Microspheres made of poly(epsilon-caprolactone)-based amphiphilic copolymers: potential in sustained delivery of proteins

Microspheres of amphiphilic multi-block poly(ester-ether)s (PEE)s and poly(ester-ether-amide)s (PEEA)s based on poly(epsilon-caprolactone) (PCL) were investigated as delivery systems for proteins. The interest was mainly focused on the effect of their molecular structure and composition on the overall properties of the microspheres, encapsulating bovine serum albumin (BSA) as a model protein. PEEs and PEEAs were prepared using a alpha,omega-dihydroxy-terminated PCL macromer (Mn= 2.0 kDa) as a hydrophobic component. Hydrophilic oxyethylene sequences were generated using poly(ethylene oxide)s (PEO)s of different molecular mass (Mn= 300-600 Da) in the case of PEEs, or 4,7,10-trioxa-1,13-tridecanediamine (Trioxy) and PEO150 (Mn= 150 Da) in the case of PEEAs. The copolymers showed a decrease of Tm and crystallinity values as compared with PCL. Within each class of copolymers, the bulk hydrophilicity increased with increasing the number of oxyethylene groups in the chain repeat unit. PEEAs were more hydrophilic than PEEs with a similar number of oxyethylene groups. Discrete spherical particles were prepared by both PEEs and PEEAs and their BSA encapsulation efficiency related to copolymer properties. Interestingly, the insertion of short hydrophilic segments is enough to significantly affect protein distribution inside microspheres and its release profiles, as compared to PCL microspheres. Different degradation rates and mechanisms were observed for copolymer microspheres, mainly depending on the distribution of oxyethylene units along the chain. The results highlight that a fine control over the structural parameters of amphiphilic PCL-based multi-block copolymers is a key factor for their application in the field of protein delivery.     

Ocimum campechianum Mill. from Amazonian Ecuador: Chemical Composition and Biological Activities of Extracts and Their Main Constituents (Eugenol and Rosmarinic Acid)

The essential oil (EO), the methanolic (MeOH), and the 70% ethanolic (70% EtOH) extracts obtained from the aerial parts of Ocimum campechianum Mill. (Ecuador) were chemically characterized through gas-chromatography coupled to mass spectrometry detector (GC-MS), high-performance liquid chromatography coupled to diode array-mass spectrometry detectors (HPLC-DAD-MS) and studied for their in vitro biological activity. The radical scavenger activity, performed by spectrophotometric 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays, highlighted significant IC₅₀ values for the EO, extracts and their main constituents (eugenol and rosmarinic acid). EO (and eugenol) showed noteworthy activity against Pseudomonas syringae pv. syringae and a moderate effect against clinical Candida strains, with possible synergism in association to fluconazole against the latter microorganisms. The extracts and pure molecules exhibited weak cytotoxic activity against the HaCat cell line and no mutagenicity against Salmonella typhimurium TA98 and TA100 strains, giving indication of safety. Instead, EO showed a weak activity against adenocarcinomic human alveolar basal epithelial cells (A549). The above-mentioned evidence leads us to suggest a potential use of the crude drug, extracts, and EO in cosmetic formulation and food supplements as antioxidant agents. In addition, EO may also have a possible application in plant protection and anti-Candida formulations.     

Time-invariant portfolio strategies in structured products with guaranteed minimum equity exposure

We introduce a new exotic option to be used within structured products to address a key disadvantage of standard time-invariant portfolio protection: the well-known cash-lock risk. Our approach suggests enriching the framework by including a threshold in the allocation mechanism so that a guaranteed minimum equity exposure (GMEE) is ensured at any point in time. To be able to offer such a solution still with hard capital protection, we apply an option-based structure with a dynamic allocation logic as underlying. We provide an in-depth analysis of the prices of such new exotic options, assuming a Heston–Vasicek-type financial market model, and compare our results with other options used within structured products. Our approach represents an interesting alternative for investors aiming at downsizing protection via time-invariant portfolio protection strategies, meanwhile being also afraid to experience a cash-lock event triggered by market turmoils.     

