Biopolymeric delivery system for controlled release of polyphenolic antioxidants

A chitosan based delivery system has been developed for the controlled release of polyphenolic antioxidants such as catechin. Placebo and catechin entrapped particulate delivery systems were prepared using the sodium tripolyphosphate ionic crosslinking technique. The particles have been characterised by transmission electron microscopy, particle size and charge distribution analysis, Fourier Transform infrared spectroscopy, differential scanning calorimetry and entrapment efficiency studies. These studies gave an understanding of the physico-chemical interactions that influence the biopolymer during particle formation and entrapment of catechin. The in vitro release of catechin was carried out in enzyme-free simulated gastric and intestinal fluids. Although nanoparticles could be formed by the crosslinking technique used, there was aggregation behaviour observed after retrieval and freeze-drying of the particles as shown by transmission electron microscopy. Both the placebo and catechin-loaded particles had mean particle size range of about 4.27-6.29 μm after freeze-drying and were charged. Fourier Transform infrared spectroscopy, differential scanning calorimetry studies indicated minor structural interactions between catechin and chitosan matrix. Entrapment efficiency of the particles ranged between 27% and 40%. In vitro release studies indicated that the release of catechin in simulated gastric and intestinal fluids was between 15% and 40%, depending on the structural interactions between catechin and the chitosan matrix.     

Apparent shear strength of hybrid glass fibre reinforced composite joints

The incorporation of nano or micro ceramic particles into fibre reinforced composites (FRC) to enhance their stiffness and durability has been widely investigated. This mechanism has been attributed to the increase in stiffness of the polymeric matrix phase and shear strength of FRCs due to the presence of particles at the interlaminar regions. In order to elucidate such effect, hybrid single-lap joints consisted of ceramic particles and glass fibre reinforced composites were evaluated to better assess the mechanical interlocking effect provided by silica and cement inclusions. A full factorial design (2³) was performed to identify the effect of the type of particle (silica and cement), particle weight fraction (2.5 and 5 wt%) and glass fibre grammage (200 and 600 g/m²) on the apparent shear strength and adherent strength of single-lap joints under tensile loading. The ceramic particle inclusions led to increased apparent shear strength and adherent strength. The inclusion of 5 wt% ceramic particles into 600 g/m² cross-ply glass fibre composites enhanced both adherent and apparent shear strengths.     

Biodegradable in situ gel-forming controlled vancomycin delivery system based on a thermosensitive mPEG-PLCPPA hydrogel

In this study, a biodegradable in situ gel-forming controlled drug delivery system based on a thermosensitive methoxy polyethylene glycol-co-poly (lactic acid-co-aromatic anhydride) (mPEG-PLCPPA) hydrogel was studied. The hydrogels were formed by micelle aggregation with rising temperature. The hydrogels underwent a temperature-dependent sol–gel–sol transition, which was a flowing sol at ambient temperature and a non-flowing gel at the physiological body temperature. The residual weight and pH value changes after degradation and the viscosity properties of the hydrogel were investigated. The in vitro release behavior of vancomycin from the mPEG-PLCPPA hydrogels at different concentrations was also investigated. The results showed that the mPEG-PLCPPA amphiphilic copolymer could self-assemble to form micelles at low concentrations, and that the particle sizes gradually increased with increasing temperature. The hydrogel maintained a stable degradation rate and provided a moderate pH microenvironment after degradation for 30 days. Vancomycin sustained a stable release profile from the hydrogel over a 10-day period. Furthermore, good biocompatibility was proven by MTT assay and live and dead test. Therefore, the mPEG-PLCPPA hydrogel shows promise as an injectable local antibiotic delivery system.     

Interactions between mammalian cells and nano- or micro-sized wear particles: Physico-chemical views against biological approaches

Total joint arthroplasty (TJA) is a more and more frequent approach for the treatment of end-stage osteoarthritis in young and active adults; it successfully relieves joint pain and improves function significantly enhancing the health-related quality of life. Aseptic loosening and other wear-related complications are some of the most recurrent reasons for revision of TJA. This review focuses on current understanding of the biological reactions to prosthetic wear debris comparing in vivo and in vitro results. Mechanisms of interactions of various types of cells with metal, polymeric and ceramic wear particles are summarised. Alternative views based on multidisciplinary approaches are proposed to consider physico-chemical, surface parameters of wear particles (such as: particle size, geometry and charge) and material (particle chemical composition and its nature) with biological effects (cellular responses).     

