Transmission Electron Microscopy of Biological Samples

During the last 70 years, transmission electron microscopy (TEM) has developed our knowledge about ultrastructure of the cells and tissues. Another aim is the determination of molecular structure, interactions and processes including structure-function relationships at cellular level using a variety of TEM techniques with resolution in atomic to nanometre range. Even with the best transmission electron microscope, it is impossible to obtain real results without optimal sample preparation, respecting both the structure and the antigenicity preservation. Preparation techniques for high-resolution study of both macromolecular complex and organelles within cellular complex are based on fast cryoimmobilisation process, where the sample is in the most native, hydrated state. Next, thin samples are directly visualised under cryo-transmission electron microscopy (cryo-TEM), while thicker samples require a thinning step via cryo-electron microscopy of vitreous sections (CEMOVIS) or cryo-focused ion beam (cryo-FIB) before visualisation. Alternatively, vitrified samples are freeze substituted and embedded in chosen resin for room temperature ultramicrotomy. This preparation technique is suitable for morphological study, 3D analysis of cellular interior and immunoelectron microscopy. A different route for immunolocalisation study is cryosectioning according to the Tokuyasu technique that is a choice for rare or methacrylate-sensitive antigens. Most recently, new hybrid techniques have been developed for difficult-to-fix organisms and antigens or labile and anoxia-sensitive tissues. Another preparation technique is, the oldest but still important, conventional chemical fixation dedicated in a wide range of research interest, involving morphological and immunolocalisation study. In this chapter, we present different sample preparation approaches for transmission electron microscopy of biological samples, including its methodological basis and applications

Pressure-assisted solvent- and catalyst-free production of well-defined poly(1-vinyl-2-pyrrolidone) for biomedical applications

In this work, we developed a fast, highly efficient, and environmentally friendly catalytic systemfor classical freeradical polymerization (FRP) utilizing a high-pressure (HP) approach. The application of HP for thermallyinduced, bulk FRP of 1-vinyl-2-pyrrolidone (VP) allowed to eliminate the current limitation of ambientpressure polymerization of ‘less-activated’ monomer (LAM), characterized by the lack of temporal control yielding polymers of unacceptably large disperisites and poor result reproducibility. By a simple manipulation of thermodynamic conditions (p ¼ 125–500 MPa, T ¼ 323–333 K) and reaction composition (twocomponent system: monomer and low content of thermoinitiator) well-defined poly(1-vinyl-2-pyrrolidone)s (PVP) in a wide range of molecular weights and low/moderate dispersities (Mn ¼ 16.2–280.5 kg mol 1, Đ ¼ 1.27–1.45) have been produced. We have found that HP can act as an ‘external’ controlling factor that warrants the first-order polymerization kinetics for classical FRP, something that was possible so far only for reversible deactivation radical polymerization (RDRP) systems. Importantly, our synthetic strategy adopted for VP FRP enabled us to obtain polymers of very high Mn in a very short time-frame (0.5 h). It has also been confirmed that VP bulk polymerization yields polymers with significantly lower glass transition temperatures (Tg) and different solubility properties in comparison to macromolecules obtained during the solvent-assisted reaction

Heat shock protein A2 is a novel extracellular vesicle-associated protein

70-kDa Heat Shock Proteins (HSPA/HSP70) are chaperones playing a central role in the proteostasis control mechanisms. Their basal expression can be highly elevated as an adaptive response to environmental and pathophysiological stress conditions. HSPA2, one of poorly characterised chaperones of the HSPA/HSP70 family, has recently emerged as epithelial cells differentiation-related factor. It is also commonly expressed in cancer cells, where its functional significance remains unclear. Previously, we have found that proteotoxic stress provokes a decrease in HSPA2 levels in cancer cells. In the present study we found that proteasome inhibition-related loss of HSPA2 from cancer cells neither is related to a block in the gene transcription nor does it relate to increased autophagy-mediated disposals of the protein. Proteotoxic stress stimulated extracellular release of HSPA2 in extracellular vesicles (EVs). Interestingly, EVs containing HSPA2 are also released by non-stressed cancer and normal cells. In human urinary EVs levels of HSPA2 were correlated with the levels of TSG101, one of the main EVs markers. We conclude that HSPA2 may constitute basic components of EVs. Nevertheless, its specific role in EVs and cell-to-cell communication requires further investigation

