The selective delivery of anticancer agents using target-sensitive liposomes

Target-sensitive (TG-S) liposomes having modified antibodies on their surface were employed to study the release of calcein and the selective delivery of the anticancer agents, doxorubicin (DOX) and methotrexate (MTX). The release of calcein from TG-S liposome occurred when the various target cells were contacted with liposomes and it was proportionally increased with the increase of antibody affinity to the target cells. Increasing the concentration of antigen molecules (major histocompatibility, MHC) on the surface of RMA-S, the release of calcein and drugs from TG-S liposomes contacting with RMA-S also rised. The destabilization of TG-S liposomes was only induced above a threshold density of surface antigen on the target cell membrane. The growth inhibition of specific target cells by the liposomal drugs was always stronger than that of the non-specific ones. For specific target cells, the IC₅₀ of liposomal DOX was about 2 times greater than that of free DOX, on the while, for non-specific target cells, more than 5 times. This indicates that the liposomal drugs were transferred preferentially to the specific target cells than the non-specific ones. Based on this phenomenon, the TG-S liposomal MTX were also applied for the selective elimination of the specific target cells in the mixed culture of specific and non-specific target cells.     

Enhanced fluorescence and thermal sensitivity of polyethylenimine modified by Michael addition

Polyethylenimine (PEI) with enhanced fluorescence and thermal sensitivity was achieved by Michael addition of divinylsulfone (DVS) and N-isopropylacrylamide (NIPAm) respectively. The fluorescence enhancement is quantitatively studied by tailoring the amount of DVS, the medium pH, the substituting acrylates, the substrate polymers with different type amine groups, and the substrate molecular weights. The results suggested that different amine groups affected the performance of fluorescence with quantum yields varied from 0.340 for primary amine (NH₂-) to 0.090 for tertiary amine (N(-C)₃), and further to 0.049 for secondary amine (-NH-). It was also found that the fluorescence enhancement was attributed to the specific molecular structure of DVS-substituted product. The fluorescence moiety is believed to involve a proton-transfer process and have O₂-dependent and pH-sensitive fluorescence properties. From the current study, it can be expected that the accurate prediction of the O₂-dependent fluorescence would be dependent on molecular orbital calculation of the small amine molecules (oxidized with O₂) and their DVS-substituted products.     

Chitosan-coated liposomes for enhanced skin permeation of resveratrol

In this study, chitosan-coated liposomes were investigated for use in enhanced transdermal delivery of resveratrol. Particle size, entrapment efficiency, stability, and skin-permeation efficiency were evaluated. The particle size was seen to increase on coating with chitosan, with higher concentrations of coating solution forming larger particles. The zeta potential of the liposomes also followed the same trend, i.e., it changed from a negative value for uncoated liposomes to increasingly positive values for the chitosan-coated ones. The chitosan coating was seen to increase the stability of the liposomes by preventing their aggregation. Transdermal delivery of uncoated and 0.1% chitosan-coated liposomes containing 0.1% resveratrol was investigated using Franz diffusion cells. The proportions of resveratrol that permeated the animal skin were 40.42% and 30.84% for the coated and uncoated liposomes, respectively. This increased skin-permeation efficiency with the coating could be explained by the tendency of positively charged liposomes to interact more strongly with the skin surface. These results indicate that chitosan-coated liposomes could be an effective transdermal delivery system for delaying skin aging using resveratrol.     

Preparation of liposomes using the supercritical anti-solvent (SAS) process and comparison with a conventional method

Two methods to produce liposomes encapsulating a fluorescent marker were compared: the supercritical anti-solvent (SAS) method and a conventional one (Bangham). Liposome size and encapsulation efficiency were measured to assess the methods. Micronized lecithin produced by the SAS process was characterized in terms of particle size, morphology and residual solvent content in order to investigate the influence of experimental parameters (pressure, CO₂/solvent molar ratio and solute concentration). It appears that when the lecithin concentration increases from 15 to 25 wt.%, at 9 MPa and 308 K, larger (20-60 μm) and less aggregated lecithin particles are formed. As concerns liposomes formed from SAS processed lecithin, size distribution curves are mainly bimodal, spreading in the range of 0.1-100 μm. Liposome encapsulation efficiencies are including between 10 and 20%. As concerns the Bangham method, more dispersed liposomes were formed; encapsulation efficiencies were about 20%, and problems of reproducibility have been raised.     

