Characterization and in vitro release studies of oral microbeads containing thiolated pectin–doxorubicin conjugates for colorectal cancer treatment

Novel oral microbeads were developed based on a biopolymer–drug conjugate of doxorubicin(DOX) conjugated with thiolated pectin via reducible disulfide bonds. The microbeads were fabricated by ionotropic gelation with cations such as Al3+, Ca2+ and Zn2+. The results showed that using zinc acetate can produce the strongest microbeads with spherical shape.However, the microbeads prepared from thiolated pectin–DOX conjugate were very soft and irregular in shape. To produce more spherical microbeads with suitable strength, the native pectin was then added to the formulations. The particle size of the microbeads ranged from 0.87 to 1.14 mm. The morphology of the microbeads was characterized by optical and scanning electron microscopy. DOX was still in crystalline form when used in preparing the microbeads, as confirmed by powder X-ray diffractometry. Drug release profiles showed that the microbeads containing thiolated pectin–DOX conjugate exhibited reduction-responsive character;in reducing environments, the thiolated pectin–DOX conjugate could uncouple resulting from a cleavage of the disulfide linkers and consequently release the DOX. The best-fit release kinetics of the microbeads containing thiolated pectin–DOX conjugate, in the medium without reducing agent, fit the Korsmeyer–Peppas model while those in the medium with reducing agent fit a zero-order release model. These results suggested that the microbeads containing thiolated pectin–DOX conjugate may be a promising platform for cancer-targeted delivery of DOX, exploiting the reducing environment typically found in tumors.

Mechanisms and characteristics of mesocarbon microbeads prepared by co-carbonization of coal tar pitch and direct coal liquefaction residue

DCLR-P was prepared by direct coal liquefaction residue (DCLR) with ash removal.In the present experiments,mesocarbon microbeads (MCMBs) were prepared by co-carbonization of coal tar pitch (CTP) and DCLR-P.With the increase of DCLR-P content,the yield of MCMBs increased from 47.8% to 56.8%.At the same time,the particle sizes distribution of MCMBs was narrowed,resulting in the decrease of D9o/D10 ratio from 154.88 to 6.53.The results showed that DCLR-P had a positive effect on the preparation of MCMBs.1H-NMR,FTIR,SEM and XRD were used to analyze the mechanisms and characteristics of MCMBs prepared by co-carbonization of CTP and DCLR-P.The results showed that the Proton Donor Quality Index (PDQI) of DCLR-P was 13.32,significantly higher than that of CTP (0.83).This indicated that DCLR-P had more naphthenic structure than CTP,which leads to hydrogen transferring in polycondensation reaction.The aliphatic structure of DCLR-P can improve the solubility and fusibility of mesophase,thereby making the structure of MCMBs more structured.The microstructure of the graphitized MCMBs had a substantially parallel carbon layer useful for its electrical performance.The performance of graphitized MCMBs as a negative electrode material for Li-ion batteries was tested.The particle sizes,tap density,specific surface area and initial charge-discharge efficiency of graphitized MCMBs met the requirements of CMB-I in GB/T-24533-2009.However,the initial discharge capacity of graphitized MCMB was only 296.3 mA h g-1 due to the low degree of graphitization of MCMBs.

Upconversion Nanoparticles-Encoded Hydrogel Microbeads-Based Multiplexed Protein Detection

