Simultaneous determination of water-soluble whitening ingredients and adenosine in different cosmetic formulations by high-performance liquid chromatography coupled with photodiode array detection

Quantification of Arbutin and its degradation products, hydroquinone and p-Benzoquinone, in hyperpigmentation topical formulation: Effect of extraction procedure and interference assessment

The utilization of Hydroquinone (HQ) in over-the-counter skincare items is subject to restrictions. Consequently, Arbutin (AR) serves as a reliable alternative for addressing hyperpigmentation in non-prescription topical formulations. Nevertheless, AR undergoes decomposition into HQ and p-Benzoquinone (BZ) when exposed to temperature stress, ultraviolet light, or dilution in an acidic environment, all of which can induce skin toxicity. The intention of this paper is to investigate the effect of extraction procedure on the conversion of AR to HQ and or BZ and to evaluate kinetics of AR hydrolysis to HQ. Meanwhile this study aims to evaluate AR and BZ interference with the United States Pharmacopoeia (USP) identification and assessment method for HQ Hydrolytic stress during extraction conditions underwent optimization through systematic screening tests. Subsequent assessment of the residual drug and its degradation products were achieved by HPLC method. The resulting data were meticulously fitted to various kinetic models. To analyze the potential interference of AR in HQ measurement using USP method, the standard concentrations of AR and HQ were analyzed through UV-VIS spectrophotometry. For enhanced certainty, a validated HPLC method analysis was also conducted. Notably, the acid hydrolysis of AR exhibited independence from its initial concentration. So, the hydrolytic degradation of AR exhibited a Zero-order kinetic profile. Furthermore, the proven interference of AR in the UV-VIS spectrophotometry method was identified within the context of the USP method. This study successfully utilized an adopted HPLC method for the concurrent quantification of AR, HQ, and BZ. The potential interference of AR in the UV-VIS spectrophotometric assay for HQ may lead to false results especially for regulatory purposes.

Simultaneous HPLC Determination of Arbutin, Niacinamide and 3-O-Ethyl Ascorbic Acid in Whitening Cream Products in the Presence of Parabens

Arbutin, niacinamide and 3-O-ethyl ascorbic acid (a new generation of vitamin C derivatives) are compounds that have a whitening effect on skin and are widely used in whitening cream products wherein parabens such as methyl paraben, ethyl paraben, propyl paraben and butyl paraben are also often added as preservatives. This study aims to develop a validated high-performance liquid chromatography (HPLC) method that can be used to determine arbutin, niacinamide and 3-O-ethyl ascorbic acid simultaneously in whitening cream products without interference from the parabens. The optimum conditions for the HPLC system were obtained using ODS-3 RP-C18 Inertsil column, mobile phase consisting of a mixture of aquabides, methanol and acetonitrile with gradient elution mode. Detection was carried out using a UV detector at 220 nm. Validation studies demonstrated a good linearity for all analytes over each range concentration with a correlation coefficient >0.999 and Vx0 < 2%. The accuracy test also met the requirements with the recoveries being 96.93-99.55%, 98.60-99.73% and 97.88-100.63% for arbutin, niacinamide and 3-O-ethyl ascorbic acid, respectively. Intra-day and inter-day precision test gave a relative standard deviation (% RSD) of <2% along with a HorRat value of <2 for all analytes. The results of this study indicate that the developed HPLC method has a good selectivity, linearity, accuracy and precision. Due to its simplicity, the method can be used to analyze arbutin, niacinamide and 3-O-ethyl ascorbic acid in the presence of parabens in whitening cream products simultaneously.

Aptamer-functionalized 2D photonic crystal hydrogels for detection of adenosine

Aptamer-functionalized two-dimensional photonic crystal (2DPC) hydrogels are reported for the detection of adenosine (AD). As a molecular recognition group, an AD-binding aptamer was covalently attached to 2DPC hydrogels. This aptamer selectively and sensitively binds AD, changing the conformation of the aptamer from a long single-stranded structure (AD-free conformation) to a short hairpin loop structure (AD-bound conformation). The AD-binding-induced changes of aptamer conformation reduced the volume of the 2DPC hydrogels and decreased the interparticle spacing of the 2DPC embedded in the hydrogel network. The particle spacing changes being dependent on AD concentration were determined by measuring 2DPC light diffraction using a simple laser pointer. The 2DPC hydrogel sensor showed a large particle spacing decrease of ~ 110 nm in response to 1 mM AD in phosphate-buffered saline (PBS). The linear range of determination of AD was 0.1 nM to 1 mM and the limit of detection was 0.09 nM. The hydrogel sensor response for real samples was then validated in diluted fetal bovine serum (FBS) and human urine. The average % difference in particle spacing changes measured between diluted FBS and pure PBS was only 3.99%. In diluted human urine, the recoveries for the detection of AD were 95-101% and the relative standard deviations were 4.9-7.8%. The results demonstrate the potential applicability of the hydrogel sensor for real samples. This sensing concept, using the aptamer-functionalized 2DPC hydrogels, allows for a simple, sensitive, selective, and reversible detection of AD. It may enable sensor development for a wide variety of analytes by simply changing the aptamer recognition group.

