Aptamer Sensors (Marrazza et al., Man et al. 2021, Wu et al 2019)

[SarahHagg]

Aptamer Sensors

Giovanna Marrazza - DOI: 10.3390/bios7010005

Aptamers

• single-stranded DNA or short RNA sequences
• isolated in vitro from a library of synthetic oligonucleotides according to heir affinity toward a target molecule (with SELEX)

Advantages of aptamers vs antibodies

• high stability
• low dimension
• high affinity for small molecules
• easy to synthesize in vitro, simple to modify -> efficient, exceptional binding constants in the micromolar to picomolar range

Some applications of aptamers as biosensors

• recognition of proteins and as enzyme mimics (Menger et al.)
• detection of intact viruses (P. K. R. Kumar)
• detection of thrombin and vascular endothelial growth factor biomarkers and aflatoxin M1 with 'whispering gallery mode resonators (WGMRs)' (Nunzi Conti et al.)
• protein biomarker analysis using electrochemichemistry electrochemiluminescence and photoelectrochemical transduction methods (Ravalli et al.)
• gluten quantification: aptamer-protein and aptamer-peptide interactions (Miranda-Castro et al.)

[SarahHagg]

A microfluidic colorimetric biosensor for in-field detection of Salmonella in fresh-cut vegetables using thiolated polystyrene microspheres, hose-based microvalve and smartphone imaging APP

Yan Man et al. (2021) DOI: 10.1016/j.foodchem.2021.129578

looks really cool, but cannot access the full article :/

• Salmonella was detected with Aptamer-PS-cysteamine conjugates
• gold nanoparticles aggregated on the surface of Salmonella-aptamer-PS-cysteamine conjugates -> resulting in a visible color change in the detection chamber
• smartphone imaging app for monitoring colorimetric signals

[SarahHagg]

A novel colorimetric aptasensor for detection of chloramphenicol based on lanthanum ion–assisted gold nanoparticle aggregation and smartphone imaging

Yang-yang Wu et al. (2019) DOI: 10.1007/s00216-019-02149-7

similar approach to use aptamers for detection, resulting in a color change that can be detected with an app

• detection of chloramphenicol (CAP)
• ssDNA-modified gold nanoparticle (AuNP) aggregation (facilitated with lanthanum (La3+) ions)
• color change from blue to violet-red when CAP is present -> app

colorimetric aptasensors better than with fluorescence, electrochemical or quartz crystal microbalance, as they do not depend on a special analysis device -> easy on-site analyses

use of metal ions (e.g. lanthanum):

• metal ions can strongly combine with the phosphate groups of aptamers specifically through coordination interactions -> aggregation of AuNPs in absence of CAP -> color change from red to blue
• aggregation of La3+-Apt-AuNPs avoided false positives phenomenon from AuNP aggregation induced by the salt conditions and the interference of other substances in food.

in presence of CAP: Apt-CAP complex -> La3+ attachment deprived -> no aggregation of AuNPs -> AuNP color change to violet-red

[nathaliaraquelx]

Wow, this type of imaging detection is really interesting.

[git-cgalan]

The protocol look super cool an easy to apply to another project