Enhanced adsorption of anionic phenol red using cationic polyethylenimine-incorporated chitosan beads

Journal of Porous Materials - In this study, a fast and simple dissolution and coagulation method was adopted to produce polyethylenimine (PEI)-incorporated chitosan beads. The beads were...     

In situ polycondensation of amino acid modified liposomes and their properties

Three amphiphilic amino acids based on glutamic acid, i.e. S-[1-carboxy-2-([N-bistetradecyl- -glutamate]carbon-yl)ethyl]cysteine (1), S-[1-carboxy-2-([N-bishexadecyl- -glutamate]carbonyl)ethyl]cysteine (2), S-[1-carboxy-2-([N-bis-octadecyl- -glutamate]carbonyl)ethyl]cysteine (3), were synthesized. The aggregation behavior of them in water or buffer solution was studied. It was found that upon hydration and sonication in water, they could form stable liposomes. This kind of amino acid modified liposome was then polycondensed locally on the liposome surface to form a polypeptide-surfaced liposome and the peptide formation was detected by Fr-IR, GPC, etc. The effect of polycondensation of amino acid on the properties of liposomes were studied by detecting the phase transition temperatures with DSC or measuring the leakage of the encapsulated fluorescent probe from the liposomes. It was observed that the phase transition temperatures of the peptide liposomes moved down and the polycondensation of amino acid moieties obviously increased the leakage of the encapsulated molecules.     

Cytotoxicity of cationic liposomes coated by N‐trimethyl chitosan and their in vivo tumor angiogenesis targeting containing doxorubicin

Doxorubicin (DOX)‐loaded cationic liposomes (DOXL) coated by N‐trimethyl chitosan (TMCs) has been previously shown to enhance DOX uptake by human umbilical vein endothelial cells (HUVECs) in vitro and the tumor inhibition on solid tumor in vivo, and the effects were both enhanced with the degree of quaternization (DQ) increase of TMCs. The aim of the present work is to study the cytotoxicity of the blank cationic liposomes (CLs) coated by TMCs with various DQ on L‐929 mouse fibroblasts, by MTT assay, using the relative proliferation rate as the indicator, and the toxicity extent was classified according to the evaluation criteria of United States Pharmacopoeia. Furthermore, the in vivo tumor angiogenesis targeting of DOXL coated by TMC60 was studied. It was found that with the increase of TMCs concentration and DQ, cytotoxicity was increased accordingly. However, the cell proliferation rates of TMCs‐coated CLs with TMCs concentrations of 0.02% and 0.05%(w/w) were all above 80%, even the concentration of TMC20 was increased to 0.2%(w/w), the cell proliferation rate was still above 80%, showing noncytotoxicity. The mouse H₂₂ tumor model was established by transplanted tumor experiment. In vivo fluorescence in tumor tissue was investigated through the tail vein injection of fluorescein isothiocyanate conjugated dextran at the 7th day after the administration of different DOX preparations. Compared with DOX solution and uncoated DOXL, the mice given TMC60‐coated DOXL showed tumor angiogenesis with good shape, uniform arrangement, and small vascular branches, and the vascular density was decreased, suggesting promising tumor angiogenesis targeting of TMC60‐coated DOXL. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Preparation and efficacy of tumor vasculature‐targeted doxorubicin cationic liposomes coated by N‐trimethyl chitosan

Cationic liposomes (CLs) can accumulate in tumor vascular endothelial cells (VECs) to show high selective targeting ability. Therefore, chemotherapeutic agent‐loaded CLs are considered as new therapeutic vehicles to enhance the treatment efficacy. This study investigated the effect of N‐trimethyl chitosan (TMC), one of derivatives of chitosan with positive charge determined by its degree of quaternization (DQ), on preparing doxorubicin (DOX)‐loaded CLs. TMCs with various DQ, i.e., 20% (TMC20), 40% (TMC40), and 60% (TMC60) were synthesized and characterized by ¹HNMR. DOX‐loaded liposomes (DOXL) were prepared by ammonium sulfate gradients followed by TMC‐coating to obtain TMC‐coated DOXL with various positive surface charges. The morphology, size, ζ‐potential and drug release in vitro of TMC‐coated DOXL were studied compared with those of DOXL. Human umbilical vein endothelial cells (HUVECs) as cell model, the vascular targeting ability of TMC‐coated DOXL was evaluated in vitro. A solid tumor, formed by implantationmurine hepatoma cells (H₂₂) into mice, as tumor model, the tumor inhibition rate and tumor histological sections stained by HE of TMC‐coated DOXL group were researched compared with those of free DOX and DOXL group. It was found that with the increase of TMC's DQ, the positive surface charge of TMC‐coated DOXL was enhanced accordingly, which had little effect on DOX release in vitro while led to the significant increase of DOX uptake by HUVECs in vitro and the treatment effect on solid tumor in vivo. Especially, TMC‐coated DOXL showed better targeting ability to the nuclei compared with free DOX and DOXL, which could further enhance the efficacy of DOX in vivo. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

