A Novel pH-sensitive Nanocomposite Based on Graphene Oxide for Improving Doxorubicin Release

BACKGROUND

Doxorubicin (DOX) as a chemotherapeutic drug has been widely used for treatment of cancer but because of adverse side effects of this drug, different drug delivery systems have been tested. One of them has been immobilization of DOX on the graphene oxide (GO) sheets through non-covalent interactions (GO-DOX) with high efficiency however the release was very low and slow due to strong forces between DOX and GO.

OBJECTIVE

The aim of this research was to increase the release of DOX and this goal was achieved through the covalent binding of DOX to the GO-poly(ethyleneimine) 2KDa conjugate.

METHODS

A novel nanocarrier for delivering DOX was fabricated using GO as a basic plane for conjugating and assembling other compounds. DOX was attached to GO-poly(ethyleneimine) 2KDa conjugate via a linker containing hydrazide bond. Drug loading and release was investigated at pH 7.5 and pH 5.5. Cytotoxicity was determined by MTT on MCF7 cells and compared with previous nanocarrier.

RESULTS

The fabrication of the nanocarrier and the covalent attachment of DOX to the nanocarrier were confirmed through FT-IR spectroscopy. The capacity of nanocarrier to load drug was as high as 383%. 96% of initial drug was loaded in the nanocarrier. The weight percentage of the drug in the nanocarrierdrug conjugate was 79%. Release of drug at pH 5.5 was two times more than release at pH 7.5 and this evidence supports conjugation of DOX to nanocarrier through hydrazide bond and pH-sensitivity of related bond. Because of the reliable results, ease of operation, safety and high reproducibility, MTT was chosen to evaluate the cytotoxicity of samples. Nanocarrier didn't show significant toxicity even at high concentrations. IC50 value for chemically-bound DOX to hydrazide-containing GO nanocomposite was 9.5 μg/ml whereas the IC50 value for GO-DOX was 39 μg/ml after 72 h. Loading of DOX via hydrazide bond was as low as 4% versus near 75% physical loading of drug while hydrazide bondcontaining nanocomposite was 4 to 6 fold more toxic than GO-DOX.

CONCLUSION

Based on the obtained data, the covalent attachment of DOX to the nanocarrier through hydrazide linkers was an interesting idea that increased drug release and toxicity despite much lower percentage of covalent attachment compared to non-covalent immobilization. As could be concluded from this study, nanocarriers based on hydrazide bond could be a good candidate for drug delivery.

Targeting Tumorigenicity of Breast Cancer Stem Cells Using SAHA/Wnt-b Catenin Antagonist Loaded Onto Protein Corona of Gold Nanoparticles

BACKGROUND

Among various theories for the origin of cancer, the "stemness phenotype model" suggests a dynamic feature for tumor cells in which non-cancer stem cells (non-CSCs) can inter-convert to CSCs. Differentiation with histone-deacetylase inhibitor, vorinostat (SAHA), can induce stem cells to differentiate as well as enforces non-CSCs to reprogram to CSCs. To avoid this undesirable effect, one can block the Wnt-βcatenin pathway. Thus, a dual delivery system of SAHA and a Wnt-βcatenin blocker will be beneficial in the induction of differentiation of CSCs. Protein corona (PC) formation in nanoparticle has a biologic milieu, and despite all problematic properties, it can be employed as a medium for dual loading of the drugs.

MATERIALS AND METHODS

We prepared sphere gold nanoparticles (GNPs) with human plasma protein corona loaded with SAHA as differentiating agent and PKF118-310 (PKF) as a Wnt-βcatenin antagonist. The MCF7 breast cancer stem cells were treated with NPs and the viability and differentiation were evaluated by Western blotting and sphere formation assay.

RESULTS

We found that both drugs loaded onto corona-capped GNPs had significant cytotoxicity in comparison to bare GNP-corona. Data demonstrated an increase in stem cell population and upregulation of mesenchymal marker, Snail by SAHA-loaded GNPs treatment; however, the combination of PKF loaded GNPs along with SAHA-loaded GNPs resulted in a reduction of stem cell populations and Snail marker. We have shown that in MCF7 and its CSCs simultaneous treatment with SAHA and PKF118-310 induced differentiation and inhibition of Snail induction.

