Study on the interaction between 2,6-dihydroxybenzoic acid nicotine salt and human serum albumin by multi-spectroscopy and molecular dynamics simulation.

As a new form of nicotine introduction for novel tobacco products, the interaction of nicotine salt with biological macromolecules may differ from that of free nicotine and thus affect its transport and distribution in vivo. Hence, the mechanism underlying the interaction between 2,6-dihydroxybenzoic acid nicotine salt (DBN) and human serum albumin (HSA) was investigated by multi-spectroscopy, molecular docking, and dynamic simulation. Experiments on steady-state fluorescence and fluorescence lifetime revealed that the quenching mechanism of DBN and HSA was dynamic quenching, and binding constant was in the order of 10^4 L mol-1. Thermodynamic parameters exhibited that the binding was a spontaneous process with hydrophobic forces as the main driving force. Fluorescence competition experiments revealed that DBN bound to site I of HSA IIA subdomain. According to the results of synchronous fluorescence, 3D fluorescence, FT-IR spectroscopy, circular dichroism (CD) spectroscopy, and molecular dynamics (MD) simulation, DBN did not affect the basic skeleton structure of HSA but changed the microenvironment around the amino acid residues. Computer simulations positively corroborated the experimental results. Moreover, DBN decreased the surface hydrophobicity and weakened the esterase-like activity of HSA, leading to the impaired function of the latter. This work provides important information for studying the interaction between DBN as a nicotine substitute and biological macromolecules and contributes to the further development and application of DBN.

Studies on local anesthetic lidocaine hydrochloride delivery via photo-triggered implantable polymeric microneedles as a patient-controlled transdermal analgesia system.

This study aimed to develop photo-triggered implantable polymeric microneedles (MNs) for successful drug delivery in a transdermal analgesia system. The prepared iron oxide nanoparticles (Fe3O4NPs) were coated with polydopamine (PDA) followed by polyvinylpyrrolidone (PVP) and polycaprolactone (PCL). While the PCL/PVP-Fe3O4NPs synthesis, the absorption band of PVP at 1656 cm-1 shifted to 1665 cm-1 which indicate the presence of interaction between Fe+ and C = O groups. The size and morphology of PCL/PVP-Fe3O4NPs were examined by scanning electron microscope and transmission electron microscope (SEM and TEM) analysis. The results confirmed that the prepared PCL/PVP-Fe3O4NPs were spherical with sizes ranging from 9 to 11 nm. The lidocaine hydrochloride content in the microneedles was 3.72 ± 0.31 mg and A + 2.2S ≤ L representing that the drug was uniformly distributed. The insertion ability of lidocaine hydrochloride@PCL/PVP-Fe3O4NPs-DMNs was tested by porcine skin. The results demonstrated outstanding insertion ability and potential for drug delivery. In addition, near-infrared (NIR) irradiation has the potential to penetrate the skin and enhance lidocaine hydrochloride-releasing activity. The in vivo experimental data confirmed that lidocaine hydrochloride@PCL/PVP-Fe3O4NPs-DMNs allowed for painless drug delivery by breaking the barrier of the stratum corneum. To conclude, lidocaine hydrochloride can be safely delivered through the transdermal analgesic system, with a quick onset time.

How hydrophilic group affects drug-protein binding modes: Differences in interaction between sirtuins inhibitors Tenovin-1/Tenovin-6 and human serum albumin.

Introduction of hydrophilic groups can improve the solubility of leading drugs but inevitably affect their interaction with proteins. This study selected sirtuin inhibitors Tenovin-1 (T1) and Tenovin-6 (T6) as drug models to determine differences in binding mode to human serum albumin (HSA). T1 and T6 quenched the endogenous fluorescence of HSA via static quenching mechanism. Introduction of hydrophilic groups greatly reduced the binding constant, i.e., from 1.302 × 104 L mol-1 for the HSA-T6 system to 0.128 × 104 L mol-1 for the HSA-T1 system. HSA-T1 system was mainly driven by electrostatic interactions while that of HSA-T6 system was hydrophobic interaction and both systems were spontaneous reactions. Site marker experiments and molecular docking indicated that both systems mainly bound to the hydrophobic site I of HSA. Molecular dynamics (MD) simulation analysis further revealed that Tyr148, Tyr150 and Arg257 residues played a key role in this recognition process for both systems. In particular, T6 maintained additional several hydrogen bonds with the surrounding residues. T1 had almost no effect on the esterase-like activity of HSA, but T6 inhibited the hydrolysis of p-NPA. Furthermore, differential scanning calorimetry (VP-DSC), circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopy confirmed that HSA in the T6 system undergone a more significant conformational transition than that in the T1 system.

