Nanoparticle Reservoirs for Paper-Only Immunosensors

Abstract

Biosensors made entirely of paper are becoming increasingly popular due to their low cost, facile fabrication, and lightweight portability for in-field measurements. However, it is difficult to store nanoparticles in paper substrates without irreversibly binding them to the cellulose matrix. This makes it challenging to fabricate biosensors incorporating nanoparticle probes in paper-based reservoirs. Here, we overcome this limitation with a new method for storing protein-decorated nanoparticles on paper substrates that also allows to release them on demand. It consists of spotting nanoparticles onto pieces of filter paper previously modified with polystyrene sulfonate. Gold nanoparticles modified with avidin or antibodies can be easily transferred from the dry reservoir to a receiving wet piece of paper by simply pressing with the finger or a clamp. Paper-based immunosensors incorporating the reservoir enabled the detection of glycoprotein B from human cytomegalovirus in serum with a limit of detection of 0.03 ng mL–1 and a total assay time of only 12 min. The low limit of detection obtained with a short assay time along with the long shelf-life of the reservoirs make the proposed paper-only biosensors ideal of point-of-care diagnostics.

Cascade of immune mechanism and consequences of inflammatory disorders

“…The IL-10 most predominant anti-inflammatory cytokines has also been found in COVID-19 patient sera ( Klein et al, 2020 ; Chen et al, 2020 ; Dong et al, 2020 ; Wang et al, 2020 ). It is also identified from other hyper-inflammatory syndromes that dysregulated inflammation is generally accompanied by immune suppression, ( Patricio et al, 2019 ) making high risk for opportunistic infections from bacteria, fungi, or even from latent human cytomegalovirus (CMV) in these patients ( Alba-Patiño et al, 2019 ; Mansfield et al, 2015 ; Monneret et al, 2011 ). The phenomenon of “Immunosenescence” ( Bektas et al, 2019 ) contributes a critical role within the age-associated severity of COVID-19.…”

Detection of low glucose levels in sweat with colorimetric wearable biosensors

“…The nanoparticles are stored in a reservoir containing polystyrene sulfonate (PSS), which prevents irreversible interactions with the paper even in dry conditions. 18 Thanks to this, the nanoparticles are carried through the paper as the wearer sweats, thus creating a red-colored trail that is related to the volume of sweat entering the biosensor (Fig. 1A and B).…”

Mobile origami immunosensors for the rapid detection of urinary tract infections

“…13 Antibody-decorated nanoparticles were obtained by adding 10 µL of biotinylated antibodies (4-5 mg mL −1 ) to 100 µL of avidin-modified gold nanoparticles ([Au] = 125 mM) for 1 hour. 12 When required, biotin-PEG was added at final concentration of 0.1 mM in order to block free avidin binding sites. Then the nanoparticles were centrifuged (7000 rpm, 6 min), the supernatant was removed, and the pellet was resuspended in 100 µL of PBST twice.…”

“…Finally, reservoirs containing anti E. coli-decorated nanoparticles were obtained by adding 1 µL of the colloidal suspension in the middle of the dried PSS spot and letting it dry at room temperature for 10 min. 12 The resulting biosensors could be stored in vacuum sealed bags at 4°C for at least 14 days without noticeable loss in performance ( Fig. S4 in ESI †).…”

“…10,11 Instead, it uses polystyrene sulfonate (PSS) in order to fabricate nanoparticle reservoirs directly on filter paper. 12 This reservoir is separated from the detection area by a wax barrier, which is easily drawn manually without using wax printers. The immunosensors were designed in order to detect pathogens above the infectious threshold as soon as possible and with the easiest analytical procedure, since these are the key points that make a biosensor useful in the doctor's office, where there is limited time to diagnose and prescribe therapies.…”