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Pakistani researchers get patents for nano-antibiotics

Nano-versions of CHL and Ciprofloxacin are more effective than the commercially available varieties.
by Dr. Akhyar Farrukh

Antibiotics are not always as effective as expected in treating bacterial infections. Conventional drug therapy shows that a range of factors affect their performance. These include irregular distribution of the drug in the body, low permeability of tissues, elevated hydrophobicity of biologically active substances, and high toxicity in blood circulation system.

To counter these factors, researchers around the world are working on drug targeting techniques like nano-based therapy that entails development of nano-versions of antibiotics, or nano-antibiotics.

Nano-antibiotics have a particle size of between one and a 100 nanometers and have lesser adverse effects and greater efficacy at targeted sites.

Against this backdrop, a team of researchers at Government College (GC) University, Lahore has developed nano-versions of two widely prescribed antibiotics in Pakistan – Chloramphenicol (CHL) and Ciprofloxacin. These drugs are used in treatment of a range of bacterial infections including typhoid fever, cholera, diarrhea as well as infections of eyes, ears, skin, and respiratory and urinary tract.

The two nano-antibiotics were patented in the United States in 2017. Chloramphenicol nanoparticle has been published with patent number US 9,393,313 B2 and Ciprofloxacin nanoparticle with patent number US 9,555,009 B2. The research team is now looking for partner universities in Pakistan to start clinical trials following which the product will be marketed.

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The nano-version of CHL allows targeted delivery of drug making it effective against commercially available CHL. The latter is characterised by poor solubility and early degradation in the gastrointestinal tract.

During the test phase, the team prepared the nano-version of the antibiotic using the sonochemical method, or application of ultrasound waves to chemical reactions. Biodegradable and biocompatible polymer like diethylaminoethyl-cellulose was used in the process in combination with iron. The latter gave the nanocomposite its magnetic characteristic and enabled sustained and prolonged delivery of drug.

When tested for antibacterial activity, CHL-loaded nanocomposite was found more effective than the commercially available CHL (0.5 percent). Over a period of 48 hours, entrapment efficiency (EE), or proportion of drug successfully absorbed in the human body, was higher for the nano-version compared to the commercially available CHL. For instance, the EE of the commercially available CHL was recorded at 91 percent in the first hour. But after every hour for the next three hours, the EE increased to 94, 97, and 97 percents, respectively. A consistent 91 percent EE was recorded for the nano-version over a 48 hour-period.

Thus, the test showed that almost all of the drug was released in a three-to-four-hour period in case of the commercially available CHL. In the nano-version, the release of drug was found to be biphasic. The initial release over the first three hours was recorded at between 52 to 71 percent. After this initial period, the degradation of the polymer and diffusion of the drug enabled a sustained release during the next 48 hours.

Similarly, the research team observed sustained release of Ciprofloxacin-loaded nanoparticles for more than eight hours. The result of our tests also showed superior antibacterial activity for the nano-version, compared to the commercially available variety.

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Among other tests, we also conducted dissolution and stability studies for Ciprofloxacin nanoparticles. In the former, drug release was monitored over a period of eight hours and it showed a sustained release pattern for nanoparticles. The stability study was done to gather information on nano-versions’ chemical, microbiological, and physical characteristics at different temperatures and humidity levels. The test showed that in nanosuspension form, the nano-version went unstable after just a month, but powdered-form remained stable throughout a six-month period.

The team also undertook a high performance liquid chromatography (HPLC) analysis at different temperatures to ascertain the integrity of the drug. The tests showed enhanced activity for the nano-version as compared to the commercially available drug.

Noteworthy benefits of nano-antibiotics are enhanced drug delivery to the targeted tissue; high solubility in water; rapid dissolution of the drug and better therapeutic response; targeted attack only on infected cells; cost effectiveness as a small quantity of the drug can be effective for several hours; and reduced gastrointestinal irritation.

Dr. Muhammad Akhyar Farrukh is Associate Professor and Principal Investigator of Projects/ Founding Director Nano-Chemistry Laboratory, GC University Lahore, Pakistan. Ms. Adarsh Shams and Mr. Muhammad Rehan Gul who completed their MS studies under his supervision were part of the research team.

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