Tilahun Ayane Debele

Drug Carrier for Photodynamic Cancer Therapy

Photodynamic therapy (PDT) is a non-invasive combinatorial therapeutic modality using light, photosensitizer (PS), and oxygen used for the treatment of cancer and other diseases. When PSs in cells are exposed to specific wavelengths of light, they are transformed from the singlet ground state (S0) to an excited singlet state (S1–Sn), followed by intersystem crossing to an excited triplet state (T1). The energy transferred from T1 to biological substrates and molecular oxygen, via type I and II reactions, generates reactive oxygen species, (1O2, H2O2, O2*, HO*), which causes cellular damage that leads to tumor cell death through necrosis or apoptosis. The solubility, selectivity, and targeting of photosensitizers are important factors that must be considered in PDT. Nano-formulating PSs with organic and inorganic nanoparticles poses as potential strategy to satisfy the requirements of an ideal PDT system. In this review, we summarize several organic and inorganic PS carriers that have been studied to enhance the efficacy of photodynamic therapy against cancer.

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.

Synthesis and evaluation of the targeted binding of RGD-containing PEGylated-PEI/DNA polyplex micelles as radiotracers for a tumor-targeting imaging probe

Site-specific labeling of molecular imaging probes necessitates the topical administration of medications during the development of homogeneous tracers. Hence, receptor-mediated gene transfer is believed to be of enormous significance in the clinical translation of a promising gene delivery technique. Plasmid DNA (pEGFP) and polycations produce polyplexes, which can be proficient probes for molecular imaging when accompanied by a gamma emitter. Therefore, this study describes the physico-biological characterization of a radiotracer for tumor imaging in a HeLa tumor-bearing mouse model. Polyplex micelles were formed with pEGFP and Arg-Gly-Asp (RGD) peptide-modified poly(ethylene glycol)-grafted polyethylenimine (E[c(RGDyK)]2-PEG-g-PEI) and were labeled with 99mTc for the in vivo study. The various PEG-g-PEIs prepared by controlling the PEG-to-PEI ratios were confirmed by 1H-NMR. The sizes and zeta potentials of the PEG-g-PEI/DNA polyplexes were 90–135 nm and 40–50 mV, respectively. The biophysical characterization of pEGFP in polyplexes was evaluated via various methods, including determination of the condensation efficiency of the polymers and the biodistribution, in vitro stability, in vivo application, and kinetics of the radiolabeled polyplexes. These characteristics were studied as a function of time using 3D-SPECT/CT images and by end-point scintillation counting. The polyplex of PEG-g-PEI/DNA fabricated with a PEG/PEI ratio of 10 : 1 and N/P = 1, i.e., PP10/D, exhibited the lowest cytotoxicity and the highest transfection efficiency. The cyclic-RGD peptide-modified polyplex PEG-g-PEI/DNA (RPP10/D) had significantly higher binding affinity and transfection efficiency than the non-targeting PP10/D did. 99mTc radio-labeled PP10/D and RPP10/D were prepared with high radiolabeling efficiency of greater than 95% and radiochemical stability above 80%, both in saline and in rat plasma, when stored for 24 h and were evaluated for their tumor-targeting capability and biodistribution. Through in vivo SPECT/CT images, it was determined that RPP10/D-99mTc presented higher uptake in the tumor than PP10/D-99mTc at all of the post-injection times studied. We found that the two tracers of radioactive complexes mainly accumulated in the liver, spleen and kidneys at 24 h after intravenous injection in female BALB/c nude mice bearing subcutaneous HeLa tumors. The accumulation of the site-specifically labeled RPP10/D-99mTc was lower in liver, kidney and spleen compared with non-targeting PP10/D-99mTc.

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.

Synthesis and characterization of dual-sensitive fluorescent nanogels for enhancing drug delivery and tracking intracellular drug delivery

Here, dual-sensitive fluorescent branched alginate-polyethyleneimine copolymer (bAPSC) nanogels were synthesized from thiolated alginate and stearoyl-derivatized branched polyethyleneimine. The formation of bAPSC conjugates was confirmed through proton nuclear magnetic resonance and Fourier transform infrared spectroscopy, whereas dynamic light scattering was used to measure the particle size and ζ potential of the nanogels. The fluorescent properties of the nanogels were confirmed through fluorescent spectroscopy and microscopy. In addition to the excitation-dependent fluorescence behavior, the fluorescence emission intensity of bAPSC was altered by both pH and γ-irradiation. This intensity was higher at a lower pH than at a higher pH, and it slightly decreased after γ-irradiation. The drug loading and encapsulation efficiency of bAPSC were 25.9% and 11.2%, respectively. An in vitro drug release study revealed that the synthesized nanogels release their doxorubicin (Dox) contents in a time-dependent manner, and the drug release was higher after 96 h of incubation. Approximately 43.74% and 88.36% of Dox was released after 96 h of incubation at pH 5.5 in the absence and presence of glutathione (GSH), respectively. However, relatively lower drug release, approximately 21.6% and 16%, was observed in the presence and absence of GSH at pH 7.4, respectively. Fluorescence microscopy confirmed that Dox-loaded bAPSC nanogels were internalized by HeLa cells, and drug distribution was easily tracked using fluorescent materials without additional probing agents. Moreover, cellular cytotoxicity and hemolysis results revealed less cytotoxicity and hemocompatibility of the synthesized nanogels, confirming that they are the most favorable alternative drug carriers for drug delivery systems.