Development of Multinuclear Polymeric Nanoparticles as Robust Protein Nanocarriers

One limitation of current biodegradable polymeric nanoparticles is their inability to effectively encapsulate and sustainably release proteins while maintaining protein bioactivity. Here we report the engineering of PLGA–polycation nanoparticles with a core–shell structure that act as a robust vector for the encapsulation and delivery of proteins and peptides. The optimized nanoparticles can load high amounts of proteins (>20 % of nanoparticles by weight) in aqueous solution without organic solvents through electrostatic interactions by simple mixing, thereby forming nanospheres in seconds with diameters <200 nm. The relationship between nanosphere size, surface charge, PLGA–polycation composition, and protein loading is also investigated. The stable nanosphere complexes contain multiple PLGA–polycation nanoparticles, surrounded by large amounts of protein. This study highlights a novel strategy for the delivery of proteins and other relevant molecules.     

Thermal Degradation Kinetics and Modeling Study of Ultra High Molecular Weight Polyethylene (UHMWP)/Graphene Nanocomposite

The incorporation of nanofillers such as graphene into polymers has shown significant improvements in mechanical characteristics, thermal stability, and conductivity of resulting polymeric nanocomposites. To this aim, the influence of incorporation of graphene nanosheets into ultra-high molecular weight polyethylene (UHMWPE) on the thermal behavior and degradation kinetics of UHMWPE/graphene nanocomposites was investigated. Scanning electron microscopy (SEM) analysis revealed that graphene nanosheets were uniformly spread throughout the UHMWPE’s molecular chains. X-Ray Diffraction (XRD) data posited that the morphology of dispersed graphene sheets in UHMWPE was exfoliated. Non-isothermal differential scanning calorimetry (DSC) studies identified a more pronounced increase in melting temperatures and latent heat of fusions in nanocomposites compared to UHMWPE at lower concentrations of graphene. Thermogravimetric analysis (TGA) and derivative thermogravimetric (DTG) revealed that UHMWPE’s thermal stability has been improved via incorporating graphene nanosheets. Further, degradation kinetics of neat polymer and nanocomposites have been modeled using equations such as Friedman, Ozawa–Flynn–Wall (OFW), Kissinger, and Augis and Bennett’s. The "Model-Fitting Method” showed that the auto-catalytic nth-order mechanism provided a highly consistent and appropriate fit to describe the degradation mechanism of UHMWPE and its graphene nanocomposites. In addition, the calculated activation energy (E_a) of thermal degradation was enhanced by an increase in graphene concentration up to 2.1 wt.%, followed by a decrease in higher graphene content.     

Modified nanoporous silicas for oral delivery of the water insoluble organotin compound: loading and release of methylphenyltin dichloride as an anti-tumor drug model

Different nanoporous silica materials, MCM-41, MCM-48 and SBA-15, were modified by pyridine and their applications for oral drug delivery system were evaluated. These pyridine functionalized nanoporous silicas were loaded with a water insoluble diorganotin(IV) dichloride complex as an antitumor drug model and its release from them were investigated by changing pH. An efficient pH-responsive carrier system was constructed by coordination of the pyridine group in modified nonoporous materials to tin complex. In vitro, releasing of loaded tin complex was studied in three different kinds of fluids, including a simulated gastric medium and a simulated body fluid. The loading and releasing of the diorganotin(IV) dichloride from various modified nanoporous silicas and also a non-porous silica (SiO₂) were investigated, and the results were compared. In addition, the effect of some factors such as pH, time of loading and releasing were investigated through this study.     

The Role of Bi3+ in Promoting and Stabilizing Iron Oxo Clusters in Strong Acid

Metal oxo clusters and metal oxides assemble and precipitate from water in processes that depend on pH, temperature, and concentration. Other parameters that influence the structure, composition, and nuclearity of “molecular” and bulk metal oxides are poorly understood, and have thus not been exploited. Herein, we show that Bi³⁺ drives the formation of aqueous Fe³⁺ clusters, usurping the role of pH. We isolated and structurally characterized a Bi/Fe cluster, Fe₃BiO₂(CCl₃COO)₈(THF)(H₂O)₂, and demonstrated its conversion into an iron Keggin ion capped by six Bi³⁺ irons ( Bi₆Fe₁₃ ). The reaction pathway was documented by X‐ray scattering and mass spectrometry. Opposing the expected trend, increased cluster nuclearity required a pH decrease instead of a pH increase. We attribute this anomalous behavior of Bi/Fe(aq) solutions to Bi³⁺, which drives hydrolysis and condensation. Likewise, Bi³⁺ stabilizes metal oxo clusters and metal oxides in strongly acidic conditions, which is important in applications such as water oxidation for energy storage.     

