embedding isotopes into structure of nanomaterials, this method is fast,
cost-effective, and with the lowest technical difficulties.
Another important goal for surface modification is to incorporate new functions
into radionanomaterials, e.g. stimuli-responsiveness. To date, selective coating of
nanomaterials with proper polymer molecules can bring tunable degradability [24],
and selective cargo release (e.g. loaded drugs or therapeutic isotopes) triggered by a
variety of stimuli including pH, heat, redox status, or enzymes [25–29]. These
properties can assist more accurate control of radionanomaterials to be used as
radionanomedicines.
Judging from these facts, how to choose the right surface modification method/
molecules for the right nanomaterials is very important and we predict that it will
continue to be a hot research area. The ideal molecules for surface modification of
radionanomaterials should preferably be biocompatible and biodegradable. Also,
these molecules should possess good affinity for the chosen radionanomaterials and
cause minimal response by the immune system [30, 31]. The decay half-life of
isotopes in radionanomaterials is usually not very long, thus the surface modification procedure should be adequately fast to prevent the isotopes from significant
decay loss. In the following section, we will discuss various strategies already used
for radionanomaterial surface modification.
10.2 Strategies for Radionanomedicine Surface
Modification
Generally there are two categories of methods for surface modification—chemical
reaction (covalent coupling) and physical interactions (Fig. 10.2). It is usually hard
to use only single strategy during the radionanomaterial surface modification, thus
in this section we will only provide a brief discussion on the basic rules in each
strategy. In Sect. 10.3, we will give representative examples for radionanomaterial
surface modification.
10.2.1 Chemical Reaction (Covalent Coupling)
There are four popular chemical groups on material surface which can be used to
attach surface-coating molecules: amine (e.g. reactable with e.g. from polyacrylic
acid (PAA), carboxymethylcellulose, PEG with –COOH terminal etc.), carboxylic
(e.g. reacting with polyethylenimine (PEI), poly(L-lysine), PEG with –NH 2 terminal
etc.), thiol (e.g. reacting with maleimide-bearing macromolecules etc.), and
hydroxyl groups [32]. Among those surface groups, hydroxyl group is quite unique
since it can react with carboxyl group on decorating molecules or cargo molecules
(e.g. anti-cancer drug) to form ester bond, which can be used for either controlled
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cost-effective, and with the lowest technical difficulties.
Another important goal for surface modification is to incorporate new functions
into radionanomaterials, e.g. stimuli-responsiveness. To date, selective coating of
nanomaterials with proper polymer molecules can bring tunable degradability [24],
and selective cargo release (e.g. loaded drugs or therapeutic isotopes) triggered by a
variety of stimuli including pH, heat, redox status, or enzymes [25–29]. These
properties can assist more accurate control of radionanomaterials to be used as
radionanomedicines.
Judging from these facts, how to choose the right surface modification method/
molecules for the right nanomaterials is very important and we predict that it will
continue to be a hot research area. The ideal molecules for surface modification of
radionanomaterials should preferably be biocompatible and biodegradable. Also,
these molecules should possess good affinity for the chosen radionanomaterials and
cause minimal response by the immune system [30, 31]. The decay half-life of
isotopes in radionanomaterials is usually not very long, thus the surface modification procedure should be adequately fast to prevent the isotopes from significant
decay loss. In the following section, we will discuss various strategies already used
for radionanomaterial surface modification.
10.2 Strategies for Radionanomedicine Surface
Modification
Generally there are two categories of methods for surface modification—chemical
reaction (covalent coupling) and physical interactions (Fig. 10.2). It is usually hard
to use only single strategy during the radionanomaterial surface modification, thus
in this section we will only provide a brief discussion on the basic rules in each
strategy. In Sect. 10.3, we will give representative examples for radionanomaterial
surface modification.
10.2.1 Chemical Reaction (Covalent Coupling)
There are four popular chemical groups on material surface which can be used to
attach surface-coating molecules: amine (e.g. reactable with e.g. from polyacrylic
acid (PAA), carboxymethylcellulose, PEG with –COOH terminal etc.), carboxylic
(e.g. reacting with polyethylenimine (PEI), poly(L-lysine), PEG with –NH 2 terminal
etc.), thiol (e.g. reacting with maleimide-bearing macromolecules etc.), and
hydroxyl groups [32]. Among those surface groups, hydroxyl group is quite unique
since it can react with carboxyl group on decorating molecules or cargo molecules
(e.g. anti-cancer drug) to form ester bond, which can be used for either controlled
188
D. Chen and H. Hong