Carboxymethylcellulose/MOF-5/Graphene oxide bio-nanocomposite as antibacterial drug nanocarrier agent

Bioimpacts, 9(1), 5-13; DOI:10.15171/bi.2019.02

Original Research

Carboxymethylcellulose/MOF-5/Graphene oxide bio-nanocomposite as antibacterial drug nanocarrier agent

Zahra Karimzadeh1, Siamak Javanbakht1, Hassan Namazi1,2,*

1 Research Laboratory of Dendrimers and Nanopolymers, Faculty of Chemistry, University of Tabriz, P.O. Box 51666, Tabriz, Iran
2 Research Center for Pharmaceutical Nanotechnology, Biomedicine Institute, Tabriz University of Medical Sciences, Tabriz, Iran

*Corresponding author: Hassan Namazi, Email: namazi@tabrizu.ac.ir

Abstract

Introduction : In recent years, more attention was dedicated to developing new methods for designing of drug delivery systems. The aim of present work is to improve the efficiency of the antibacterial drug delivery process, and to realize and to control accurately the release.

Methods : First, graphene oxide (GO) was prepared according to the modified Hummers method then the GO was modified with carboxymethylcellulose (CMC) and Zn-based metal-organic framework (MOF-5) through the solvothermal technique.

Results : Performing the various analysis methods including scanning electron microscope (SEM), X-ray diffraction (XRD), EDX, Fourier transform infrared (FTIR) spectroscopy and Zeta potentials on the obtained bio-nanocomposite showed that the new modified GO has been prepared. With using common analysis methods the structure of synthesized materials was determined and confirmed and finally, their antibacterial behavior was examined based on the broth microdilution methods.

Conclusion : Carboxymethylcellulose/MOF-5/GO bio-nanocomposite (CMC/MOF-5/GO) was successfully synthesized through the solvothermal technique. Tetracycline (TC) was encapsulated in the GO and CMC/MOF-5/GO. The drug release tests showed that the TC-loaded CMC/MOF5/GO has an effective protection against stomach pH. With controlling the TC release in the gastrointestinal tract conditions, the long-time stability of drug dosing was enhanced. Furthermore, antibacterial activity tests showed that the TC-loaded CMC/MOF-5/GO has an antibacterial activity to negatively charge E. coli bacteria in contrast to TC-loaded GO.


Keywords: Antibacterial, Bio-nanocomposite, Carboxymethylcellulose, Graphene oxide, Metal-organic framework, Nanocarrier

Introduction

In recent years, various de novo methods have been developed for designing drug delivery systems (DDSs).1,2 An ideal DDS should convey a suitable concentration of drug to targeting sites and enhance the drug efficacy.3,4 Thus, one of the main challenges to reach this aim is finding a suitable delivery carrier.5,6 Currently, among various carriers including polymeric particles,7,8 nanomaterials,6 microspheres,9 dendrimers10 and liposomes11 which were used as potential drug carriers, nanomaterial demonstrate advantages for drug delivery.12 The efficiency of conventional drugs and facilitate many of the free drug therapeutic pitfalls can be enhanced by nanoparticle-based therapeutics. Nanocarriers can improve considerably the effect and delivery of drugs, especially when drugs are poorly water-soluble. Nanoparticle–drug conjugates under different stages were developed in clinical therapies and illustrates the clinical success of nanoparticle therapies.4,13

Recently, several reports have announced the synthesis of metal-organic framework (MOF) and graphene oxide (GO) nanocomposites.14-16 MOF is self-assembled from various organic linkers and metal ions as nodes.15,17,18 GO is a compound of carbon, oxygen, and hydrogen in variable ratios that could be obtained by treating graphite with strong oxidizers.19-21 The hydroxyl and epoxy functional groups of GO permit the act of metal ions in MOFs to be formed as composite hence, the idea of MOF-GO nanocomposites is developed. So, by merging the complementary features of 2 materials, GO becomes dense arrays of layers and nonporous. The critical drawback of MOF is void space and is not beneficial for the retention of small molecules such as drug molecule under ambient conditions.22 Moreover, the critical drawbacks of MOFs and GO may resolve by the composition of GO and MOFs.23 Recently, some new results about MOF–GO hybrids24 have reported using various MOFs, for example, Zn-based MOF (MOF-5),22 Cu-based MOF (HKUST-1 or Cu3(BTC)2, BTC = 1,3,5-benzene tricarboxylate),25 Zr-based MOF (UiO-66)26 and Fe-based MOF (MIL-100).27 However, as far as we know, there are still few studies on the potential of the MOF-GO composites in the drug delivery systems, so evaluation of this system has a good novelty for controlling the drug release.

Typically, many of nanoparticles, for instance, MOF-GO composites suffer from low solubility in the physiological conditions; therefore, these materials need to be modified for the improvement of solubility. Carboxymethylcellulose (CMC) is an anionic water-soluble biopolymer that is one of the cellulose derivatives.28-30 CMC have unique characteristics such as pH-sensitivity, hydrophilicity, non-toxicity, biodegradability, and biocompatibility.31-33 In biomedical applications because of these CMC features, considerable interests have been focused on CMC prepared carriers.8,34,35 Therefore, for modification of the nanoparticle, CMC can be a good candidate.36

Tetracycline (TC) is an industrially available antibiotic used to treat a number of infections. This includes acne, cholera, brucellosis, plague, malaria, and syphilis.37 One of the major side effects which were observed after oral administration of TC is irritation of the gastrointestinal tract (GIT). To decrease the high GIT side effects, which caused by the oral use of TC , the drug can be encapsulated into biocompatible support as enteric coated dosage forms. As well as, nanomaterial supports with the high surface area such as GO could enhance the medicinal efficiency, and also the medical performance can be improved even more through modification of nanoparticle.

