Tivadar Feczkó

Poloxamers for surface modification of hydrophobic drug carriers and their effects on drug delivery

Tri-block copolymer poloxamers are successfully employed for reducing adsorption of proteinous molecules onto hydrophobic surfaces which will protect them from quick engulfing by macrophages. For sustained systemic circulation of hydrophobic drug carriers, particle surfaces need suitable modification for avoiding phagocytosis and this can be successfully done by poloxamers. They can affect the drug release profile, which makes them a very promising agent for targeted delivery. This review discusses the structure, characteristics, and advantages of poloxamers. Poloxamer adsorption onto hydrophobic surfaces and adlayer thickness, relative phagocytic uptake, and drug release profiles of coated drug loaded particles have been described in detail.

Surface modification of HSA containing magnetic PLGA nanoparticles by poloxamer to decrease plasma protein adsorption.

Lifetime prolongation for hydrophobic drug carriers has been the focus of interest for many years. Poloxamer (Pluronic F68, PF68) has been employed in this study for modifying the surface of magnetic poly(d,l-lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) loaded with human serum albumin (HSA) model drug. Surface characteristics of untreated and PF68 treated NPs were analyzed by size, zeta potential and electrophoretic mobility studies. UV-vis spectroscopic analysis, isothermal titration calorimetry (ITC) and dynamic light scattering methods were used to investigate serum protein (bovine serum albumin, BSA) adsorption. Results showed the successful surface attachment of PF68. Among different concentrations (0.1-1%, wt/vol) of PF68 studied, 0.5% was found to be the most useful, since a higher concentration can issue in micelle formation. 50% less BSA tended to be adsorbed on the treated NPs in comparison to the untreated ones.

Co-encapsulation of human serum albumin and superparamagnetic iron oxide in PLGA nanoparticles: Part II. Effect of process variables on protein model drug encapsulation efficiency

Abstract This study investigates encapsulation efficiency of model drug, encapsulated by magnetic poly d,l-lactic-co-glycolic acid (PLGA) nanoparticles (NPs). This is the following part of our preceding paper, which is referred in this paper as Part I. Magnetic nanoparticles and model drug human serum albumin (HSA)-loaded PLGA NPs were prepared by the double emulsion solvent evaporation method. Among five important process variables, concentration of PLGA and concentration of HSA in the inner aqueous phase along with their cross-effect had the strongest influence on the encapsulation efficiency. Encapsulation efficiency of nanoparticles ranged from 18% to 97% depending on the process conditions. Higher encapsulation efficiencies can be achieved by using low HSA and high PLGA concentrations. The optimization process, carried out by exact mathematical tools using GAMSTM/MINOS software makes it easier to find out optimum process conditions to achieve comparatively high encapsulation efficiency (e.g. 92.3%) for relatively small-sized PLGA NPs (e.g. 155 nm).

Co-encapsulation of human serum albumin and superparamagnetic iron oxide in PLGA nanoparticles: Part I. Effect of process variables on the mean size

Abstract PLGA (poly d,l-lactic-co-glycolic acid) nanoparticles (NPs) encapsulating magnetite nanoparticles (MNPs) along with a model drug human serum albumin (HSA) were prepared by double emulsion solvent evaporation method. This Part I will focus on size and size distribution of prepared NPs, whereas encapsulation efficiency will be discussed in Part II. It was found that mean hydrodynamic particle size was influenced by five important process variables. To explore their effects, a five-factorial, three-level experimental design and statistical analysis were carried out using STATISTICA® software. Effect of process variables on the mean size of nanoparticles was investigated and finally conditions to minimize size of NPs were proposed. GAMS™/MINOS software was used for optimization. The mean hydrodynamic size of nanoparticles ranged from 115 to 329 nm depending on the process conditions. Smallest possible mean particle size can be achieved by using low polymer concentration and high dispersion energy (enough sonication time) along with small aqueous/organic volume ratio.