Self-assembled phospholipid-based mixed micelles for improving the solubility, bioavailability and anticancer activity of lenvatinib.

The clinical efficacy of lenvatinib (LFT) is limited by its poor aqueous solubility and low bioavailability. In this work, LFT-loaded soy phospholipid and sodium glycocholate mixed micelles (LFT-MMs) were prepared through classical co-precipitation. And it was served as an oral administration to address these shortcomings. The preparation conditions were optimized by single-factor experiments. The mass ratio of PC, SGC and LFT, and the species of dispersing media were proved to be decisive factors in controlling the properties of LFT-MMs. The optimal LFT-MMs presented prominent enhancement (500-fold) in LFT solubility, high encapsulation efficiency (87.6 %) as well as suitable stability (>1 month at 4 °C). The biocompatibility of LFT-MMs was estimated by in vitro serum stability measurement and hemolysis test. It showed that serum proteins hardly adhered to the surface of LFT-MMs, and insignificant hemolytic rate (<0.5 %) was observed at the micelles concentration below 1 mg/mL. Cytotoxicity test (MTT assay) was carried out to judge the in vitro antitumor activity. LFT-MMs showed an enhanced inhibitory activity against two main kinds of differentiated thyroid cancer cells over LFT and LFT Mesylate. To estimate the in vivo oral bioavailability of LFT-MMs, SD rats were used as animal model. Notably, the relative bioavailability of LFT-MMs compared with the original form of LFT was 176.7 %. These superior characteristics indicated that the mixed micelles are promising water-soluble formulations suitable for LFT oral delivery.

Study of conformational and functional changes caused by binding of environmental pollutant tonalide to human serum albumin.

Tonalide (AHTN) is a new category of pollutants with a wide range of potential environmental and organismal hazards due to its persistence and lipophilicity, and the safety evaluation of this pollutant under physiological condition is a pressing issue. This study investigated the mechanism of interaction between AHTN and human serum albumin (HSA) that is an important transporter in plasma using multiple spectroscopic, molecular docking, and dynamics simulation methods. The steady-state fluorescence and fluorescence lifetime experiments showed that AHTN quenches the inherent fluorescence of HSA through a static quenching mechanism. Thermodynamic parameters exhibited that the binding constant of AHTN and HSA is of the order of 10^4 L/mol, and the binding is a spontaneous process of moderate strength with hydrophobic forces as the main driving force. Site competition revealed that AHTN binds to site I of HSA IIA subdomain, which was evidenced by the molecular docking results. AHTN altered the HSA amino acid microenvironment and conformation can be derived from three-dimensional fluorescence, circular dichroism spectroscopy, and molecular dynamics simulation. The computer simulations corroborate the experimental results positively. Moreover, AHTN acted as a competitive inhibitor to weaken the esterase-like activity of HSA, leading to impaired function of HSA. Results suggest that interactions between AHTN and HSA may affect the normal structure and activities of the protein, this insight will be helpful to provide some basic information to further explore the potential hazards of AHTN in humans.

Characterization and In Vitro Evaluation of the Complexes of Posaconazole with ß- and 2,6-di-O-methyl-ß-cyclodextrin.

Posaconazole is a triazole antifungal drug that with extremely poor aqueous solubility. Up to now, this drug can be administered via intravenous injection and oral suspension. However, its oral bioavailability is greatly limited by the dissolution rate of the drug. This study aimed to improve water solubility and dissolution of posaconazole through characterizing the inclusion complexes of posaconazole with ß-cyclodextrin (ß-CD) and 2,6-di-O-methyl-ß-cyclodextrin (DM-ß-CD). Phase solubility studies were performed to calculate the stability constants in solution. The results of FT-IR, PXRD, 1H and ROESY 2D NMR, and DSC all verified the formation of the complexes in solid state. The complexes showed remarkably improved water solubility and dissolution rate than pure posaconazole. Especially, the aqueous solubility of the DM-ß-CD complex is nine times higher than that of the ß-CD complex. Preliminary in vitro antifungal susceptibility tests showed that the two inclusion complexes maintained high antifungal activities. These results indicated that the DM-ß-CD complexes have great potential for application in the delivery of poorly water-soluble antifungal agents, such as posaconazole.

Multispectroscopic and docking studies on the binding of chlorogenic acid isomers to human serum albumin: Effects of esteryl position on affinity.