Fluorescently encoded microbeads are in demand for multiplexed applications in different fields.Compared to organic dye-based commercially available Luminex's x MAP technology, upconversion nanoparticles(UCNPs) are better alternatives due to their large antiStokes shift, photostability, nil background, and single wavelength excitation. Here, we developed a new multiplexed detection system using UCNPs for encoding poly(ethylene glycol) diacrylate(PEGDA) microbeads as well as for labeling reporter antibody. However, to prepare UCNPs-encoded microbeads, currently used swellingbased encapsulation leads to non-uniformity, which is undesirable for fluorescence-based multiplexing. Hence,we utilized droplet microfluidics to obtain encoded microbeads of uniform size, shape, and UCNPs distribution inside. Additionally, PEGDA microbeads lack functionality for probe antibodies conjugation on their surface.Methods to functionalize the surface of PEGDA microbeads(acrylic acid incorporation, polydopamine coating)reported thus far quench the fluorescence of UCNPs. Here,PEGDA microbeads surface was coated with silica followed by carboxyl modification without compromising the fluorescence intensity of UCNPs. In this study, droplet microfluidics-assisted UCNPs-encoded microbeads of uniform shape, size, and fluorescence were prepared.Multiple color codes were generated by mixing UCNPs emitting red and green colors at different ratios prior to encapsulation. UCNPs emitting blue color were used to label the reporter antibody. Probe antibodies were covalently immobilized on red UCNPs-encoded microbeads for specific capture of human serum albumin(HSA) as a model protein. The system was also demonstrated for multiplexed detection of both human C-reactive protein(hCRP) and HSA protein by immobilizing anti-h CRP antibodies on green UCNPs.

Bimetallic NiCo2S4 Nanoneedles Anchored on Mesocarbon Microbeads as Advanced Electrodes for Asymmetric Supercapacitors

Bimetallic Ni–Co sulfides are outstanding pseudocapacitive materials with high electrochemical activity and excellent energy storage performance as electrodes for high-performance supercapacitors.In this study,a novel urchin-like NiCo2S4@mesocarbon microbead(NCS@MCMB) composite with a core–shell structure was prepared by a facile two-step hydrothermal method.The highly conductive MCMBs offered abundant adsorption sites for the growth of NCS nanoneedles,which allowed each nanoneedle to fully unfold without aggregation,resulting in improved NCS utilization and efficient electron/ion transferin the electrolyte.When applied as an electrode material for supercapacitors,the composite exhibited a maximum specific capacitance of 936 Fg-1 at 1 Ag-1 and a capacitance retention of 94% after 3000 cycles at 5 Ag-1,because of the synergistic effect of MCMB and NCS.Moreover,we fabricated an asymmetric supercapacitor based on the NCS@MCMB composite,which exhibited enlarged voltage windows and could power a light-emitting diode device for several minutes,further demonstrating the exceptional electrochemical performance of the NCS@MCMB composite.

Synthesis and Photocatalytic Activity of Fe-doped TiO_2 Supported on Hollow Glass Microbeads

In this paper, Fe-doped TiO_2 photocatalyst supported on hollow glass microbeads(Fe-TiO_2 /beads)is prepared by dip-coating method, which uses hollow glass microbeads as the carriers and tetrabutylorthotitanate [Ti(OC_4H_9)_4] as the raw material. The phase structure, ingredient, morphologies, particle size and shell thickness of the products are characterized by X-ray powder diffraction(XRD), energy-dispersive spectroscopy(EDS) and field emission scanning electron microscope(FESEM). The feasibility of photocatylic degradation of Rhodamine B(Rh B) under illumination of UV-vis light is studied. The results show that the core-shell structure catalyst is composed of Fe-doped anatase TiO_2 and hollow glass microbeads, and the catalytic activity of the TiO_2 is markedly enhanced by Fe ion doping. The optimum concentration of Fe ion is 0.1%(molecular fraction) in the precursor and the photocatalytic activity can be increased to 98% compared with that of the undoped one. The presence of ferrum elements neither influences the transformation of anatase to rutile, nor creates new crystal phases. The possible mechanism of photocatalytic oxidation is also discussed.