G-quadruplexes: targets in anticancer drug design

G-quadruplexes are special secondary structures adopted in some guanine-rich DNA sequences. As guanine-rich sequences are present in important regions of the eukaryotic genome, such as telomeres and the regulatory regions of many genes, such structures may play important roles in the regulation of biological events in the body. G-quadruplexes have become valid targets for new anticancer drugs in the past few decades. Many leading compounds that target these structures have been reported, and a few of them have entered preclinical or clinical trials. Nonetheless, the selectivity of this kind of antitumor compound has yet to be improved in order to suppress the side effects caused by nonselective binding. As drug design targets, the topology and structural characteristics of quadruplexes, their possible biological roles, and the modes and sites of small-ligand binding to these structures should be understood clearly. Herein we provide a summary of published research that has set out to address the above problem to provide useful information on the design of small ligands that target G-quadruplexes. This review also covers research methodologies that have been developed to study the binding of ligands to G-quadruplexes.     

pH/redox/thermo-stimulative nanogels with enhanced thermosensitivity via incorporation of cationic and anionic components for anticancer drug delivery

To explore the potential biomedical applications of nanogels, it is a key factor to improve their thermosensitivity. In this paper, triple-responsive nanogels poly(N-isopropylacrylamide–N,N′-dimethylaminoethyl methacrylate–acrylic acid) (PNDA) were synthesized via in situ incorporating both cationic components and anionic components into a normal thermosensitive polymer matrix. The triple-monomer constructed PNDA nanogels displayed an enhanced thermosensitivity as compared with dual-monomer constructed PND nanogels. The PNDA nanogels presented higher encapsulation efficiency (～89%) and exhibited better pH/redox/thermo-responsivenesses in an anticancer drug delivery. In vitro biological study indicated that the PNDA nanogels have excellent biocompatibility and improved anticancer cytotoxicity to A549 cells after loading drug DOX.     

Quantitative analysis of the cross-linked structure of microgels using fluorescent probes

Properties of polymeric microgels are influenced by the internal polymer cross-linked structure, but tools to quantitatively analyze this internal structure are limited. With the finding that polymer networks alter the diffusivity and subsequent excimer formation of pyrene, this study used the ratio between pyrene excimer and monomer emission to determine the number of cross-links (N) and average pore size (ξ) in poly(ethylene glycol) diacrylate (PEGDA) microgels. A calibration curve to relate pyrene emission to N and ξ in PEGDA hydrogels was prepared and used to calculate N and ξ in PEGDA microgels. The pyrene emission indicated that PEGDA microgels had a higher cross-linking density and a smaller average pore size when compared with bulk cross-linked hydrogels of the same PEGDA concentration. The analytical method demonstrated in this study may be useful for fine-tuning polymeric microgel properties for a broad array of applications.     

Optimized flurbiprofen cationic liposomes in situ gelling system of thermosensitive polymers for ocular delivery

A Flurbiprofen (FP) cationic liposomes in situ gelling system (CLIGS) of thermosensitive polymers was proposed; we investigated its in vitro and in vivo properties, and its potential use in ocular drug delivery was evaluated. This system, optimized via center composite design, was conceived from a combination of polymer‐ and lipid‐based delivery systems. Therefore, the system could integrate the advantages of both cationic liposomes and in situ gels and further improve the poor stability of cationic liposomes. Cationic liposomes were characterized for their particle size, shape, entrapment efficiency, ζ potential, and photograph of transmission electron microscopy. The in vitro penetration capability and precorneal retention time of the FP CLIGS were evaluated by a vertical Franz‐type cell method and γ scintigaraphy, respectively. The FP CLIGS showed an improved stability during a 30‐day storage period over than of FP cationic liposomes. In conclusion, CLIGS serves as a means to overcome a major limitation of cationic liposomes with a prolonged precorneal retention time, enhanced stability, and convenient administration due to the modified gelatinization temperature; this justifies their use as a carrier adjuvant for ocular delivery behaviors. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Encapsulation of inorganic nanoparticles into block copolymer micellar aggregates: Strategies and precise localization of nanoparticles

