Aqueous two phase system (ATPS) is a liquid-liquid extraction method which employs two aqueous phases having applications in the field of biotechnology for the separation and purification of biological materials such as proteins, enzymes, nucleic acids, virus, antibodies and cell organelles. This review discusses the basic principles of ATPS, the factors affecting partitioning, optimization by design of experiments and the recent applications like extractive fermentation, membrane supported liquid-liquid extraction and aqueous two phase floatation. A comparative study between ATPS and other conventional methods is also discussed. The emphasis is given to PEG/salt two-phase systems because of the low cost of the system.

In recent times, plant-mediated synthesis of nanoparticles has garnered wide interest owing to its inherent features such as rapidity, simplicity, eco-friendliness and cheaper costs. For the first time, silver nanoparticles were successfully synthesized using Calliandra haematocephala leaf extract in the current investigation. The as-formed silver nanoparticles were characterized by UV-Vis spectrophotometer and the characteristic surface plasmon resonance peak was identified to be 414 nm. The morphology of the silver nanoparticles was characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) was used to detect the presence of elemental silver. X-ray diffraction (XRD) was employed to ascertain the crystalline nature and purity of the silver nanoparticles which implied the presence of (1 1 1) and (2 2 0) lattice planes of the face centered cubic (fcc) structure of metallic silver. Fourier transform infrared spectroscopy (FTIR) was used to key out the specific functional groups responsible for the reduction of silver nitrate to form silver nanoparticles and the capping agents present in the leaf extract. The stability of the silver nanoparticles was analyzed by zeta potential measurements. A negative zeta potential value of À17.2 mV proved the stability of the silver nanoparticles. The antibacterial activity against Escherichia coli -pathogenic bacteria -and the capacity to detect hydrogen peroxide by the silver nanoparticles were demonstrated which would find applications in the development of new antibacterial drugs and new biosensors to detect the presence of hydrogen peroxide in various samples respectively. ª 2015 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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