In our ongoing research program, related to developing the new drug delivery system38,39 based on our previous investigations on GO,40,41 the CMC-modified MOF-5/GO bio-nanocomposite was prepared as a novel drug delivery system. Antibacterial drug TC was highly loaded to the CMC/MOF-5/GO, then the release behavior was investigated. Drug loading and release manner of prepared CMC/MOF-5/GO by combining the complementary features of the three materials (CMC, MOF-5 and GO) was well optimized. The obtained results showed that this desired carrier system could be potentially used in the antibacterial oral delivery systems.

Experimental

Material

CMC with the degree of substitution (DS) 0.55–1.0 and viscosity 15000 MP/s (1% in H2O, 25°C) were obtained from Nippon Paper Chemicals Co., Ltd., Japan. TC was purchased from Sigma–Aldrich. Zinc nitrate hexahydrate, 1,4-benzenedicarboxylate (BDC), N,N-dimethylformamide (DMF), CHCl3 and all other materials were purchased from Merck.

Characterization and analysis

UV–Vis absorption spectra were obtained on a Shimadzu 1700 Model UV–Vis spectrophotometer. The Fourier transform infrared (FTIR) spectra were recorded on an FT-IR spectrometer (Bruker Instruments, model Aquinox 55, Germany) in the 4000–400 cm−1 range at a resolution of 0.5 cm−1 as KBr pellets. X-ray diffraction (XRD) measurements were performed at room temperature by Siemens diffractometer with using Cu-Kα radiation at 35 kV in the scan range of 2θ from 5 to 25°. The surface morphology and EDX of the samples were investigated using a scanning electron microscope (SEM) (LEO 1430VP) after coating the samples with gold films. The dynamic light scattering (DLS) and zeta potential measurements were obtained with a DLS-ZP/Particle Sizer (Microtrac, model Nanotrac Wave).

Synthesis of CMC/MOF-5/GO bio-nanocomposite

According to the modified Hummers method, GO was prepared from graphite powder.42 A flask emblematic 46 mL of H2SO4 (98%) was immersed into an ice bath. Then 2.0 g graphite was added to the flask and stirred vigorously. Next, 6.0 g KMnO4 was slowly added into the flask and for about 30 minutes the reaction temperature was kept below 20°C in an ice bath. The flask containing the reaction mixture was then heated with a water bath at a temperature of 35°C, and until a thick paste was formed the reaction mixture was stirred for about 45 minutes. 46 mL water was added to the flask and the reaction temperature was increased to 90°C then the reaction mixture was stirred for about 30 minutes. Finally, 280 mL water was added to the mixture, followed by a slow addition of 10 mL of 30% aq. H2O2. A yellow dispersion was obtained and until about pH 7 the mixture was washed severally with deionized water to remove the remained salt, then the product was dried under vacuum (50°C) for about 24 hours.

The GO (0.33 g) was dispersed in DMF solution by sonication to get DMF emulsion of GO. The CMC/MOF-5/GO bio-nanocomposite was prepared via the solvothermal route with some modifications on MOF-5.14,43 In a typical reaction, zinc nitrate hexahydrate (5.2 g), BDC (1.0 g), and CMC (0.33 g) were mixed in 35 mL of GO/DMF solution. The mixture was treated solvothermal at 120°C for 25 hours. Finally, the resulted solid sample was washed with DMF and CHCl3, and CMC/MOF-5/GO was obtained by vacuum drying at 80°C using desiccator equipped with a heater. In order to the synthesis of pure MOF-5, the same procedure was applied without the employment of CMC and GO.

Drug loading and release studies

In purpose of drug loading in the GO and CMC/MOF-5/GO, equal mass (200 mg) from each sample was immersed in 20 mL aqueous solution of 100 ppm drug concentration. After a continuous shaking for 72 hours in the dark, the TC loading capacity was determined using UV–Vis spectrophotometer at 276 nm. The TC-loaded GO (TC@GO) and TC-loaded CMC/MOF-5/GO (TC@CMC/MOF-5/GO) were collected by centrifuging and washed thoroughly to remove unloaded drug then dried at 40°C in the oven.

To study the release of TC, in a typical experiment, 10 mg of TC@GO and TC@CMC/MOF-5/GO were immersed in 10 mL buffered solution. For this propose, during a specific period of time, the carrier was suspended in the mediums with pH 1.2, pH 6.8 and pH 7.4 which respectively mimicked the pH of the simulated gastric fluid, the first zone of intestinal fluid and the second zone of intestinal fluid. Firstly, they were immersed to pH 1.2 (for 2 hours), then to pH 6.8 (for 2 hours), and subsequently to pH 7.4 (for 4 hours). At the certain time intervals, adequate amounts of samples were taken up and in order to maintain the volume of buffer constant, the same amount of fresh buffered was replaced.

The loading capacity and cumulative release data were obtained by using a predetermined calibration curve for TC drug. The amount of loaded and released drug respectively was calculated with the following 2 formulas (Eq. 1 and Eq. 2):

\[Drug\;loading\;of\;carrier\;(wt\% ) = \frac{{the