Preparation and evaluation of ascorbyl glucoside and ascorbic acid solid in oil nanodispersions for corneal epithelial wound healing

The objective of this study was to develop and evaluate an effective topical formulation to promote corneal epithelial wound healing. Ascorbyl glucoside (AA-2G), a stable prodrug of AA, was formulated in solid in oil (S/O) nanodispersions by emulsifying AA-2G solutions in cyclohexane using Span 85 as an emulsifying agent and freeze-drying emulsions to produce AA-2G - surfactant complex. The complexes were then dispersed in castor oil to produce S/O nanodispersions which were evaluated in terms of their particle size, polydispersity index, encapsulation efficiency, morphology, physical stability as well as the transcorneal permeation and accumulation of AA-2G. The same preparation procedure was used to prepare S/O nanodispersions of AA. S/O nanodispersions of AA and AA-2G were formulated into oily drops that were tested for efficacy in promoting wound healing after corneal epithelial depredation. AA-2G was loaded efficiently in S/O nanodispersions (EE > 99%) in the form of spherical nanoparticles. S/O nanodispersions were physically stable and resulted in improved permeation (18x) and accumulation (7x) of AA-2G in transcorneal diffusion experiments in comparison to AA-2G solutions. Oily eye drops of AA-2G and AA showed no irritation and significant improvement in epithelial healing in vivo in comparison to AA-2G and AA solutions.

Efficient dermal delivery of ascorbic acid 2-glucoside with photoacoustic waves

OBJECTIVE

Ascorbic acid (i.e., vitamin C) is an important antioxidant present in skin. The protective role of vitamin C against photoaging motivated numerous attempts to promote its topical delivery, with a success limited by its chemical instability and poor skin permeability. Vitamin C precursors, such as ascorbic acid 2-glucoside (AA2G), that are metabolized to vitamin C by enzymes present in the skin, solve the problem of stability but are limited by low skin permeability. We developed a 2% (w/v) gel formulation of AA2G application (viscosity 4.30 × 10⁴ Pa.s, pH 5.94) and compared its passive dermal delivery with the delivery promoted by photoacoustic waves that transiently perturb the skin barrier.

METHODS

Photoacoustic (PA) waves were generated by laser pulses absorbed by piezophotonic (light-to-pressure) transducers. Pig skin samples were exposed to the 2% AA2G formulation alone or combined with 5 minutes of PA waves. One hour later, AA2G was extracted from the skin and quantified by reverse-phase HPLC. AA2G transdermal fluxes using Franz cells with 760 μm thick pig skin samples were also measured.

RESULTS

PA waves transiently enhanced skin permeability and increased dermal delivery of AA2G. AA2G was released from the formulation nearly quantitatively (92.6 ± 6.2%) in 24 hours, showing a non-Fickian behaviour controlled by diffusion and swelling. AA2G dermal delivery with exposure for 5 minutes to PA waves was compared with passive delivery to pig skin. PA waves increased the delivery of AA2G to the skin by a factor of 15 fold with respect to passive delivery, as measured from skin extracts after 1 hour of contact of the formulation with the skin.

CONCLUSION

5 minutes of exposure to PA waves is a safe and effective method to deliver large quantities of AA2G to the skin.

Simultaneous Analysis of Hydroquinone, Arbutin, and Ascorbyl Glucoside Using a Nanocomposite of Ag@AgCl Nanoparticles, Ag2S Nanoparticles, Multiwall Carbon Nanotubes, and Chitosan

A nanocomposite comprising Ag nanoparticles on AgCl/Ag2S nanoparticles was decorated on multi-walled carbon nanotubes and used to modify a glassy carbon electrode. Chitosan was also formulated in the nanocomposite to stabilize Ag2S nanoparticles and interact strongly with the glucose moiety of arbutin (AR) and ascorbyl glucoside (AA2G), two important ingredients in whitening lotion products. The modified electrode was characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) and cyclic voltammetry and used for the simultaneous analysis of hydroquinone (HQ), AR, and AA2G. The electrode showed excellent electrocatalysis towards the analytes by shifting the anodic peak potential to a negative direction with ≈5-fold higher current. The sensor displayed a linearity of 0.91-27.2 μM for HQ, 0.73-14.7 μM for AR, and 1.18-11.8 μM for AA2G, without cross-interference. A detection limit was 0.4 μM for HQ, 0.1 μM for AR, and 0.25 μM for AA2G. The sensor was applied to determine HQ, AR, and AA2G spiked in the whitening lotion sample with excellent recovery. The measured concentration of each analyte was comparable to that of the high performance liquid chromatographic (HPLC) method.

