A MINI REVIEW ON NANOSPONGE DRUG DELIVERY SYSTEM

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ABOUT AUTHOR:
Surya Prakash Singh*
Vaagdevi College of Pharmacy,
Dept. of Pharmaceutics, Warangal,
pin:506001, Warangal, A.P, India

surya.prakashsingh@yahoo.com

ABSTRACT:
Nanotechnology, a multi disciplinary science has received considerable attention in the recent times in the discovery of new chemical entities, diagnosis and treatment of several ailments[1]. It has created a remarkable impact on healthcare sector as an offshoot called nanomedicine. Many newer drugs show promising invitro effect but lack invivo effect due to decreased bioavailability. Nanomedicine has developed many drug delivering systems like nanoparticles, nanoemulsions, nanosuspensions, nanosponges etc., to overcome the problems of bioavailability out of which nanosponge is an advanced drug delivery system which offers diverse advantages than the other available systems. In this review, an attempt is made to summarize the methods of development, evaluation techniques and possible areas of applications and future of nanosponge drug delivery systems.

REFERENCE ID: PHARMATUTOR-ART-2053

INTRODUCTION
Many drugs face the problem of bioavailability and every year around $65 billion is wasted because of poor bioavailability[2]. Preventing the delivery of a drug at the undesired location is as important as to deliver a drug at a desired location. The main challenges faced by the drug formulator are the bio availability and the side effects. A very potent drug can be fatal, if it is delivered in a wrong region. So a novel drug delivery system is gaining demand in the recent time and huge money is invested in the formulation research and development.

Some of the achievements made using nanomedicine are
·  Development of one dose a day ciprofloxacin
·  Tumor targeted taxol delivery[3]
·  Improved ophthalmic delivery using smart hydrogel nanoparticles[4]
·  Oral insulin formulation using nano particles[5]
·  Liposomal based Amphotericin B formulation

Nanosponges are innovative carriers consisting of cross linked cyclodextrins able to incorporate molecules within their structures[6]. One can imagine nanosponge, as “a 3D picture of a sponge having cross-linked network of polymers with a pore size in the range of few nanometers”.

The nanosponge is about the size of a virus with a ‘backbone’ (a scaffold structure) of naturally degradable polyester. The long polyester strands are mixed with small molecules that have an affinity for certain portions of the polyester. They ‘cross link’ segments of the polyester to form a spherical shape that has many pockets (or cavities) where drugs can be stored. You might wonder about polyester; this particular version is predictably biodegradable, which means that when it breaks up in the body, the drug contained can be released on a known schedule. Better still the nanosponge can be engineered to be of specific size and to release drugs over time  not just in the ‘burst’ mode common with other delivery methods. The engineering capacity of nanosponge is due to the relatively simple chemistry of its polyesters and linking material (peptides); compared to many other nanoscale drug delivery systems, nanosponge should be able to scale (e.g. ramp up to commercial production levels) without requiring unusual equipment or procedures.

figure 1: a model representing the release of nanomed from the formulation


Nanosponge is water soluble. This does not mean the molecules chemically break up in water, but it means that nanosponge particles can mix with water and use it as a transport fluid, for example to be injected. Most other forms of nanoparticle delivery systems must use various chemical transports (for example, adjuvant reagent), which may have side effects. Many authors have described nanosponge in different ways and with different geometry. The efficiency of nanosponge depends on its particle size. Earlier the particle size isexpected to be in the range of 150-400 nm, but most recently the scientists have developed nanosponge with a particle size of 50nm. The size varies depending on the method adopted for formulation.

ADVANTAGES:

1.  It can be used as controlled as well as targeted drug delivery system.

2.  It offers predictable release of drug which becomes the major advantage when compared to other nanoparticle delivery systems under development.

3.  It can also be used for hydrophobic drugs.

4.  The solubility of drugs can be increased using nanosponge technology.

5.  Method of preparation requires simple chemistry.

METHODS
Three basic methods are employed in the development of nanosponges, each one differs in diverse chemistry from the other. They are

1.  Emulsion solvent diffusion method

2.  Ultra sonication method

3.  Click chemistry

emulsion solvent diffusion method
Fick’s first law of diffusion relates, the diffusive flux to concentration, by postulating the flux goes from regions of high concentration to regions of low concentration, with a magnitude that is proportional to the concentration gradient. In one dimension this is

figure2: ficks first law.


Where,

·   J is the “diffusion flux” (amount of substance) per unit area per unit time.

·   D is the diffusion coefficient or diffusivity.

·   ø is the concentration

·   x is the position

Using this method nanosponges are prepared by crosslinking the polymers by using a cross linking agents and a volatile solvent[7]. The mixture of drug, polymer and crosslinking agent is added to the solvent being continuously agitated at 1000rpm. The formed nanosponges were filtered and dried in oven at 40?C for 24hrs.

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