Design, synthesis, and biological activity evaluation of BACE1 inhibitors with antioxidant activity.

The proteolytic enzyme ß-secretase (BACE1) plays a central role in the synthesis of the pathogenic ß-amyloid peptides (Aß) in Alzheimer's disease (AD), antioxidants could attenuate the AD syndrome and prevent the disease progression. In this study, BACE1 inhibitors (D1-D18) with free radical-scavenging activities were synthesized by molecular hybridization of 2-aminopyridine with natural antioxidants. The biological activity evaluation showed that D1 had obvious inhibitory activity against BACE1, and strong antioxidant activity in 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS+• ) assay, which could be used as a lead compound for further study.

Design, synthesis and evaluation of 2-amino-imidazol-4-one derivatives as potent ß-site amyloid precursor protein cleaving enzyme 1 (BACE-1) inhibitors.

Inhibition of ß-site amyloid precursor protein cleaving enzyme 1 (BACE1) to prevent brain ß-amyloid (Aß) peptide's formation is a potential effective approach to treat Alzheimer's disease. In this report we described a structure-based optimization of a series of BACE1 inhibitors derived from an iminopyrimidinone scaffold W-41 (IC50 = 7.1 µM) by Wyeth, which had good selectivity and brain permeability but low activity. The results showed that occupying the S3 cavity of BACE1 enzyme could be an effective strategy to increase the biological activity, and five compounds exhibited stronger inhibitory activity and higher liposolubility than W-41, with L-5 was the most potent inhibitor against BACE1 (IC50 = 0.12 µM, logP = 2.49).

Preparation and In vitro Evaluation of FDM 3D-Printed Ellipsoid-Shaped Gastric Floating Tablets with Low Infill Percentages.

The aim of the study is to investigate the feasibility of fabricating FDM 3D-printed gastric floating tablets with low infill percentages and the effect of infill percentage on the properties of gastric floating tablets in vitro. Propranolol hydrochloride was selected as a model drug, and drug-loaded polyvinyl alcohol (PVA) filaments were produced by hot melt extrusion (HME). Ellipsoid-shaped gastric floating tablets with low infill percentage of 15% and 25% (namely E-15 and E-25) were then prepared respectively by feeding the extruded filaments to FDM 3D printer. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM) were employed to characterize the filaments and 3D-printed tablets, and a series of evaluations were performed to the 3D-printed tablets, including the weight variation, drug content, hardness, in vitro floating behavior, and drug release of the tablets. The SEM results showed that the drug-loaded filaments and 3D-printed tablets appeared intact without defects, and the printed tablets were composed of filaments deposited uniformly layer by layer. The model drug and the excipients were thermally stable under the process temperature of extruding and printing, with a small amount of drug crystals dispersing in the drug-loaded filaments and 3D-printed tablets. Both E-15 and E-25 could float on artificial gastric fluids without any lag time and released in a sustained manner. Compared with E-15, the E-25 presented less weight variation, higher tablet hardness, shorter floating time, and longer drug release time.

A novel and efficient synthesis of phenanthrene derivatives via palladium/norbornadiene-catalyzed domino one-pot reaction.

Herein we report a novel palladium-catalyzed reaction that results in phenanthrene derivatives using aryl iodides, ortho-bromobenzoyl chlorides and norbornadiene in one pot. This dramatic transformation undergoes ortho-C-H activation, decarbonylation and subsequent a retro-Diels-Alder process. Pleasantly, this protocol has a wider substrate range, shorter reaction times and higher yields of products than previously reported methods.

Preparation and In Vitro Evaluation of a MRI Contrast Agent Based on Aptamer-Modified Gadolinium-Loaded Liposomes for Tumor Targeting.

