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In this study, a FRET-based fluorescent aptasensor for the detection of ochratoxin A (OTA) was optimized based on the quenching efficiency of single-walled carbon nanotubes (SWCNTs) and the binding affinity of aptamers. OTA aptamers were conjugated with quantum dots and adsorbed to the surface of both acid-modified and unmodified SWCNTs. The maximum fluorescence quenching efficiency of the SWCNTs were compared. Acid-modified SWCNTs (amSWCNTs) have moderate quenching efficiency, providing an optimal sensitivity for qualitative fluorescence-enhancement biosensor assays. The binding parameters of the QD-modified OTA aptamers (1.12.2 and A08min) on the surface of amSWCNTs were compared. Based on our results, the A08min aptamer is a better candidate for OTA detection. Using the A08min aptamer, the SWCNT method had a limit of detection (LOD) of 40 nM. The amSWCNT method had a significantly lower LOD of 14 nM. Turn-on fluorescent nano-aptasensors are emerging as an effective diagnostic tool for simple detection of mycotoxins. Nanocomplexes designed for the detection of mycotoxins in solution and paper-based tests have proven to be useful.

Despite evidence showing that polymer brushes (PBs) are a powerful tool used in biosensing for minimizing nonspecific interactions, allowing for optimization of biosensing performance, and the fact that GaAs semiconductors have proven to have a remarkable potential for sensitive biomolecule detection, the combination of these two robust components has never been considered nor evaluated as a platform for biosensing applications. This work reports different methodologies to prepare and tune PBs on the GaAs interface (PB–GaAs) and their potential as useful platforms for antibody grafting, with the ultimate goal of demonstrating the innovative and attractive character of the PB–GaAs interfaces in the enhanced capture of antibodies and control of nonspecific interactions. Three different functionalization approaches were explored, one “grafting-to” and two “grafting-from,” in which atom transfer radical polymerization (ATRP) was performed, followed by their corresponding characterizations. Demonstration of the compatibility of Escherichia coli (E. coli) and Legionella pneumophila (Lp) antibodies with the PB–GaAs platform compared to the results obtained with conventional biosensing architectures developed for GaAs indicates the attractive potential for operation of a sensitive biosensor. Furthermore, these results showed that by carefully choosing the nature and preparation methodology of a PB–GaAs interface, it is possible to effectively tune the affinity of PB–GaAs-based sensors toward E. coli and Lp antibodies ultimately demonstrating the superior specificity of the developed biosensing platform.

This review summarises developments on the analysis of various matrices for mycotoxins published in the period from mid-2019 to mid-2020. Notable developments in all aspects of mycotoxin analysis, from sampling and quality assurance/quality control of analytical results, to the various detection and quantitation technologies ranging from single mycotoxin biosensors to comprehensive instrumental methods are presented and discussed. Aside from sampling and quality control, discussion of this past year’s developments is organised by detection and quantitation technology and covers chromatography with targeted or non-targeted high resolution mass spectrometry, tandem mass spectrometry, detection other than mass spectrometry, biosensors, as well as assays that use alternatives to antibodies. This critical review aims to briefly present the most important recent developments and trends in mycotoxin determination as well as to address limitations of the presented methodologies.

Metallic nanoparticles, in particular silver and gold nanoparticles, have been used in various fields for centuries. In the last few decades, their plasmon resonance has made them particularly attractive to biochemists because of their unparalleled optical properties, making them ideal probes for molecular detection. In this article, a new approach to dopamine detection based on ultrastable gold nanoparticles is presented. A dopamine-binding aptamer was used to modify ultrastable gold nanoparticles for the sensitive and selective detection of different concentrations of dopamine without inducing gold nanoparticles aggregation. Indeed, when dopamine binds to the aptamer present at the surface of the gold nanoparticle, the latter exhibits a plasmon shift relative to the dopamine concentration, allowing measurement of its dosage. Besides that, the target molecules can be filtered out to permit nanoparticles reuse. The detection assay showed good linearity between the dopamine concentration and gold nanoparticles’ plasmon shift while common interfering molecules, such as ascorbic acid and tyramine, induced no or little plasmon shift.