Assemblies of poly(styrene/⇌-tert-butoxy-ω-vinyl-benzyl-poryglycidol) Microspheres with different diameters deposited on mica plates

Formation of poly(styrene/α-tert-butoxy-ω-vinyl-benzyl-polyglycidol) microsphere assemblies on mica plates modified with 3-aminopropyltriethoxysilane was investigated. Microsphere assemblies contained two types of particles similar with respect of their chemical structure but with different diameters (D _n = 1000 and 350 nm). Methods of particle deposition included: deposition from water suspension of a mixture of small and large particles on mica plates placed at the bottom of suspension container, deposition of particles from a drop of ethanol suspension (containing large and small microspheres) placed on the mica substrate, deposition of microspheres on modified mica plates crossing the liquid-air interface-sequential deposition of large and small particles, and one-batch deposition from a mixed water suspension of large and small microspheres. Deposition from water suspension containing large and small microspheres on plates placed on the bottom of suspension container yielded assemblies with large particles randomly distributed among the small ones. Fraction of large particles in adsorbed particle assembly was smaller than fraction of large particles in suspension. Particle assemblies prepared by placement of ethanol suspension of large and small microspheres on mica were composed of quite regularly distributed large particles among the small ones. A two step process consisting of withdrawal of mica plate from water suspension of large particles and then on using this plate as substrate in a second step during which the plate was withdrawn from suspension of small particles yielded particle assemblies containing aggregates of large particles randomly distributed among the small ones. Withdrawal of mica plates from water suspension of large and small microspheres resulted in particle assemblies composed of regularly distributed stripes of large and small microspheres. Formation of the described above microsphere assemblies is possible only in case of reversible adsorption of particles.     

Quinone-based molecular electrochemistry and their contributions to medicinal chemistry: A look at the present and future

Molecular electrochemistry is closely linked to life sciences. Electron transfers play important roles in the bioactivation of redox-active drugs, in their metabolism/catabolism, and in their targeted release at precise destinations and frequently promote their ligand–target interactions. Altogether, this rich chemistry and the complexity of cellular environments and biocompartmentation often impede full investigation in situ of the whole chain of processes that sustain their therapeutic applications. Conversely, electrochemical ex situ investigations of drug properties and interactions performed in aqueous/aprotic/micellar/membrane/cell-mimetic media, combined with in vitro and in vivo data, are expected to provide extremely useful information on these processes. Therein, considering the ubiquitous case of quinones, we exemplified how such strategies allow controlling their beneficial or negative impact on cellular environments.     

Effect of Electrode Pattern on the Column Structure and Yield Stress of Electrorheological Fluids

For electrorheological (ER) suspensions, the aggregate structures of particles were observed in electric fields by the use of transparent cells with different electrode patterns. Although the suspension is dispersed to noninteracting particles without electric fields, many aggregates are formed on the electrode surface in electric fields. Since the dipole–dipole interactions cause chain structures of particles and equilibrium conformations of chains are always aligned with electric field, the aggregates indicate the presence of columns spanning the electrode gap. The particle concentration in columns which are developed between parallel-plate electrodes is about 22 vol %. In striped electrodes, the particles construct striped aggregates along the electrodes and no particles remain in the insulating region. The particle concentration in striped aggregates is about 35 vol %. The nonuniformity of electric field is responsible for the high particle concentration. The increase in particle concentration of column lead to the high yield stress of electrified suspension. Therefore, the ER performance of suspension as an overall response can be improved by the electrode design.     

Particle Network Self-Assembly of Similar Size Sub-Micron Calcium Alginate and Polystyrene Particles Atop Glass

Particle-mediated self-assembly, such as nanocomposites, microstructure formation in materials, and core-shell coating of biological particles, offers precise control over the properties of biological materials for applications in drug delivery, tissue engineering, and biosensing. The assembly of similar-sized calcium alginate (CAG) and polystyrene sub-micron particles is studied in an aqueous sodium nitrate solution as a model for particle-mediated self-assembly of biological and synthetic mixed particle species. The objective is to reinforce biological matrices by incorporating synthetic particles to form hybrid particulate networks with tailored properties. By varying the ionic strength of the suspension, the authors alter the energy barriers for particle attachment to each other and to a glass substrate that result from colloidal surface forces. The particles do not show monotonic adsorption trend to glass with ionic strength. Hence, apart from DLVO theory—van der Waals and electrostatic interactions—the authors further consider solvation and bridging interactions in the analysis of the particulate adsorption-coagulation system. CAG particles, which support lower energy barriers to attachment relative to their counterpart polystyrene particles, accumulate as dense aggregates on the glass substrate. Polystyrene particles adsorb simultaneously as detached particles. At high electrolyte concentrations, where electrostatic repulsion is largely screened, the mixture of particles covers most of the glass substrate; the CAG particles form a continuous network throughout the glass substrate with pockets of polystyrene particles. The particulate structure is correlated with the adjustable energy barriers for particle attachment in the suspension.     