The aim of this study was to prepare aptamer-modified liposomes loaded with gadolinium (Gd) to enhance the effective diagnosis for tumor by MRI. A modified GBI-10 (GBI-10m) was used to prepare targeted liposomes (GmLs). Liposomes with GBI-10 aptamer (GLs) and without aptamer (non-targeted liposomes (NLs)) were also prepared as controls. The particle size and zeta potential of GmLs, GLs, and NLs were all assayed. A clinical 3.0 T MR scanner was employed to assess the imaging efficiency and measure the longitudinal relaxivity (r 1) of the above liposomes. Confocal laser scanning microscopy and flow cytometry were used to analyze and compare the targeting effects of GmLs, GLs, and NLs to MDA-MB-435s cells at 37°C. The particle size of the prepared liposomes was scattered at 100-200 nm, and their values of r 1 were ∼4 mM-1 s-1. The images of confocal laser scanning microscopy showed that GmLs in the cytoplasm were significantly more than GLs and both GmLs and GLs were more than NLs. The fluorescence intensity of GmLs was increased by about two times than that of GLs and three times than that of NLs by flow cytometry. Therefore, the GmLs in this initial study were suggested to be a potential MRI contrast agent at 37°C for diagnosing tumors with the protein of tenascin-C over-expressed.

[Preparation and in vitro evaluation of crosslinked polyvinyl alcohol microspheres for embolization].

OBJECTIVE: To develop and study the properties of crosslinked polyvinyl alcohol microspheres (PVA-Ms) for embolization. METHODS: The PVA-Ms were produced by emulsion chemical crosslinking method. Fourier transform infrared spectroscopy (FT-IR) was used to investigate the special functional groups of PVA-Ms; the morphology and particle size of PVA-Ms were determined by optical microscope; the ratio of water absorption and the swelling ratio were also investigated; the compressibility was examined by texture analyzer. A new device was designed to measure the pressure of PVA-Ms during their delivery through catheter for embolization. RESULTS: The crosslinking reaction of PVA and formaldehyde was proved by FT-IR. The PVA-Ms were round with smooth surface. The average diameter of lyophilized PVA-Ms was 574.2 µm with a range of 80-1 800 µm and of wet PVA-Ms was 602.2 µm with a range of 100-1 900 µm. The average ratio of water absorption was 175% and the swelling ratio was 48.6%. The PVA-Ms were mechanically stable with appropriate elasticity and delivered through the catheter without any difficulty, and the pressure was higher for larger size of microspheres to be delivered. CONCLUSION: PVA-Ms prepared in this study was supposed to be suitable for clinical embolization according to the physicochemical properties. The study provides a series of methods to evaluate the properties of microspheres systemically for embolization in vitro.

[Preparation and investigation of MRI-traceable Eudragit-E liquid embolic agent].

OBJECTIVE: To develop and investigate the properties of MRI-traceable Eudragit-E liquid embolic agent (MR-E). METHODS: Polyethylene glycol-modified superparamagnetic iron oxides (PEG-SPIO) was synthesized by chemical co-precipitation method. MR-E was prepared by mixing PEG-SPIO and Eudragit-E liquid embolic agent homogeneously. An in vitro MR phantom study was carried out to measure MR traceability of MR-E and to determine the concentration of PEG-SPIO for further studies. The microcatheter deliverability and sol-gel transition process of MR-E were investigated. MR-E was injected into the kidney of a Japanese white big ear rabbit via an angiographic microcatheter, and detected by MRI. RESULTS: A PEG-SPIO concentration of 2 g/L was considered to be suitable for further studies. MR-E was injected through the microcatheter without any difficulty. MR-E instantly solidified on release into saline. Then 0.2 mL of MR-E effectively embolized distal renal arteries, and MR-E could be detected by MRI in the embolized kidney. CONCLUSION: MR-E seems to be a promising MRI-traceable liquid embolic agent.

[Preparation and property study of doxorubicin loaded microspheres].