OPTICALLY TRACKING THE MOTION OF MICROBEADS TO STUDY PHYSICAL BEHAVIORS OF THE LIVING CELL IN RESPONSE TO TRANSIENT STRETCH OR COMPRESSION

Optical magnetic twisting cytometry and traction force microscopy are two advanced cell mechanics research tools that employ optical methods to track the motion of microbeads that are either bound to the surface or embedded in the substrate underneath the cell.The former measures rheological properties of the cell such as cell stiffness,and the latter measures cell traction force dynamics.Here we describe the principles of these two cell mechanics research tools and an example of using them to study physical behaviors of the living cell in response to transient stretch or compression.We demonstrate that,when subjected to a stretch
unstretch manipulation,both the stiffness and traction force of adherent cells promptly reduced,and then gradually recover up to the level prior to the stretch.Immunofluorescent staining and Western blotting results indicate that the actin cytoskeleton of the cells underwent a corresponding disruption and reassembly process almost in step with the changes of cell mechanics.Interestingly,when subjected to compression,the cells did not show such particular behaviors.Taken together,we conclude that adherent cells are very sensitive to the transient stretch but not transient compression,and the stretch-induced cell response is due to the dynamics of actin polymerization.

Preparation of Cibacron Blue F3GA Bonded Poly (styrenedivinylbenzene) (PSDVB) Microbeads Used for High Performance Affinity Chromatography

Rigid PSDVB microbeads have been modified with poly(vinyl alcohol) (PVA) adsorbed on their surface to produce an affinity medium. Then Cibacron Blue F3GA was covalently attached to the supports. The initial concentration of PVA has effect on the adsorption of PVA. The non-specific interaction of bovine serum albumin (BSA) on the microbeads decreases with the PVA adsorbed. The pH stability test shows that the affinity medium is stable up to pH 11.0. And it has specific interaction with lysozyme, but not with pepsin.

Hydrogen Bonding-Assisted Synthesis of Silica/Oxidized Mesocarbon Microbeads Encapsulated in Amorphous Carbon as Stable Anode for Optimized/Enhanced Lithium Storage

The practical application of silica-based composites as an alternative to commercial graphite anode materials is hampered by their large volumetric expansion,poor conductivity,and low Coulombic efficiency.In this work,a novel silica/oxidized mesocarbon microbead/amorphous carbon(SiO2/O’MCMB/C)hierarchical structure in which SiO2 is sandwiched between spherical graphite and amorphous carbon shell was succes sfully fabricated through hydrogen bonding-assisted self-assembly and post-carbon coating method.The obtained three-layer hierarchical structure effectively accommodates the volumetric expansion of SiO2 and significantly enhances the electronic conductivity of composite materials.Moreover,the outer layer of amorphous carbon effectively increases the diffusion rate of lithium ions and promotes the formation of stable SEI film.As a result,the SiO2/O’MCMB/C composite exhibits superior electrochemical performance with a reversible capacity of 459.5 mA h/g in the first cycle,and the corresponding Coulombic efficiency is 62.8%.After 300 cycles,the capacity climbs to around 600 mA h/g.This synthetic route provides an efficient method for preparing SiO2 supported on graphite with excellent electrochemical performance,which is likely to promote its commercial applications.

Formation of mesophase microbeads from bulk mesophase pitch induced by fullerene

A transformation of naphthalene-based coalescenced mesophase pitch(NMP)to mesophase microbeads was achieved by heating a mixture of NMP and fullerene(C_(60)).This is different from the conventional process of the liquid-phase carbonization of isotropic pitch to the emergence of carbon microbeads in the matrix and finally their growth to form a 100%anisotropic bulk meso-phase,but rather a reverse transformation.The effects of C_(60) loading and reaction temperature on the morphological transformation of mesophase were investigated by polarizing optical and scanning electron microscopies.The physical changes in the NMP induced by C_(60) were characterized by thermogravimetric analysis,Fourier transform infrared spectroscopy,X-ray diffractometry and Raman spectroscopy.The results show that the coalesced NMP can be converted to a spherical type at 300-320℃ with the addition of 5%C_(60),and the size of the mesophase microbeads increases with increasing temperature.Furthermore,a model is established to ex-plain the unique induction effect of C_(60) in the transformation process.This work makes the morphological transformation of MP con-trollable,and provides a new idea for the understanding and research of mesophase pitch.

