Efficient Synthesis and Characterization of New Photoactive Dextran Esters Showing Nanosphere Formation

Synthesis, characterization, and cytotoxicity evaluation of dextran-myristoyl-ECGKRK peptide conjugate

CGKRK is a well-known tumor homing peptide with significant specificity for many types of cancer tissues. Herein, we describe the synthesis of a novel drug delivery system based on dextran decorated with myristoyl-ECGKRK peptide. The myristoylated peptide was synthesized and conjugated to dextran via an ester bond followed by purification. FT-IR and NMR confirmed the success of the conjugation reaction, while the surface morphology examination revealed that the conjugate has a characteristic porous network-like structure. Dynamic-light scattering measurements indicated the ability of the conjugate to self-assemble into nanoparticles with an average size of 248 ± 6.33 nm, and zeta potential of 10.7 mV. The cytotoxicity profiles for the peptide, dextran (Dex0), and dextran-peptide conjugate (Dex1) were evaluated against triple-negative breast cancer cells (MDA-MB-231), breast cancer cells (MCF-7), and human embryonic normal kidney cells (HEK-293). The results revealed that myristoyl-ECGKRK was noncytotoxic on the two different breast cancer cell lines up to 50 μM, but the cell viability was minimally reduced to 85% at 50 μm in HEK-293 cells. Similarly, Dex0 showed a neglected cytotoxicity profile at all tested concentrations. The Dex1 was not toxic to the cells up to a concentration of 8.3 mg/mL.

Studies about the design of magnetic bionanocomposite

Magnetic nanocomposites are a class of smart materials that have attracted recent interest as drug delivery systems or as medical implants. A new approach toward the biocompatible nanocomposites suitable for remote melting is presented. It is shown that magnetite nanoparticles (MNPs) can be embedded into a matrix of biocompatible thermoplastic dextran esters. For that purpose, fatty acid esters of dextran with adjustable melting points in the range of 30–140 °C were synthesized. Esterification of the polysaccharide by activation of the acid as iminium chlorides guaranteed mild reaction conditions leading to high-quality products as confirmed by Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy as well as by gel permeation chromatography (GPC). A method for the preparation of magnetically responsive bionanocomposites (BNCs) was developed consisting of combined dissolution/suspension of the dextran ester and hydrophobized MNPs in an organic solvent followed by homogenization with ultrasonication, casting of the solution, drying and melting of the composite for a defined shaping. This process leads to a uniform distribution of MNPs in BNC as revealed by scanning electron microscope (SEM). Samples of different geometries were exposed to high-frequency alternating magnetic field (AMF). It could be shown that defined remote melting of such biocompatible nanocomposites is possible for the first time. This may lead to a new class of magnetic remote-control systems, which are suitable for controlled release applications or self-healing materials. BNCs containing biocompatible dextran fatty acid ester melting close to human body temperature were prepared and loaded with Rhodamine B (RhB) or green fluorescent protein (GFP) as model drugs to evaluate their potential use as drug delivery system. The release of the model drugs from the magnetic BNC investigated under the influence of a high-frequency AMF (20 kA/m at 400 kHz) showed that on-demand release is realized by applying the external AMF. The BNC possessed a long-term stability (28 d) of the incorporated iron oxide particles after incubation in artificial body fluids. Temperature-dependent mobility investigations of MNP in the molten BNC were carried out by optical microscopy, magnetometry, alternating current (AC) susceptibility, and Mössbauer spectroscopy measurements. Optical microscopy shows a movement of agglomerates and texturing in the micrometer scale, whereas AC susceptometry and Mössbauer spectroscopy investigations reveal that the particles perform diffusive Brownian motion in the liquid polymer melt as separated particles rather than as large agglomerates. Furthermore, a texturing of MNP in the polymer matrix by a static magnetic field gradient was investigated. First results on the preparation of cross-linkable dextran esters are shown. Cross-linking after irradiation of the BNC prevents melting that can be used to influence texturing procedures.

Dual Photo- and pH-Responsive Spirooxazine-Functionalized Dextran Nanoparticles

A dual photo- and pH-responsive spirooxazine-functionalized polymer was synthesized by functionalization of dextran with a spirooxazine derivative (SO-COOH). The functionalized dextran derivatives can form nanoparticles in aqueous medium. Under UV light irradiation, the spirooxazine-functionalized dextran (Dex-SO) nanoparticles isomerize to zwitterionic merocyanine-functionalized dextran (Dex-MC), which leads to aggregation. However, the process is reversible upon irradiation with visible light. Under acidic conditions, the hydrophobic spirooxazine is protonated, and the nanoparticles aggregate or swell at pH values of 5 or 3, respectively. The encapsulation of the hydrophobic fluorescent dye Nile Red as model drug allowed us to gain more information about the structural changes under stimulation of UV light and acid treatment.

Novel amphiphilic dextran esters with antimicrobial activity

New amphiphilic dextran esters were obtained by polysaccharide functionalization with different substituted 1,2,3-triazoles-4-carboxylic acid via in situ activation with N, N'-carbonyldiimidazole. Nitrogen-containing heterocyclic derivatives were achieved by copper(I)-catalyzed cycloaddition reaction between organic azides and ethyl propiolate. Structural characteristics of the compounds were studied by elemental analysis, Fourier transform infrared and nuclear magnetic resonance spectroscopy (¹H and ¹³C-NMR). Thermogravimetric analysis, differential scanning calorimetry and wide-angle X-ray diffraction were used for esters characterization. Properties of polymeric self-associates, formed in aqueous solution, were studied by dynamic light scattering and transmission electron microscopy. The critical aggregation concentration values for dextran esters, determined by fluorescence spectroscopy, were in the range of 4.1-9.5 mg/dL. Antimicrobial activity, investigated for some of the polymers by disc-diffusion method, pointed out that polysaccharide esters were active.