Innovative methodology for developing a bone grafting composite biomaterial starting from the seashell of Rapana thomasiana

Bone grafts are used in a wide array of clinical settings to augment bone repair and regeneration. This article reports a new method for the elaboration of a hybrid biomaterial in the form of sponge based on collagen gel, CaCO₃ from recycled Rapana thomasiana seashell, and Na₂HPO₄·2H₂O. Practically, collagen acts as a matrix through which calcium and phosphate ions are diffusing during in situ hydroxyapatite synthesis. The organic–inorganic interactions among biomaterial components have been studied by infrared spectroscopy, and the surface morphology was investigated by scanning electron microscopy technique. Moreover, the developed biomaterials were studied for in vitro biocompatibility with MG63 human osteoblasts. The results obtained demonstrated that the developed hybrid material does not exhibit a significant cytotoxicity and supports cell proliferation. Consequently, it holds great promise for applications in bone tissue engineering.     

Tunable magnetophoretic method for distinguishing and separating wear debris particles in an Fe-PDMS-based microfluidic chip

Wear debris analysis provides an early warning of mechanical transmission system aging and wear fault diagnosis, which has been widely used in machine health monitoring. The ability to detect and distinguish the ferromagnetic and nonmagnetic debris in oil is becoming an effective way to assess the health status of machinery. In this work, an Fe-poly(dimethylsiloxane) (PDMS)-based magnetophoretic method for the continuous separation of ferromagnetic iron particles by diameter and the isolation of ferromagnetic particles and nonmagnetic particles with similar diameter by type is developed. The particles experience magnetophoretic effects when passing through the vicinity of the Fe-PDMS where the strongest gradient of the magnetic fields exists. By choosing a relatively short distance between the magnet and the sidewall of the horizontal main channel and the length of Fe-PDMS with controlled particles flow rate, the diameter-dependent separation of ferromagnetic iron particles, that is, smaller than 7 µm, in the range of 8–12 µm, and larger than 14 µm, and the isolation of ferromagnetic iron particles and nonmagnetic aluminum particles based on opposite magnetophoretic behaviors by types are demonstrated, providing a potential method for the detection of wear debris particles with a high sensitivity and resolution and the diagnostic of mechanical system.     

Fluorescent probes for detection and bioimaging of leucine aminopeptidase

Leucine aminopeptidase (LAP) is one of important proteolytic enzymes and closely related with pathogenesis of cancer and liver injury. Determination of LAP activity in serum is used clinically for liver disorder diagnosis. The level of expressed LAP is very low in normal cells, but overexpressed in tumors and liver diseases, especially drug-induced hepatitis. LAP has become a predictive biomarker for many cancers and diverse physiological processes. Therefore, in situ dynamic monitoring and identifying intracellular LAP is imperative for LAP-related disease diagnosis. This review focuses on LAP-specific fluorescence imaging probes for the detection and tracking of intracellular LAP actively in vitro and in vivo. The progress suggests that fluorescence imaging is a vital and rapidly growing technology for early diagnosis of tumors.     

Degradation of electrospun SF/P(LLA-CL) blended nanofibrous scaffolds in vitro

Nanofibrous scaffolds of silk fibroin (SF) and poly(l-lactic acid-co-?-caprolactone) (P(LLA-CL)) blends fabricated via electrospinning possessed good mechanical property and biocompatibility, as demonstrated by a previous study in vitro. However, the degradation behavior of the scaffolds, which may significantly influence tissue repair and regeneration, needs further exploration. In this study, in vitro degradation of pure SF, P(LLA-CL) and SF/P(LLA-CL) blended nanofibrous scaffolds were performed in phosphate-buffered saline (PBS, pH 7.4 ± 0.1) at 37 °C for 6 months. A series of analyses and characterizations (including morphologic changes, loss weight, pH changes of PBS solutions, DSC, XRD and FTIR-ATR) were conducted to the nanofibrous scaffolds after degradation and the results showed that the pure SF nanofibrous scaffolds were not completely degradable in PBS while pure P(LLA-CL) nanofibrous scaffolds had the fastest degradation rate. Moreover, the addition of SF reduced the degradation rate of P(LLA-CL) in SF/P(LLA-CL) blended nanofibrous scaffolds. This was probably caused by the intermolecular interactions between SF and P(LLA-CL), which hindered the movement of P(LLA-CL) molecular chains.     