OBJECTIVE: To prepare doxorubicin-loaded polyvinylalcohol-acrylic acid (PVA-AA) microspheres and evaluate properties of this chemoembolic agent. METHODS: PVA-AA microspheres were synthesized by inverse suspension polymerization method and then verified by infrared spectroscopy. drug loading (DL) and entrapment efficiency (EE%) were measured after doxorubicinwas loaded on PVA-AA microspheres. Their morphology and elasticity were investigated by optical microscope, environmental scanning electron microscope and texture analyzer, respectively. T-cell apparatus was used to evaluate the in vitro release behavior of doxorubicin-loaded microspheres.The external carotid of the rabbit was chosen as an embolization site to evaluate the in vivo embolic property of the microspheres. RESULTS: PVA-AA microspheres, which were transparent spheres,turned into red spheres after doxorubicin loading. DL of the microspheres was (20.56 ± 0.69)g/L and (23.25 ± 0.27) g/L,and EE% was 82.22% ± 2.76% and 93.00% ± 1.06% within 20 min and 6 h, respectively. The in vitro release results showed a significantly delayed release of the drug for 10.32% ± 0.47% after 24 h. The Young's modulus was (178.30 ± 12.33) kPa and (213.29 ± 15.61) kPa for blank microspheres and doxorubicin-loaded microspheres, respectively. Both blank microspheres and doxorubicin-loaded microspheres exhibited good elasticity. In vivo embolization showed that 0.3 mL of microspheres could produce distal embolic efficiency. CONCLUSION: The doxorubicin-loaded microspheres are expected to be a promising new chemoembolic agent.

[Optimization and property evaluation of gelatin microspheres for embolization].

OBJECTIVE: To optimize the preparation of gelatin microspheres for embolization and to evaluate the physicochemical properties of the optimized microspheres. METHODS: The gelatin microspheres were prepared using emulsification crosslink method. The response surface methodology (RSM) was used in order to achieve gelatin microspheres with satisfactory degradable time and elasticity. The response values considered in this study were degradable time and elasticity, and the factors were the concentration of formaldehyde solution and the time of cross-linking reaction. The optimized microspheres were achieved by RSM. The properties of the optimized microspheres were investigated, including degradable time, elasticity, particle size, ratio of water absorption and the swelling ratio. RESULTS: The elasticity of the optimized microspheres was appropriate. The degradable time of the optimized microspheres was 2-3 weeks. The average diameter for dried gelatin microsphere was 377.6 µm, and for wet gelatin microsphere was 535.6 µm. The gelatin microsphere achieved the rate of water absorption balance at 20 min, and the average swelling ratio of gelatin microsphere was 41.9%. CONCLUSION: The gelatin microspheres optimized by RSM seemed to be suitable for clinical embolization according to the physicochemical properties.

[Optimization of calcium alginate floating microspheres loading aspirin by artificial neural networks and response surface methodology].

OBJECTIVE: To investigate the preparation and optimization of calcium alginate floating microspheres loading aspirin. METHODS: A model was used to predict the in vitro release of aspirin and optimize the formulation by artificial neural networks (ANNs) and response surface methodology (RSM). The amounts of the material in the formulation were used as inputs, while the release and floating rate of the microspheres were used as outputs. The performances of ANNs and RSM were compared. RESULTS: ANNs were more accurate in prediction. There was no significant difference between ANNs and RSM in optimization. Approximately 90% of the optimized microspheres could float on the artificial gastric juice over 4 hours. 42.12% of aspirin was released in 60 min, 60.97% in 120 min and 78.56% in 240 min. The release of the drug from the microspheres complied with Higuchi equation. CONCLUSION: The aspirin floating microspheres with satisfying in vitro release were prepared successfully by the methods of ANNs and RSM.

[Preparation and in vitro evaluation of tanshinone IIA pulsatile release pellets].

OBJECTIVE: To develop pulsatile release pellets using tanshinone II as model drug and evaluate their properties in vitro. METHODS: The tanshinone II pusatile release pellets with rupturable coatings were prepared by fluid bed. Hydroxy propyl methyl cellulose (HPMC), low-substituted hydroxy propyl cellulose (L-HPC)/HPMC, and HPMC/Sureleae were used as swelling agents respectively, and aqueous ethylcellulose dispersion Surelease as the material of controlled layer. Dissolution experiments were employed to evaluate the effects of different swelling agents and weight gain of each coating layer. Cross-sections of pellets with different swelling agents were observed by scanning electron microscope (SEM). The release profiles of tanshinone II from the coated pellets were fitted into various mathematic models. RESULTS: Pellets with HPMC or L-HPC/HPMC as swelling agents could not present a significant release lag time. However, the pellets with the mixture of HPMC and Surelease as swelling agents could. As the ratio of Surelease increased in swelling layer, the lag time could be extended. As to the controlled layer, the thicker the controlled layer, the longer the lag time could be. When the controlled layer was coated by 30%-40% weight gains, 3-5 h lag time was realized. The fitted model suggested that first order equation could explain the drug release from tanshinone II pulsatile release pellets. CONCLUSION: Using HPMC/Surelease mixture as swelling agents, and Surelease as the material of controlled layer, tanshinone II pulsatile release pellets with 3-5 h lag time were successfully prepared.

