Shewaye Lakew Mekuria

Polysaccharide based nanogels in the drug delivery system: Application as the carrier of pharmaceutical agents

Polysaccharide-based nanoparticles have fascinated attention as a vesicle of different pharmaceutical agents due to their unique multi-functional groups in addition to their physicochemical properties, including biocompatibility and biodegradability. The existence of multi-functional groups on the polysaccharide backbone permits facile chemical or biochemical modification to synthesize polysaccharide based nanoparticles with miscellaneous structures. Polysaccharide-based nanogels have high water content, large surface area for multivalent bioconjugation, tunable size, and interior network for the incorporation of different pharmaceutical agents. These unique properties offer great potential for the utilization of polysaccharide-based nanogels in the drug delivery systems. Hence, this review describes chemistry of certain common polysaccharides, several methodologies used to synthesize polysaccharide nanoparticles and primarily focused on the polysaccharide (or polysaccharide derivative) based nanogels as the carrier of pharmaceutical agents.

IL-6 Antibody and RGD Peptide Conjugated Poly(amidoamine) Dendrimer for Targeted Drug Delivery of HeLa Cells.

In this study, PAMAM dendrimer (G4.5) was conjugated with two targeting moieties, IL-6 antibody and RGD peptide (G4.5-IL6 and G4.5-RGD conjugates). Doxorubicin anticancer drug was physically loaded onto G4.5-IL6 and G4.5-RGD with the encapsulation efficiency of 51.3 and 30.1% respectively. The cellular internalization and uptake efficiency of G4.5-IL6/DOX and G4.5-RGD/DOX complexes was observed and compared by confocal microscopy and flow cytometry using HeLa cells, respectively. The lower IC50 value of G4.5-IL6/DOX in comparison to G4.5-RGD/DOX is indication that higher drug loading and faster drug release rate corresponded with greater cytotoxicity. The cytotoxic effect was further verified by increment in late apoptotic/necrotic cells due to delivery of drug through receptor-mediated endocytosis. On the basis of these results, G4.5-IL6 is a better suited carrier for targeted drug delivery of DOX to cervical cancer cells.

Encapsulation of Gadolinium Oxide Nanoparticle (Gd2O3) Contrasting Agents in PAMAM Dendrimer Templates for Enhanced Magnetic Resonance Imaging in Vivo

There has been growing interest in the research of nanomaterials for biomedical applications in recent decades. Herein, a simple approach to synthesize the G4.5-Gd2O3-poly(ethylene glycol) (G4.5-Gd2O3-PEG) nanoparticles (NPs) that demonstrate potential as dual (T1 and T2) contrasting agents in magnetic resonance imaging (MRI) has been reported in this study. Compared to the clinically popular Gd-DTPA contrasting agents, G4.5-Gd2O3-PEG NPs exhibited a longer longitudinal relaxation time (T1) and better biocompatibility when incubated with macrophage cell line RAW264.7 in vitro. Furthermore, the longitudinal relaxivity (r1) of G4.5-Gd2O3-PEG NPs was 53.9 s-1 mM-1 at 7T, which is equivalent to 4.8 times greater than to the Gd-DTPA contrasting agents. An in vivo T1-weighted MRI results revealed that G4.5-Gd2O3-PEG NPs significantly enhanced signals in the intestines, kidney, liver, bladder, and spleen. In addition, the T2-weighted MRI results revealed darker contrast in the kidney, which proves that G4.5-Gd2O3-PEG NPs can be exploited as T1 and T2 contrasting agents. In summary, these findings suggest that the G4.5-Gd2O3-PEG NPs synthesized by an alternative approach can be used as dual MRI contrasting agents.

Synthesis and characterization of bioreducible heparin-polyethyleneimine nanogels: application as imaging-guided photosensitizer delivery vehicle in photodynamic therapy

Herein, we synthesized and characterized novel bioreducible heparin polyethyleneimine (HPC) nanogels consisting of heparin, branched polyethyleneimine (PEI) and L-cysteine. 1H-NMR and FTIR analysis confirmed the formation of HPC nanogels while TEM and dynamic light scattering revealed uniform spherical nanoparticles with average diameter of <200 nm. Zinc phthalocyanine (ZnPC) was encapsulated via the dialysis method and the drug is released in vitro from disulfide-containing HPC nanogels in a redox-sensitive manner at low pH. Additionally, HPC nanogels possess bright blue fluorescence which eliminates the use of additional probing agent in image-guided drug delivery. Moreover, singlet oxygen detection revealed that nanogels prevented ZnPc aggregation thus enhancing 1O2 generation and photodynamic therapy (PDT) efficacy. These results showed that disulfide crosslinked HPC nanogels are promising vehicles for stimulated photosensitizer delivery in advanced PDT.

