Norased Nasongkla

Dependence of Pharmacokinetics and Biodistribution on Polymer Architecture: Effect of Cyclic Versus Linear Polymers

The ability of a polymer to reptate through a nanopore has an influence on its circulatory half-life and biodistribution, since many physiological barriers contain nanopores. A cyclic polymer lacks chain ends, and therefore, cyclic polymers with molecular weights greater than the renal threshold for elimination should circulate longer than their linear-polymer counterparts when injected into animals. As predicted, radiolabeled cyclic polymers with molecular weights greater than the renal threshold have longer blood circulation times in mice than do linear polymers of comparable molecular weight.

Enhancement of Solubility and Bioavailability of β-Lapachone Using Cyclodextrin Inclusion Complexes

AbstractPurpose. To explore the use of cyclodextrins (CD) to form inclusion complexes with β-lapachone (β-lap) to overcome solubility and bioavailability problems previously noted with this drug. Methods. Inclusion complexes between β-lap and four cyclodextrins (α-, β-, γ-, and HPβ-CD) in aqueous solution were investigated by phase solubility studies, fluorescence, and 1H-NMR spectroscopy. Biologic activity and bioavailability of β-lap inclusion complexes were investigated by in vitro cytotoxicity studies with MCF-7 cells and by in vivo lethality studies with C57Blk/6 mice (18-20 g). Results. Phase solubility studies showed that β-lap solubility increased in a linear fashion as a function of α-, β-, or HPβ-CD concentrations but not γ-CD. Maximum solubility of β-lap was achieved at 16.0 mg/ml or 66.0 mM with HPβ-CD. Fluorescence and 1H-NMR spectroscopy proved the formation of 1:1 inclusion complexes between β-CD and HPβ-CD with β-lap. Cytotoxicity assays with MCF-7 cells showed similar biologic activities of β-lap in β-CD or HPβ-CD inclusion complexes (TD50 = 2.1 μM). Animal studies in mice showed that the LD50 value of β-lap in an HPβ-CD inclusion complex is between 50 and 60 mg/kg. Conclusions. Complexation of β-lap with HPβ-CD offers a major improvement in drug solubility and bioavailability.

Doxorubicin and β-Lapachone Release and Interaction with Micellar Core Materials: Experiment and Modeling:

Polymer micelles with two different core-forming blocks, poly(d,l -lactide) (PLA) and poly(ε-caprolactone) (PCL), but the same coronal material, poly(ethylene glycol) (PEG), were investigated in this study as nanoscopic drug carriers. The release of two different drugs, doxorubicin (DOX) and β-lapachone (β-lap), from PEG(5k)-b-PCL(5k) and PEG(5k)-b-PLA(5k) micelles was studied at pH 5.0 and 7.4. Mathematical solutions of both Higuchi’s model and Fickian diffusion equations were utilized to elucidate the differences between the micelle core materials for the two drugs. The neutral and smaller of the two drugs tested, β-lap, demonstrated faster, pH-independent release, suggesting that no substantial changes occurred in either micelle core at lower pH. In contrast, the release rate of DOX was found to noticeably increase at lower pH with a larger cumulative amount of drug released. Different core materials were shown to have considerable influence on the release kinetics of both drugs: in both cases, the more hydrophobic PCL core showed slower drug release rates compared with the less hydrophobic PLA core.

Comparative studies of poly(ε-caprolactone) and poly(D,L-lactide) as core materials of polymeric micelles

Polymeric micelles have been successfully used to deliver a variety of therapeutic agents. Nonetheless, several limitations and considerations must be clarified and well-studied to achieve the highest therapeutic effect. In this study, a series of methoxy poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-b-PCL) and methoxy poly(ethylene glycol)-block-poly(D,L-lactide) (PEG-b-PLA) with varying molecular weight (MW) of hydrophobic core segment were synthesized. These block copolymers can form micelle with PCL or PLA as core-forming blocks and PEG as a coronal material. The effect of MW on micelle size and critical micelle concentration (CMC) was studied. DOX (DOX) was encapsulated inside the micelle core. Drug-loading content and size of micelles were studied. Drug release studies inside cells were evaluated by confocal laser scanning microscopy. In summary, the PLA core which is less hydrophobic than PCL showed higher CMC, smaller micelle size and faster DOX release inside nucleus.

