Interaction of cetylpyridine bromide with nucleic acids and determination of nucleic acids at nanogram levels based on the enhancement of resonance Rayleigh light scattering

One-step synthesis of red emission multifunctional carbon dots for label-free detection of berberine and curcumin and cell imaging

In this work, the red emission multifunctional carbon dots (R-CDs) were prepared via one-pot hydrothermal strategy of neutral red (NR) and ethylenediamine (EDA) for the label-free detection of berberine and curcumin, cell imaging, and fluorescent flexible film. The as-fabricated R-CDs not only possess good water dispersibility and excellent fluorescence stability, but also were successfully employed as a photoluminescent nanoprobe for label-free monitoring of berberine (BRH) and curcumin (Cur) based on dynamic quenching and internal filter effect (IFE), respectively. More importantly, as-proposed R-CDs displayed outstanding cellular permeability and lower cytotoxicity for cellular applications, which was consistent with the results of confocal fluorescence imaging and cell viability measurement of SMMC7721 cells. Thus, the multifunctional R-CDs may provide a rich tool library for biosensing and cellular imaging reagent applications. Interestingly, R-CDs were also used to manufacture R-CDs/PVA composites as fluorescent flexible films. To the best of our knowledge, this is the first demonstration of a label-free multifunctional fluorescent nanoprobe for berberine and curcumin based on red emission CDs.

Resonance light scattering spectroscopy of procyanidin-CPB-DNA ternary system and its potential application

A new method for the determination of calf thymus DNA at nanogram level was proposed based on the enhanced resonance light scattering (RLS) signals of DNA in the presence of procyanidin and cetylpyridinium bromide dihydrate (CPB). Under the experimental conditions, the RLS intensity of DNA at 291.0 nm was greatly enhanced by procyanidin-CPB at pH 7.0. There was a good linear relationship (r=0.9993) between the enhanced RLS intensity (ΔI(RLS)) and DNA concentration of 0.0084-3.36 μg mL(-1). The limit of detection (LOD) was 2.27 ng mL(-1) (3S0/S). Three synthetic DNA samples were measured with satisfactory, and the recovery was 102.3-107.2%.

Study of the interaction of salmon sperm DNA with myricitrin-CPB based on the enhanced resonance light scattering signal and its potential application

A new assay of salmon sperm DNA at nanogram level was established based on enhanced resonance light scattering (RLS) signals of DNA with myricitrin and cetylpyridinium bromide dihydrate (CPB). The RLS spectral characteristics of DNA with myricitrin-CPB and the optimum conditions for determination of DNA samples have been studied. At pH 7.4, myricitrin-CPB could enhance the intensity of RLS signal of DNA at 468 nm. The enhanced RLS intensity was directly proportional to DNA concentration in the range of 0.076-4.2 μg mL(-1) with a good linear relationship (r=0.9944). The detection limit was 4.1 ng mL(-1). The synthetic samples were analyzed with satisfactory results that the recovery was 100.9-102.6% and RSD was 1.4-2.1%, which proved that the new method was reliable and applicable.

The analytical application and spectral investigation of DNA-CPB-emodin and sensitive determination of DNA by resonance Rayleigh light scattering technique

A new sensitive DNA probe containing cetylpyridinium bromide (CPB) and emodin (an effective component of Chinese herbal medicine) was developed using the resonance Rayleigh light scattering (RLS) technique. A novel assay was first developed to detect DNA at nanogram level based on the ternary system of DNA-CPB-emodin. The RLS signal of DNA was enhanced remarkably in the presence of emodin-CPB, and the enhanced RLS intensity at 340.0 nm was in direct proportion to DNA concentration in the range of 0.01-2.72 μg mL(-1) with a good linear relationship. The detection limit was 1.5 ng mL(-1). Three synthetic DNA samples were measured obtaining satisfactory results, the recovery was 97.6-107.3%.

Resonance light scattering method for the determination of DNA with cationic methacrylate based polymer nanoparticle probes

Narrowly distributed cationic poly (methyl methacrylate-co-diacetone acrylamide) (P(MMA-DAAM)) nanoparticles were successfully prepared by microemulsion polymerization. Photon correlation spectrometer (PCS) measurement and transmission electron microscope (TEM) observation revealed that z-average particle size of P(MMA-DAAM) is ∼27.5 nm. It was found that these cationic nanoparticles interact with DNA through electrostatic interaction to form P(MMA-DAAM)-DNA complex, which significantly enhances the resonance light scattering (RLS) signal. Therefore, a novel method using this polymer nanoparticle as a new probe for the detection of DNA by RLS technique is developed in this paper. The results showed this method is very convenient, sensitive, and reproducible.