A pH-sensitive micelle composed of heparin, phospholipids, and histidine as the carrier of photosensitizers: Application to enhance photodynamic therapy of cancer

In this study, we describe the synthesis of a stable, pH-sensitive micelle composed of heparin, 1, 2-distearoyl-sn-glycerol-3-phosphoethanolamine, and l-histidine (HDH) through 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS) chemistry. 1H-Nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR) analyses confirmed the formation of HDH copolymers and dynamic light scattering (DLS) measurements indicated a particle size of 111.57±12.36nm and zeta potential of -59.8±5.2mV for the nanoparticles. The drug-loading and encapsulation efficiency of the micelles were 14.52±1.2% and 65.47±1.87%, respectively. Drug release studies showed approximately 91% zinc phthalocyanine (ZnPc) release from micelles in acidic conditions (pH 5.0) in comparison with 63% in physiological conditions (pH 7.4) after 96h of incubation. Singlet oxygen (1O2) detection revealed that the micelles prevented ZnPc aggregation and enhanced 1O2 generation. Cellular uptake of ZnPc-loaded micelles (ZnPc-HDH) was observed using confocal microscopy. Phototoxicity experiments in HeLa cells showed that ZnPc-loaded micelles had higher toxicity than that shown by the same concentration of free ZnPc. Hence, pH-sensitive HDH micelles are a promising carrier for hydrophobic ZnPc and improving PDT efficacy.

PAMAM dendrimer based targeted nano-carrier for bio-imaging and therapeutic agents

In the last several decades, researchers have focused on developing suitable drug carriers to deliver pharmaceutical agents to treat cancer diseases. PAMAM dendrimers have been studied as potential delivery systems for targeting, imaging, and/or delivering therapeutic agents specifically to diseased tissues because of their unique properties, such as: multiple functionalities at the periphery or in the cavity, biocompatibility, tunable size, and monodispersity. Anti-cancer agents may be incorporated into the interior void space or conjugated to the surface of PAMAM to enhance the delivery of cytotoxic drugs. In addition, targeting ligands can also be attached to the dendrimer surface to allow active targeting and minimize harm to normal cells. In summary, this review highlights the contributions of PAMAM dendrimers to the field of nanotechnology with the intent to aid researchers in exploring dendrimers for targeted drug delivery, contrasting and bio-imaging agents.

Preparation of self-assembled core-shell nano structure of conjugated generation 4.5 poly (amidoamine) dendrimer and monoclonal Anti-IL-6 antibody as bioimaging probe.

In this article, interleukin-6 (IL-6)-conjugated anionic generation 4.5 (G4.5) poly(amidoamine) (PAMAM) was synthesized through EDC/NHS coupling chemistry and evaluated for its optical properties in vitro. Conjugation was confirmed using Fourier-transformed infrared spectroscopy (FT-IR) and 2-dimensional nuclear magnetic resonance (2D NMR). After IL-6 conjugation, nanoparticle size increased to approximately 70 nm and zeta potential increased from -56.5 ± 0.2 to -19.1 ± 2.4 mV due to neutralization of negatively charged G4.5. Wide-angle X-ray scattering (WAXS) suggested that a layered nanoparticle structure was formed by the G4.5/IL-6 conjugate. Most interestingly, the intrinsic fluorescence of G4.5 significantly increased after IL-6 conjugation and underwent a blue shift as a result of H-aggregation. Furthermore, the cellular uptake of the conjugates by HeLa cells was significantly enhanced in comparison to free G4.5, as demonstrated by confocal microscopy and flow cytometry. These results indicated that the described system may be a potential bioimaging probe in vitro.