Precise assembly and localization of preformed inorganic nanoparticles (NPs) in block copolymer (BCP) assemblies are of great importance in realizing the formation of nano-hybrids with high performance. Properties of the nanocomposites depend not only on those of individual building blocks but also on their spatial organization at different length scales, demonstrating unique optical, electrical, and magnetic properties. With the aid of the BCPs, NPs can form a broader range of structures in the nanoscopically confined geometry. Thus, many studies have focused on the selective localization of NPs in BCP aggregates. In this paper, we will outline recent advances in the preparation strategies for precise localization of inorganic NPs into BCP micelles, including co-precipitation, supramolecular assembly, interfacial instabilities of emulsion droplets, heating–cooling, electrostatic interaction, and others. Manipulating the balance between enthalpic and entropic contributions provides one of the opportunities to precisely control the spatial distribution of NPs in BCPs assemblies. We will focus on the principles of precise control of dispersion and localization of the NPs in BCP micelles. Potential applications of the hybrid micelles will finally be discussed, followed by the summary and outlook of this emerging area.     

Diffusion of drugs from hydrogels and liposomes as drug carriers

BACKGROUND: The mass transfer of model drugs Lidocaine hydrochloride and Dihydroquercetin from hydrogels (the usual carriers for topical drugs), and hydrogels containing liposomes, as novel drug vehicles, was studied. Diffusion experiments were performed using a Franz diffusion cell. Experimental data were used to calculate drug diffusion coefficients across membranes, and their effective diffusion coefficients from hydrogels and liposome containing hydrogels. For the first time the diffusion resistance of all drug carriers was determined from corresponding diffusion coefficients. The main aim of this work was the study of drug diffusion coefficients from liposomes and their comparison with related diffusion coefficients from hydrogels to find how liposomes contribute to prolonged and controlled drug release. RESULTS: Drug diffusion coefficients were: 1.38 · 10^?8m² s^?1 for Lidocaine hydrochloride and 5.96 · 10^?9m² s^?1 for Dihydroquercetin, while corresponding effective diffusion coefficients from hydrogels were: 7.82 · 10^?10m² s^?1 and 7.98 · 10^?10m² s^?1, respectively. Effective diffusion coefficients from liposome‐containing hydrogels were:4.82 · 10^?10m² s^?1 (Lidocaine hydrochloride) and 4.305 · 10^?10m² s^?1 (Dihydroquercetin). Diffusion resistances for the two hydrogels were almost the same. Very similar values of diffusion resistances for all liposome dispersions were obtained. CONCLUSION: Calculated diffusion coefficients and resistances demonstrate that liposomes, as drug carriers, significantly affect diffusion rates. The results obtained could be used whenever diffusion‐controlled drug release is required. Copyright © 2010 Society of Chemical Industry     

Surface functionalization of SBA-15 nanorods for anticancer drug delivery

SBA-15 nanorods with high surface area (1010 m² g⁻¹) were functionalized by post grafting method with three different alkoxysilanes including (3-aminopropyl) triethoxysilane (APTES), 3-[bis(2-hydroxyethyl)amino] propyl triethoxysilane (HAPS) and 3-[2-(2-aminoethylamino) ethylamino] propyl trimethoxysilane (AEPS). The prepared materials were used as nanocarriers for an anticancer drug (gemcitabine). The obtained samples were characterized by SAXS, elemental analysis, TGA, N₂ adsorption/desorption, SEM, TEM, FTIR and UV spectroscopies. The adsorption and release properties of all samples were investigated. It was found that the surface functionalization increases the interaction between the carrier and gemcitabine and results in the loading enhancement of the drug. In addition, the adsorption of gemcitabine on the modified mesoporous matrix depends on the type and the amount of alkoxysilanes groups. The maximum content of the deposited drug in the modified SBA-15 nanorods is close to 22 wt.%. The rate of the drug release from the modified samples containing NH₂ groups on their surfaces is pH dependent.     