Study on naringenin-CTMAB-DNA system by resonance light scattering technique and its analytical application

A new high-sensitivity determination method of deoxyribonucleic acid (DNA) with detection limit at nanogram levels was proposed. Based on the measurement of resonance light scattering (RLS), it was found DNA could combine with naringenin and cetyltrimethylammonium bromide (CTMAB) in basic Tris-HCl buffer and produce enhanced RLS signal. The optimum conditions for this system were studied in detail. The enhanced intensity of RLS of naringenin-CTMAB at 353 nm was directly proportional to the concentration of DNA in the range of 0.017-1.7 μg mL(-1). The detection limit was 5.06 ng mL(-1). Using the proposed method, the synthetic samples were analyzed with satisfactory results, the recovery was 99.3-105.0% and RSD was 0.7-3.7%.

[Determination of netilmicin in rat serum using high performance liquid chromatography and resonance Rayleigh scattering]

A method was developed for the direct determination of netilmicin in rat serum using high performance liquid chromatography and resonance Rayleigh scattering (RRS). The separation was carried out on a C18 column with the isocratic elution of the mixture of 20 mmol/L sodium acetate aqueous solution and methanol containing 0.22% trifluoroacetic acid (92:8, v/v). With the molecular recognition probe of pontamine sky blue, netilmicin formed an ion-association complex and enhanced the intensity of RRS. The RRS signal was detected by a commercial fluorescence detector at 365 nm of both excitation wavelength (lambda ex) and emission wavelength (lambda em). Under the optimized conditions, the limit of detection (LOD, S/N = 3) for the netilmicin was 0.7 mg/L. With the internal standard (IS) of tobramycin, a linear calibration curve ranged from 1.2 mg/L to 30 mg/L was obtained. The presented method can be used for the pharmacokinetics study of netilmicin in rat serum, and can be a new choice for the determination of aminoglycoside antibiotics in biological samples.

A study of complex formation between polyacrylic acid and poly(ethylene oxide) by near resonance Rayleigh scattering

A series of near resonance Rayleigh scattering (NRRS) experiments has been performed on the phase behavior of complex formation between polyacrylic acid (PAA) and poly(ethylene oxide) (POE). On the basis of the theory of resonance scattering, as one new method compared to resonance Rayleigh scattering (RRS), NRRS was demonstrated to investigate polymer solutions. The results indicated that the complex formation induces an increase of the intensity of resonance scattering and the phase segregation leads to distortion of the resonance scattering spectrum with decreasing pH value. The collapse of macromolecular chains is attributed to the contraction of PAA chains and association between PAA and POE. Moreover, NRRS can show more information than RRS on the basis of their scattering spectra.

Resonance light scattering technique for the determination of proteins with polymethacrylic acid (PMAA)

As a resonance light scattering (RLS) probe, the polyelectrolyte polymethacrylic acid (PMAA) was applied in this assay. The bovine serum albumin (BSA) and human serum albumin (HSA) were determined by the electrostatic interaction of PMAA and proteins. At pH 3.8 Na(2)HPO(4)-citric acid buffer solution, the RLS intensities of PMAA-BSA (HSA) system were greatly enhanced. The characteristic peaks were appeared at the wavelength 320, 546 and 594 nm. The optimization conditions of the reaction were also examined and selected. Under the selected conditions, the RLS intensities were proportional to the protein concentrations in the range of (0.0200-2.00) x 10(-6) mol/L for BSA and (0.0200-2.40) x 10(-6) mol/L for HSA. The influences of some foreign substances were also examined. The synthetic samples containing proteins and some real samples were analyzed and the results obtained were satisfactory.

Investigation of the interaction between curcumin and nucleic acids in the presence of CTAB

It is found that nucleic acid can enhance the resonance light scattering (RLS) enhancement effect of curcumin (CU) in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB). The investigation indicates that in BR (pH 4.3) buffer, both the positive CTAB and negative yeast RNA (yRNA) combine and form a positive large association, then which is bound on the two carbon atoms of the carbonyls of CU through hydrogen bond and hydrophobic force and form CU-CTAB-yRNA ternary complex, resulting in the RLS enhancement of this system. Based on it, a sensitive method for determination of nucleic acids at ngml(-1) is established.

