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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 10 (1993), S. 970-974 
    ISSN: 1573-904X
    Keywords: polymeric micelles ; drug delivery systems ; cancer therapy ; Adriamycin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Polymeric micelles have potential utility as drug carriers. To this end, polymeric micelles based on AB block copolymers of polyethylene oxide (PEG) and poly(aspartic acid) [p(Asp)] with covalently bound Adriamycin (ADR) were prepared. The micelle forming polymer–drug conjugates [PEO-p(Asp(ADR)] were radiolabeled and their biodistribution was investigated after intravenous injection in mice. Long circulation times in blood for some compositions of PEO-p[Asp(ADR)] conjugates were evident, which are usually atypical of colloidal drug carriers. This was attributed to the low interaction of the PEO corona region of the micelles with biocomponents (e.g., proteins, cells). Low uptake of the PEO-p(Asp(ADR)] conjugates in the liver and spleen was determined. The biodistribution of the PEO-p[Asp(ADR)] conjugates was apparently dependent on micelle stability; stable micelles could maintain circulation in blood, while unstable micelles readily formed free polymer chains which rapidly underwent renal excretion. Long circulation times in blood of PEO-p(Asp(ADR)] conjugates are thought to be prerequisite for enhanced uptake at target sites (e.g., tumors).
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-904X
    Keywords: polymeric micelles ; AFM ; DLS ; pyrene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To directly visualize and evaluate the aqueous block copolymeric micelles, poly(ethylene oxide)-poly(β-benzyl L-aspartate) (PEO-PBLA) chemically conjugated with pyrene fluorescence molecule, by nanotechnology of atomic force microscopy (AFM). Methods. The block copolymers' PEO-PBLA-Pyrene was first synthesized by reacting with pyrene sulfonyl chloride and PEO-PBLA in tetrahydrofuran (THF) solution and were identified by GPC reflect index, UV and fluorescence detectors. The characterization of physical and chemical properties of PEO-PBLA-Pyrene polymeric micellar solution were examined by the dynamic light scattering (DLS) and critical micelles concentrations (CMC). In addition, the nanotechnology of AFM was used to directly visualize the size and shape of nanopolymeric micelles. Results. The pyrene fluorescence molecule were successfully conjugated at the amino group of the end of PBLA chain by GPC with three different detectors. The size of the aqueous PEO-PBLA-Pyrene polymeric micelles was detected around 57 nm with unimodal distribution by DLS measurement. As a result of this finding, the CMC test was also found out that the fluorescence intensity was increasing around 0.01 ∼ 0.05 mg/ml. Using AFM evaluation of polymeric micellar solution, the morphology of aqueous PEO-PBLA-Pyrene polymeric micelles was observed on round shape and with the narrow dispersity of size range 50 ∼ 80 nm. Conclusions. The presence of PEO-PBLA copolymers with pyrene in an aqueous system formed in a spherical and nano range of polymeric micelles.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-904X
    Keywords: polymeric micelles ; FITC ; endothelial ; endocytosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To determine aortic endothelial cells permeation ability and mechanisms of the aqueous block copolymeric micelles, poly(ethylene oxide)-poly ((β-benzyl L-aspartate) (PEO-PBLA) chemically conjugated with fluroescein isothiocyanate (FITC) by transport study and confocal laser scanning microscopy. Methods. The block copolymers' PEO-PBLA-FITC was first synthesized and characterized by gel permeation chromatography (GPC) reflect index, UV, fluorescence detectors, and critical micelles concentrations (CMC), and atomic force microscopy (AFM). Permeation ability and mechanisms of polymeric micelles in aortic endothelial cells were evaluated by incubating with NaF, NaN3, wortmannin, cytochalasin B inhibitors, at 20°C, and under reverse conditions. FITC and latex particles (40 nm) were also used for comparison of transport ability. The extent of localization of uptake polymeric micelles was established by confocal laser scanning microscopy. Results. The size of the aqueous PEO-PBLA-FITC polymeric micelles was detected at around 56 nm with unimodal distribution by AFM. The CMC test revealed the fluorescence intensity increased to around 0.01 ∼ 0.05 mg/ml. NaF, NaN3, wortmannin, cytochalasin B, 20°C, and reverse experiments inhibited the absorption of polymeric micelles through aortic endothelial cells with apparent permeability coefficients (P) of 18.07 ± 1.03 to 12.98 ± 0.93, 11.31 ± 0.77, 12.44 ±1.23, 6.40 ± 0.23, 11.11 ± 0.46, and 10.22 ± 1.09 X 10−7 cm/sec, respectively. Also, the permeation of FITC and latex on aortic endothelial cells was 70.02 ±4.71, and 2.05± 0.41 X 10−7 cm/sec, respectively. Confocal laser microscopy showed that fluorescent compounds were distributed in the intracellular cytoplasm and nucleus. Conclusions. PEO-PBLA-FITC copolymeric micelles in an aqueous system were transported by energy-dependent endocytosis with 18.07 X 10−7 cm/sec penetrated range and were localized on intracellular and nucleus endothelial cells.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-904X
    Keywords: Adriamycin ; polymeric micelles ; AB block copolymer ; drug delivery systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The entrapment of Adriamycin (ADR) in micelles composed of AB block copolymers (poly(ethylene oxide-co-β-benzyl L-aspartate) (PEO-PBLA)) was investigated. The loading process involved transfer of ADR and PEO-PBLA into an aqueous milieu from dimethyl-formamide (DMF) through a dialysis procedure. Evidence for the physical entrapment of ADR in the polymeric micelles was derived from fluorescence spectroscopy and gel permeation chromatography (GPC). The total fluorescence intensity of ADR was low, suggesting that the drug was self-associated in the micelles. In addition, quenching experiments, using a water-soluble quencher (iodide (I–)), showed that the fluorescence of ADR present in micellar solutions was largely unaffected by I–, whereas the fluorescence of free ADR was readily quenched. From Stern-Volmer plots, quenching constants (KSV) of 2.2 and 17 M−l were determined for ADR in micellar solutions and free ADR, respectively. As a result of the entrapment of ADR in the micelles, ADR binds only slightly serum albumin as evidenced by GPC. In contrast, ADR readily binds serum albumin in aqueous solutions. The findings suggest that ADR is stably entrapped in PEO-PBLA micelles. ADR entrapment in polymeric micelles is expected to affect markedly the pharmacokinetics of ADR.
    Type of Medium: Electronic Resource
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