Small-Molecule Fms-like Tyrosine Kinase 3 Inhibitors: An Attractive and Efficient Method for the Treatment of Acute Myeloid Leukemia.

Fms-like tyrosine kinase 3 (FLT3) is an important member of the class III receptor tyrosine kinase (RTK) family, which is involved in the proliferation of hematopoietic cells and lymphocytes. In recent years, increasing evidence have demonstrated that the activation and mutation of FLT3 is closely implicated in the occurrence and development of acute myeloid leukemia (AML). The exploration of small-molecule inhibitors targeting FLT3 has aroused wide interest of pharmaceutical chemists and is expected to bring new hope for AML therapy. In this review, we specifically highlighted FLT3 mediated JAK/STAT, RAS/MAPK, and PI3K/AKT/mTOR signaling. The structural properties and biological activities of representative FLT3 inhibitors reported from 2014 to the present were also summarized. In addition, the major challenges in the current advance of novel FLT3 inhibitors were further analyzed, with the aim to guide future drug discovery.

Total synthesis, chemical modification and structure-activity relationship of bufadienolides.

Bufadienolides are a type of natural cardiac steroids and originally isolated from the Traditional Chinese Medicine Chan'Su, they have been used for the treatment of heart disease in traditional remedies as well as in modern medicinal therapy with potent anti-tumor activities. Due to their unique molecular structures with unsaturated six-membered lactones attached to the steroid core, bufadienolides have received great attention in the synthetic organic community. This review presents total synthetic efforts to some representative bufadienolides, chemical modification of bufadienolides will also be given to discuss their structure-activity relationship in anti-tumor.

[Optimization of riboflavin sodium phosphate loading to calcium alginate floating microspheres by response surface methodology].

OBJECTIVE: To investigate the preparation, optimization and in vitro properties of riboflavin sodium phosphate floating microspheres. METHODS: The floating microspheres composed of riboflavin sodium phosphate and calcium alginate were prepared using ion gelatin-oven drying method. RESULTS: The properties of the microspheres were investigated, including the buoyancy, release, appearance and entrapment efficiency. The formulation was optimized by response surface methodology (RSM). CONCLUSION: The optimized microspheres were round. The entrapment efficiency was 57.49%. All the microspheres could float on the artificial gastric juice over 8 hours. The release of the drug from the microspheres complied with Fick's diffusion.

[Preparation and property study of ion-exchange embolic microspheres for delivering pingyangmycin].

OBJECTIVE: To develop and study the properties of ion-exchange polyvinyl alcohol-acrylic acid microspheres (PVA-AA-Ms) for embolization. METHODS: The PVA-AA-Ms were produced by the method of inverse suspension polymerization. The morphology and particle size were determined by optical microscope; FT-IR was used to investigate the special functional groups of PVA-AA-Ms; the carboxyl content of PVA-AA-Ms was measured by chemical titration; the compression elasticity was examined by texture analyzer (TA-plus). Pingyangmycin (bleomycin A(5)) was used as model drug to prepare drug-loaded PVA-AA-Ms. Drug loading and entrapment efficiency were measured through UV-spectrophotometer; in vitro drug release characteristic was detected by constant temperature vibration dialysis assay. RESULTS: The PVA-AA-Ms were round and integrated. The average diameter of PVA-AA-Ms was 500 microm with a range of 150-1 000 microm. The carboxyl vibration was demonstrated by FT-IR and the content of carboxyl was 8.905 mmol/g. PVA-AA-Ms were mechanically stable with appropriate elasticity. Drug loading and entrapment efficiency were 30 g/L and 99.4%, respectively. The drug release rate was slow in phosphate buffer solution (PBS), 88.3% of the drug was released after 24 h and the t(50) was 2.19 h. CONCLUSION: PVA-AA-Ms prepared in this study were supposed to be suitable for clinical embolization according to the physicochemical properties. The high carboxyl content of PVA-AA-Ms which allowed them to load cationic drugs (e.g., drug with amino group) through ion-exchange mechanism brought broad prospects for combination of embolization and chemotherapy.

