Nanoscale drug delivery systems using nanoparticles are emanating technologies for targeted and localized delivery of the therapeutic drug. The use of nanoparticles offers several advantages including enhanced pharmacokinetic drug profile, controlled and sustained release of drug and reduced toxicity. This opinion article briefs the important classes of the nanoparticles as drug carrier systems.
Keywords: Nanotechnology; Nanoparticles; Drug delivery; Therapeutics
Nanotechnology is a promising scientific approach to manufacture, engineer and fabricate materials, such as nanoparticles whose size ranges between 1-1000nm scale . Their extremely small size, large surface area to volume ratio and potential to functionalize their surface provide nanoparticles excellent physico-chemical properties for their various applications . The potential uses and benefits of nanotechnology are enormous. Over the last few decades, nanotechnology has gathered a lot of attention in the field medicine, pharmaceutical science, materials science and food technology . Nanoparticles have been extensively explored for diagnostic and therapeutic applications in medical and pharmaceutical industry to cure diseases such as cancer.
Nanoparticles loaded with the therapeutic drug can be transported to disease site for targeted drug delivery using active, passive or physical targeting method. Active targeting involves modifying the nanoparticle surface by binding ligands such as antibodies and proteins onto the surface of nanoparticle in order to increase their uptake by target site . Small size, morphology and electrochemical properties of nanoparticles influence the enhanced permeation retention effect, thus increasing the ability of tumor cells to absorb the nanoparticles compared to the normal cells. Hence the nanoparticles can be passively targeted to the site [5,6]. Physical targeting uses external stimuli to guide the nanoparticle to the target site . The external stimuli also control the drug release process. For example, in case of photothermal therapy light is used whereas in magnetic hyperthermia therapy, magnetic field is used to guide the nanoparticles to the target site.
Lipids are integral part of all living things and exist in nature as bi-layered nanostructure . Liposomes are lipid based nanostructures which are mimics of these naturally occurring bi-layered structures. Liposomes provide biocompatible nanoparticles and have been extensively studied over the years for drug delivery applications [3,9,10]. Doxil and DaunoXome are some of the liposome formulations that have been approved by the Food and Drug Administration (FDA) for cancer therapy [11-13].
Due to their biocompatibility and biodegradability, polymeric nanoparticles are particularly promising in the field of drug delivery. The polymeric matrices that are widely explored are poly (glycolic acid) (PGA), poly (lactic-co-glycolic acid) (PLGA), poly (lactic acid) (PLA) and poly(caprolactone) (PCL) [14-16]. Some of the polymeric nanoparticle formulations are either FDA approved or currently in clinical trials [17-19].
Gold, Silver and Iron oxide nanoparticles, especially magnetite (Fe3O4), are the most studied metal-based nanoparticles in biomedical field [20,21]. Ferumoxide has been FDA approved Magnetic Resonance Imaging contrast agent and iron oxide has also been EU approved for cancer therapy.
In addition to liposomes, polymeric and metallic
nanoparticles, carbon nanotubes [3,9], titanium nanotubes ,
peptide based nanoparticles  and quantum dots [23,24]
have also been researched in this regard. More recently, cell
membrane coated nanoparticles are emerging as biomimetic
strategy wherein a nanoparticle core is camouflaged with cell
membrane derived from natural cell such as erythrocyte or
white blood cell or cancer cell. These bio-inspired cell membrane
coated nanoparticles have shown strong potential not only in
drug delivery but also in immune modulation, vaccination and
Even with the tremendous benefits of nanoparticles in drug
delivery, very few have made the ‘bench to market’ translation.
The reasons behind this are: several of these particulate systems
suffer from lack of structural integrity, instability during storage
and most often these are quite toxic to the cells of the body. The
physico-chemical properties such as size and surface charge
play important roles in determining stability and toxicity of the
nanoparticles. Thus, these challenges must be overcome in order
to enhance the properties of the nanoparticles and improve their
suitability in drug delivery applications.
Over the years, nanoparticles have proven to provide an
excellent drug carrier system for smart and targeted delivery.
By clever engineering it has been possible to manufacture and
fabricate various types of nanoparticles, each with its own
advantages and suitability for nanotechnology applications.
Nanoparticles, thus, hold tremendous promise to revolutionize
nanomedicine and to provide treatment for a myriad of
important human diseases such as cancer.