Structural differences among various dietary polyphenols affect their absorption, metabolism, and bioactivities. In this work, chlorogenic acid (CA) and its two positional isomers, neochlorogenic acid (NCA) and cryptochlorogenic acid (CCA), were investigated for their binding reactions with human serum albumin (HSA) using fluorescence, ultraviolet-visible, Fourier transform infrared and circular dichroism spectroscopies, as well as molecular docking. All three isomers were bound to HSA at Sudlow's site I and affected the protein secondary structure. CCA presented the strongest ability of hydrogen-bond formation, and both CA and NCA generated more electrostatic interactions with HSA. The albumin-binding capacity of these compounds decreased in the order CCA>NCA>CA. The compound with 4-esteryl structure showed higher binding affinity and larger conformational changes to HSA than that with 3- or 5-esteryl structures. These comparative studies on structure-affinity relationship contributed to the structural modification and design of phenolic food additives or new polyphenol-like drugs.

Investigation on the Interaction of Norgestrel with Human Serum Albumin Using Spectroscopy and Molecular-Docking Method.

The interaction of norgestrel with human serum albumin (HSA) was investigated by spectroscopy and molecular-docking methods. Results of spectroscopy methods suggested that the quenching mechanism of norgestrel on HSA was static quenching and that the quenching process was spontaneous. Negative values of thermodynamic parameters (ΔG, ΔH, and ΔS) indicated that hydrogen bonding and van der Waals forces dominated the binding between norgestrel and HSA. Three-dimensional fluorescence spectrum and circular dichroism spectrum showed that the HSA structure was slightly changed by norgestrel. Norgestrel mainly bound with Sudlow site I based on a probe study, as confirmed by molecular-docking results. Competition among similar structures indicated that ethisterone and norethisterone affected the binding of norgestrel with HSA. CH3 in R1 had little effect on norgestrel binding with HSA. The surface hydrophobicity properties of HSA, investigated using 8-anilino-1-naphthalenesulfonic acid, was changed with norgestrel addition.

Monitoring of the manufacturing process for ambroxol hydrochloride tablet using NIR-chemometric methods: compression effect on content uniformity model and relevant process parameters testing.

This study aimed at using near-infrared (NIR) spectroscopy to monitor compaction pressure for simultaneously determining the tensile strength and content uniformity, as well as moisture and mean particle size of ambroxol hydrochloride tablets. The content uniformity, compression force and tensile strength of the laboratory samples were obtained by pressing a mixture of active principle and excipient components into tablets. To reduce the spectral baseline shift of the laboratory samples, the compaction pressure applied to the mixture was assessed by a variable pressure test. Production samples were added to the test and subjected to principal component analysis. The expanded partial least-squares (PLS) calibration model used to quantify the active content was more accurate than the model constructed from laboratory samples using the production tablets included in the calibration set. The model showed good predictability, with correlation coefficient (R) 0.9977. The validation and reliability of the content model were evaluated to determine trueness and reliability for the measurement of individual production tablets and the laboratory tablets with drug content ranging from 24 to 36 mg. The PLS calibration models for compression force and tensile strength were constructed using the same spectral set assuming both were highly related. These models yielded high R values (0.9955 and 0.9910). The R values of the moisture and mean particle size were 0.9994 and 0.9919, respectively. This study demonstrated that NIR spectroscopy combined with chemometric techniques can be successfully used to quantitatively monitor the tablet manufacturing process in the pharmaceutical industry.

A simple, rapid and sensitive ultraviolet-visible spectrophotometric technique for the determination of ultra-trace copper based on injection-ultrasound-assisted dispersive liquid-liquid microextraction.

In this work, a simple, rapid and sensitive UV-visible spectrophotometric technique for the determination of copper based on injection-ultrasound-assisted dispersive liquid-liquid microextraction (IUSA-DLLME) was developed, using sodium diethyl-dithiocarbamate (Na-DDTC) as a complexing agent. The fabrication of a home-made microporous plastic tip was first reported, and by using it, contamination from a metallic tip was avoided; moreover cloudy solutions were easily obtained. Several parameters were investigated including the extraction solvent type and volume, pH of the reaction solution, concentration of DDTC, salt addition, reaction time and temperature, and sonication and centrifugation time. The results showed that carbon tetrachloride was a better extraction solvent. Under the optimal conditions, the calibration curve was linear in the range of 0.5-50 ng mL(-1) of copper with a R(2) of 0.9996. The relative standard deviation (RSD) for the determination of 0.5 ng mL(-1) copper was ±3.3% (n = 7), and the detection limit (3*Sb*c/m) was 0.05 ng mL(-1) in the original solution. An enrichment factor of 222 was obtained. The developed method was validated by analysis of a certified reference solution and applied successfully to the determination of copper in tap water, bottled pure water and river water. The advantages of the IUSA-DLLME method are simplicity of operation, rapidity, low cost, low LOD and high enrichment factor.