Aptamer-conjugated gold nanoparticles for portable, ultrasensitive naked-eye detection of C-reactive protein based on the Tyndall effect

BACKGROUND

C-reactive protein (CRP) represents an early clinical biomarker that indicates the presence of inflammatory or infectious conditions in the human body. Today's procedures approved by the Food and Drug Administration (FDA) imply expensive equipment and highly trained personnel to perform the test. Therefore, a new diagnostic method with high detection efficiency and less cost is urgently needed for delivering rapid and timely results in point-of-care (POC) service.

RESULTS

Herein, we propose a new, equipment-free, and portable sensing method for the future POC detection of CRP based on the Tyndall effect (TE). In our study, aptamer-conjugated citrate-stabilized gold nanoparticles (apta-AuNPs) are exploited as the sensing platform. The apta-AuNPs' interaction with CRP in a saline environment leads to their aggregation, thus enhancing the scattering of light when the solution is exposed to a 640 nm pointer laser line. Firstly, the enhancement of the scattering light as a function of increasing concentration of CRP in solution is measured spectroscopically using a typical 90-degree angle spectrofluorometer and then the measurements are compared to the classic colorimetric detection using an UV-Vis spectrophotometer. Finally, to achieve high portability and accessibility, we demonstrate that the measurement of CRP concentration can be performed with similar accuracy but in a more direct and inexpensive way by using a laser pointer pen as the excitation source and a camera of a low-budget smartphone as a quantitative reader instead of most expensive spectrofluorometer.

SIGNIFICANCE

The portable TE-based assay exhibits a wide linear dynamic range (1-60 μg/mL) for the detection of CRP with a limit of detection (LOD) of 92 ng/mL The proposed method is capable to integrate both standard and high-sensitivity CRP analysis in a single procedure with increased sensitivity and prompt delivery of analysis results. Moreover, the sensing procedure is significantly faster than the FDA approved ones with a detection time of only 10 min. Finally, as a proof-of-concept, our findings demonstrate excellent recovery for CRP detection in spiked and diluted urine samples, highlighting the strong potential of this sensing method for POC applications.

ULTRASONOGRAPHIC FEATURES OF NON-VASCULAR COMPLICATIONS OF HYALURONIC ACID FILLERS: A RETROSPECTIVE STUDY AT A REFERENCE CENTER FOR DERMATOLOGIC ULTRASONOGRAPHY

Hyaluronic acid (H.A.) filler injections have been associated with early, temporary, and delayed-onset onset complications. High-resolution ultrasound (HRUS) with Doppler analysis has been increasingly used to detect and identify such complications. We describe comprehensively the most common ultrasonographic findings of non-vascular complications associated with H.A. filler injections. This retrospective, cross-sectional observational study was conducted at a reference center for dermatologic ultrasound in Bogotá, Colombia. Ultrasound reports documented the ultrasonographic findings of non-vascular complications of H.A. filler injections. Fifty-two complications were documented in a cohort of 50 patients (women, 88%). The infraorbital region was the most common site affected (23%), followed by the nasolabial (22%). The Tyndall effect was the most common complication (25% of all), followed by changes in rheology (21%) and pseudo-sarcoidal (foreign body granuloma) reaction (15%). The Tyndall effect stood out for its distinctive ultrasonographic characteristics. We discuss the ultrasonographic findings and pathogenesis of other complications, including filler migration, early hypersensitivity, aseptic abscess, overcorrection, and filler material interaction. The clinical presentation of H.A. filler complications can be confusing, delaying timely diagnosis and treatment. HRUS with Doppler analysis is a valuable tool for avoiding unnecessary treatments and ensuring timely diagnosis and treatment.