Organic nanoparticulate photochromes

Photochromic organic dyes can be widely used in materials for optically rewritable data storage, photonic switches, memories, sensors, or actuators. In recent years photochromic materials based on nanoparticles became particularly focused, since they can be dispersed in colloidal aqueous suspensions or incorporated in thin films, avoiding problems of light scattering or shallow light penetration in bulk materials. Spiropyrans, spirooxazines and diarylethenes were by far the most researched photochromes in nanoparticulate systems. Great effort was made to investigate photochromic dyes incorporated into organic nanoparticles via self-assembly strategies, covalent linkage or dispersion of the molecular species in polymers (doping). Nanoparticles composed of solely photochromic dyes were prepared by laser ablation and reprecipitation techniques. Photochromic dyes were microencapsulated by self-assembly, soap free-, emulsion/microemulsion/miniemulsion or free radical- (co)polymerization. Sol-gel processing from silane precursors to poly(organo)siloxane matrix is a common method to synthesize doped or core-shell photochromic organogels. Coloured forms of some photochromes display fluorescence; however, a more effective strategy for fluorescence modulation with photochromic molecules is integrating them, covalently or noncovalently, with a separate fluorophore in the same nanoparticles. These photoresponsive nanoparticles may find applications particularly in biological fields such as cell labelling and bioimaging. The purpose of this review is to summarize the preparation methods of organic nanoparticles containing photochromic dyes and to investigate their typical properties derived from their nanoparticulate character.

Encapsulation of human serum albumin in submicrometer magnetic poly(lactide-co-glycolide) particles as a model system for targeted drug delivery

Abstract Two types of iron oxide nanoparticles were synthesized by coprecipitation of Fe(II) and Fe(III) chlorides: water-dispersible γ-Fe2O3 and organic solvent-dispersible oleic acid-coated Fe3O4 particles. The nanoparticles, together with human serum albumin (HSA) serving as a model for a protein-type drug, were then incorporated in poly(lactide-co-glycolide) (PLGA) particles using double emulsion solvent evaporation technique. Morphology, size and particle size distribution of the resulting particles was analyzed by electron microscopy and dynamic light scattering. Iron oxide and HSA encapsulating efficiency was determined by Prussian Blue staining and micro-BCA assay, respectively.

Dual Drug Delivery of Sorafenib and Doxorubicin from PLGA and PEG-PLGA Polymeric Nanoparticles

Combinatorial drug delivery is a way of advanced cancer treatment that at present represents a challenge for researchers. Here, we report the efficient entrapment of two clinically used single-agent drugs, doxorubicin and sorafenib, against hepatocellular carcinoma. Biocompatible and biodegradable polymeric nanoparticles provide a promising approach for controlled drug release. In this study, doxorubicin and sorafenib with completely different chemical characteristics were simultaneously entrapped by the same polymeric carrier, namely poly(d,l-lactide-co-glycolide) (PLGA) and polyethylene glycol-poly(d,l-lactide-co-glycolide) (PEG-PLGA), respectively, using the double emulsion solvent evaporation method. The typical mean diameters of the nanopharmaceuticals were 142 and 177 nm, respectively. The PLGA and PEG-PLGA polymers encapsulated doxorubicin with efficiencies of 52% and 69%, respectively, while these values for sorafenib were 55% and 88%, respectively. Sustained drug delivery under biorelevant conditions was found for doxorubicin, while sorafenib was released quickly from the PLGA-doxorubicin-sorafenib and PEG-PLGA-doxorubicin-sorafenib nanotherapeutics.

In vitro IFN-α release from IFN-α- and pegylated IFN-α-loaded poly(lactic-co-glycolic acid) and pegylated poly(lactic-co-glycolic acid) nanoparticles.