Objective: An important clinical question in the determination of the extent of thrombosis-related vascular conditions is the identification of blood clot location. Fibrin is a major molecular constituent of blood clots and can, therefore, be utilized in molecular imaging. In this proof-of-concept study, we sought to prepare a fibrin-targeting magnetic resonance imaging contrast agent, using a Gd(III)-loaded fibrinogen aptamer (FA) chelate conjugate (Gd(III)-NOTA-FA) (NOTA = 1,4,7-triazacyclononane-1,4,7-triacetic acid), to endow the ability to specifically accumulate at the location of blood clots, thereby enhancing contrast capabilities. Methods: The binding affinity of FA for fibrin was confirmed by fluorescence microscopy and microscale thermophoresis. The preparation and effective loading of the chelate-aptamer conjugates were confirmed by mass spectrometry and a xylenol orange colorimetric test. Longitudinal and transverse relaxivities and the effects of target binding were assessed using T1- and T2-map sequences at 7 T. T1- and T2-weighted images were acquired after blood clots were treated with Gd(III)-NOTA-FA. Collagen was used as the protein control, while an unrelated aptamer sequence, FB139, was used as the aptamer control. Results: FA demonstrated a high affinity and selectivity toward the polymeric protein, with a Kd of 16.6 nM, confirming an avidity over fibrinogen. The longitudinal (r1) and transverse (r2) relaxivities of Gd(III)-NOTA-FA demonstrated that conjugation to the long aptamer strand shortened T1 relaxation times and increased T2 relaxation times (3.04 and 38.7 mM-1 s-1, respectively). These effects were amplified by binding to the fibrin target (1.73 and 46.5 mM-1 s-1, respectively). In vitro studies with thrombin-polymerized human blood (clots) in whole blood showed an unexpected enhancement of signal intensity (hyperintense) produced exclusively at the location of the clot during the T2-weighted scan, while the presence of fibrinogen within a whole blood pool resulted in T1 signal intensity enhancement throughout the pool. This is advantageous, as simply reversing the type of a scan from a typical T1-weighted to a T2-weighted would allow to selectively highlight the location of blood clots. Conclusions: Gd(III)-NOTA-FA can be used for molecular imaging of thrombi, through fibrin-targeted delivery of contrast to the location of blood clots in T2-weighted scans.

Purpose The purpose of our study was to compare the effectiveness of transincisional (TI) versus laparoscopic-guided (LG) rectus sheath block (RSB) for pain control following pediatric single-incision laparoscopic cholecystectomy (SILC). Methods Forty-eight patients 10–21 years old presenting to a single institution for SILC from 2015 to 2018 were randomized to TI or LG RSB. Apart from RSB technique, perioperative care protocols were identical between groups. Pain scores were assessed with validated measures upon arrival in the postanesthesia care unit (PACU) and at regular intervals until discharge. The patients and those assessing them were blinded to RSB technique. The primary outcome was pain score 60 min after PACU arrival. Secondary outcomes included pain scores throughout the PACU stay, opioids (reported as morphine milligram equivalents (MME) per kg bodyweight) administered in PACU, length of stay, outpatient pain scores and opioid use, and adverse events. Groups were compared on outcomes using t test and generalized estimating equations for continuous variables and Fisher's exact test for categorical variables with significance at α = 0.05. Results Mean age of the 48 subjects was 15 years (range = 11–20). The majority (79%) were female. Indications for surgery included symptomatic cholelithiasis (n = 41), acute cholecystitis (n = 4), gallstone pancreatitis (n = 2) and choledocholithiasis (n = 1). Mean (standard deviation) operative time was 61 (± 23) min overall. No statistically significant differences in demographics, indication, operative time, or intraoperative analgesia were observed between TI (n = 24) and LG (n = 24) groups. The mean 60-min pain score was 3.4 (± 2.6) in the LG group versus 3.8 (± 2.1) in the TI group (p = 0.573). No significant differences were detected between groups in overall PACU or outpatient pain scores, PACU or outpatient opioid use, length of stay, or incidence of complications. Overall, mean opioid use was 0.1 MME/kg in the PACU and 0.5 MME/kg in the outpatient setting. Mean postoperative length of stay was 0.2 day. There were no major complications. Conclusion Laparoscopic-guided rectus sheath block is not superior to transincisional rectus sheath block for pain control following pediatric single-incision laparoscopic cholecystectomy. The single-incision laparoscopic approach combined with rectus sheath block resulted in effective pain control, low opioid use, and expedited length of stay with no major complications. Level of evidence Level I, treatment study, randomized controlled trial.