Structural Determination and Chemical Synthesis of the N-Glycan from the Hyperthermophilic Archaeon Thermococcus kodakarensis

Asparagine-linked protein glycosylations (N-glycosylations) are one of the most abundant post-translational modifications and are essential for various biological phenomena. Herein, we describe the isolation, structural determination, and chemical synthesis of the N-glycan from the hyperthermophilic archaeon Thermococcus kodakarensis. The N-glycan from the organism possesses a unique structure including myo-inositol, which has not been found in previously characterized N-glycans. In this structure, myo-inositol is highly glycosylated and linked with a disaccharide unit through a phosphodiester. The straightforward synthesis of this glycan was accomplished through diastereoselective phosphorylation and phosphodiester construction by S_N2 coupling. Considering the early divergence of hyperthermophilic organisms in evolution, this study can be expected to open the door to approaching the primitive function of glycan modification at the molecular level.     

Dittrichia graveolens (L.) Greuter,a Rapidly Spreading Invasive Plant: Chemistry and Bioactivity

Dittrichia graveolens L. Greuter belonging to the Asteraceae family, is an aromatic herbaceous plant native to the Mediterranean region. This plant species has been extensively studied for its biological activities, including antioxidant, antitumor, antimicrobial, antifungal, anti-inflammatory, anticholinesterase, and antityrosinase, and for its peculiar metabolic profile. In particular, bioactivities are related to terpenes and flavonoids metabolites, such as borneol (40), tomentosin (189), inuviscolide (204). However, D. graveolens is also well known for causing health problems both in animals and humans. Moreover, the species is currently undergoing a dramatic northward expansion of its native range related to climate change, now including North Europe, California, and Australia. This review represents an updated overview of the 52 literature papers published in Scopus and PubMed dealing with expansion, chemistry (262 different compounds), pharmacological effects, and toxicology of D. graveolens up to October 2021. The review is intended to boost further studies to determine the molecular pathways involved in the observed activities, bioavailability, and clinical studies to explore new potential applications.     

Assessment of immobilized PGA orientation via the LC-MS analysis of tryptic digests of the wild type and its 3K-PGA mutant assists in the rational design of a high-performance biocatalyst

The mutant penicillin G acylase (PGA) 3K-PGA contains three additional Lys residues on the surface opposite the active site. This protein was designed to selectively drive its immobilization on aldehyde supports. We describe here a modified bottom-up proteomic method to assess the orientation of the immobilized wild-type and mutant proteins to verify our hypothesis of a driven immobilization induced by the mutations introduced. Tryptic digestion of the immobilized enzymes followed by liquid chromatography–tandem mass spectrometry (LC-MS/MS) analysis of released peptides was performed. This protocol generated peptides from the most accessible surface areas of the immobilized protein, thus not directly bound to the solid support, providing direct evidence of the areas involved in the linkage to the solid matrix. The results obtained suggest that 72 % of the wild-type PGA is immobilized on aldehyde agarose mainly through the Lys residues on the same side of the active site, whereas 3K-PGA reacted with the same support preferentially through the additional Lys residues introduced by mutation on the opposite side. This demonstrates that the active site of the 3K-PGA faces mostly (63 %) toward the reaction medium, resulting in significantly improved accessibility to the substrates. This finding is supported by the catalytic properties of the immobilized biocatalysts. The two immobilized preparations were tested in the synthesis of mandelyl-7-aminocephalosporanic acid (mandelyl-7-ACA) by N-acylation of the β-lactam nucleus (7-aminocephalosporanic acid) with mandelic acid methyl ester: upon immobilization, the synthetic properties of wild-type PGA strongly decreased, whereas those of 3K-PGA were unaffected. Furthermore, the activity of 3K-PGA was not influenced by the physicochemical nature of the support used for immobilization (glyoxyl agarose or aldehyde Sepabeads) unlike that of wild-type PGA, whose active site is close to the matrix. The results obtained from the analytical characterization correlate well with those obtained by investigation of the synthetic properties of the immobilized enzymes both in the synthesis of mandelyl-7-ACA and in the preparative synthesis of cefazolin. This work highlights the effect exerted by site-directed mutagenesis on the orientation of PGA upon immobilization on solid matrices and suggests how protein engineering tools can be exploited in a synergistic fashion to rationally develop efficient biocatalysts.

