimethyl sulfoxide (DMSO) on MCF-7 breast adenocarcinoma cells. Amphiphilic cyclodextrin nanoparticles showed higher anticancer efficacy than PLGA or PCL nanoparticles loaded with CPT and the CPT solution in DMSO. These results indicated that CPT-loaded amphiphilic cyclodextrin nanoparticles might provide a promising carrier system for the effective delivery of this anticancer drug having bioavailability problems.

Controlled Release Camptothecin Tablets based on Pluronic and Poly(acrylic acid) Copolymer. Effect of Fabrication Technique on Drug Stability, Tablet Structure, and Release Mode

Poly(ethylene oxide)-b-poly(propylene oxide)-b-(polyethylene oxide)-g-poly(acrylic acid), a graft-comb copolymer of Pluronic 127 and poly(acrylic acid) (Pluronic-PAA), was explored as an excipient for tablet dosage form of camptothecin (CPT). The tablets were prepared by either direct compression of the drug-polymer physical blend, suspension in ethanol followed by evaporation, or compression after kneading and characterized with respect to their physical structures, drug stability, and release behavior. Porosity and water uptake rate were strongly dependent on the fabrication procedure, ranking in the order: direct compression of physical blend > compression after suspension/evaporation in ethanol > compression after kneading. Tablets prepared by compression of physical blends swelled in water with a rapid surface gel layer formation that impeded swelling and disintegration of the tablets core. These tablets were able to sustain the CPT release for a period of time longer than those observed with the tablets made by either suspension/evaporation or kneading, which disintegrated within a few minutes. Despite the tablet disintegration, the CPT release was impeded for at least 6 hr, which was attributed to the ability of the Pluronic-PAA copolymers to form micellar aggregates at the hydrated surface of the particles. Physical mixing did not alter the fraction of CPT being in the pharmaceutically active lactone form, whilst the preparation of the tablets by the other two methods caused a significant reduction in the lactone form content. Tablets prepared from the physical blends demonstrated CPT release rates increasing with the pH due to the PAA ionization leading to the increase in the rate and extent of the tablet swelling. The results obtained demonstrate the potential of the Pluronic-PAA copolymers for the oral administration of chemotherapeutic agents.

Mixed PEG-PE/vitamin E tumor-targeted immunomicelles as carriers for poorly soluble anti-cancer drugs: improved drug solubilization and enhanced in vitro cytotoxicity

Two poorly soluble, potent anti-cancer drugs, paclitaxel and camptothecin, were successfully solubilized by mixed micelles of polyethylene glycol-phosphatidyl ethanolamine (PEG-PE) and vitamin E. Drug-containing micelles were additionally modified with anti-nucleosome monoclonal antibody 2C5 (mAb 2C5), which can specifically bring micelles to tumor cells in vitro. The optimized micelles had an average size of about 13-22 nm and the immuno-modification of micelles did not significantly change it. The solubilization of both drugs by the mixed micelles was more efficient than by micelles made of PEG-PE alone. Solubilization of camptothecin in micelles prevented also the hydrolysis of active lactone form of the drug to inactive carboxylate form. Drug-loaded mixed micelles and mAb 2C5-immunomicelles demonstrated significantly higher in vitro cytotoxicity than free drug against various cancer cell lines.

In vivo antitumor activity of camptothecin incorporated in liposomes formulated with an artificial lipid and human serum albumin

Camptothecin (CPT) is a strong antitumor agent, but its use limited by its low solubility and the instability of the active lactone form. To overcome these difficulties, liposomes incorporating CPT (CPT liposomes) were designed and tested. CPT liposomes were formulated by the addition of 3,5-bis(dodecyloxy)benzoic acid (DB) to polyethylene glycol-containing liposomes, and by coating the surface of the liposomes with human serum albumin (HSA, HSA-DB-L). HSA-DB-L successfully entrapped CPT with about 80% efficiency and with a particle size of about 150 nm. HSA-DB-L showed attenuated drug release and storage stability. Pharmacokinetics studies in mice showed that i.v. injection of HSA-DB-L (2.5 mg/kg) led to prolonged circulation in the plasma; the area under the curve was 22-fold higher than that of CPT solution. The tumor growth in mice with subcutaneous transplantation of colon 26 tumor cells was significantly inhibited after a single i.v. injection of HSA-DB-L at a dose of 15 mg/kg without any significant body weight loss. HSA-DB-L increased the accumulation of CPT in tumor tissue significantly (9.6-fold) more efficiently than CPT solution 24 h after i.v. injection. These findings suggest that HSA-DB-L could increase the stability and the antitumor effect of CPT. CPT delivery by novel liposome formulations is a potential approach for effective treatment of cancer.