3D-printed Mechanically Strong Calcium Phosphate Cement Scaffold with Metformin/Stem Cell-encapsulating Alginate Microbeads for Bone Tissue Engineering

The utilization of Calcium Phosphate Cement(CPC)is limited due to its low mechanical strength and difficulty to seed cells deep into the scaffold.The objectives of this study were to:(1)develop a 3D-printed CPC-dopamine-metformin scaffold encapsulating human periodontal ligament stem cells(hPDLSCs),(2)investigate the effect of dopamine on the performance of CPC,and(3)evaluate the effect of microbead degradation and metformin release on the osteogenic differentiation of the released hPDLSCs.The mechanical property of the CPC scaffolds was elevated by adding dopamine,and the CPC scaffold with 7 wt.%dopamine had the highest compressive strength(7.35 MPa).Four types of microbeads with different content of alginate(oxidized alginate),hPDLSCs,and 2%metformin were fabricated.Morphological and cell counting kit tests confirm that the hPDLSCs are protected by microbeads encapsulation during the CPC setting process.The alkaline phosphatase test indicates that the osteogenic differentiation of hPDLSCs was enhanced by the fast release of cells and metformin.The microbeads consisting of 2%oxidized alginate and 2%metformin were optimal for cell delivery due to favorable cell release and osteogenic differentiation.This CPC scaffold is promising used for bone regeneration in dental,craniofacial,and orthopedic applications.

Improvement of Immunoassay Detection Sensitivity by Using Well-Defined Raspberry-Like Magnetic Microbeads as Carriers

Well-defined raspberry-like magnetic microbeads(RMMBs) as immunoassay solid carriers were prepared by chemical covalent binding between Fe3O4 magnetic microspheres and SiO2 nanoparticles. These RMMBs were not as agglomerative as nano-sized magnetie particles(< 200 nm), which was an advangtage for high efficient magnetic separation. When compared to Fe3O4@SiO2core-shell magnetic microbeads(CMMBs) with smooth surface, RMMBs exhibited stronger capacity to bind biomolecules. Limit of blank(LoB) and limit of detection(LoD) of HBsAg detection using RMMBs as carriers via chemiluminiscence immunoassay(CLIA) were 0.472 and1.022 μg/L, respectively, showing a notable improvement compared with CMMBs whose LoB and LoD were 1.017 and 1.988 μg/L, respectively. All these indicated a great potential of RMMBs in immunoassay application.

Photocatalytic decomposition of oil films floating on water using TiO_2 supported on hollow glass microbeads by sunlight

The feasibility of photocatalytic decomposition of oil films floating on water using TiO2 supported on hollow glass microbeads was studied.The results showed that 100% of ethylbenzene and 78% of dodecane can be photocatalytically removed after 8 h illumination with sunlight.The TiO2 supported on the hollow glass microbeads was not easily detached from the beads.After 150 h illumination there was no significant loss of the photocatalytic activity of TiO2 Some intermediate products of photocatalytic decomposition of dodecane were detected.

Photocatalytic reduction of dichromate by titanium dioxide supported on hollow glass microbeads

The photocatalytic reduction of dichromate using TiO2/beads as a photocatalyst was studied. The results showed hat 3.8 × 104 mol/dm3 of dichromate can be completely reduced into Cr3+ after illumination far 35 min with a 375 W medium pressure mercury lamp. The effects of factors such as the amount of TiO2/beads, initial concentration of dichromate, initial pH, nitrogen and oxygen atmosphere, and concentration of Fe3+ on the photocatalytic reduction of dichromate were investigated. A possible mechanism of the photocatalytic reaction was proposed. After illumination for 200 h, no significant loss of photocatalytic activity of TiO2/beads was observed.