Simple, sensitive, colorimetric detection of pyrophosphate via the analyte-triggered decomposition of metal-organic frameworks regulating their adaptive multi-color Tyndall effect

This paper describes initially the application of the Tyndall effect (TE) of metal-organic framework (MOF) materials as a colorimetric signaling strategy for the sensitive detection of pyrophosphate ion (PPi). The used MOF NH2-MIL-101(Fe) was prepared with Fe3+ ions and fluorescent ligands of 2-amino terephthalic acid (NH2-BDC). The fluorescence of NH2-BDC in MOF is quenched due to the ligand-to-metal charge transfer effect, while the NH2-MIL-101(Fe) suspension shows a strong TE. In the presence of PPi analyte, the MOFs will undergo decomposition because of the competitive binding of Fe3+ by PPi over NH2-BDC, resulting in a significant decrease in the TE signal and fluorescence restoration from the released ligands. The results demonstrate that the new method only requires a laser pointer pen (for TE creation) and a smartphone (for portable quantitative readout) to detect PPi in a linear concentration range of 1.25-800 μM, with a detection limit of ~210 nM (3σ) which is ~38 times lower than that obtained from traditional fluorescence with a spectrophotometer (linear concentration range, 50-800 µM; detection limit, 8.15 µM). Moreover, the acceptable recovery of PPi in several real samples (i.e., pond water, black tea, and human serum and urine) ranges from 97.66 to 119.15%.

DNAzyme amplified dispersion state change of gold nanoparticles and its dual optical channels for ultrasensitive and facile detection of lead ion in preserved eggs

A dual-mode sensing platform for Pb2+ was constructed based on the dual optical channels of Au NPs system with the amplification of DNAzyme, and it was successfully applied for Pb2+ determination in preserved egg with satisfactory results. The presence of Pb2+ activated the DNAzyme and induced the dispersion change of Au NPs in high salt concentration. The sequent absorption change of Au NPs was translated to the fluorescence change of carbon dots through FRET, and the scattering change was transferred to grey value of images involving the Tyndall effect. Thus, a sensing platform based on fluorescence and colorimetric dual-technique was achieved for Pb2+ detection, under the optimized conditions. With the assistance of DNAzyme, the linear range of fluorometric and colorimetric method were 2.0 × 10-14 ∼ 8.0 × 10-10 mol/L and 2.4 × 10-13 ∼ 9.5 × 10-9 mol/L, respectively. The dual-mode sensing platform demonstrated its promising application in the environmental monitoring and food safety field.

Smartphone-based low-cost and rapid quantitative detection of urinary creatinine with the Tyndall effect

This research aims to develop a robust and quantitative method for measuring creatinine levels by harnessing the enhanced Tyndall effect (TE) phenomenon. The envisioned sensing assay is designed for practical deployment in resource-limited settings or homes, where access to advanced laboratory facilities is limited. Its primary objective is to enable regular and convenient monitoring of renal healthcare, particularly in cases involving elevated creatinine levels. The creatinine sensing strategy is achieved based on the aggregation of gold nanoparticles (AuNPs) triggered via the direct crosslinking reaction between creatinine and AuNPs, where an inexpensive laser pointer was used as a handheld light source and a smartphone as a portable device to record the TE phenomenon enhanced by the creatinine-induced aggregation of AuNPs. After evaluation and optimization of parameters such as AuNP concentrations and TE measurement time, the subsequent proof-of-concept experiments demonstrated that the average gray value change of TE images was linearly related to the logarithm of creatinine concentrations in the range of 1-50 μM, with a limit of detection of 0.084 μM. Meanwhile, our proposed creatinine sensing platform exhibited highly selective detection in complex matrix environments. Our approach offers a straightforward, cost-effective, and portable means of creatinine detection, presenting an encouraging signal readout mechanism suitable for point-of-care (POC) applications. The utilization of this assay as a POC solution exhibits potential for expediting timely interventions and enhancing healthcare outcomes among individuals with renal health issues.

Quantitative colorimetric sensing of heavy metal ions via analyte-promoted growth of Au nanoparticles with timer or smartphone readout

This work describes two new colorimetric nanosensors for label-free, equipment-free quantitative detection of nanomolar copper (II) (Cu²⁺) and mercury (II) (Hg²⁺) ions. Both are based on the analyte-promoted growth of Au nanoparticles (AuNPs) from the reduction of chloroauric acid by 4-morpholineethanesulfonic acid. For the Cu²⁺ nanosensor, the analyte can accelerate such a redox system to rapidly form a red solution containing dispersed, uniform, spherical AuNPs that is related to these particles' surface plasmon resonance property. For the Hg²⁺ nanosensor, on the other hand, a blue mixture consisting of aggregated, ill-defined AuNPs with various sizes can be created, showing a significantly enhanced Tyndall effect (TE) signal (in comparison with that produced in the red solution of AuNPs). By using a timer and a smartphone to quantitatively measure the time of producing the red solution and the TE intensity (i.e., the average gray value of the corresponding image) of the blue mixture, respectively, the developed nanosensors are well demonstrated to achieve linear ranges of 6.4 nM to 100 μM and 6.1 nM to 1.56 μM for Cu²⁺ and Hg²⁺, respectively, with detection limits down to 3.5 and 0.1 nM, respectively. The acceptable recovery results obtained from the analysis of the two analytes in the complex real water samples including drinking water, tap water, and pond water ranged from 90.43 to 111.56%.

A dual-mode sensor based on colorimetric and Tyndall effect of gold nanoparticles for ultra-sensitive detection of Hg2

Mercury ion (Hg²⁺) is the most widespread and highly toxic environmental pollutant, which exerts numerous adverse effects on environmental and human health. There is an urgent need to develop a convenient method for detecting Hg²⁺. Herein, a novel dual-mode sensor based on colorimetric and Tyndall effect of gold nanoparticles was developed for ultra-sensitive determination of Hg²⁺. In this strategy, a polyA-modified Au probe with high uniformity was assembled successfully. Both modes were based on Hg²⁺-induced aggregation of the probes. Hg²⁺ was reflected according to the color variations of solution and the Tyndall effect of Au reporter. With the aid of a laser pointer, the Tyndall mode demonstrated about 615-fold improvement on sensitivity compared with the colorimetry way. Taking advantages of low cost and convenient assembly of polyA-based Au probe and the combination of colorimetry and Tyndall effect, our strategy determined the Hg²⁺ with high sensitivity and wide range. By changing probes or nanoparticles, the proposed strategy is expected to be a universal platform for detecting other analytes in environmental and even biological samples. A novel dual-mode sensor based on colorimetric and tyndall effect of gold nanoparticles for ultra-sensitive determination of Hg2+ was exploited.

Tyndall-Effect-inspired assay with gold nanoparticles for the colorimetric discrimination and quantification of mercury ions and glutathione

This work initially reports a new nanosening method for simple, sensitive, specific, visual detection of mercury (II) (Hg²⁺) and glutathione (GSH) using the Tyndall Effect (TE) of the same colloidal gold nanoparticle (GNP) probes for efficient colorimetric signaling amplification. For the TE-inspired assay (TEA) method, arginine (Arg) molecules are pre-modified on the GNPs' surfaces (Arg-GNPs). Upon the Hg²⁺ introduction, it can be specifically coordinated with the terminal -NH₂ and -COOH groups of the Arg molecules to make the Arg-GNPs aggregate, producing a significantly-enhanced TE signal in the reaction solution after its irradiation by a 635-nm red laser pointer pen. On the other hand, the introduction of the GSH results in the production of the original Arg-GNPs' weak TE response, as it is able to bind such metal ion via mercury-thiol reactions to inhibit the above aggregation. Under the optimal conditions, the utility of the new TEA method is well demonstrated to quantitatively detect the Hg²⁺ and GSH with the aid of a smartphone as a portable TE reader during the linear concentration ranges of 50-3000 and 10-3000 nM, respectively. The detection limits for the Hg²⁺ and GSH are estimated to be as low as ∼3.5 and ∼0.3 nM, respectively. The recovery results obtained from the detection of Hg²⁺ in the complex tap and pond water samples and the assay of GSH in real human serum and urine samples are also satisfactory.

Non-invasive Instrument-Based Tests for Quantifying Anterior Chamber Flare in Uveitis: A Systematic Review

Purpose: Anterior chamber (AC) flare is a key sign for anterior uveitis. New instrument-based techniques for measuring AC flare can offer automation and objectivity. This review aims to identify objective instrument-based measures for AC flare.Methods: In this systematic review, we identified studies reporting correlation between instrument-based tests versus clinician AC flare grading, and/or aqueous protein concentration, as well as test reliability.Results: Four index tests were identified in 11 studies: laser-flare photometry (LFP), optical coherence tomography, ocular flare analysis meter (OFAM) and the double-pass technique. The correlation between LFP and clinician grading was 0.40-0.93 and 0.87-0.94 for LFP and protein concentration. The double-pass technique showed no correlation with clinician grading and insufficient information was available for OFAM.Conclusion: LFP shows moderate to strong correlation with clinician grading and aqueous protein concentration. LFP could be a superior reference test compared to clinician AC flare grading for validating new index tests.