Colorimetric adenosine aptasensor based on DNA cycling amplification and salt-induced aggregation of gold nanoparticles

An aptamer based assay is described for the colorimetric detection of adenosine. The presence of adenosine triggers the deformation of hairpin DNA oligonucleotide (HP1) containing adenosine aptamer and then hybridizes another unlabeled hairpin DNA oligonucleotide (HP2). This leads to the formation of a double strand with a blunt 3' terminal. After exonuclease III (Exo III)-assisted degradation, the guanine-rich strand (GRS) is released from HP2. Hence, the adenosine-HP1 complex is released to the solution where it can hybridize another HP2 and initiate many cycles of the digestion reaction with the assistance of Exo III. This leads to the generation of a large number of GRS strands after multiple cycles. The GRS stabilize the red AuNPs against aggregation in the presence of potassium ions. If, however, GRS forms a G-quadruplex, it loses its ability to protect gold nanoparticles (AuNPs) from salt-induced AuNP aggregation. Therefore, the color of the solution changes from red to blue which can be visually observed. This colorimetric assay has a 0.13 nM detection limit and a wide linear range that extends from 5 nM to 1 μM. Graphical abstract Schematic presentation of a colorimetric aptamer biosensor for adenosine detection based on DNA cycling amplification and salt-induced aggregation of gold nanoparticles.

An aptamer-based fluorescence bio-sensor for chiral recognition of arginine enantiomers

In this study, a novel aptamer - based fluorescence bio-sensor (aptamer-AuNps) was developed for chiral recognition of arginine (Arg) enantiomers based on aptamer and gold nanoparticles (AuNps). Carboxyfluorescein (FAM) labeled aptamers (Apt) were absorbed on AuNps and their fluorescence intensity could be significantly quenched by AuNps based on fluorescence resonance energy transfer (FRET). Once d-Arg or l-Arg were added into the above solution, the aptamer specifically bind to Arg enantiomers and released from AuNps, so the fluorescence intensity of d-Arg system and l-Arg system were all enhanced. The affinity of Apt to l-Arg is tighter to d-Arg, so the enhanced fluorescence signals of l-Arg system was stronger than d-Arg system. What's more, the enhanced fluorescence were directly proportional to the concentration of d-Arg and l-Arg ranging from 0-300 nM and 0-400 nM with related coefficients of 0.9939 and 0.9952, respectively. Furthermore, the method was successfully applied to detection l-Arg in human urine samples with satisfactory results. Eventually, a simple "OR" logic gate with d-Arg &l-Arg as inputs and AuNps aggregation state as outputs was fabricated, which can help us understand the chiral recognition process deeply.

G-quadruplex based Exo III-assisted signal amplification aptasensor for the colorimetric detection of adenosine

Adenosine is an endogenous nucleotide pivotally involved in nucleic acid and energy metabolism. Its excessive existence may indicate tumorigenesis, typically lung cancer. Encouraged by its significance as the clinical biomarker, sensitive assay methods towards adenosine have been popularized, with high cost and tedious procedures as the inevitable defects. Herein, we report a label-free aptamer-based exonuclease III (Exo III) amplification colorimetric aptasensor for the highly sensitive and cost-effective detection of adenosine. The strategy employed two unlabeled hairpin DNA oligonucleotides (HP1 and HP2), where HP1 contained the aptamer towards adenosine and HP2 embedded the guanine-rich sequence (GRS). In the presence of adenosine, hairpin HP1 could form specific binding with adenosine and trigger the unfolding of HP1's hairpin structure. The resulting adenosine-HP1 complex could hybridize with HP2, generating the Exo III recognition site. After Exo III-assisted degradation, the GRS was released from HP2, and the adenosine-HP1 was released back to the solution to combine another HP2, inducing the cycling amplification. After multiple circulations, the released ample GRSs were induced to form G-quadruplex, further catalyzing the oxidation of TMB, yielding a color change which was finally mirrored in the absorbance change. On the contrary, the absence of adenosine failed to unfold HP1, remaining color unchanged eventually. Thanks to the amplification strategy, the limit of detection was lowered to 17 nM with a broad linear range from 50 nM to 6 μM. The proposed method was successfully applied to the detection of adenosine in biological samples and satisfying recoveries were acquired.

A turn-on fluorescence aptasensor based on carbon dots for sensitive detection of adenosine

A novel turn-on fluorescence aptasensor was designed for adenosine detection based on FRET from ssDNA-CDs to aptamer-AuNPs.