CONCLUSION

Our study reveals the PC-coated GNPs as a biocompatible career for both hydrophilic (PKF) and hydrophobic (SAHA) agents which can decrease breast cancer stem cell populations along with reduced stemness state regression.

BMP-2 can promote the osteogenic differentiation of human endometrial stem cells

Background: Human endometrial-derived stem cells (hEnSCs) as multipotent accessible source of cells are known as useful cell candidates in the field of bone tissue engineering. However, the effect of bone morphogenic protein-2 (BMP-2) as an osteoinductive growth factor has not been clearly ascertained.

Objective: To evaluate the effect of the remarkable osteoinductive growth factor BMP-2, on promotion of osteogenic differentiation in hEnSCs.

Methods: Endometrial biopsies were obtained from healthy women referred to the hospital for infertility treatment. After tissue digestion in collagenase, the isolated endometrial cells were expanded in Dulbecco’s modified Eagle medium (DMEM) supplemented with 10% FBS. The propagated cells were characterized based on the expression of endometrial (CD90, CD105), endothelial (CD31), and hematopoietic (CD34, CD133) stem cell markers. Cells were differentiated in osteogenic medium containing DMEM supplemented with 10% FBS, 10 nM dexamethasone, 50 μg/ml Ascorbic acid, and 10 mM β-glycerophosphate in the presence or absence of BMP-2 for 21 days. Alizarin red staining was performed to verify the matrix mineralization. Immunocytochemical staining was conducted to detect the expression of OCT-4, CD133, and osteopontin as well as osteocalcin. The expression of osteoblast transcripts, including osteopontin, osteonectin, and alkaline phosphatase (ALP) were analyzed by semi quantitative PCR.

Results: The expanded EnSCs were spindle shaped. They were positive for the expression of Oct-4, CD90, and CD105, while they were negative for endothelial and hematopoietic markers. The matrix mineralization was confirmed by Alizarin red in both groups at day 21. Although the expression of osteopontin and osteocalcin was detected in both groups by immunological staining, the expression of osteocalcin was more intense in the presence of BMP-2. ALP, Osteonectin and osteopontin transcripts were expressed in all groups; however, the expression of ALP and osteopontin was upregulated in the presence of BMP-2.

Conclusion: BMP-2 as an osteoinductive growth factor, could promote the osteogenic differentiation of EnSCs in vitro.

Dual and opposing modulatory effects of serotonin on crayfish lateral giant escape command neurons

Serotonin modulates afferent synaptic transmission to the lateral giant neurons of crayfish, which are command neurons for escape behavior. Low concentrations, or high concentrations reached gradually, are facilitatory, whereas high concentrations reached rapidly are inhibitory. The modulatory effects rapidly reverse after brief periods of application, whereas longer periods of application are followed by facilitation that persists for hours. These effects of serotonin can be reproduced by models that involve multiple interacting intracellular signaling systems that are each stimulated by serotonin. The dependence of the neuromodulatory effect on dose, rate, and duration of modulator application may be relevant to understanding the effects of natural neuromodulation on behavior and cognition and to the design of drug therapies.

Altered excitability of the crayfish lateral giant escape reflex during agonistic encounters

The excitability of the lateral giant escape reflex of socially dominant and submissive crayfish at rest and during agonistic encounters was studied and compared. During agonistic encounters the excitability of the lateral giant reflex falls, substantially in subordinates and slightly in dominants, whereas at rest excitability seems to be independent of social status. Thus, paradoxically, socially dominant animals are more likely to execute lateral giant escape reactions during interactions than are subordinates. It is suggested that subordinates under threat of attack tend to engage circuitry involved in flexible, nonreflex ("voluntary") types of escape not mediated by giant neurons and therefore inhibit giant neuron-mediated reflex circuitry that produces prompt, but less adaptive, responses. In contrast, dominants go about their business, mainly ignoring their conspecifics and relying on reflex escape to protect them from unexpected attack. Consistent with this view, escape of subordinates during agonistic encounters is mediated by nongiant, not reflex, circuitry. These observations and their interpretation suggest a possible functional role for recently described social status-dependent serotonergic modulation of the lateral giant reflex, which is inhibitory in sign in subordinates and facilitatory in dominants.