Nanoparticles Based on Hydrophobic Polysaccharide Derivatives-Formation Principles, Characterization Techniques, and Biomedical Applications

Polysaccharide (PS) nanoparticles (NP) are fascinating materials that combine huge application potential with the unique beneficial features of natural biopolymers. Different types of PS-NP can be distinguished depending on the basic preparation principles (top-down vs bottom-up vs coating of nanomaterials) and the material from which they are obtained (native PS vs chemically modified PS derivatives vs nanocomposites). This review provides a comprehensive overview of an approach towards PS-NP that has gained rapidly increasing interest within the last decade; the nanoself-assembling of hydrophobic PS derivatives. This facile process is easy to perform and offers a broad structural diversity in terms of the PS backbone and the additional functionalities that can be introduced. Fundamental principles of different NP preparation techniques along with useful characterization methods are presented in this work. A comprehensive summary of PS-NP prepared by different techniques and with various PS backbones and types/amounts of hydrophobic substituents is given. The intention is to demonstrate how different parameters determine the size, size distribution, and zeta-potential of the particles. Moreover, application trends in biomedical areas are highlighted in which tailored functional PS-NP are evaluated and constantly developed further.

Regulated basal and bolus insulin release from glucose-responsive core-shell microspheres based on concanavalin A-sugar affinity

Individual insulin therapy considering the heterogeneity of insulin resistance between patients may bring more benefits than conventional therapy. Therefore, in glucose-responsive insulin delivery systems, more attention should be paid on further regulation of insulin release to meet individual requirements. Our study shows the feasibility of using a photo-crosslinkable shell layer to regulate basal and bolus insulin release from glucose-responsive Con A-polysaccharides network. Core-shell microspheres were fabricated through a two-step high-speed shear-emulsification method. The morphology was observed by SEM and TEM, and the core-shell structure was confirmed by the differences in chemical composition between core-shell and single-layer microspheres obtained from XPS and IR analysis. In vitro insulin release test revealed that the core-shell microspheres with or without light-irradiation could maintain corresponding bolus and basal insulin release in response to different glucose concentration but enable much lower burst release compared with single-layer microspheres without shell. Meanwhile, insulin release rate and amount could be further decreased upon light-irradiation owing to the photo-induced cycloaddition of cinnamate pendant groups of the shell material. The released insulin was proved to remain active according to fluorescence and circular dichroism analysis. The HDF cell viability assessment suggested that the core-shell microspheres possessed no in vitro cytotoxicity.

Dual Wavelength-Triggered Gold Nanorods for Anticancer Treatment

Gold nanomaterials with light-responsive properties can be exploited as light-triggered delivery vehicles to enhance the therapeutic efficacy of anticancer drugs. Additionally, different wavelengths of light can be utilized to achieve the combined effects of light-triggered release of therapeutics and light-induced localized heating, which results in improved anticancer efficacy. Herein, we describe methods to develop gold nanorod (AuNR) complexes that provide drug delivery or photothermal therapy when activated by ultraviolet (UV) or near-infrared (NIR) wavelengths of light, respectively. The surface functionalization of AuNRs with three key components is presented. The first component, cyclodextrin, serves to encapsulate drugs of interest. The second component, dextran-phenyl-azo-benzoic acid (DexAzo), serves as a capping agent that undergoes a conformational change upon UV light activation to expose the drugs for release. The third component is a folic acid-based targeting ligand that provides efficient delivery of the AuNR complexes to cancer cells. The dual wavelength activation of these drug-loaded AuNR complexes, which enables one to achieve highly efficient anticancer therapy through the combined effects of UV-triggered drug release and NIR-induced hyperthermia, is also described.

A dual wavelength-activatable gold nanorod complex for synergistic cancer treatment

A multifunctional gold nanorod (AuNR) complex is described with potential utility for theranostic anticancer treatment. The AuNR was functionalized with cyclodextrin for encapsulation of doxorubicin, with folic acid for targeting, and with a photo-responsive dextran-azo compound for intracellular controlled drug release. The interaction of a AuNR complex with HeLa cells was facilitated via a folic acid targeting ligand as displayed in the dark-field images of cells. Enhanced anticancer efficacy was demonstrated through the synergistic combination of promoted drug release upon ultraviolet (UV) light irradiation and photothermal therapy upon infrared (IR) irradiation. This multifunctional AuNR-based system represents a novel theranostic strategy for spatiotemporal delivery of anticancer therapeutics.

Xylan-based nanoparticles: prodrugs for ibuprofen release

Esterification of xylan with ibuprofen via activiation of the carboxylic acid with N,N'-carbonyldiimidazole (CDI) yields products of high drug loadings. Subsequent sulfation of xylan ibuprofen esters using the gentle agent SO(3)/DMF was successfully carried out in order to modify hydrophobicity of the xylan esters. The structure of the novel xylan esters was evaluated by means of NMR spectroscopy. The resulting xylan derivatives self assemble into spherical nanoparticles with mean diameters ranging from 162 to 472 nm. Preliminary stability measurements indicate that hydrolytic stability decreases with increase in degree of substitution of sulfate groups. Thus, a new concept toward improved drug delivery from polysaccharide-based nanoparticles can be established here.