Cross-sectional imaging (CSI) may be clinically unnecessary in the evaluation of pectus excavatum (PE). The purpose of our study was to prospectively evaluate the accuracy and reliability of the modified percent depth (MPD), derived from caliper-based external measurements, in identifying PE.Children 11-21 years old presenting for evaluation of PE or to obtain thoracic cross-sectional imaging for other indications were measured to derive the Modified Percent Depth. The Haller Index (HI) and Correction Index (CI) were calculated from CSI. Receiver-Operator Characteristic (ROC) analysis was used to compare the sensitivity and specificity of MPD, HI, and CI. Interrater reliability was assessed using Spearman's correlation coefficient and Cohen's Kappa coefficient.Of 199 patients, 76 (38%) had severe PE. Median age was 16 years (range = 11-21). The median Modified Percent Depth was 21.4% (IQR = 16.2-26.3) among those with PE versus 4.1% (IQR = 1.7-6.4) in those without (p 0.001). MPD ≥ 11% exhibited similar sensitivity and specificity to HI ≥ 3.25 and CI ≥ 10 for identifying PE (ROC 0.98 vs. 0.97 vs. 0.98, respectively, p = 0.41). With respect to interrater reliability, independent clinicians' caliper measurements exhibited 87% agreement when identifying MPD ≥ 11% (p 0.001) with excellent correlation (Spearman's ρ 0.71, p 0.001).Caliper-based, physical examination measurements of the Modified Percent Depth reliably identify pectus excavatum and represent an alternative to CSI-based measurements for the assessment of PE.Diagnostic test.Level II.

Targeting of molecular constituents of thrombi with aptamer functionalized core-shell nanoparticles (CSN) allowed for high resolution clot delineation in T2-weighted magnetic resonance imaging. Meanwhile, the gold-coating demonstrated sufficient contrast capabilities in computed tomography (1697 HU μM

Consider for a moment the rate of advancement in the scientific understanding of DNA. It is formidable; from Fredrich Miescher’s nuclein extraction in the 1860s to Rosalind Franklin’s double helix X-ray in the 1950s to revolutionary next-generation sequencing in the late 2000s. Now consider the scientific paper, the medium used to describe and publish these advances. How is the scientific paper advancing to meet the needs of those who generate and use scientific information? We review four essential qualities for the scientific paper of the future: ( i) a robust source of trustworthy information that remains peer reviewed and is ( ii) communicated to diverse users in diverse ways, ( iii) open access, and ( iv) has a measurable impact beyond Impact Factor. Since its inception, scientific literature has proliferated. We discuss the continuation and expansion of practices already in place including: freely accessible data and analytical code, living research and reviews, changes to peer review to improve representation of under-represented groups, plain language summaries, preprint servers, evidence-informed decision-making, and altmetrics.

Background Discrepancies in controlled substance documentation are common and can lead to legal and regulatory repercussions. We introduced a visual analytics dashboard to assist in a quality improvement project to reduce the discrepancies in controlled substance documentation in the operating room (OR) of our free-standing pediatric hospital. Methods Visual analytics were applied to collected documentation discrepancy audit data and were used to track progress of the project, to motivate the OR team, and in analyzing where further improvements could be made. This was part of a seven-step improvement plan based on the Theory of Change with a logic model framework approach. Results The introduction of the visual analytics dashboard contributed a 24% improvement in controlled substance documentation discrepancy. The project overall reduced documentation errors by 71% over the studied period. Conclusion We used visual analytics to simultaneously analyze, monitor, and interpret vast amounts of data and present them in an appealing format. In conjunction with quality-improvement principles, this led to a significant improvement in controlled substance documentation discrepancies.