The Effects of Duodenojejunal Omega Switch in Combination with High-Fat Diet and Control Diet on Incretins, Body Weight, and Glucose Tolerance in Sprague-Dawley Rats

Background: Despite excellent results of bariatric surgery in the treatment of type 2 diabetes and weight loss in human subjects, some patients do not obtain desired results. One of the reasons for this is that not all patients follow caloric intake recommendations. Aim: The aim of this study was to investigate the effect of duodenojejunal omega switch (DJOS) surgery on body weight, glucose tolerance, and incretins in rats. Methods: DJOS and SHAM surgery were performed on rats maintained for 8 weeks on high-fat diet (HF) and control diet (CD), respectively. After surgery, four groups were kept on the same diet as before the surgery, and four groups had a changed diet (CD vs. HF and HF vs. CD) for the next 8 weeks. Glucose tolerance, insulin tolerance, glucose-stimulated insulin, glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide/glucose-dependent insulinotropic polypeptide (GIP) secretion, food intake, and body weight were measured. Results: A change of diet after surgery resulted in reduced glucose tolerance. Plasma insulin levels were lowered between DJOS and SHAM surgeries for the HF/HF and CD/HF groups. DJOS surgery did not reduce body weight in the studied groups, irrespective of diet. In the HF/HF group, ΔGLP-1 was lower for DJOS surgery in comparison with other groups. Differences of weight changes were observed for groups HF/HF and HF/CD. After DJOS surgery, ΔGIP was lower in the CD/HF group compared with HF/HF. Conclusions: Our results show that applications of different types of diets, before and after surgery, is a sensitive method for studies of mechanism of glucose intolerance after DJOS surgery

A different ultrastructural face of ribbon synapses in the rat retina

Abstract Ribbon synapses located exclusively within retinal, cochlear and vestibular connections belong to the most interesting cellular structures but their molecular nature and functions had remained unclear. The study has provided a descriptive morphological analysis of rat eye ribbon synapses using high-resolution transmission electron microscopy (TEM). An original collection of untypical, rarely present in the literature sagittal or tangential sections through the single RIBEYE domain of the particular ribbon have been delivered

Synthetic strategy matters : the study of a different kind of PVP as micellar vehicles of metronidazole

Poly(1-vinyl-2-pyrrolidone) (Povidone, PVP) is one of the most interesting and versatile synthetic polymers utilised in the pharmaceutical and cosmetic industries. Its large-scale commercial production offers an assortment of products in a wide range of molecular weights but poorly-controlled (macro)structural parameters (i.e., dispersity, functionality) limiting the efficiency of PVP-based drug delivery systems (DDS). In this work, synthesised linear and star-shaped PVPs with a strictly defined structure and functionality were compared with the linear, commercially-supplied product and explored as potential vehicles for physical entrapment of metronidazole (MTZ). Here, a question is addressed how differences in their macromolecular properties affect the amorphisation of MTZ, drug encapsulation, the stability of drug-loaded micellar structures and their in vitro release from the carrier. The X-ray diffraction studies and calorimetric measurements revealed that MTZ crystallises in all investigated herein systems reducing the glass transition temperature of the binary mixture significantly. Transmission electron microscopy and dynamic light scattering analysis revealed that MTZ-loaded DDS are able to form ultrasmall regular nanocarriers with an increasing effect of regularity and sphericity from star-shaped DDS to linear-based ones. We founded that synthesised linear-based DDS is the most effective for MTZ entrapment (PVP:MTZ = 1:1 weight ratio) due to their smallest hydrodynamic radius dh = 14.7 nm, the highest stability of micellar structures −2.37 mV, and the highest values of loaded drug 76.5%. Moreover, all applied PVP-based DDS revealed an initial burst release effect of MTZ (pH = 7.4) reaching up to 60% of drug released within the first 5 h (the first-order release model fits). The marked efficiency of MTZ-loaded DDS of strictly defined structural parameters indicates the great importance of polymer preparation strategy in the targeted therapy