Waste marble dust-filled sustainable polymer composite selection using a multi-criteria decision-making technique

This research works with the optimal design of marble dust-filled polymer composites using a multi-criteria decision-making (MCDM) technique. Polylactic acid (PLA) and recycled polyethylene terephthalate (rPET)-based composites containing 0, 5, 10, and 20 wt% of marble dust were developed and evaluated for various physicomechanical and wear properties. The results showed that the incorporation of marble dust improved the modulus and hardness of both PLA and rPET. Moreover, a marginal improvement in flexural strength was noted while the tensile and impact strength of the matrices were deteriorating due to marble dust addition. The outcomes of wear analysis demonstrated an improvement in wear resistance up until 10 wt% filler reinforcement, after which the incidence of dust particles peeling off from the matrix was observed, thereby reducing its efficiency. The best tensile modulus of 3.23 GPa, flexural modulus of 4.39 GPa, and hardness of 83.95 Shore D were obtained for 20 wt% marble dust-filled PLA composites. The lowest density of 1.24 g/cc and the highest tensile strength of 57.94 MPa were recorded for neat PLA, while the highest impact strength of 30.94 kJ/m² was recorded for neat rPET. The lowest wear of 0.01 g was obtained for the rPET containing 5 wt% marble dust content. The experimental results revealed that for the examined criteria, the order of composite preference is not the same. Therefore, the optimal composite was identified by adopting a preference selection index-based MCDM technique. The findings demonstrated that the 10 wt% marble dust-filled PLA composite appears to be the best solution with favorable physical, mechanical, and wear properties.     

Oriented UHMW-PE/CNT composite tapes by a solution casting-drawing process using mixed-solvents

Ultra-high molecular weight polyethylene/multi-wall carbon nanotube (UHMW-PE/MWNT) composites have been prepared by a novel approach which involves the use of a mixture of solvents during the gelation process. By combining one of the best known organic solvents for nanotubes, N,N-dimethylformamide (DMF) with xylene and use this mixed-solvent in the gelation/crystallisation process for UHMW-PE/MWNT composite fabrication, an attempt is made to improve the dispersion of carbon nanotubes in UHMW-PE. The obtained films were drawn to obtain highly oriented tapes, which were characterized in terms of electrical and mechanical properties. The conductivity of the drawn tapes is maintained at 10⁻⁴ S/m at draw ratio 30, two orders of magnitude higher than the minimum level required to provide electrostatic discharge. Although the mechanical properties are compromised by use of DMF and MWNTs, the Young’s modulus still remains at 25 GPa, in comparison with 35 GPa for pure UHMW-PE tape at draw ratio 30.     

Excess molar volumes of the binary mixtures of polyethylene glycol 300 with ethoxyethanols at various temperatures

Densities at T = (293.15, 298.15, 303.15, 308.15, and 313.15) K in the binary liquid mixtures of polyethylene glycol 300 with 2-ethoxyethanol, 2-(2-ethoxyethoxy)ethanol, or 2-{2-(2-ethoxyethoxy)ethoxy}ethanol have been measured over the entire range of mixture compositions. These data have been used to compute the excess molar volumes. The excess molar volumes are negative over the entire range of composition for all studied mixtures. The results are discussed in terms of intermolecular interactions in the bulk binary mixtures.     

Development and evaluation of osteogenic PMMA bone cement composite incorporating curcumin for bone repairing

Acrylic resin (PMMA - polymethylmethacrylate) is a material widely used in orthopedics to fill gaps or cavities in the bone marrow, bone defects, and implants fixation. However, even if it possesses high mechanical strength and is considered bioinert, its use has various limitations related to the lack of positive additional bioactive effects, such as osteogenesis stimulation. This work reports a preliminary assessment of the effects of curcumin incorporated in PMMA bone cements at different concentrations (4, 5, 7.5, and 10 wt%), and in particular, its osteoinductivity and osteoconductivity in vitro, tested with KUSA-A1 cells. The different samples were characterized using a combination of microscopic and spectroscopic techniques before and after in vitro testing. Results showed that curcumin and PMMA can produce a homogeneous composite material in a wide range of concentrations, up to at least 10 wt%. By increasing the percentage of curcumin both cellular adhesion and bone production are improved, without sacrificing the quality of the bone tissue formed. Addition of curcumin over a threshold of about 5% results in a sudden loss of ultimate strength with an increase of the elongation to failure. Samples containing about 5% of curcumin proved to have good in vitro performances without compromising the mechanical properties. This suggests how curcumin can be considered as a low-cost additive useful not only for its well-known antimicrobial activity but also in the bone regeneration improving the bioactive properties of the PMMA.     