We demonstrate high-sensitivity detection of metastatic breast cancer cells using terahertz (THz) chemical microscopy (TCM) with aptamers as ligands. For the aptamers, we use previously developed synthetic single stranded (ss) DNA aptamers mammaglobin B1 (MAMB1) and mammaglobin A2 (MAMA2) that bind to mammaglobin B and mammaglobin A proteins, respectively, which are overexpressed on the surface of MCF7 and MDA-MB-415 breast cancer cells. Each aptamer was immobilized on the surface of a sensing plate, and the amplitude of the THz signal was measured upon the binding of each aptamer to different number (10–106) of its target breast cancer cells. A change in the THz amplitude was observed when MAMB1 and MAMA2 bind to MCF7 and MDA-MB-415, respectively. We find that this change was linear as a function of the log number of breast cancer cells used. No change in the THz amplitude was observed when the same number of normal breast cells (MCF 10A) were used. Moreover, MAMB1 and MAMA2 did not show binding to the counter breast cancer cells, indicating high selectivity. We have demonstrated that the TCM using aptamers as ligands has a limit of detection as small as 1 breast cancer cell in 100 μL of sample. Results described here indicate that the TCM could be a powerful tool to detect metastatic breast cancer cells.

Graphical abstract, Magnetic separation has gained new popularity as a versatile partitioning method with the recent growth in nanotechnology and related biotechnology applications. In this study, iron oxide magnetic nanoparticles were synthesized via solvothermal methods and directly coated with gold to form core-shell gold-coated magnetic nanoparticles (Fe3O4-AuNPs). High-resolution transmission electron microscopy with Energy dispersive X-ray spectroscopy results suggests that temperature and reaction time play an important role in the formation of small, monodisperse Fe3O4-AuNPs. We also demonstrate that increased 4- dimethyl(amino)pyridine (DMAP) concentrations and vigorous stirring were required to successfully transfer Fe3O4-AuNPs into aqueous solution. The structure and morphology of the synthesized and transferred Fe3O4-AuNPs was further confirmed by UV–vis absorption spectroscopy and solubility experiments. • Direct coating of Fe3O4 with Au: Slowly heating by (10 °C/ min) until 180–190 °C without exceeding this reaction temperature and increasing the reaction time to 3 h from 1.5 h • High yield transfer of Fe3O4-AuNPs was achieved using 4- dimethyl(amino)pyridine (DMAP) as phase transfer catalyst

Agricultural biosensing can aid decisions about crop health and maintenance, because crops release root exudates that can inform about their status. l-Serine has been found to be indicative of nitrogen uptake in wheat and canola. The development of a biosensor for l-serine could allow farmers to monitor crop nutrient demands more precisely. The development of robust l-serine-binding DNA aptamers is described. Because small molecules can be challenging targets for Systematic Evolution of Ligands by EXponential enrichment (SELEX), three separate DNA libraries were used for SELEX experiments. A l-homocysteine aptamer was randomized to create a starting library for a l-serine selection (randomized SELEX). The final selection rounds of the l-homocysteine selection were also used as a starting library for l-serine (redirected SELEX). Finally, an original DNA library was used (original SELEX). All three SELEX experiments produced l-serine-binding aptamers with micromolar affinity, with Red.1 aptamer having a Kd of 7.9 ± 3.6 μM. Truncation improved the binding affinity to 5.2 ± 2.7 μM, and from this sequence, a Spiegelmer with improved nuclease resistance was created with a Kd of 2.0 ± 0.8 μM. This l-serine-binding Spiegelmer has the affinity and stability to be incorporated into aptamer-based biosensors for agricultural applications.