Injectable block copolymer hydrogels for sustained release of a PEGylated drug

The paper employs the spontaneous physical gelling property of a biodegradable polymer in water to prepare an injectable sustained release carrier for a PEGylated drug. A series of thermogelling PLGA-PEG-PLGA triblock copolymers were synthesized. The PEGylated camptothecin (CPT) was also prepared and employed as the model of a PEGylated drug, and the solubility of this hydrophobic drug was significantly enhanced to over 150mg/mL. The model drug was completely entrapped into the polymeric hydrogel, and the sustained release lasted for 1 month. The mechanism of the sustained release was diffusion-controlled at the first stage and then was the combination of diffusion and degradation at the late stage. In vivo anti-tumor tests in mice further confirmed the efficacy of the model PEGylated drug released from the hydrogel. This work also revealed the specificity of the PEGylated drug in such a kind of carrier systems by decreasing the critical gelling temperature and increasing the viscosity of the sol. Due to the very convenient drug formulation and highly tunable release rate, an injectable carrier platform for PEGylated drugs is thus set up.

Camptothecin-incorporating N-phthaloylchitosan-g-mPEG self-assembly micellar system: Effect of degree of deacetylation

Amphiphilic grafted copolymers, N-phthaloylchitosan-grafted poly (ethylene glycol) methyl ether (PLC-g-mPEG), were synthesized from chitosan with different degree of deacetylation (DD=80%, 85%, 90% and 95%). Due to their amphiphilic characteristic, these copolymers could form micelle-like nanoparticles. The critical micelle concentration (CMC) of these nanoparticles with different DD in water was similar (28microg/ml). Under transmission electron microscope (TEM), the nanoparticles exhibited a regular spherical shape with core-shell structure. The particle sizes determined by dynamic light scattering were in the range of 100-250nm, and increased as the %DD of chitosan increased. The cytotoxicity of phthaloylchitosans (PLC) and PLC-g-mPEG in Hela cells line were evaluated. The results showed that cytotoxicity of PLC and PLC-g-mPEG increased with increasing %DD of chitosan. The cytotoxicity of PLC-g-mPEG was significantly lower than that of PLC. Camptothecin as a model drug was loaded into the inner core of the micelles by dialysis method. It was found that %DD of chitosan, corresponding to the N-phthaloyl groups in the inner core of the nanoparticle obtained, was a key factor in controlling %yield, stability of the drug-loaded micelles, and drug release behavior. As the %DD increased, the CPT-loaded micelles stability increased. Release of CPT from the micelles was dependent on the %DD and a sustained release was obtained in high %DD.

Indocyanine green nanoparticles useful for photomedicine

OBJECTIVE

The aim of this study was to evaluate the potential application of biodegradable nanoparticles (NPs) containing indocyanine green (ICG) in photodynamic therapy (PDT).

METHODS

Important parameters, such as particle size and external morphology, were established by dynamic light scattering (DLS) and scanning electron microscopy (SEM). Also, drug encapsulation efficiency and in vitro release behavior were evaluated by spectroscopic methods.

RESULTS

The particles are spherical in shape, they exhibit an 817-nm diameter, and they have a low tendency to aggregate. The loading efficiency was 65%. ICG photophysical parameters showed a bathocromic shift in ICG-loaded nanoparticles (ICG-NP). Analysis of the cell P388-D1 in the presence of the ICG-NP by SEM showed that the majority of the nanoparticles were uptaken by phagocytic cells after 2 h of incubation. After laser irradiation photodamage was observed in P388-D1 cells where ICG-NPs had been uptaken by phagocytic cells.

CONCLUSION

Polymeric NPs work as an efficient drug delivery system for PDT drugs, and this approach can be used in the administration of amphiphilic photosensitizers in the treatment of neoplasic cells.