Selective potassium uptake via biocompatible zeolite–polymer hybrid microbeads as promising binders for hyperkalemia

Patients with chronic kidney disease are at high risk of hyperkalemia that is associated with various lifethreatening complications.Treatments primarily rely on orally administered potassium binding agents,along with low curative effects and various side effects.Herein,direct serum potassium uptake was realized via zeolite–heparin-mimicking-polymer hybrid microbeads.The preparation process involved the synthesis of the heparin-mimicking polymer via the in situ cross-linking polymerization of acrylic acid and N-vinylpyrrolidone in polyethersulfone solution,the fabrication of microbeads via zeolite-mixing,electro-spraying and phase-inversion,and the subsequent aqueous-phase modifications based on ion-exchange and metal-leaching.An ultra-high(about 88%)amount of zeolite could be incorporated and well locked inside the polymer matrix.Potassium uptake capability was verified in water,normal saline and human serum,showing high selectivity and fast adsorption.The microbeads exhibited satisfying blood compatibility,negligible hemolysis ratio,prolonged clotting time,inhibited contact activation,and enhanced antifouling property toward serum proteins and cells.The proposed approach toward zeolite–heparin-mimicking-polymer hybrid microbeads provided a cheap,efficient and safe treatment protocol of hyperkalemia for the high-risk patients.

Adsorption Study of Methane on Activated Meso-carbon Microbeads by Density Functional Theory

A combined method of density functional theory (DFT) and statistics integral equation (SIE) for the determina-tion of the pore size distribution (PSD) is developed based on the experimental adsorption data of nitrogen on acti-vated mesocarbon microbead (AMCMB) at 77 K. The pores of AMCMB are described as slit-shaped with PSD. Based on the PSD, methane adsorption and phase behavior are studied by the DFT method. Both nitrogen and methane molecules are modeled as Lennard-Jones spherical molecules, and the well-known Steeles 10-4-3 poten-tial is used to represent the interaction between the fluid molecule and the solid wall. In order to test the combined method and the PSD model, the Intelligent Gravimetric Analyzer (IGA-003) was used to measure the adsorption of methane on the AMCMB. The DFT results are in good agreement with the experimental data. Based on these facts, we predict the adsorption amount of methane, which can reach 32.3 w at 299 K and 4 MPa. The results indicate that the AMCMBs are a good candidate for adsorptive storage of methane and natural gas. In addition, the capillary condensation and hysteresis phenomenon of methane are also observed at 74.05 K.

Curcumin encapsulated dual cross linked sodium alginate/montmorillonite polymeric composite beads for controlled drug delivery

The aim of the present work is fabrication of dual cross linked sodium alginate(SA)/montmorillonite(MMT) microbeads as a potential drug vehicle for extended release of curcumin(CUR). The microbeads were prepared using in situ ion-exchange followed by simple ionotropic gelation technique. The developed beads were characterized by Fourier transform infrared spectroscopy(FTIR), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), X-ray diffraction(X-RD) and scanning electron microscopy(SEM). The effect of MMT on encapsulation efficiency of CUR and intercalation kinetics was investigated. Dynamic swelling study and in vitro release study were investigated in simulated intestinal fluid(pH 7.4) and simulated gastric fluid(pH 1.2) at 37 ℃. Results suggested that both the swelling and in vitro release studies were influenced by the pH of test media, which might be suitable for intestinal drug delivery. The release mechanism was analyzed by fitting the release data into KorsmeyerPeppas equation.

TiO_2/beads as a photocatalyst for the degradation of X_(3B) azo dye

The feasibility of photocatalytic degradation of X 3B azo dye by TiO 2/beads photocatalyst was studied. The effects of parameters such as the amount of TiO 2/beads, airflow, as well as the concentrations of H 2O 2, Fe 3+ , Mg 2+ and Na + on the photocatalytic degradation of X 3B azo dye were also studied. The results showed that 25 mg/dm 3 X 3B azo dye can be photocatalytically degraded completely by 30 min illumination with a 375W medium pressure mercury lamp. Adding a small amount of H 2O 2 or Fe 3+ , the efficiencies of photocatalytic degradation of X 3B azo dye were increased rapidly. The mechanisms of the reaction and the role of the additives were also investigated. After 120 hours TiO 2/beads showed no significant loss of the photocatalytic activity.