Cryptosporidium spp. are one of the most important waterborne pathogens worldwide and a leading cause of mortality from waterborne gastrointestinal diseases. Detection of Cryptosporidium spp. in water can be very challenging due to their low numbers and the complexity of the water matrix. This review describes the biology of Cryptosporidium spp. and current methods used in their detection with a focus on C. parvum and C. hominis. Among the methods discussed and compared are microscopy, immunology-based methods using monoclonal antibodies, molecular methods including PCR (polymerase chain reaction)-based assays, and emerging aptamer-based methods. These methods have different capabilities and limitations, but one common challenge is the need for better sensitivity and specificity, particularly in the presence of contaminants. The application of DNA aptamers in the detection of Cryptosporidium spp. oocysts shows promise in overcoming these challenges, and there will likely be significant developments in aptamer-based sensors in the near future.

A plasmonic optical fiber grating aptasensor was developed for real-time detection of the HER2 breast cancer biomarker. The designed biosensor shows an accurate and selective sensing of HER2 with respect to a biomarker negative control.

Optical fiber-based surface plasmon resonance (OF-SPR) sensors have demonstrated high versatility and performances over the last years, which propelled the technique to the heart of numerous and original biosensing concepts. In this work, we contribute to this effort and present our recent findings about the detection of breast cancer HER2 biomarkers through OF-SPR optrodes. 1 cm-long sections of 400 μm core-diameter optical fibers were covered with a sputtered gold film, yielding enhanced sensitivity to surface refractive index changes. Studying the impacts of the gold film thickness on the plasmonic spectral response, we improved the quality and reproducibility of the sensors. These achievements were correlated in two ways, using both the central wavelengths of the plasmon resonance and its influence on the bulk refractive index sensitivity. Our dataset was fed by additional biosensing experiments with a direct and indirect approach, relying on aptamers and antibodies specifically implemented in a sandwich layout. HER2 biomarkers were specifically detected at 0.6 μg/mL (5.16 nM) in label-free while the amplification with HER2-antibodies provided a nearly hundredfold signal magnification, reaching 9.3 ng/mL (77.4 pM). We believe that these results harbinger the way for their further use in biomedical samples.

Objective: Random formation of thrombi is classified as a pathological process that may result in partial or complete obstruction of blood flow and limited perfusion. Further complications include pulmonary embolism, thrombosis-induced myocardial infraction, ischemic stroke, and others. Location and full delineation of the blood clot are considered to be two clinically relevant aspects that could streamline proper diagnosis and treatment follow-up. In this work, we prepared two types of X-ray attenuating contrast formulations, using fibrinogen aptamer as the clot-seeking moiety. Methods: Two novel aptamer-targeted formulations were designed. Iodine-modified bases were directly incorporated into a fibrinogen aptamer (iodo-FA). Isothermal titration calorimetry was used to confirm that these modifications did not negatively impact target binding. Iodo-FA was tested for its ability to produce concentration-dependent contrast enhancement in a phantom CT. It was subsequently tested in vitro with clotted human and swine blood. This allowed for translation into ex vivo testing, using fluoroscopy. FA was also used to functionalize gold nanoparticles (FA-AuNPs), and contrast capabilities were confirmed. This formulation was tested in vitro using clotted human blood in a CT scan. Results: Unmodified FA and iodo-FA demonstrated a nearly identical affinity toward fibrin, confirming that base modifications did not impact target binding. Iodo-FA and FA-AuNPs both demonstrated excellent concentration-dependent contrast enhancement capabilities (40.5 HU mM-1 and 563.6 HU μM-1, respectively), which were superior to the clinically available agent, iopamidol. In vitro CT testing revealed that iodo-FA is able to penetrate into the blood clots, producing contrast enhancement throughout, while FA-AuNPs only accumulated on the surface of the clot. Iodo-FA was thereby translated to ex vivo testing, confirming target-binding associated accumulation of the contrast material at the location of the clot within the dilation of the external carotid artery. This resulted in a 34% enhancement of the clot. Conclusions: Both iodo-FA and FA-AuNPs were confirmed to be effective contrast formulations in CT. Targeting of fibrin, a major structural constituent of thrombi, with these novel contrast agents would allow for higher contrast enhancement and better clot delineation in CT and fluoroscopy.