Confined flow of polymer blends

The influence of confinement on the steady-state morphology of two different emulsions is investigated. The blends, made from polybutene (PB) in polydimethylsiloxane (PDMS) and polybutadiene (PBD) in PDMS, are sheared between two parallel plates, mostly with a standard gap spacing of 40 microm, in the range of shear rates at which the transition from "bulk" behavior toward "confined" behavior is observed. For both cases, the influence of the concentration was systematically investigated, as well as the shear rate effects on the final steady-state morphology. By decreasing the shear rate, for each blend, the increasing droplets, i.e., increasing confinement for a fixed gap spacing, arrange themselves first into two layers, and when the degree of confinement reaches an even higher value, a single layer of droplets is formed. The ratio between the drop diameters and the gap spacing at which this transition occurs is always lower than 0.5. While decreasing the shear rate, the degree of confinement increases due to drop coalescence. Droplets arrange themselves in superstructures like ordered pearl necklaces and, at the lower shear rates, strings. The aspect ratio and the width of the droplet obtained from optical micrographs are compared to predictions of the single droplet Maffettone-Minale model (MM model(1)). It is found that the theory, meant for unconfined shear flow, is not able to predict the drop deformation when the degree of confinement is above a critical value that depends on the blends considered and the shear rate applied. A recently developed extension of the MM model is reported by Minale (M model(2)) where the effect of the confinement is included by using the Shapira-Haber correction.3 Further extending this M model, by incorporating an effective viscosity as originally proposed by Choi and Showalter,4 we arrive at the mM model that accurately describes the experiments of blends in confined flow.     

Transient interfacial tension of partially miscible polymers

The interfacial tension of three different binary polymer blends has been measured as function of time by means of a pendent drop apparatus, at temperatures ranging from 24 degrees C to 80 degrees C. Three grades of polybutene (PB), differing in average molecular weight and polydispersity, are used as dispersed phase, the continuous phase is kept polydimethylsiloxane (PDMS), ensuring different asymmetry in molecular weight across the interface. The interfacial tension changes with time and, therefore, this polymer blends can not be considered fully immiscible. Changes in interfacial tension are attributed to the migration of low-molecular weight components from the source phase into the interphase and, from there, into the receiving phase. In the early stages of the experiments, just after the contact between the two phases has been established, the formation of an interphase occurs and the interfacial tension decreases with time. As time proceeds, the migration process slows down given the decrease in driving force which is the concentration gradient and, at the same time, molecules accumulated in the interphase start to migrate into the "infinite" matrix phase. A quasi-stationary state is found before depletion of the low-molecular weight fraction in the drop occurs and causes the interfacial tension sigma(t) to increase. The time required to reach the final stationary value, sigma(stat), increases with molecular weight and is a function of temperature. Higher polydispersity leads to lower sigma(stat) and a weaker dependence of sigma(stat) on temperature is found. A model coupling the diffusion equation in the different regimes is applied in order to interpret the experimental results. Numerical solutions of the diffusion equation are proposed in the cases of a constant and a changing interphase thickness. In the latter case, the interphase is defined by tracking with time a fixed limiting concentration in the transient concentration profiles and the variations found in sigma(t) are attributed to the changes in the interphase thickness. A discrete version of this continuous model is proposed and scaling arguments are reported in order to compare the results obtained with the predictions of the continuous model. The kinetic model as proposed by Shi et al. [T. Shi, V.E. Ziegler, I.C. Welge, L. An, B.A. Wolf, Macromolecules 37 (2007) 1591-1599] appears as a special case of the discrete model, when depletion is not taken into account. Using the models, time scales for the diffusion process can be derived, which fit the experimental results quite well.     

Study of the interference effects in an optical cavity for organic light-emitting diode applications

The interference effects generated in a bottom-emitting electroluminescent device fabricated on a polymer underlayer introduced with the aim of improving the anode roughness have been studied. The analysis of the interference fringes at different detection angles and the spatial coherence demonstrates that this phenomenon is due to multiple internal reflections that propagate in the polymer layer. This effect can be eliminated by modifying the polymer thickness and the incidence angle of the electromagnetic radiation at the anode-polymer interface. Inkjet etching technology is adopted for microcavities-shaped polymer structuring to destroy the resonator effect of the optical cavity.