8 Aptamers for the Diagnosis of Infectious Diseases
227
8.4.1.3 Microfluidics-Based-Integrated Aptasensors
Integrated detection platform will increase both efficiency and robustness of detection procedures via reducing manual operations. Microfluidics is an efficient tool to
construct integrated aptasensors. Tanner [95] improved their study and presented a
microfluidic APTEC biosensor for malaria diagnosis. Microfluidic chambers were
designed to integrate with APTEC biosensor. The biosensor performed high sensitivity and specificity in Pf LDH detection for both parasite samples and clinical
samples from malaria. It is a successful application of microfluidic technology in
malaria diagnosis.
With the wide usage of microfluidic technology [96], origami scaffolds have also
been used for malaria detection. Godonoga et al. [85] attempted to incorporate a
malaria-detecting molecule onto a DNA origami scaffold. They combined DNA
aptamers specific for the malaria biomarker Pf LDH with a DNA origami scaffold.
Aptamers were integrated into a rectangular DNA origami, and the specific binding
ability of aptamers to the target protein was observed by AFM. 1000 nM Pf LDH
protein was incubated with 12 nM aptamer on origami at room temperature for 1 h,
and subsequently visualized under AFM (Fig. 8.8c). The work demonstrates the
ability of DNA aptamers to recognize a malaria biomarker whilst being integrated
within a supramolecular DNA scaffold, and provides malaria with new diagnostic
approaches based on DNA nanotechnology.
Based on the combinations of 3D printing and fluidic technologies, fabrication of point-of-care device was feasible. Aptamer-based point-of-care diagnostic
devices for malaria using 3D printing rapid prototyping were developed. Tanner’s
[86] study sought to develop point-of-care malaria diagnostic tests which use the
APTEC sensing system with3D printing technology as a platform for rapid prototyping (Fig. 8.8d). When capturing the malaria biomarker Pf LDH from samples,
it will generate a visible blue color in response to Plasmodium positive samples.
Both 3D printing rapid prototyping and magnetic bead-based well test had the capability to successfully detect recombinant Pf LDH with low sample concentrations
(ng/mL) and volumes (20 µL) from blood samples. The assay showed a very superior
sensitivity with a low LOD of 4.9 ng/mL.
8.4.1.4 Cellular Detection
The gold standard diagnostic method of malaria recommended by WHO is microscopic examination of blood smears. However, microscopy methods may be often
unfeasible in the field where facilities, supplies and expertise are limited. Compared
to microscopic techniques, non-invasive is painless and less technical which can
improve the diagnosis efficiency of malaria. Aryanyijuka et al. [97] developed a
scheme to enable non-invasive malaria diagnosis by a mobile phone. The research
evaluated the ability to analyze fluorescence light emitted by aptamers conjugated
with acridine orange. Furthermore, the aptamers can be used to label malaria-infected
red blood cells.
227
8.4.1.3 Microfluidics-Based-Integrated Aptasensors
Integrated detection platform will increase both efficiency and robustness of detection procedures via reducing manual operations. Microfluidics is an efficient tool to
construct integrated aptasensors. Tanner [95] improved their study and presented a
microfluidic APTEC biosensor for malaria diagnosis. Microfluidic chambers were
designed to integrate with APTEC biosensor. The biosensor performed high sensitivity and specificity in Pf LDH detection for both parasite samples and clinical
samples from malaria. It is a successful application of microfluidic technology in
malaria diagnosis.
With the wide usage of microfluidic technology [96], origami scaffolds have also
been used for malaria detection. Godonoga et al. [85] attempted to incorporate a
malaria-detecting molecule onto a DNA origami scaffold. They combined DNA
aptamers specific for the malaria biomarker Pf LDH with a DNA origami scaffold.
Aptamers were integrated into a rectangular DNA origami, and the specific binding
ability of aptamers to the target protein was observed by AFM. 1000 nM Pf LDH
protein was incubated with 12 nM aptamer on origami at room temperature for 1 h,
and subsequently visualized under AFM (Fig. 8.8c). The work demonstrates the
ability of DNA aptamers to recognize a malaria biomarker whilst being integrated
within a supramolecular DNA scaffold, and provides malaria with new diagnostic
approaches based on DNA nanotechnology.
Based on the combinations of 3D printing and fluidic technologies, fabrication of point-of-care device was feasible. Aptamer-based point-of-care diagnostic
devices for malaria using 3D printing rapid prototyping were developed. Tanner’s
[86] study sought to develop point-of-care malaria diagnostic tests which use the
APTEC sensing system with3D printing technology as a platform for rapid prototyping (Fig. 8.8d). When capturing the malaria biomarker Pf LDH from samples,
it will generate a visible blue color in response to Plasmodium positive samples.
Both 3D printing rapid prototyping and magnetic bead-based well test had the capability to successfully detect recombinant Pf LDH with low sample concentrations
(ng/mL) and volumes (20 µL) from blood samples. The assay showed a very superior
sensitivity with a low LOD of 4.9 ng/mL.
8.4.1.4 Cellular Detection
The gold standard diagnostic method of malaria recommended by WHO is microscopic examination of blood smears. However, microscopy methods may be often
unfeasible in the field where facilities, supplies and expertise are limited. Compared
to microscopic techniques, non-invasive is painless and less technical which can
improve the diagnosis efficiency of malaria. Aryanyijuka et al. [97] developed a
scheme to enable non-invasive malaria diagnosis by a mobile phone. The research
evaluated the ability to analyze fluorescence light emitted by aptamers conjugated
with acridine orange. Furthermore, the aptamers can be used to label malaria-infected
red blood cells.