Biocompatibility study of glycofurol in rat brains

Glycofurol (GF) has been used clinically as a solvent for parenteral drug delivery systems. However, the application and toxicity of GF in the brain have not been reported. This study was carried out to assess the systemic and neurologic reactions of GF in rats upon intracranial injection. Hematological and neuropathological assessments of rats were performed during the acute, subacute and chronic period after the injection. Injection of the GF solution (GF 25 μL + PBS 25 μL) into the brain cortex showed that it did not cause any deaths or clinical neurobehavioral abnormalities. At the same volume as phosphate-buffered saline (PBS) injection, it had mild effects on all hematological data and histopathology of brain tissues. Nevertheless, histomorphologic assessments of the brain tissues treated with PBS 70 μL revealed different tissue responses compared with those of 70 μL GF solution (30 μL + PBS 40 μL) where tissues around the administration site showed elevated polymorphonuclear leukocytes, macrophages and gliosis. These results demonstrated that the GF solution (GF 25 μL + PBS 25 μL) administration was well tolerated and caused minor inflammatory responses of cerebral cortex. This suggests possibilities of GF for drug delivery systems in the brain parenchymal tissues.

Preparation and in vitro characterization of SN-38-loaded, self-forming polymeric depots as an injectable drug delivery system

This work describes the preparation and characterization of anticancer-loaded injectable polymeric depots that consisted of D,L-lactide (LA), ε-caprolactone (CL), and poly(ethylene glycol) (PEG) or [poly(ε-caprolactone)-random-poly(D,L-lactide)]-block-poly(ethylene glycol)-block-[poly(ε-caprolactone)-random-poly(D,L-lactide)] (PLEC) copolymers for malignant gliomas treatment. PLECs were polymerized with different percentages of LA to deliver 7-ethyl-10-hydroxycamptothecin (SN-38), a highly potent anticancer drug. SN-38-loaded depots could form directly in phosphate buffer saline with more than 98% encapsulation efficiency. The release rate of SN-38 from depots was found to depend on the amount of LA in PLECs, loading content of SN-38 in the depots, and depot weight. Encapsulation of SN-38 inside depots could enhance the stability of SN-38 where all of SN-38 released after 60 days was in an active form. Depots without SN-38 were evaluated as noncytotoxic against U-87MG, whereas SN-38-loaded depots showed cytotoxic effect as a function of concentration.

Solubility enhancement and in vitro evaluation of PEG-b-PLA micelles as nanocarrier of semi-synthetic andrographolide analogue for cholangiocarcinoma chemotherapy

Abstract Background: Semi-synthetic andrographolide analogue (19-triphenylmethyl ether andrographolide, AG 050) is a C-19 substituted andrographolide which is the major constituent from Andrographis Paniculata Nees (Acanthaceae). The analogue has previously been reported to be highly cytotoxic against several cancer cell lines. Nevertheless, its poor water solubility limits clinical applications of this compound. Objectives: To improve the aqueous solubility and bioavailability of AG 050 by protonation and encapsulation in poly(ethylene glycol)-b-poly(d,l-lactide) (PEG-b-PLA) polymeric micelles. Materials and methods: PEG-b-PLA micelle was employed as a nanocarrier for AG 050. The physicochemical properties and in vitro cytotoxicity against cholangiocarcinoma (CCA) (KKU-M213) cell line were done in this study. Result and discussion: Hydrochloride salt of AG 050 (AG 050-P) greatly enhanced the solubility of this compound (15-fold). PEG-b-PLA was able to encapsulate AG 050-P in hydrophobic core with a significant increase in the amount of AG 050-P in aqueous solution (280-fold). Film sonication method provided greater results in drug-loading study as compared to micelles via solvent evaporation. In addition, the encapsulated AG 050-P exhibited sustained release pattern and excellent cytotoxicity activity against KKU-M213 with IC50 of 3.33 µM. Conclusion: Nanoencapsulation of AG 050-P implicated its potential development for clinical use in CCA treatment.

