Liposomes and micelles. Image credit: buzzle.comLiposomes and micelles. Image credit: buzzle.comBiological Applications of Nanoparticles

Introduction

Nanotechnology is the study of the behavior and use of structures between 1 nanometer (nm) and 100 nm in size. To have a perspective about the sizes we are talking about, on average a human hair is 90,000 nm thick and a sheet of regular paper is 100,000 nm thick. One nanometer is one billionth of a meter. A formal definition, according to the National Nanotechnology Initiative (NNI, a multiagency U.S. government program initiated in 2001), nanotechnology is defined as the science and engineering involved in the design, synthesis, characterization and application of materials and devices with at least one of the dimensions in the nanoscale (typically 1–100 nanometers) (NNI, 2005).

What makes nanomaterials and nano devices unique is the fact that when a material has dimensions at the nanoscale, its physical, chemical and biological properties are different to when the material is at a normal scale. A piece of gold, for instance, has its well-known color when the piece is at a normal dimension, but its color changes when we look at a gold piece at the nanoscale. The density, magnetic properties, optical properties, boiling point, hardness and many other properties are different for the same material at the nanoscale dimension. It is this unique dynamic that makes nanomaterials useful in scientific and technical applications. By making use of these properties, mainstream and startup companies have taken up the challenge to produce better sunscreen lotions, tennis rackets, consumer lighting, next generation of transistors that can be used in devices that can store the whole Library of Congress on the head of a pin and so forth. Nowadays, nano solutions exist to improve household lighting or consumer electronics; a vision of the future based on nanotechnology looks bright.

Dendrimers. Image credit: University of California, IrvineDendrimers. Image credit: University of California, IrvineNanotechnology in Medicine

Medicine using nano techniques is called nanomedicine, and in a broad sense represents the application of nanoscale technology and materials to the practice of medicine. Nanomedicine has been an important subproduct of nanotechnology from the beginning of the technology. An important contribution of nanomedicine is the start of a revolution in molecular imaging that will lead to the detection of single molecules or single cells in complex biological environments. Nanomedicine targets specific diseases, trying to do better on a molecular level than what physiology, pathology and the various other specialized medical sciences have been doing so far. Some of the advantages of nanomedicine over conventional medicine include low toxicity and less adverse effects of drugs, target delivering of therapeutic drugs, more precision and less time consuming, among others.

Magnetic nanoparticles. Image credit: Medscape.comMagnetic nanoparticles. Image credit: Medscape.comNanoparticles

We can define a nanoparticle as a particle with at least one of its dimensions less than 100 nm. The history of nanoparticles goes back to the 9th century in Mesopotamia where artisans, without knowing it, used some compounds, to cover pots. These “paints” produced a glittering effect on the surface of the pots. We still can see the luster today, if the pots are not oxidized. The paints used by the artisans contained silver and copper nanoparticles. The technique at the time was to mix silver and copper salts with vinegar, ochre and clay and to apply it to the surface of the pots. Then, the pots were heated to 600 degree Celsius, a process that forces the ions of silver and copper to migrate to the outer layer of the mixture.

Because of its size, a nanoparticle exhibits unique optical, physical and chemical properties such as excellent electrical and heat conductivity, photoemission and excellent catalytic activity, among others.

In particular, nanoparticles with physical properties produced or driven by electromagnetic fields are of special interest in biological sciences because they can be used for imaging purposes, for curative purposes like in drug delivery or for magnetic hyperthermia therapies.

Some of the uses of nanoparticles in biology and medicine include the following:

  • Creating fluorescent biological labels, biological markers and molecules for diagnosis of diseases
  • Gene delivery systems in gene therapy
  • For biological detection of disease causing organisms and diagnosis
  • Detection of antibodies and proteins
  • Genetic and tissue engineering
  • Destruction of tumors with drugs or heat
  • Drug delivery systems

Probably the most prevalent use of nanoparticles in medicine today is in drug delivery systems. The advantages are many over traditional delivery systems. Some of these are:

  • Targeted drugs may be developed.
  • The characteristics of nanoparticles can be easily designed.
  • Nanoparticles can control and sustain the release of the drug during the transportation as well as the location of the release.
  • Several routes of administration can be used, including oral, nasal, injection, intra-ocular (within the eyes), etc.

There are many types of nanoparticles (or nanodevices) suitable to be used in disease care. Without going into details, we will mention here the names and applications of some of the most important nanoparticles used today. The number in parenthesis is the approximate size of the particle:

  • liposomes and micelles (10 – 100 nm) used for drug delivery;
  • dendrimers (2 – 10 nm), used for drug delivery; nanocantilivers, used for cancer detection and diagnosis;
  • quantum dots (less than 10 nm), used for sensing and detection of biomarkers, diagnosis;
  • magnetic nanoparticles (10 – 100 nm), used for targeted cancer drug delivery;
  • gold nanoparticles (less than 50 nm), used for attaching proteins and antibodies for biological detection;
  • silver nanoparticles (1 – 100 nm), used for molecular diagnostics and therapeutics.

The following is an interesting video of drug delivery of nanoparticles: