Application of Localized Surface Plasmon Resonance of Conjugated Gold Nanoparticles in Spectral Diagnosis of SARS-CoV-2: A Numerical Study.

Severe respiratory syndrome COVID-19 (SARS-CoV-2) outbreak has became the most important global health issue, and simultaneous efforts to fast and low-cost diagnosis of this virus were performed by researchers. One of the most usual tests was colorimetric methods based on the change of color of gold nanoparticles in the presence of viral antibodies, antigens, and other biological agents. This spectral change can be due to the aggregation of the particles or the shift of localized surface plasmon resonance due to the electrical interactions of surface agents. It is known that surface agents could easily shift the absorption peak of metallic nanocolloids which is attributed to the localized surface plasmon resonance. Experimental diagnosis assays for colorimetric detection of SARS-CoV-2 using Au NPs were reviewed, and the shift of absorption peak was studied from the viewpoint of numerical analysis. Using the numerical method, the refractive index and real and imaginary parts of the effective relative permittivity of the viral biological shell around Au NPs were obtained. This model gives a quantitative description of colorimetric assays of the detection of SARS-CoV-2 using Au NPs.

Synthesis, band gap structure and third order non-linear optical properties of zinc tungsten oxide nanocomposite using a single CW laser beam.

In this study, a composite of zinc tungsten oxide nanoparticles (W-ZnO NPs) has been synthesized via mixing Na2WO4 and zinc acetate in water, followed by dropwise addition of NaOH. The synthesized W-ZnO NPs were characterized using measurement methods such as XRD, dynamic light scattering (DLS), Scanning electron microscopy (SEM) and UV-Vis. Also, the results were compared with the pure synthesized ZnO and WO3 NPs. Non-linear optical properties of the synthesized composite were measured using the Z-scan technique with a continuous wave Nd-Yag laser. The negative non-linear absorption coefficient of the components was obtained which indicates that the saturation absorption occurred in this composite. In comparison with pure ZnO NPs, non-linear absorption decreases which can be attributed to the negligible optical response of WO3 structures. Also, the negative value of the close aperture Z-scan curve shows that the thermal lensing effect is the main reason for the third-order non-linear refraction.

Simple Method for Optical Detection and Characterization of Surface Agents on Conjugated Gold Nanoparticles.

In this article, we propose a simple method to calculate electrical permittivity and refractive index of surface agents of gold nanoparticles (Au NPs), in which it is possible to find the refractive index of surface agents shell by using the absorption peak of the gold nano-colloid. One of the usual tests for detection of surface agents is colorimetric methods based on the change of color of Au NPs. The color change is mainly due to the shift of localized surface plasmon resonance which is related to electrical interactions of surface agents. Although there are many mathematical models for simulating the absorption spectrum and calculating the plasmonic peak, using them is not simple and possible for everyone due to the need for programming. Here, the necessary simulations have been performed for different values ​​of refractive index of surface agents and particle size, and absorption peaks have been obtained. Using numerical methods, a simple formula is obtained between the wavelength of plasmonic peak, the ratio of hydrodynamic diameter to Feret size of the particles, and the refractive index of the surface agents. This method can help researchers to obtain the refractive index and consequently the type or concentration of surface agents around Au NPs without the need for programming or complex mathematical operations. It can also open new horizons in analyzing colorimetric diagnosis of biological agents such as viral antibodies, antigens, and other biological agents.

Cation-π aggregation-induced white emission of moisture-resistant carbon quantum dots: a comprehensive spectroscopic study.

Controlling mechanisms involved in the aggregation of carbon quantum dots (CQDs) can lead to new application developments for these quantum dot materials. In this study, an unusual aggregation-induced white emission of CQDs with strong intrinsic green emission is reported. Due to the deprotonation/protonation of the surface functional groups during the aggregation of CQDs induced by pH variations of the solution through the addition of sodium hydroxide, and hydrophobic interactions between CQDs, it results in the formation of aggregated CQDs through an avalanche-like process. Our results suggest that sodium hydroxide not only plays a critical role in the formation of strong cation-π interactions, but also polishes the surface of CQDs, leading to the formation of the aggregated CQDs. The aggregated CQDs present excellent dispersibility characteristics in water. Moreover, optical studies suggest a combined aggregation mechanism in the presence of both J-type and H-type aggregation monoliths involved in forming the aggregated CQDs. The findings obtained from the deconvolution of the as-synthesized CQDs can perceptively elucidate the cation-π aggregation process.

In situ synthesis of holey g-C3N4 nanosheets decorated by hydroxyapatite nanospheres as efficient visible light photocatalyst.

The interesting g-C3N4 nanosheet morphology has drawn huge attention in photocatalytic applications because of its special features. Nonetheless, the relative activity of these nanosheets is still controversial due to the low available active sites and the high recombination probability of photo-induced charge carriers. In this work, in situ sol-gel approach was applied to synthesize holey g-C3N4 nanosheets/hydroxyapatite (HAp) nanospheres with plentiful in-plane holes. Herein, the presence of Ca2+ plays a key role in the formation of holey defects on 2D g-C3N4. In-plane holes provide nanosheets with more active edges and diffusion channelsv, resulting in a tremendous enhanced mass and photo-induced charge transfer speed. Moreover, the holes make highly numbered boundaries, which lead to the prevention of aggregation. On the other hand, distributed nano-HAp spheres on these nanosheets can form effective heterojunctions having high photo-degradation ability of pollutants. Intrinsic O-vacancies inside HAp unit cells mainly affect the capture of photogenerated electrons, pollutant molecules, and O2 gas. The synergistic presence of O-vacancies and holey defects (C-vacancies) on 2D g-C3N4 plays a key role in raising the photocatalytic performance of holey g-C3N4/HAp. It can be concluded that the proposed preparation method is a promising approach for simultaneous synthesis of holey g-C3N4 and surface heterojunctions of Ca-based materials. This new structure has shown significant degradation ability of bisphenol A, a prominent pollutant, with a low amount (0.01 g) and short time.

Effect of conjugation with organic molecules on the surface plasmon resonance of gold nanoparticles and application in optical biosensing.

The problem of functionalizing and coating nanoparticles with surfactants dispersed in a colloid is a prevalent case in nanoscience and related studies. It is known that surfactants could easily cause a shift in the absorption peak in metallic nanoparticles (NPs). Here, a precise theoretical model is presented to simulate the ultraviolet-visible (UV-vis) absorption spectrum of a colloid containing gold nanoparticles (Au NPs) in the presence of different surfactants. Based on the Lorentz-Drude model, this model is able to justify the fact that surfactants with a higher refractive index lead to movement of the absorption peak toward longer wavelengths (red shift). Also, relative concentrations of agents in a solvent can be analyzed using this model. The presented descriptive model illustrates gold-based biosensors with a physical point of view that leads to an increase in their efficiency. Several experimental cases are considered and are examined to calculate and compare the refractive index of the surfactants. In accordance with the results, it is found that this model is compatible with a wide range of molecular sizes, and here, the model is applied for a typical size range of micromolecules such as citrate ions to macromolecules such as polyethylene glycol (PEG) as a polyether. The suggested method revealed that it is appropriate for different surfactants with various chemical structures and refractive indexes. Utilization of approximations in this theoretical model is limited, thus, a method with the least deviation from real measurements has been introduced. The applicability of this model can be extended to practical purposes, including optical bio-sensors and detectors of organic and biological moieties such as viruses and antibodies.

The effects of glucose and glucose oxidase on the Uv-vis spectrum of gold nanoparticles: A study on optical biosensor for saliva glucose monitoring.

In this study we have investigated the effect of glucose and glucose oxidase (GOD) on the absorption spectrum of gold nanoparticles (Au NPs) with 10-13 nm diameter, in order to improve optical methods of glucose monitoring using surface plasmon resonance of these particles. Different concentrations of glucose solution in water were prepared in the range of human saliva intensity. Two procedures are applied to study glucose effects on the particles; mixing the glucose to the nanocolloid and then adding the GOD, and reversely mixing the glucose and GOD solutions and then pouring in to the nanocolloid. Two different results were obtained that are analyzed based on optical properties. In each method, the effect of glucose and GOD on the size and Uv-vis spectrum of gold nanoparticles has been investigated. Results were interpreted by the physical concept of surface Plasmon resonance (SPR) of Au NPs. This study can open new insight about optical glucose sensing based on surface plasmon of metal nanoparticles.

Photocatalytic efficacy of supported tetrazine on MgZnO nanoparticles for the heterogeneous photodegradation of methylene blue and ciprofloxacin.

MgZnO@SiO2-tetrazine nanoparticles were synthesized and their photocatalytic efficiency was demonstrated in the decomposition of ciprofloxacin and methylene blue (MB). This new heterogeneous nanocatalyst was characterized by FT-IR, XRD, UV-vis, DRS, FE-SEM, ICP, and CHN. Distinctive variables including photocatalyst dose, pH, and degradation time were investigated. Up to 95% photodegradation was gained under the optimum conditions (20 mg photocatalyst, 3.5 ppm MB, pH 9) by using MgZnO@SiO2-tetrazine nanoparticles after 20 min. An elementary kinetic study was carried out, and a pseudo-first-order kinetic with a reasonably high rate-constant (0.068 min-1) was derived for the MB decay. Photoluminescence (PL) studies confirmed that the photocatalytic activity of MgZnO@SiO2-tetrazine was almost consistent with the Taugh plots. Thus, it can be envisaged that the photocatalytic activity is closely related to the optical absorption. Furthermore, a photoreduction mechanism was suggested for the degradation process. Addition of scavengers and some mechanistic studies also revealed that O2˙- is the original radical accounting for the degradation of MB, considering this latter compound as a model type pollutant. Finally, efficacy of the present photocatalytic process was assessed in the degradation of ciprofloxacin as a model drug under the optimum reaction conditions.

Meatoplasty in Canal wall down Surgery: Our Experience and Literature Review.

INTRODUCTION: Meatoplasty is the final and essential step in performing effective canal wall down surgery for chronic otitis media. In this article we review some previous techniques and discuss our preferred method. MATERIALS AND METHODS: In this observational case series study, we used this technique in 53 patients (28 male and 25 female) between January 2005 and January 2008. Our survey was completed in 31 patients. RESULTS: Twenty-six patients (83.9%) said their ear appeared normal after the procedure, but five patients (16.1%) complained of some minor change in the shape of their ear. Twenty-nine patients (93.5%) had a completely wide ear canal. The ear canal had some degree of stenosis in two patients (6.5%) post-operatively. CONCLUSION: This technique offers good functional and cosmetic results with minimal manipulation and minimal anatomic disruption.

Occult Laryngeal Foreign Body Mimicking Normal Thyroid Cartilage.

INTRODUCTION: Foreign body aspiration is common especially in children. The absence of history of choking does not rule out the diagnosis. Diagnosis required high index of suspicion. CASE PRESENTATION: Undiagnosed foreign body aspiration mostly occurs in bronchial airway rather than larynx and can cause severe complications. In this article, we report a silent laryngeal foreign body aspiration to show that careful history taking and accurate evaluation of radiography are important factors for diagnosis. CONCLUSIONS: The single most significant factor leading to detect of tracheobronchial foreign body aspiration is a high index of suspicion; this case highlights the possibility of a foreign body in the airway in patients who presents with a recent onset of chronic respiratory complaints.

Application of modified Rintala flap in nasal tip reconstruction.

INTRODUCTION: For nasal tip reconstruction, we must consider optimal results including color match, good tissue coverage, excellent flap viability, and good aesthetic result. METHODS: In this study, 25 patients who had nasal tip skin tumors were included, and reconstruction of the defects by dorsal nasal advancement flap (Rintala) was done. The advantages and disadvantages of the Rintala flap were described for all patients with nasal tip basal cell carcinoma (BCC). All patients filled out the consent form before reconstruction and tumor surgery. RESULTS: In this study, 25 patients (11 women and 14 men) ranging from 25 to 72 years old (mean, 53 years) underwent operation with dorsal nasal advancement flap (Rintala). Reconstruction of nasal tip defects after complete tumor excision was done with free margin. After sedation analgesia, we used bilateral parallel incision in both sides of the nasal sidewalls from corner to glabellar region; Burow triangles are excised bilaterally in lateral to the base of the flap. CONCLUSIONS: In case of midline tip defects with 1.5 to 2.5 cm in diameter, a modified Rintala flap is a good choice for reconstruction of this difficult area. This is a superiority-based randomized flap that makes an aesthetic nasal tip after tumor excisions without any fear from ischemia or necrosis of the flap.

Anatomic variations found on dissection of depressor septi nasi muscles in cadavers.

OBJECTIVES: To define variations of the depressor septi muscle in Iranians; to provide guidance for modification of this muscle during rhinoplasty in patients with an active muscle and short upper lip; and to correlate our findings with our clinical experience to develop the applied algorithms. METHODS: This study was conducted by dissecting 82 depressor septi nasi muscles in 41 Iranian cadavers. Origin and insertion points of each muscle were studied. RESULTS: Three variations were found in muscle insertion points: periosteal, orbicularis oris, and floating. Forty-four percent of the muscles were inserted into the periosteum of the maxilla (n = 36); 39% of muscles were inserted into the orbicularis oris muscle (n = 32); and 17% were diminutive or floating (n = 14). Periosteal insertion was thicker and stronger than the other variations. In all cadavers, the origin of the muscle was medial crus of alar cartilage and caudal of the nasal septum. CONCLUSIONS: This cadaveric dissection showed that the percentage of depressor septi muscle insertions is not similar to that found in other surveys. In this study, periosteal insertion of the depressor septi muscle was the most common variation.

Carpal tunnel syndrome: the role of occupational factors among 906 workers.

BACKGROUND: Carpal tunnel syndrome (CTS) is common in the industrial setting. However,there is a controversy about the sole role of occupational ergonomic hazards in CTS. OBJECTIVES: This study was conducted among assembling workers of a detergent factory and computer users with the aims of A) determination of CTS prevalence and B) evaluation of personal risk factors and level of exposure to occupational risk factors via Quick Exposure Check (QEC). MATERIALS AND METHODS: In this descriptive cross-sectional study, 906 cases (332 assembling workers and 574 computer workers) were enrolled. CTS was assessed by symptoms on the Katz hand diagram and physical examination. QEC technique was applied to evaluate physical exposure to the risk factors. RESULTS: According to this study, the prevalence of probable CTS was 14% in men and 8.9% in women; the rate of probable CTS was significantly higher in assembly workers than in computer users (P < 0.001). Mean age and work duration in the probable CTS group was statistically higher than in non-CTS group. But both groups were in the same range (fewer than 30, P = 0.024, 0.004); BMI in the probable CTS group was slightly lower than in non CTS group, but BMI in both groups were in the normal range. Wrist ratio > 0.7 correlated with increased risk of probable CTS (P < 0.001) Prevalence of probable CTS was significantly higher in third and fourth levels of QEC (P < 0.001). CONCLUSIONS: Although this article had limitations, our findings suggest that the level of occupational exposure is an indicator of CTS development.

Effect of Ilioinguinal Neurectomy on Chronic Pain following Herniorrhaphy.

BACKGROUND: Inguinal hernia is one of the most common male diseases all over the world with an incidence rate of 18-24% throughout life. Chronic inguinal pain is one of the complications that prolong return to work time. OBJECTIVES: The main aim of this study was to determine the effect of ilioinguinal neurectomy on postoperative chronic pain (PCP) in patients that underwent open inguinal hernia repair via the Lichtenstein method. MATERIALS AND METHODS: IN THIS RANDOMISED CONTROLLED CLINICAL TRIAL, MALE PATIENTS WITH UNILATERAL INGUINAL HERNIA WERE RANDOMIZED INTO TWO GROUPS: 74 cases in the preserved-nerve group and 66 cases in the nerve-excised group. The method of herniorrhaphy was the classic Lichtenstein method. Pain and numbness were evaluated at 1 day, 1 week, 1 month, 6 months and 1 year after surgery via visual analogue scale (VAS) system. We used SPSS ver.16 for analysis. RESULTS: All patients were male with mean age of 39.1 years (with a range of 18 to 68 years). The follow-up rate was 100% after 1 year. Pain severity was significantly lower in nerve-excised patients at 1 day, 1week, 1 month and 6 months after surgery; but it was not significant after one year, although overall pain severity was low. Numbness was significantly higher in excised patients at all endpoints (1 day, 1month, 3 months, 6 months and one year after surgery). CONCLUSIONS: Ilioinguinal nerve excision at the time of inguinal hernia repair decreased post-surgical inguinal pain, and it can be used as a routine method in herniorrhaphy.

Experience with reverse sural flap to cover defects of the lower leg and foot.

BACKGROUND: Coverage of traumatic soft-tissue defects in the lower limb is a common procedure. OBJECTIVES: The purpose of this prospective case series study was explore the capacity of the perforator-based sural flap in reconstruction surgery of patients with high velocity gunshot wounds in the distal third of the leg and heel pad of the foot. PATIENTS AND METHODS: A prospective case series study was undertaken to assess the sural fasciocutaneous flap carried out in our hospital, from 2010 to 2011. This case series study comprised eight patients, seven men and one woman with an average age of 35 years (19-55) and with a mean follow-up duration of 13 months (6-24 months). All patients had a history of a gunshot wound in distal part of the leg and heel pad of the foot with large soft-tissue defects; treatment was done using the reverse sural flap. RESULTS: We performed reverse sural flaps in eight gunshot patients, to cover the defects of the lower leg and foot. Surgical site infection observed in one patient (12.5%) was treated successfully with antibiotic therapy. The reverse sural flap provided a satisfactory coverage for gunshot defects in all the patients. CONCLUSIONS: Reverse sural flap is a useful and versatile reconstructive method in patients with gunshot wounds of the lower leg and foot.

Intraosseous ganglion cyst of the lunate.

Intraosseous ganglia can affect the carpal bones of the hand and must be considered in the differential diagnosis of wrist pain. A 38-year-old female presented with a 14-month history of left wrist pain and a radiolucent cystic lesion was seen computed tomography (CT) scanning. Characteristic radiographic findings of a cyst in association with a fine sclerotic rim was apparent. We report an unusual presentation of a ganglion cyst in the lunate bone with excellent treatment outcome.