AIM Interferon alpha (IFN-α) controlled release of nanoparticles was investigated under in vitro conditions. MATERIALS & METHODS IFN-α and pegylated IFN-α (PEG-IFN-α) were encapsulated by poly(lactic-co-glycolic acid) (PLGA) and pegylated PLGA (PEG-PLGA) copolymers using double emulsion solvent evaporation method. RESULTS The size of resulting four nanoparticles (IFN-α in poly(lactic-co-glycolic acids), IFN-α in poly(lactic-co-glycolic acid)-polyethylene glycol, PEG-IFN-α in poly(lactic-co-glycolic acids) and PEG-IFN-α in poly(lactic-co-glycolic acid)-polyethylene glycol) was below 130 nm diameter. IFN-α encapsulation efficiency of the nanoparticles was between 78 and 91%. CONCLUSION The in vitro drug release studies conducted in phosphate-buffered saline and human plasma highlighted the role of incubation medium on the IFN release from the nanoparticles. The PEG-IFN-α in poly(lactic-co-glycolic acid)-polyethylene glycol was the most promising nanoparticle among the four formulations because of its remarkably constant release in both phosphate-buffered saline and plasma.

Preparation of spherical agglomerates from potash alum

Salt hydrates are low-cost, readily available PCMs (phase change materials). As a core material for encapsulation the salt agglomerates can be prepared by spherical agglomeration, a well-known method to produce drug loaded microspheres in the pharmaceutical industry, but not used for PCM formulation. The two basic mechanisms in spherical crystallization are spherical agglomeration (SA) and the quasi emulsion solvent diffusion (QESD) processes. The spherical agglomerates of aluminium potassium sulfate dodecahydrate (potash alum dodecahydrate), a highly water soluble material, were produced by spherical crystallization technique in four different solvent systems. In water (good solvent)–ethanol–dichloromethane (poor solvent) ternary solvent system the agglomeration takes place by the SA mechanism. In water–ethanol–n-hexane, water–ethanol and water–isopropyl alcohol solvent systems spherical particles were produced by the QESD method. Both procedures were proved to be feasible for the preparation of spherical salt hydrate particles as core material for microencapsulation. This method gives important basis to produce phase change materials from suitable salt hydrates. The potash alum content in the spherical agglomerates was analysed by conductivity and thermogravimetric measurements and their composition by XRD. Volume weighted mean diameters (D(4,3)) of the microparticles were 66 μm, 79 μm, 89 μm, and 684 μm formed in water–ethanol–n-hexane, water–ethanol, water–isopropyl alcohol, and water–ethanol–dichloromethane solvent system, respectively. Potash alum dodecahydrate is a double salt. Due to its different solubility in the four different solvent systems it crystallized out not only as potash alum, but also in other salt forms. The enthalpy changes of spherical agglomerates produced from different solvent systems were increased proportionally with potash alum contents.

Thermal Energy Storage By Microcomposite Of A Phase Change Material And Ethyl Cellulose

Abstract Phase change materials (PCMs) are capable of storing and releasing large amounts of latent heat thermal energy when undergoes phase change. They are developed for various building applications such as thermal energy storage, thermal protection, cooling, air-conditioning, waste heat recovery and for solar heating systems. Paraffin PCMs have low cost and a moderate thermal energy density, though a low thermal conductivity. PCM microencapsulation is one of the best tools to enhance the heat transfer rate by enlarging the surface area. In this work ethyl cellulose as an environmental friendly encapsulating material was used to entrap n-hexadecane PCM by an emulsion-solvent evaporation method using poly(vinyl alcohol) (PVA), Tween 80 or poly(methacrylic acid sodium salt) (PMAA) emulsifier. The structure of the forming microparticles was predicted by determining the interfacial tensions between the phases. Both theoretically and in the experiments, composites prepared with PMAA showed the most desirable properties regarding the size (average: 80 m) and the latent heat storage capacity (of melting and freezing were 111.4 J/g and 117.9 J/g, respectively), furthermore, there was no significant temperature and enthalpy change observed after 1000 heating-cooling thermal cycles, thus, this microcomposite can be considered as suitable encapsulated PCM for thermal energy storage applications.