Synthesis and characterization of redox-sensitive heparin-β-sitosterol micelles: Their application as carriers for the pharmaceutical agent, doxorubicin, and investigation of their antimetastatic activities in vitro

Although there are several clinical attempts to treat tumors at the primary site, only few therapies can inhibit the spread of metastatic cancers. In this study, we synthesized redox-sensitive heparin-β-sitosterol micelles that show antimetastatic activity. Proton nuclear magnetic resonance and Fourier transform infrared analyses confirmed the formation of bioreducible heparin-β-sitosterol (bHSC) conjugates, whereas dynamic light scattering was used to measure the particle size and zeta potential. Both 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and flow cytometry assays confirmed the low toxicity of the synthesized micelles. Doxorubicin (Dox) was encapsulated via the dialysis method, and its loading and encapsulation efficiencies were 16.49±1.2% and 58.47±1.87%, respectively. An in vitro release study showed that approximately 89% and 52% of Dox were released after 48h in the presence and absence of reduced glutathione, respectively. The hemocompatibility and antimetastatic effects of bHSC were evaluated using the hemolysis and scratch assays, respectively. F-Actin fluorescence microscopy showed that heparin- and bHSC-treated HeLa cells had poorly oriented stress fibers. In summary, the synthesized bHSC micelles are good candidates as drug delivery systems owing to their low toxicity, excellent hemocompatibility, and antimetastatic effects.

Radiation-Sensitive Dendrimer-Based Drug Delivery System

Abstract Combination of chemotherapy and radiotherapy is used to enhance local drug delivery while reducing off‐target tissue effects. Anticancer drug doxorubicin (DOX) is loaded into l‐cysteine modified G4.5 dendrimer (GC/DOX) and released at different pH values in the presence and absence of γ‐radiation. Presence of γ‐radiation significantly improves DOX release from the GC/DOX under acidic pH conditions, suggesting that GC dendrimer is a radiation‐sensitive drug delivery system. GC/DOX is further evaluated by determining cytotoxicity in uterine cervical carcinoma HeLa cells. GC/DOX shows high affinity for cancer cells and effective drug release following an external stimulus (radiation exposure), whereas an in vivo zebrafish study confirms that l‐cysteine acts as a radiosensitizer. GC/DOX treatment combined with radiotherapy synergistically and successfully inhibits cancer cell growth.

Bioinspired, Manganese-Chelated Alginate–Polydopamine Nanomaterials for Efficient in Vivo T1-Weighted Magnetic Resonance Imaging

Manganese-based nanomaterials are an emerging new class of magnetic resonance imaging (MRI) contrast agents (CAs) that provide impressive contrast abilities. MRI CAs that can respond to pathophysiological parameters such as pH or redox potential are also highly in demand for MRI-guided tumor diagnosis. Until now, synthesizing nanomaterials with good biocompatibility, physiochemical stability, and good contrast effects remains a challenge. This study investigated two new systems of calcium/manganese cations complexed with either alginate-polydopamine or alginate-dopamine nanogels [AlgPDA(Ca/Mn) NG or AlgDA(Ca/Mn) NG]. Under such systems, Ca cations form ionic interactions via carboxylic acids of the Alg backbone to enhance the stability of the synthetic nanogels (NGs). Likewise, complexation of Mn cations also increased the colloidal stability of the synthetic NGs. The magnetic property of the prepared CAs was confirmed with superconducting quantum interference device measurements, proving the potential paramagnetic property. Hence, the T1 relaxivity measurement showed that PDA-complexed synthetic NGs reveal a strong positive contrast enhancement with r1 = 12.54 mM-1·s-1 in 7.0 T MRI images, whereas DA-complexed synthetic NGs showed a relatively lower T1 relaxivity effect with r1 = 10.13 mM-1·s-1. In addition, both the synthetic NGs exhibit negligible cytotoxicity with >92% cell viability up to 0.25 mM concentration, when incubated with the mouse macrophage (RAW 264.7) and HeLa cells, and high biocompatibility under in vivo analysis. The in vivo MRI test indicates that the synthetic NG exhibits a high signal-to-noise ratio for longer hours, which provides a longer image acquisition time for tumor and anatomical imaging. Furthermore, T1-weighted MRI results revealed that PEGylated AlgPDA(Ca/Mn) NGs significantly enhanced the signals from liver and tumor tissues. Therefore, owing to the enhanced permeability and retention effect, significantly enhanced in vitro and in vivo imagings, low cost, and one-pot synthesis method, the Mn-based biomimetic approach used in this study provides a promising and competitive alternative for noninvasive tumor detection and comprehensive anatomical diagnosis.