Preparation of camptothecin-loaded polymeric micelles and evaluation of their incorporation and circulation stability

To improve its aqueous solubility and stability in biological fluid, CPT was physically loaded in polymeric micelles. Polymeric micelles were composed of various poly(ethylene glycol)-poly(aspartate ester) block copolymers (PEG-P(Asp(R))). The incorporation and circulation stability of CPT micelles were evaluated by measuring the CPT in micelle using gel-permeation chromatography and by CPT concentration measurement after intravenous injection using HPLC, respectively, in terms of chemical structure of block copolymers. The stability of CPT-loaded micelles in vivo depended on the amount of benzyl esters, and length of PEG in the polymers to a greater degree than it did in vitro. A stable formulation of CPT-loaded micelles was obtained using PEG-P(Asp) with PEG of 5,000 (MW), 27 Asp units, and 57-75% benzyl esterification of Asp residue. This CPT-loaded micelles showed about a 17-fold lower blood clearance value than unstable micelles. The CPT-loaded micelles are potentially delivered to tumor sites owing to an extended circulation in the blood stream.

Block copolymer design for camptothecin incorporation into polymeric micelles for passive tumor targeting

PURPOSE

Polymeric micelles were designed for targeting of a water-insoluble anticancer agent, camptothecin (CPT). Chemical structures of inner core segment were optimized to achieve high incorporation efficiency and stable CPT-loaded micelles.

METHODS

Poly(ethylene glycol)-poly(beta-benzyl L-aspartate) block copolymer (PEG-PBLA) was synthesized. The PBLA chain was modified by alkaline hydrolysis of its benzyl group followed by esterification with benzyl, n-butyl, and lauryl groups. Incorporation of CPT into micelles was carried out by an evaporation method. The stability of drug-loaded micelles was studied by gel-permeation chromatography (GPC), and their in vitro release behaviors were analyzed.

RESULTS

CPT was incorporated into polymeric micelles constructed by various block copolymers. Among the esterified groups, block copolymers with high benzyl ester contents showed high CPT loading efficiency and stable CPT-loaded micelles. In chain lengths, 5-27 Bz-69 showed the highest incorporation efficiency. In contrast, 5-52 Bz-67, which had a longer hydrophobic chain, showed low incorporation efficiency. Release of CPT from the micelles was dependent on the benzyl contents and chain lengths. Sustained release was obtained when the benzyl content was high.

CONCLUSIONS

CPT was successfully incorporated into polymeric micelles with high efficiency and stability by optimizing chemical structures of the inner core segment.

Solubilization and stabilization of camptothecin in micellar solutions of pluronic-g-poly(acrylic acid) copolymers

The capability of a family of copolymers comprising Pluronic (PEO-PPO-PEO) surfactants covalently conjugated with poly(acrylic acid) (Pluronic-PAA) to enhance the aqueous solubility and stability of the lactone form of camptothecin (CPT) was studied. The unprotected lactone form of CPT, which possesses cytotoxic activity, is rapidly converted to the ring-opened carboxylate form under physiological conditions. Firstly, surfactant properties such as critical micellization concentration (CMC) of Pluronic-PAA copolymers were characterized. Then, the equilibrium solubility partitioning and hydrolysis of the lactone form of CPT in the presence of Pluronic-PAA in water and in human serum were analyzed. CPT solubility in polymer micellar solutions was ca. 3- to 4-fold higher than that in water at pH 5. The amount of CPT solubilized per PPO was considerably greater in the Pluronic-PAA solutions than in the parent Pluronic solution, which suggests that the drug is not only solubilized by the hydrophobic cores and also by the hydrophilic POE-PAA shells of the micelles. The equilibrium partition coefficient of the CPT lactone between Pluronic-PAA solutions and water exceeded (2-3) x 10(3). The complete solubilization of CPT and the absence of chemical interactions between CPT and Pluronic-PAA were confirmed by modulated temperature differential scanning calorimetry (MTDSC), infrared spectroscopy, and X-ray diffraction of films. The loading of CPT into the Pluronic-PAA micelles was able to prevent the hydrolysis of the lactone group of the drug for 2 h at pH 8 in water. When compared to the unprotected CPT, the kinetics of the CPT hydrolysis in human serum was about 10-fold slower in the Pluronic-PAA formulations.