The sensitive determination of nucleic acids using resonance light scattering quenching method

It is found that in hexamethylene tetramine (HMTA)-HCl buffer of pH 7.00, nucleic acids can quench the resonance light scattering (RLS) of europium (III) (Eu3+)-2-thenoyltrifluoroacetne (TTA)-1,10-phenanthroline (Phen) system. Based on this, a sensitive method for the determination of nucleic acids is proposed. The experiments indicate that under the optimum conditions, the quenched RLS intensity is in proportion to the concentration of nucleic acids in the range of 1.0x10(-10) to 2.0x10(-6) g ml-1 for fish sperm (fsDNA), 1.0x10(-11) to 1.0x10(-6) g ml-1 for yeast RNA (yRNA), 5.0x10(-11) to 5.0x10(-7) g ml-1 for calf thymus DNA (ctDNA). Their detection limits (S/N=3) are 0.03, 0.006 and 0.002 ng ml-1, respectively. Therefore, the proposed method is the most sensitive RLS method for the determination of nucleic acids so far. The interaction between nucleic acids and Eu3+-TTA-Phen is also discussed.

Nanogold plasmon resonance-based glucose sensing. 2. Wavelength-ratiometric resonance light scattering

Gold colloids are well known to display strong plasmon absorption bands due to electron oscillations induced by the incident light. When the colloids are in proximity, the plasmon absorption bands are often perturbed. This has enabled us recently to successfully develop a glucose sensing platform based on the disassociation of dextran-coated gold colloids, cross-linked with Con A, by glucose. However, a much more useful and simpler property of gold colloids, which has been ill explored with regard to sensing, is their ability to efficiently scatter excitation light. We have found that our nanogold sensing aggregates are indeed efficient light scatters around the nanogold plasmon absorption band. By measuring the ratio of scattered light intensities at two different arbitrary wavelengths, 560 and 680 nm, glucose concentrations can be readily determined from a few millimolar up to approximately 60 mM, using a simple white light LED and detection system. Further, by measuring the ratio of the scattered intensities, this sensing approach is independent of the total sensing aggregate concentration and the excitation and detection instrumentation fluctuations or drifts. This simplistic and low-cost approach to glucose sensing, coupled with the sensing aggreagates' ability to scatter red light, suggests the potential use of these aggregates for use in physiological transdermal glucose monitoring, either for implantable skin sensors or glucose sensing tattoos (discussed later).

Study on the interaction between nucleic acids and cationic surfactants

The interactions of nucleic acids and cationic surfactants (cetylpyridine bromide (CPB) and cetyltrimethylammonium bromide (CTMAB)) in aqueous solution have been studied using the techniques of resonance light scattering (RLS) spectroscopy, the absorption spectroscopy, zeta potential assay and NMR assignment measurement. It is considered that CPB or CTMAB can assemble on the surface of nucleic acid via electrostatic and hydrophobic forces, which results in the formation of large associate of nucleic acid-cationic surfactant and RLS enhancement of nucleic acid. Besides these forces, the pi-pi stacking force between CPB and nucleic acid also exists in the associate. In comparison with CTMAB, CPB has larger enhancement on RLS of nucleic acid, which is attributed to that the enhancement of the former is only due to the absorption of the bases of nucleic acid, while the enhancement of the latter is own to the synergetic resonance caused by the absorption of both bases of nucleic acid and the pyridyl in CPB. These results have important implication for understanding the influence of surfactants on nucleic acid functionality in life science.

The interaction of poly(ethylenimine) with nucleic acids and its use in determination of nucleic acids based on light scattering

For the first time, poly(ethylenimine) (PEI) was used to determine nucleic acids with a light scattering technique using a common spectrofluorometer. The interaction of PEI with DNA results in greatly enhanced intensity of light scattering at 300 nm, which is caused by the formation of the big particles between DNA and PEI. Based on this, a new quantitative method for nucleic acid determination in aqueous solutions has been developed. Under the optimum conditions, the enhanced intensity of light scattering is proportional to the concentration of nucleic acid in the range of 0.01-10.0 microg ml(-1) for herring sperm DNA (hsDNA), 0.02-10.0 microg ml(-1) for calf thymus DNA (ctDNA), 0.02-20.0 microg ml(-1) for yeast RNA (yRNA). The detection limits are 5.3, 9.9, and 13.7 ng ml(-1), respectively. Synthetic samples were determined satisfactorily. At the same time, the light scattering technique has been successfully used to obtain the information on the effects of pH and ionic strength on the formation and the stability of the DNA/PEI complex, which is important in some fields such as genetic engineering and gene transfer. Using ethidium bromide (EB) as a fluorescent probe, the binding of PEI with hsDNA was studied. Both the binding constant of EB with DNA and the number of binding sites per nucleotide decrease with increasing concentration of PEI, indicating noncompetitive inhibition of EB binding to DNA in the presence of PEI. And the association constant of PEI to DNA obtained is 1.2 x 10(5) M(-1). IR-spectra show that PEI interacts with DNA through both the phosphate groups and the bases of DNA and the formation of DNA/PEI complex may cause the change of the conformation of the DNA secondary structure, which is also proved by UV-spectra.