Discrete Versions of Jensen–Fisher,Fisher and Bayes–Fisher Information Measures of Finite Mixture Distributions

In this work, we first consider the discrete version of Fisher information measure and then propose Jensen–Fisher information, to develop some associated results. Next, we consider Fisher information and Bayes–Fisher information measures for mixing parameter vector of a finite mixture probability mass function and establish some results. We provide some connections between these measures with some known informational measures such as chi-square divergence, Shannon entropy, Kullback–Leibler, Jeffreys and Jensen–Shannon divergences.     

Segmental relaxation and partial crystallization of chain‐extended Poly(l‐lactic acid) reinforced with carboxylated carbon nanotube

Temperature‐modulated differential scanning calorimetry (TMDSC) and broadband dielectric spectroscopy (BDS) were employed to study the glass transition, size of the cooperative rearranging regions (CRRs), crystallization kinetics, and dielectric relaxation response of nanocomposites constituted by chain‐extended poly(L‐lactide) (PLLA) and carboxylated carbon nanotubes (f‐CNTs). The CRR size and the number of relaxing structural units decreased in the presence of crystals during isothermal crystallization. All samples displayed both a primary (α) and secondary (β) relaxation in BDS spectra. The relaxation dynamics of PLLA chains was barely affected by the presence of the f‐CNT. Constrained polymer chains and thickness of interphase (t _i) were measured using dielectric spectra in tan δ representation. t _i values were found to be 46 and 24 nm for sample containing 0.2 and 0.5% weight fraction of f‐CNT, respectively. All samples underwent partial crystallization (with roughly 30% of final crystalline fraction) some 15 or 20° above their glass‐transition temperature (T _g). Crystallization leads to a fragile‐to‐strong transition in the temperature dependence of the cooperative α relaxation and to the increased visibility of a Maxwell–Wagner–Sillars (MWS) interfacial relaxation, which appears to be present in all samples. The heterogeneity of the polymeric samples was quantified in terms of a new parameter, the heterogeneity index (H). © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 222–233     

Soft lithography microfabrication of functionalized thermoplastics by solvent casting

A soft lithographic method is described for casting functional thermoplastic devices with microscale features without the need for specialized tools or equipment. In the thermoplastic soft lithography process, termed solvent casting, low temperature supersaturated solutions of thermoplastic are poured over solvent permeable PDMS molds which allow omnidirectional solvent removal as they template functional microstructures into the thermoplastic layers. Rapid gelation of supersaturated solutions enables the deposition of multiple patterned layers of varying composition, with self‐adhesion of the solvent‐laden thermoplastic ensuring intimate bonding between adjacent layers. This latter feature is further used in this work to realize sealed thermoplastic microfluidic devices with high fidelity replication of microchannel features with negligible channel deformation. The incorporation of functional dopants into patterned thermoplastic layers allows the fabrication of thermoplastic devices with embedded fluorescent sensors and integrated conductive elements. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1315–1323     

Microwave-Induced Solvent-free Synthesis of β-Keto Esters Using Montmorillonite KSF and K10 Clays as Efficient and Recyclable Heterogeneous Solid Acids

Montmorillonite KSF and K10 clays catalyzed effectively the reaction of methyl diazoacetate with various aldehydes using microwave irradiation under solvent-free conditions affording the corresponding β-keto esters in good yields and short reaction time. The present method is an improvement for the previous known synthetic methods and has many obvious advantages compared to them including the high efficiency, generality, high yields, operational simplicity, environmental benignity, and possibility of recycling the natural solid clays.     

Stereoselective synthesis of acetoacetate-derived enol triflates

A highly stereoselective method for preparing ( Z)- and ( E)-enol triflates derived from substituted acetoacetate derivatives is described. The salient feature of this methodology is the use of Schotten-Baumann-type conditions to control enolate geometry using either aqueous LiOH ( Z-selective) or aqueous (Me)(4)NOH ( E-selective) in combination with triflic anhydride to provide a practical and predictable approach to these valuable substrates.