[Preparation and evaluation of radiopaque microspheres].

OBJECTIVE: To develop lipiodol-containing calcium alginate microspheres (LAMs) for embolization, and study the characterization for emoblization and the radiopacity. METHODS: LAMs were prepared by dripping method. The preparation of LAMs was optimized by orthogonal experiment which involved effects of three factors (the volume ratio of lipiodol to the external aqueous solution, airflow rate, and the weight pushing the injector) at three levels on the responses to the size, polydisperse index and entrapment efficiency of LAMs. The morphology of LAMs was observed under microscope. The elasticity of LAMs was investigated by texture analyzer. The capability injected through catheter of LAMs was monitored by video spinning-drop tensionmeter. The radiopacity of LAMs was measured by X-ray imaging system after LAMs were injected into vas of a rat. RESULTS: The optimal condition for preparation of LAMs was: the volume ratio of lipiodol to the external aqueous solution was 3:10, airflow rate was 40 g/mL and the weight pushing the injector was 100 g. According to the optimized condition, LAMs were prepared and characterized. The mean diameter of LAMs was (493.9 +/- 42.6) microm, the polydisperse index was 1.02 and the entrapment efficiency was (88.97 +/- 1.09) %. The LAMs were with round shape and smooth surface in view of photograph of microscope. The maximum average load was (1.09 +/- 0.18) N when LAMs were compressed to 60%. The LAMs were injected through catheter without much difficulty. The radiopacity of LAMs in rats was demonstrated to be visible under X-ray photography system. CONCLUSION: The radiopaque LAMs developed are suitable for the arterial embolization, with round shape, proper size, good elasticity, easy handling character and visible property under X-ray imaging. The radiopaque embolic agent is supposed to be useful for emoblization therapy.

Synthesis and Biological Evaluation of Scutellarein Alkyl Derivatives as Preventing Neurodegenerative Agents with Improved Lipid Soluble Properties.

BACKGROUND: Exogenous antioxidants are considered as a promising therapeutic approach to treat neurodegenerative diseases since they could prevent and/or minimize the neuronal damage by oxidation. OBJECTIVE: Three series of lipophilic compounds structurally based on scutellarein (2), which is one metabolite of scutellarin (1) in vivo, have been designed and synthesized. METHODS: Their antioxidant activity was evaluated by detecting the 2-thiobarbituric acid reactive substance (TBARS) produced in the ferrous salt/ascorbate-induced autoxidation of lipids, which were present in microsomal membranes of rat hepatocytes. The lipophilicity of these compounds indicated as partition coefficient between n-octanol and buffer was investigated by ultraviolet (UV) spectrophotometer. RESULTS: This study indicated that compound 5e which had a benzyl group substituted at the C4'- OH position showed a potent antioxidant activity and good lipophilicity. CONCLUSION: 5e could be an effective candidate for preventing or reducing the oxidative status associated with the neurodegenerative processes.

MRI Detectable Polymer Microspheres Embedded With Magnetic Ferrite Nanoclusters For Embolization: In Vitro And In Vivo Evaluation.

