NanoPharmaceuticals: Nanocrystals, Polymeric Nanoparticles

NanoPharmaceuticals are the pharmaceuticals designed using "nanotechnology". What is nanotechnology? It is a science of creation and utilization of materials, devices, and systems through the control of matter on the nanometer-length scale. Nano” means dwarf in Greek; a nanometer is one billionth of a meter i.e. 10^-9 meter. This definition covers a wide range of differing scientific fields, from lithography to nanomachanics, nanorobots, nano biotechnology and nanopharmaceuticals etc.

image from nanoparticledrugdelivery.blogspot.com/2007/09...

Polymeric Nanoparticles

As name only suggest polymeric nanoparticles are nanoparticles which are prepared from polymers. The drug is dissolved, entrapped, encapsulated or attached to a nanoparticles and depending upon the method of preparation, nanoparticles, nanospheres or nanocapsules can be obtained. Nanocapsules are vesicular systems in which the drug is confined to a cavity surrounded by a polymer membrane, while nanospheres are matrix systems in which the
drug is physically and uniformly dispersed.In recent years, biodegradable polymeric nanoparticles have attracted considerable attention as potential drug delivery devices in view of their applications in drug targeting to particular organs/tissues, as carriers of DNA in gene therapy, and in their ability to deliver proteins, peptides and genes through a per oral route of administration.In spite of development of various synthetic and semi synthetic polymers, natural polymers still enjoy their popularity in drug delivery; some of them are listed below.

·         Gums (Ex. Acacia, Guar, etc.)

·         Chitosan

·         Gelatin

·         Sodium alginate

·         Albumin

A range of materials have been employed to delivery of bioactive agents. Pharmaceutical Scientist borrowed polymers intended for other, non biological uses. A polymer used in controlled drug delivery formulations, must be chemically inert, non-toxic and free of leachable impurities. It must also have an appropriate physical structure, with minimal undesired aging,
and be readily processable. Some of the polymeric materials are listed below.

· Cellulosics.

· Poly (2-hydroxy ethyl methacrylate).

· Poly (N-vinyl pyrrolidone).

· Poly (methyl methacrylate).

· Poly (vinyl alcohol).

· Poly (acrylic acid).

· Polyacrylamide.

· Poly (ethylene-co-vinyl acetate).

· Poly (ethylene glycol).

· Poly (methacrylic acid).

However, in recent years additional polymers are designed primarily for medical applications and have entered the arena of controlled release of bioactive agents. Many of these materials are designed to degrade within the body, most popular ones are;

· Polylactides (PLA).

· Polyglycolides (PGA).

· Poly (lactide-co-glycolides) (PLGA).

· Polyanhydrides.

· Polyorthoesters.

· Polycyanoacrylates.

· Polycaprolactone.

Originally, polylactides and polyglycolides were used as absorbable suture material. The main advantage of these degradable polymers is that they are broken down into biologically acceptable molecules that are metabolized and removed from the body via normal metabolic pathways. However, biodegradable materials do produce degradation by-products that must be tolerated with little or no adverse reactions within the biological environment.

Nanocrystals

When the size of the material is reduced to less than 100 nanometers, the realm of quantum physics takes over and materials begin to demonstrate entirely new properties. Hence nano-design of drugs by various techniques like milling, high pressure homogenization, controlled precipitation etc., are explored to produce, drug nanocrystals, nanoparticles, nanoprecipitates, nanosuspensions (which for ease of understanding commonly mentioned as nanocrystals).  As decreased size will increase the solubility of drugs hence, this technology is explored to increase oral bioavailability of sparingly water soluble drugs.

On the other hand engineering of nanocrystals will avoid the use of toxic solvents and surfactants to develop injectable solutions of sparingly water soluble drugs.  It is also possible to develop formulations for various routes of administration where size is the critical factor (injectables, ophthalmics and topical preparation). Many nanotechnologies are developed and are under investigation for their application.  

As this area of research is in its early stage of growth one can hope for many more surprises and new applications.