studies are allowed for less than 100 ng amount of radiopharmaceuticals. This
amount can be given to human volunteers without preclinical studies in animals.
The allowance is because of two issues; there should be the difference between
human being and animals either large or small, and this amount per humans with
normal body weight must not cause any problem with experimental systemic
injection. The other way of knowing the distribution of novel drug with this amount
is injecting it and doing mass spectrometry. Radiolabeling of a novel radiopharmaceutical shall allow tracing the tracks of injected radiolabeled radiopharmaceuticals in the human body and this is the basis of tracer technology of nuclear
medicine.
Nanomedicine is recently coined term which indicates the emerging field of
medicine using nanomaterials. Nanomaterials are the composite chemicals having
nanometer-sized superstructures larger than biomacromolecules. Peptides or antibodies have the dimension of a few nanometers to tens of nanometers in their long
diameters but are not called as nanomaterials. Living organisms are using those
biological materials for running bodily chemical or physiological functions and we
call them biologics. In contrast, nanomaterials were first named based on their
unique ingenuity of fabrication to make a homogeneous artefactual superstructures
made of inorganic materials. Now nanomaterials consist of inorganic to organic
materials, which implies that as well as we could fabricate new larger nanomaterials
we could understand their behaviors in biological milieu. Thus, the term nanomedicine immediately implies that people started to use nanomaterials for human
being for diagnostic or therapeutic purposes. Systemic injection of nanomaterials
should be without any toxicity and with desired biological effects. Even the combination of biologics and nanomaterials are very often proposed for clinical and
human use.
The barrier of nanomedicine against popular clinical human use is the concerns
about the possible toxicity of nanomaterials. Or in other words, the possible toxicity
is in fact the lack of knowledge about the behavior of nanomaterials in vivo. We
already know that cadmium is toxic in certain amount but we don’t know the
perpetual effect of cadmium of CdSe quantum dots if injected in vivo or in humans.
Possible toxicity can be prevented by not using the nanomaterials of interest;
however, lack of knowledge does not let us advance or withdraw attractive novel
nanomaterials. Sometimes, the side effects of nanomaterials are easily unraveled
even with its plausible mechanism of toxicity. Carbon nanotubes are examples, in
that the shape of carbon nanotubes were toxic to the alveolar epithelial cells because
of the shape, which immediately reminded medical doctors of the toxicity of
asbestos and silica. Textbook knowledge leads us to be concerned about pneumoconiosis, which almost thwarted the hype of fancy possibility of using carbon
nanotubes in humans for clinical purposes.
However, many other nanomaterials are not composed of frankly toxic substances such as iron oxides, carbons (graphenes), silica and other inert-looking
substances. The only concern is the amount of these nanomaterials and again the
lack of understanding the fates of these nanomaterials in vivo or in humans after
systemic injection. Targeted delivery is always hoped and proven by animal
2
D. S. Lee
amount can be given to human volunteers without preclinical studies in animals.
The allowance is because of two issues; there should be the difference between
human being and animals either large or small, and this amount per humans with
normal body weight must not cause any problem with experimental systemic
injection. The other way of knowing the distribution of novel drug with this amount
is injecting it and doing mass spectrometry. Radiolabeling of a novel radiopharmaceutical shall allow tracing the tracks of injected radiolabeled radiopharmaceuticals in the human body and this is the basis of tracer technology of nuclear
medicine.
Nanomedicine is recently coined term which indicates the emerging field of
medicine using nanomaterials. Nanomaterials are the composite chemicals having
nanometer-sized superstructures larger than biomacromolecules. Peptides or antibodies have the dimension of a few nanometers to tens of nanometers in their long
diameters but are not called as nanomaterials. Living organisms are using those
biological materials for running bodily chemical or physiological functions and we
call them biologics. In contrast, nanomaterials were first named based on their
unique ingenuity of fabrication to make a homogeneous artefactual superstructures
made of inorganic materials. Now nanomaterials consist of inorganic to organic
materials, which implies that as well as we could fabricate new larger nanomaterials
we could understand their behaviors in biological milieu. Thus, the term nanomedicine immediately implies that people started to use nanomaterials for human
being for diagnostic or therapeutic purposes. Systemic injection of nanomaterials
should be without any toxicity and with desired biological effects. Even the combination of biologics and nanomaterials are very often proposed for clinical and
human use.
The barrier of nanomedicine against popular clinical human use is the concerns
about the possible toxicity of nanomaterials. Or in other words, the possible toxicity
is in fact the lack of knowledge about the behavior of nanomaterials in vivo. We
already know that cadmium is toxic in certain amount but we don’t know the
perpetual effect of cadmium of CdSe quantum dots if injected in vivo or in humans.
Possible toxicity can be prevented by not using the nanomaterials of interest;
however, lack of knowledge does not let us advance or withdraw attractive novel
nanomaterials. Sometimes, the side effects of nanomaterials are easily unraveled
even with its plausible mechanism of toxicity. Carbon nanotubes are examples, in
that the shape of carbon nanotubes were toxic to the alveolar epithelial cells because
of the shape, which immediately reminded medical doctors of the toxicity of
asbestos and silica. Textbook knowledge leads us to be concerned about pneumoconiosis, which almost thwarted the hype of fancy possibility of using carbon
nanotubes in humans for clinical purposes.
However, many other nanomaterials are not composed of frankly toxic substances such as iron oxides, carbons (graphenes), silica and other inert-looking
substances. The only concern is the amount of these nanomaterials and again the
lack of understanding the fates of these nanomaterials in vivo or in humans after
systemic injection. Targeted delivery is always hoped and proven by animal
2
D. S. Lee