Preparation and optimization of chlorophene-loaded nanospheres as controlled release antimicrobial delivery systems

Abstract Chlorophene-loaded nanospheres with various formulation parameters were evaluated. The optimal formulation was found at 0.1% w/v of poloxamer 407, 15 mL of ethyl acetate and 20% initial chlorophene loading that provided the suitable size (179 nm), the highest loading content (19.2%), encapsulation efficiency (88.0%) and yield (91.6%). Moreover, encapsulation of chlorophene in nanospheres was able to prolong and sustain drug release over one month. Chlorophene-loaded nanospheres were effective against Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans), the main cause of hospital-acquired infections. Chlorophene-loaded nanospheres were effective against S. aureus (>46 µg/mL) and C. albicans (>184 µg/mL). These nanospheres appeared to have profound effect on the time-dependent hemolytic activity due to gradual release of chlorophene. At the concentration of 46 µg/mL, nearly no HRBC hemolysis in 24 h compared to 80% of hemolysis from free drug. In conclusion, polymeric nanospheres were successfully fabricated to encapsulate chlorophene which can eliminate inherent toxicity of drugs and have potential uses in prolonged release of antimicrobial.

Antitumor efficacy and intratumoral distribution of SN-38 from polymeric depots in brain tumor model:

We investigate antitumor efficacy and 2D and 3D intratumoral distribution of 7-ethyl-10-hydroxycamptothecin (SN-38) from polymeric depots inside U-87MG xenograft tumor model in nude mice. Results showed that polymeric depots could be used to administer and controlled release of a large amount of SN-38 directly to the brain tumor model. SN-38 released from depots suppressed tumor growth, where the extent of suppression greatly depended on doses and the number of depot injections. Tumor suppression of SN-38 from depots was three-fold higher in animals which received double injections of depots at high dose (9.7 mg of SN-38) compared to single injection (2.2 mg). H&E staining of tumor sections showed that the area of tumor cell death/survival of the former group was two-fold higher than those of the latter group. Fluorescence imaging based on self-fluorescent property of SN-38 was used to evaluate the intratumoral distribution of this drug compared to histological results. The linear correlation between fluorescence intensity and the amount of SN-38 allowed quantitative determination of SN-38 in tumor tissues. Results clearly showed direct correlation between the amount of SN-38 in tumor sections and cancer cell death. Moreover, 3D reconstruction representing the distribution of SN-38 in tumors was obtained. Results from this study suggest the rationale for intratumoral drug administration and release of drugs inside tumor, which is necessary to design drug delivery systems with efficient antitumor activity.

Imidazole-modified deferasirox encapsulated polymeric micelles as pH-responsive iron-chelating nanocarrier for cancer chemotherapy

Deferasirox (Def) is an iron-chelating drug used to reduce iron overload in β-thalassemia patients. After the discovery of its tumor growth inhibition, this drug gained tremendous attention in cancer chemotherapy. Herein, deferasirox and its derivatives including methoxy (mDef) and imidazole-modified (iDef) deferasirox were encapsulated in polymeric micelles. Results showed that the release of deferasirox from polymeric micelles was faster at pH 7.4 (physiological condition) than at pH 4.5 (lysosomal condition). However, the release of mDef was pH-independent where both Def and mDef are not suitable for in vivo applications. Therefore, iDef was synthesized to change the pKa from 3.7 (carbonyl group of Def) to 6.8 (imidazole group of iDef) without interfering the iron-chelating efficacy. Interestingly, the release rate of imidazole-modified deferasirox was conversed from that of deferasirox where it exhibited slow release at physiological condition and faster release at the lysosomal condition. This release profile showed a pH-response and an ON–OFF release behavior where iDef is encapsulated in micelles during systemic circulation and released inside cancer cells after intracellular endosomes/lysosome. Cytotoxicity of deferasirox and modified deferasirox were also investigated, and it was found that the IC50 against PC-3 and HepG2 cell lines were in the range of micromolar to submicromolar. Flow cytometry analysis confirmed a decrease in the amount of iron inside lysosome when cells were treated by iDef-loaded micelles. Therefore, iDef-loaded micelles have potential application in cancer treatment as a pH-responsive iron-chelating nanocarrier.