Aptamers are single-stranded oligonucleotides selected by SELEX (Systematic Evolution of Ligands by EXponential Enrichment) able to discriminate target molecules with high affinity and specificity, even in the case of very closely related structures. Aptamers have been produced for several targets including small molecules like mycotoxins, however, the high affinity for their respective target molecules is a critical requirement. In the last decade, the screening through computational methods of aptamers for their affinity against specific targets has greatly increased and is becoming a commonly used procedure due to its convenience and low costs. This paper describes an in-silico approach for rapid screening of ten ssDNA aptamer sequences against fumonisin B1 (FB1, n = 3), aflatoxin B1 (AFB1, n = 2) and ochratoxin A (OTA, n = 5). Theoretical results were compared with those obtained by testing the same aptamers by fluorescent microscale thermophoresis and by magnetic beads assay for their binding affinity (KD) revealing a good agreement.

Islet amyloid polypeptide (IAPP) is a neuroendocrine hormone from pancreatic β-cells. Misfolded, aggregated IAPP is believed to be toxic to islet cells and amyloid deposits in the pancreas are pathological hallmarks of type 2 diabetes. Rapid fibrillization of this peptide makes it difficult to study in its soluble form, impeding a better understanding of its role. In this study, a variety of popular pretreatment methods were tested for their ability to delay aggregation of IAPP, including solutions of hexafluoroisopropanol, sodium hydroxide, hydrochloric acid, phosphate buffered saline, ammonium hydroxide, as well as tris buffer at different pH and containing either calcium (II), zinc (II), or iron (II). Aggregation was assessed using the thioflavin T fluorescence assay as well as by transmission electron microscopy. Tris buffer at pH 8.1 containing Zn(II) was found to have the best balance of temporary inhibition of aggregation and biological relevance., Graphical abstract Image 1

In the biomedical detection context, plasmonic tilted fiber Bragg gratings (TFBGs) have been demonstrated to be a very accurate and sensitive sensing tool, especially well-adapted for biochemical detection. In this work, we have developed an aptasensor following a triple strategy to improve the overall sensing performances and robustness. Single polarization fiber (SPF) is used as biosensor substrate while the demodulation is based on tracking a peculiar feature of the lower envelope of the cladding mode resonances spectrum. This method is highly sensitive and yields wavelength shifts several tens of times higher than the ones reported so far based on the tracking of individual modes of the spectrum. An amplification of the response is further performed through a sandwich assay by the use of specific antibodies. These improvements have been achieved on a biosensor developed for the detection of the HER2 (Human Epidermal Growth Factor Receptor-2) protein, a relevant breast cancer biomarker. These advanced developments can be very interesting for point-of-care biomedical measurements in a convenient practical way.

DNA aptamers generated by cell-SELEX against bacterial cells have gained increased interest as novel and cost-effective affinity reagents for cell labelling, imaging and biosensing. Here we describe the selection and identification of DNA aptamers for bacterial cells using a combined approach based on cell-SELEX, state-of-the-art applications of quantitative real-time PCR (qPCR), next-generation sequencing (NGS) and bioinformatic data analysis. This approach is demonstrated on Enterococcus faecalis (E. faecalis), which served as target in eleven rounds of cell-SELEX with multiple subtractive counter-selections against non-target species. During the selection, we applied qPCR-based analyses to evaluate the ssDNA pool size and remelting curve analysis of qPCR amplicons to monitor changes in pool diversity and sequence enrichment. Based on NGS-derived data, we identified 16 aptamer candidates. Among these, aptamer EF508 exhibited high binding affinity to E. faecalis cells (KD-value: 37 nM) and successfully discriminated E. faecalis from 20 different Enterococcus and non-Enterococcus spp. Our results demonstrate that this combined approach enabled the rapid and efficient identification of an aptamer with both high affinity and high specificity. Furthermore, the applied monitoring and assessment techniques provide insight into the selection process and can be highly useful to study and improve experimental cell-SELEX designs to increase selection efficiency.