Complications of Periocular Dermal Fillers

Dermal fillers, in particular hyaluronic acid gel (HAG) fillers, are used in the treatment of aging changes in the periocular area. Filler treatment requires in-depth knowledge of specific issues relating to product performance and administration, safety protocols, and recognition and treatment of complications. There are different approaches to treatment of the tear trough. Prior filler treatment must be suspected in patients presenting for aesthetic evaluation, and the possibility of migration with a dysmorphic appearance and/or Tyndall effect appearance always is kept in mind. Treatment with hyaluronidase injection generally is effective in reducing overcorrection or migration of HAG in this area.

[Laser flare photometry for identification of high-risk patients for proliferative vitreoretinopathy]

Proliferative vitreoretinopathy (PVR) is a complication of rhegmatogenous retinal detachment and trauma, which occurs in approximately 10% following vitreoretinal surgery. The visual prognosis for established PVR is poor and so far there is no established conservative treatment for PVR. In the currently recruiting PRIVENT trial the aim is to find a prophylactic treatment possibility for PVR. The PRIVENT study examines the influence of intraoperative adjuvant pharmacotherapy on reducing the incidence of PVR; however, this requires the identification of eyes with increased risk for PVR. Laser flare photometry is a simple method to predict the individual risk for PVR. It is a non-invasive technique that objectifies the Tyndall effect. Various laser flare meter devices are available on the market. In previous studies it could be shown that laser flare photometry can predict the development of PVR in eyes with primary rhegmatogenous retinal detachment with a sensitivity of 80%. The identification of these high-risk eyes for PVR could be the first step towards solving the problem of PVR.

Impact of sodium chloride on the expansion of a liquid-liquid miscibility gap in an API/water system. Case study of Brivaracetam

Brivaracetam, or (2S)-2-[(4R)-2-oxo-4-propyl-pyrrolidin-1-yl] butanamide, is an active pharmaceutical ingredient designed for the treatment of epilepsy. During the development of the IV administration mode, a liquid-liquid miscibility gap has been observed with pure water, isotonic and hypertonic solutions (vehicle at 0.9% w/w and 5%w/w NaCl respectively). The study reveals that the NaCl concentration has a direct impact on the extent of the demixing domain; from a sub-micronic demixing in pure water towards a macroscopic miscibility gap in hypertonic aqueous solutions. The thorough exploration of these heterogeneous equilibria led to define experimental parameters for safe IV injections without risk of liquid - liquid miscibility gap at 37°C.

Vulvar hidradenoma papilliferum (HP) is located on the sites of mammary-like anogenital glands (MLAGs): Analysis of the photographs of 52 tumors

BACKGROUND

Hidradenoma papilliferum (HP) is a benign tumor that primarily affects the anogenital area of adult women. Previously considered apocrine tumors, anogenital HP tumors are now interpreted as adenomas of mammary-like anogenital glands based on their histologic features.

OBJECTIVE

This clinical study was undertaken to determine whether vulvar HP is located on mammary-like anogenital gland sites and to describe its morphologic features.

METHODS

The clinical photographs of 52 histologically confirmed vulvar HP provided by 7 vulva specialists were analyzed.

RESULTS

In all, 90.4% of the HP were located on the interlabial sulcus, adjacent zone, or the perineum. These tumors were polymorphous in terms of number (1 or multiple), size (<1-4.5 cm), color (pink, red, blue), surface (ulcerated or not), and architecture (unilobular or multilobular).

LIMITATIONS

Eight histologic reports could not be reviewed by the authors but the contributors confirmed that the photographs sent were only those of histologically confirmed HPs.

CONCLUSIONS

Vulvar HP is mainly located on mammary-like anogenital gland sites, thereby providing further evidence to their histogenesis. Although a nonulcerated or ulcerated tumor of the interlabial sulcus should evoke a HP diagnosis, the latter must be confirmed histologically.