Aptamer-functionalized porous phospholipid nanoshells for direct measurement of Hg2+ in urine

Abstract

A porous phospholipid nanoshell (PPN) sensor functionalized with a specific aptamer sensor agent was prepared for rapid detection of Hg2+ in human urine with minimal sample preparation. Aptamer sensors provide an important class of optical transducers that can be readily and reproducibly synthesized. A key limitation of aptamer sensors, and many other optical sensors, is the potential of biofouling or biodegradation when used in complex biological matrices such as serum or urine, particularly when high levels of nucleases are present. We prepared Hg2+-responsive, PPN-encapsulated aptamer sensors that overcome these limitations. PPNs provide a protective barrier to encapsulate the aptamer sensor in an aqueous environment free of diffusional restrictions encountered with many polymer nanomaterials. The unique porous properties of the PPN membrane enable ready and rapid transfer of small molecular weight ions and molecules into the sensor interior while minimizing the macromolecular interactions between the transducer and degradants or interferents in the exterior milieu. Using Hg2+-responsive, PPN-encapsulated aptamer sensors, we were able to detect sub-100 ppb (chronic threshold limit from urine test) Hg2+ in human urine with no sample preparation, whereas free aptamer sensors yielded inaccurate results due to inteferences from the matrix. The PPN architecture provides a new platform for construction of aptamer-functionalized sensors that target low molecular weight species in complex matrices, beyond the Hg2+ demonstrated here.

Versatile Integration of Liquid-Phase Microextraction and Fluorescent Aptamer Beacons: A Synergistic Effect for Bioanalysis

“…This indicated that the complex sample matrices originating from biological samples significantly disturbed the recognition capability of the FAB toward Hg 2+ . In addition, it was reported that the low compatibility of FABs toward biological samples was mainly due to the degradation of FABs by the DNase in complex matrices. ,, To verify that the challenges with biological samples originated from the sample matrices, the recognition of Hg 2+ by FAB in water samples with and without DNase were compared as shown in Figure C. The experimental results confirmed the previous observations and verified the hypothesis in Figure B that the complex sample matrices in biological samples significantly disturbed the recognition capability of FABs.…”

“…As reported, although the modified aptamers were resistant to nuclease digestion, these modifications might affect the aptamer structure and its function (recognition capability). 11 Alternatively, the integration of aptamer beacons with nanomaterials such as porous phospholipid nanoshells, 15 polyacrylamide nanoparticles, 16 DNA hydrogels, 17 carbon nanotubes, 18 T h i s c o n t e n t i s graphene oxides, 19 and gold nanoparticles 20 was another efficient way to increase the biocompatibility of FABs, since the nanomaterials could impede the interaction between the aptamer beacons and the interference substances. However, the aptamer modification and nanomaterial integration might increase the difficulty in the synthesis of FABs.…”

Fluorescent Sensors for the Detection of Heavy Metal Ions in Aqueous Media

“…As explained previously, the fluorescent emission of the dyes can also be attenuated by a quencher linked to the opposite termini of the sensitive aptamer. One which has been widely employed with this aim is 4-([4-(dimethylamino)phenyl]azo)benzoic acid (DABCYL) [66], owing to its broad absorption spectrum [67]: the sensor reported by Li and co-authors [68] presented a linear calibration curve between 10 nM and 200 nM, with a LOD of 10 nM Hg 2+ . Furthermore, in order to avoid the biodegradation of the aptamer, it was encapsulated in a porous phospholipid nanoshell (PPN), allowing its utilization in human urine samples.…”

Development of an Aptamer Based Luminescent Optical Fiber Sensor for the Continuous Monitoring of Hg2+ in Aqueous Media

“…The utilization of this sequence involves a key advantage over other ON sequence-based Hg 2+ sensors, as the T-Hg 2+ -T mismatches absorb the electrons emitted by the labelled atto390 (consequently quenching the fluorescent emission), there is no need to use either a quencher [31] or a complementary sequence [32]. This also allows the sequence to become directly attached onto the optical fiber, as it is explained hereafter.…”