Chitosan Sub-micron Particles Prepared Using Sulfate Ion Salt as Bacteriostatic Materials in Neutral pH Condition

In this paper, the newly developed ion exchange phase separation method to create chitosan sub-micron particles is introduced: 1) chitosan was dissolved in a lactic acid aqueous solution. 2) the obtained chitosan solution was added stepwise in a sodium sulfate aqueous solution and cooled down to 5℃ to become slightly turbid through agglutination. 3) desalinating and deacidifying of the mixture was carried out by a dialyzing tube method. IR spectroscopy and elemental analysis indicated that the agglutination of chitosan was induced by crosslinking effect with an electrostatic interaction between sulfate anions and amino groups in the glucosamine unit although large excess of Na2SO4 caused undesirable further agglutination of the resultant chitosan particles. As a result, the proper amount of Na2SO4 was approximately 1.0 - 10.0 equivalent for the amino group to create the chitosan particles with a sub-micron size. In addition, we investigated an antibacterial activity test for Escherichia coli of the obtained chitosan particles. The significant antibacterial activity was observed in incubation even at neutral pH condition while the chitosan microbeads (size: ca 200 ∫m) prepared by the conventional method and chitosan granules (size: ca 600 ∫m) as starting materials showed almost no antibacterial activity in the same condition.

Design and in vitro evaluation of controlled release alginate beads of diltiazem hydrochloride

Objective:Oral slow and sustained release drug delivery system can release their drug content with a controlled manner,producing a desirable blood serum level,reduction in drug toxicity and improving the patient compliance by prolonging dosing intervals.The major drawback of orally administered drug like diltiazem as a calcium channel blocker for the treatment of angina pectoris,arrhythmia and hypertension.Its has higher aqueous solubility and shorter elimination half-life.Methods:To overcome these drawbacks associated with diltiazem,an attempt has been made to develop a sustained release dosage form of diltiazem embedded alginate microbeads by ionotropic gelation technique employing various concentrations of polymer and keeping the drug concentration constant.Results:The beads were characterized for its particle size,drug content and in vitro release studies. The results revealed that the surface adhering drug was found to release immediately and a steady state of release was obtained up to 12 h from all the batches.The results indicated there was an inverse relationship between the concentration of alginate and drug release.The drug release was found to follow non-fickian diffusion obeying first order kinetics.Conclusion:The developed alginate microbeads offered a sustained release of diltiazem. Hence,the formulated microbeads were found to be potential,cost effective,possess satisfactory in vitro release studies.

Comparative Study on Super Fine Mesophase Powder and MCMB Used to Manufacture High-Density Isotropic Carbon Bulks

Mesocarbon microbeads （MCMB） and super fine mesophase powder （SFMP） were prepared firstly from a coal tar pitch and then hot-condensed into high-density isotropic carbon （HDIC） bulks under 160 MPa and finally sintered at 1 000 ℃. By analyzing the thermogravimetric behavior of the MCMB and SFMP powders, their volume shrinkage and weight loss during sintering and the bulk density and flexural strengths of their sintered bulks, it was found that the smaller sizes and the richer β-resin contents of SFMP ha）re facilitated formation of sintered bulks with more compact isotropic structure and higher flexural strengths than MCMB. Because of the filling and bonding effects of SFMP on MCMB bulks, addition of SFMP, albeit a little, can greatly increase the flexural strengths of sintered bulks of MCMB. However, adding MCMB, even a slight amount, into SFMP can severely impair the flexural strength of sintered bulks. This might be attributed to both the crack initiation along the boundaries between MCMB and SFMP and the formation of layered texture of MCMB sphere.