OBJECTIVE: The objective of this study was to develop magnetic embolic microspheres that could be visualized by clinical magnetic resonance imaging (MRI) scanners aiming to improve the efficiency and safety of embolotherapy. METHODS AND DISCUSSION: Magnetic ferrite nanoclusters (FNs) were synthesized with microwave-assisted solvothermal method, and their morphology, particle size, crystalline structure, magnetic properties as well as T2 relaxivity were characterized to confirm the feasibility of FNs as an MRI probe. Magnetic polymer microspheres (FNMs) were then produced by inverse suspension polymerization with FNs embedded inside. The physicochemical and mechanical properties (including morphology, particle size, infrared spectra, elasticity, etc.) of FNMs were investigated, and the magnetic properties and MRI detectable properties of FNMs were also assayed by vibrating sample magnetometer and MRI scanners. Favorable biocompatibility and long-term MRI detectability of FNMs were then studied in mice by subcutaneous injection. FNMs were further used to embolize rabbits' kidneys to evaluate the embolic property and detectability by MRI. CONCLUSION: FNMs could serve as a promising MRI-visualized embolic material for embolotherapy in the future.

[Preparation and physicochemical characterization of hydrogel microspheres for embolization].

OBJECTIVE: To develop and characterize the hydrogel microspheres for embolization. METHODS: N-[tris (hydroxymethyl) methyl] acrylamide-gelatin microspheres (TGMs) were prepared by an inverse suspension polymerization approach. Effects of materials on size, water absorption rate and elasticity of the microspheres were investigated. The materials which were included consisted of gelatin in the range of 10.0-100.0 g/L, N-[tris (hydroxymethyl)methyl]acrylamide in the range of 33.3-200 g/L, cross-linking agent N,N'-methylene-bis-acrylamide in the range of 3.3-10.0 g/L, surfactant Span 80 in the range of 0.5-1.8 g/L, and initiator ammonium persulfate in the range of 1.0-5.0 g/L. The appearance of TGMs was observed under microscope. TGMs were analyzed by infrared spectrum (IR). RESULTS: The TGMs were round with smooth surface in view of photograph of microscope. The average diameter of TGMs was increased with the increase of gelatin, monomer or cross-linking agent concentrations but decreased with the increase of surfactant or initiator Concentration. The water adsorption rate of the microspheres was decreased with the increase of gelatin or cross-linking agent concentration but not affected by surfactant concentration. The elasticity of TGMs was increased with the increase of monomer or cross-linking agent concentration, decreased with the increase of gelatin concentration, but not affected by surfactant or initiator concentration. All factors above considered, the final prepared TGMs consisted of 10 g/L gelatin, 100.0 g/L monomer, 6.7 g/L cross-linking agent, 0.9 g/L surfactant, and 3.0 g/L initiator. The average diameter of TGMs obtained was about 700.0 microm. The water adsorption rate and the elasticity in accordance with the maximum diameter of the microspheres passed through a microcatheter of TGMs were 12.4 (g/g), and 1 600.0 microm, respectively. The results of IR spectra confirmed the polymerization of monomer, resulting in Nj[tris(hydroxymethyl)methyl]acrylamidegelatin microspheres. CONCLUSION: The developed TGMs seemed to be suitable for clinical embolization according to the surface, average diameter, elastic and hydrophilic property of TGMs.

Poly(acrylic acid) microspheres loaded with superparamagnetic iron oxide nanoparticles for transcatheter arterial embolization and MRI detectability: In vitro and in vivo evaluation.

To develop embolic microspheres with MRI detectability, superparamagnetic iron oxide nanoparticles (SPIONs) were synthesized and mixed with monomer of acrylic acid to prepare SPIONs-loaded polymerized microspheres (SPMs) by inverse suspension polymerization method. The SPMs were evaluated for the ability of embolization by investigating the morphology, particle size, elasticity and renal arterial embolization to rabbits. Meanwhile, the loading of SPIONs was verified by optical microscope, transmission electron microscope, Fourier transform infrared spectrum, vibrating sample magnetometer, X-ray diffraction and X-ray photoelectron spectroscopy, and the content of SPIONs in SPMs was measured quantitatively. Furthermore, the MRI detectability of SPMs was testified in gel phantom, mice and rabbits respectively by a clinical 3.0T MRI scanner. The results revealed the SPMs were potential MRI detectable embolic microspheres for improving the effectiveness and safety of embolotherapy in the future.