Microfiltration of cationic dyes using nano-clay membranes

Water resources cover 70% of earth surface with only 3% as fresh and the remaining frozen or unavailable. As a result, water and wastewater treatment have attracted a great deal of attention during last decades. Among various pollutants, dyes in textile wastewaters can have serious impacts on the environment. In the present study, low-cost ceramic nano-clay microfiltration membranes with low sintering temperature were fabricated via dry pressing, with natural zeolite as pore former. Flat disks were fabricated by sintering a mixture with various proportions of clay, zeolite and polyethylene glycol at 900 °C and characterized using FE-SEM, open porosity test, zeta potential, water permeability and acid-base treatment. Also, Membrane porosity was enhanced by increasing the zeolite content reaching 30.2% at 30 wt% and then decreased. The 30% zeolite membrane was selected for microfiltration of methylene blue, crystal violet and methyl orange from aqueous solutions. Initial and time filtered solution concentrations for each dye were measured using a UV–visible spectrophotometer. Methylene blue and crystal violet are cationic dyes due to the presence of NC(CH)₃ ⁺ while SO₃^- makes methyl orange anionic. The membrane had negative charge at pH = 6, suggesting adsorption of cationic dyes as the removal mechanism. 95.55% removal of crystal violet was obtained for the 54 mg L⁻¹ solution at 1 bar and 90.23% removal of methylene blue was obtained at optimal conditions with a 35.76 mg L⁻¹ concentration and 1.5 bar transmembrane pressure. However, less than 10% methyl orange removal was obtained, due to its negative charge. Membranes can be recovered completely by eliminating the adsorbed dyes via heat treatment at 300 °C for 1 h. The results approve the as-fabricated clay membranes cost-effective with high rejection of cationic dyes.     

Study on the electrochemical behaviour of the anticancer herbal drug emodin

The electrochemical behaviour of the anticancer herbal drug emodin was investigated by cyclic voltammetry (CV) at glassy carbon electrode. In 0.05 M NH₃-NH₄Cl (50% ethanol, pH 7.2) buffer solution, a pair of quasi-reversible redox peaks at potentials of Ep1 = −0.688 V and Ep2 = −0.628 V and one irreversible anodic peak, which was a typical anodic peak of emodin, at Ep3 = −0.235 V appeared at a scan rate of 100 mV/s. The irreversible anodic peak currents are linearly related to the emodin concentrations in a range from 8.9 × 10⁻⁸ M to 7.8 × 10⁻⁶ M with a pre-concentration time of 80 s under −0.620 V. Using the established method without pretreatment and pre-separation, emodin in herbal drug was determined with satisfactory results. Moreover, the electrode process dynamics parameters were also investigated by electrochemical techniques.     

Encapsulation of hydrophobic anticancer drug in nano-scale porous ceramic materials for photodynamic therapy

A hydrophilic nano-scale porous ceramic material, silica nano-carrier, was prepared using microemulsion method to deliver hypocrellin A (HA), a hydrophobic photosensitive anti-cancer drug, to cancer cells in vitro. The result hypocrellin A encapsulated silica nano-carrier delivery systems (HA-SNDS) are spherical, highly monodispersed, stable in aqueous system and own high drug encapsulation ability. Irradiation of the HA-SNDS with light of suitable wavelength results in efficient generation of singlet oxygen; further more the photo-stability of HA-SNDS is superior to free HA. In aqueous medium, the fluorescence intensity of the entrapped drug is stronger than the free drug, permitting use of fluorescence mediated bioimaging studies. In addition, HA-SNDS was stable at a wide range of pH. In vitro studies have demonstrated the active uptake of HA-SNDS into the cytosol of tumor cells. Comparative studies with free HA and HA-SNDS have demonstrated that the in vitro PDT efficacy of encapsulated HA is obvious superior to free HA. All these properties of HA-SNDS could make it a promising candidate for photodynamic therapy.     

PMMA‐based microgels for controlled release of an anticancer drug

Methyl methacrylate (MMA), methoxy poly(ethylene glycol) monomaleate (MPEG), and acrylamidoglycolic acid (AGA) terpolymeric microgels (MGs) have been synthesized by free‐radical surfactant‐free emulsion polymerization. MPEG was synthesized from maleic anhydride and methoxy poly(ethylene glycol). The MGs were crosslinked with ethylene glycol dimethacrylate, and the chemical crosslinking was confirmed by Fourier transform infrared spectroscopy. 5‐Fluorouracil (5‐FU), a model anticancer drug, has been loaded into the MGs by in situ and adsorption methods. Empty as well as drug‐loaded MGs were then characterized by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and X‐ray diffraction (XRD). DSC and XRD studies indicated a molecular level dispersion of the drug in PMMA MGs during in situ loading. TEM images showed the formation of spherical MGs. In vitro release of 5‐FU from the crosslinked poly(MMA‐co‐AGA‐co‐MPEG) MGs were investigated at both pH 7.4 and 1.2 buffer medium that controlled release of the drug up to ～ 18 h. Both the encapsulation efficiency and the release patterns were dependent on the amount of crosslinking agent and the amount of drug loaded. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009