Diamond-like carbon films for polyethylene femoral parts: Raman and FT-IR spectroscopy before and after incubation in simulated body liquid

In artificial prosthetics for knee, hip, finger or shoulder joints, ultrahigh molecular weight polyethylene (UHMW-PE) is a significant material. Several attempts to reduce the wear rate of UHMW-PE, i.e. the application of suitable coatings, are in progress. A surface modification of polyethylene with wear-resistant hydrogenated diamond-like carbon is favourable, owing to the chemical similarity of polyethylene (–C–H₂–) _n and C:H or amorphous C:H (a–C:H) coatings with diamond-like properties. In the present study, the microstructure of a–C:H coatings on UHMW-PE substrates was investigated by Raman and Fourier transform infrared (FT-IR) spectroscopy. FT-IR spectroscopy shows very broad absorption lines, which point to the disorder and diversity of different symmetric, asymmetric aromatic, olefin sp ²-hybridized or sp ³-hybridized C–H groups in the amorphous diamond-like carbon coating. Following a long incubation of 12 months in a simulated body liquid, the structural investigations were repeated. Furthermore, fractured cross-sections and the wetting behaviour with polar liquids were examined. After incubation in simulated body liquid, Raman spectroscopy pointed to a reduction of the C–H bonds in the diamond-like carbon coatings. On the basis of these findings, one can conclude that hydrogenated diamond-like carbon is able to interact with salt solutions by substituting the hydrogen with appropriate ions.     

Speeds of sound,densities, isentropic compressibilities of the system (methanol + polyethylene glycol dimethyl ether 250) at temperatures from 293.15 to 333.15 K

In this work, our objective is to contribute to the knowledge of the mixtures (alcohol + polyalkyl ether glycol) used in absorption refrigeration systems and heat pumps. The determination of different thermophysical properties is essential to understand the interactions among different molecules in liquid mixtures. Therefore, experimental data of speed of sound and density together with calculated values of isentropic compressibility for the refrigerant-absorbent system (methanol + polyethylene glycol dimethyl ether 250) (or Pegdme 250) have been gathered here over the whole range of composition at temperatures from T=293.15 to 333.15 K and atmospheric pressure. The two previous experimental properties were measured with a digital vibrating tube analyser Anton Paar DSA-48. Also, the excess molar volumes and the increments of the speed of sound and the isentropic compressibility have been determined for each composition and they were fitted to a variable-degree polynomial equation.     

Experimental evidence of size effect in nano-reinforced polymers: Case of silica reinforced PMMA

This study aims at quantifying the nano-size effect in terms of elastic and thermal properties in nano-reinforced polymers. Nano-reinforced PMMA with 4% volume fraction of silica nanoparticles was prepared using particle diameters of 15 nm, 25 nm, 60 nm, 150 nm and 500 nm. Uniaxial tensile tests showed an increase in Young's modulus with decreasing particle diameter when the volume fraction was kept constant. This increase is the signature of the nano-size effect on the macroscopic mechanical properties. Conversely to mechanical properties, the presence of particles in the matrix induced a decrease in glass transition, possibly due to weak interactions between the matrix and silica nanoparticles.     

Engineering polyzwitterion with acylsulfonamide-based betaine structure for protonated switch of surface chemistry at tumoral pH and reductive responsive drug release of polymeric micelles

The surface chemistry of stimulus-responsive nanoparticles plays an important role in mediating nano-bio interactions in cancer nanomedicine by targeting the unique features of the tumor microenvironment, such as low extracellular pH. To develop therapeutic nanoparticles with high sensitivity and instant response to slight pH differences in the systemic circulation, we produced a novel polyzwitterion with acylsulfonamide-based betaine structure by one-step modification of polycarboxybetaine (PCB) with benzene sulfonamide. The zwitterionic micellar shells show high antifouling in the blood circulation and acutely convert into positive charge via acylsulfonamide protonation, thereby improving cell affinity at tumor sites. Moreover, a disulfide bond between the shell and poly-ε-caprolactone (PCL) core allows for reductive-responsive release of doxorubicin (DOX) after internalization of the polymeric micelles. Finally, in vitro and in vivo competition assays demonstrated that dual responsive drug-loaded micelles have better anticancer efficiency than free DOX or micelles without zwitterionic pH-responsive properties. Thus, we have developed a simple and valuable strategy to enhance pH sensitivity of micellar carriers for cancer treatment.