Sugar decorated star-shaped (co)polymerswith resveratrol-based core – physicochemicaland biological properties

Star-shaped glycopolymers due to the attractive combination of the physicochemical, morphological, self-assembly properties along with biological activity have gained increased attention as innovative agents in novel cancer therapies. Unfortunately, the production of these highly desirable biomaterials remains a challenge in modern macromolecular chemistry. The main reason for that is the low polymerizability of ionic glycomonomers originated from their steric congestion and the occurrence of ionic interactions that generally negatively influence the polymerization progress and hinder controllable reaction pathway. In this work, the new ionic sugar monomer was (co)polymerized for the first time via Activator Generated by Electron Transfer Atom Transfer Radical Polymerization (AGET ATRP) using a three-arm resveratrol-based core to obtain star-like (co)polymers. The obtained products were examined in terms of their physicochemical properties and morphology. Aside from the synthesis of these new glycopolymers, also a thorough description of their thermal properties, ability to self-assembly, the formation of stable superstructures was studied in detail. It was found that examined (co)polymers did not show any heterogeneities and phase separation, while their variation of glass transition temperature (Tg) was strictly related to the change in the number of glycomonomer. Also, the stability and shapes of formed superstructures strictly depend on their composition and topology. Finally, we have shown that synthesized carbohydrate-based polymers revealed high antiproliferative activity against several cancer cell lines (i.e., breast, colon, glioma, and lung cancer). The cytotoxic activity was particularly observed for star-shaped polymers that were systematically enhanced with the growing concentration of amine moieties and molecular weight. The results presented herein suggest that synthesized star-shaped glyco(co)polymers are promising as drug or gene carriers in anticancer therapies or anti-tumor agents, depending on their cytotoxicity. Graphical abstrac

Sweetness covert in polymers

Artykuł jest poświęcony tematyce wykorzystywania węglowodanów, w szczególności pełniących funkcję inicjatora, do otrzymywania syntetycznych polimerów za pomocą metod kontrolowanych, w tym polimeryzacji rodnikowej (CRP). Użycie CRP umożliwia syntezę makrocząsteczek o różnorodnym składzie i złożonej budowie z jednoczesnym zachowaniem kontroli nad ich strukturą. Ponadto przybliżono wpływ, jaki wywiera obecność cząsteczek cukrowych na właściwości otrzymanych polimerów, ze szczególnym naciskiem na ich potencjalne zastosowanie.This article is devoted to carbohydrates utilization, in particular acting as initiators, to obtain synthetic polymers using controlled methods, including radical polymerization (CRP). The use of CRP enables the synthesis of macromolecules with different compositions and complex architectures, whereas control over their structures is maintained. Moreover, the influence of sugar moieties on the properties of the polymers will be shown, with particular emphasis on their potential uses

4-n-Butylresorcinol-Based Linear and Graft Polymethacrylates for Arbutin and Vitamins Delivery by Micellar Systems

A novel initiator, bromoester modified 4-n-butylresorcinol (4nBREBr2), was prepared and utilized in controlled atom transfer radical polymerization (ATRP) to obtain three series of amphiphilic copolymers. The V-shaped copolymers of methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), and poly(ethylene glycol) methyl ether methacrylate (MPEGMA), abbreviated to P(HEMA–co–MMA), P(HEMA–co–MPEGMA), and P(MMA–co–MPEGMA), were synthesized. Moreover, P((HEMA–graft–PEG)–co–MMA) graft copolymers were prepared by combining the pre-polymerization modification of HEMA and a “click” reaction using a “grafting onto” approach. All copolymers could form micelles with encapsulated active substances (vitamin C (VitC), vitamin E (VitE), arbutin (ARB)), which are used in cosmetology. In vitro studies carried out in a PBS solution (pH 7.4) demonstrates that in most cases the maximum release of active substance was after 1 h. The polymeric systems presenting satisfactory encapsulation characteristics and release profiles are attractive micellar carriers of cosmetic substances, which show a positive effect on the skin condition