Biomedical Engineering Reference
In-Depth Information
FIGURE 12.22
Regulation of enzyme reactor by chemical stimulus.
The LDH activity was evaluated under the UV and visible light irradiations in the presence of Cu
2
+
,
and the higher LDH activity was observed for the system containing the
trans
-receptor than that for
the
cis
-system. Unfortunately, the reversible switching of the LDH activity by the alternate UV or vis-
ible irradiation failed, because long-time exposure of the LDH to Cu
2
+
caused irreversible inactivation
of the LDH. Instead, we conducted a model experiment in which several solutions of the correspond-
ing mixtures without LDH component were prepared, and UV and visible lights were irradiated on
the solutions in various sequences. Freshly prepared LDH solution was added to every mixture and
its activity was evaluated. As a result, the activities corresponding to the
trans
- and
cis
-systems were
independently observed for the samples for various photoirradiation sequences. This result encour-
aged us to achieve the proposed fi nal goal, because the appropriate selection of a stable enzyme and a
mediator system would lead to reversible photoregulation of the nanosized enzyme reactor.
As described above, the presented biohybrid nanomaterials have potential in application to
switching devices, which can be regulated by chemical stimuli and photo-stimuli. A combination
of both the responses to this biohybrid would lead to the development of a logic device, as shown
in Figure 12.24. Coapplication of a chemical signal and a photo-signal in appropriate combina-
tion can only activate the enzymatic reaction. Enzymatic activity as the output was obtained
only when both types of light irradiations and chemical application were present. Therefore, this
system can be regarded as an AND-type logic gate. Other types of logic gates would be similarly