Many methods have been reported to detect Cryptosporidium parvum (C. parvum) oocysts in the water environment using monoclonal antibodies. Herein, we report the use of DNA aptamers as an alternative ligand. We present the highly sensitive detection of C. parvum oocysts in wastewater samples based on aptamer-conjugated magnetic beads. A previously selected DNA aptamer (R4-6) that binds to C. parvum oocysts with high affinity and selectivity was rationally truncated into two minimer aptamers (Min_Crypto1 and Min_Crypto2), and conjugated to micro-magnetic beads. In flow cytometry tests with phosphate buffer, river water, and wastewater samples, both the minimers showed improved affinity and specificity toward C. parvum oocysts than the parent R4-6. Moreover, Min_Crypto2 showed higher affinity to its target than the parent aptamer when testing in wastewater, indicating superior binding properties in a complex matrix. Using a fluorescence microplate-based assay, and when incubated with different numbers of oocysts, Min_Crypto2 showed a limit of detection as low as 5 C. parvum oocysts in 300 μL of wastewater. Results described here indicate that Min_Crypto2 has superior specificity and sensitivity for the detection of C. parvum oocysts, and has a strong potential to be used successfully in a sensor.

Computed tomography (CT) and magnetic resonance imaging (MRI) are among the most well-established modalities in the field of noninvasive medical imaging. Despite being powerful tools, both suffer from a number of limitations and often fall short when it comes to full delineation of pathological tissues. Since its conception, molecular imaging has been commonly utilized to further the understanding of disease progression, as well as monitor treatment efficacy. This has naturally led to the advancement of the field of targeted imaging. Targeted imaging research is currently dominated by ligand-modified contrast media for applications in MRI and CT imaging. Although a plethora of targeting ligands exist, a fine balance between their size and target binding efficiency must be considered. This review will focus on aptamer- and peptide-modified contrast agents, outlining selected formulations developed in recent years while highlighting the advantages offered by these targeting ligands.

The detection of circulating tumor cells (CTCs) represents an important goal in oncological diagnosis and treatment, as CTCs are responsible for metastasis in several forms of cancer and are present at very low concentration. Their detection should occur at around 1-10 cells/mL of blood for diagnosis purpose. In this work, we propose an all-fiber plasmonic aptasensor featuring multiple narrowband resonances in the near-infrared wavelength range to detect metastatic breast cancer cells. To this aim, specific aptamers against mammaglobin-A proteins were selected and immobilized as bioreceptors on the optical fiber surface. In vitro assays confirm that label-free and real-time detection of cancer cells (LOD of 49 cells/mL) occurs within 5 minutes, while the additional use of functionalized gold nanoparticles allows a two-fold amplification of the biosensor response. Differential measurements on selected optical resonances were used to process the sensor response and results were confirmed by microscopy analysis. The detection of only 10 cancer cells/mL was performed with relevant specificity against non-target cells with comparable sizes and shapes.

We report two label-free fluorescent aptasensor methods for the detection of S. typhimurium. In the first method, we have used a ‘‘turn off’’ approach in which the aptamer is first intercalated with SYBR Green I (SG), leading to a greatly enhanced fluorescence signal. The addition of S. typhimurium (approximately 1530–96938 CFU/mL), which specifically binds with its aptamer and releases SG, leads to a linear decrease in fluorescence intensity. The lowest detection limit achieved with this approach was in the range of 733 CFU/mL. In the second method, a ‘‘turn on’’ approach was designed for S. typhimurium through the Forster resonance energy transfer (FRET) between Rhodamine B (RB) and gold nanoparticles (AuNPs). When the aptamer and AuNPs were mixed with RB, the fluorescence of RB was significantly quenched via FRET. The aptamer adsorbs to the AuNP surface to protect them from salt-induced aggregation, which leads to the fluorescence quenching of RB in presence of AuNPs. Upon the addition of S. typhimurium, S. typhimurium specifically binds with its aptamer and loses the capability to stabilize AuNPs. Thus, the salt easily induces the aggregation of AuNPs, resulting in the fluorescence recovery of the quenched RB. S. typhimurium concentrations ranging from 1530 to 96938 CFU/mL with the detection limit of 464 CFU/mL was achieved with this methodology. Given these data, some insights into the molecular interactions between the aptamer and the bacterial target are provided. These aptasensor methods also may be adapted for the detection of a wide variety of targets.