Phenothiazine based compounds are well known for their successful application in bio-medicine [1] and opto-electronics [2]. The main issue that reduces the application area of the phenothiazine derivatives is their low solubility in ordinary solvents [3]. To overcome this issue, this study aims to obtain new PEGylated phenothiazine derivatives with improved water solubility. To do this, a series of three new PEGylated phenothiazine derivatives were prepared by grafting PEG chains to the phenothiazine core by three different linkers: ether, ester or amide units. The structure of the targeted molecules was confirmed by NMR spectra by the occurrence of the characteristic protons in the expected ratio of their integrals, and also by the disappearing of the band at 4.59 ppm specific for hydroxyl proton from poly(ethylene glycol) reagent. Moreover, the FTIR spectra presented the characteristic bands for each compound, i.e. amide carbonyl group at 1690 cm^-1 and ester carbonyl group at 1742
cm^-1. The capacity of the synthetized compounds to self-assembly in water was studied by DLS and UV-vis techniques, which allowed finding the hydrodynamic diameter of the aggregates. The particularities of the formed aggregates were investigated by fluorescence spectroscopy, SEM, AFM, POM and UV light microscopy. Their biocompatibility was assessed on normal human dermal fibroblasts and five human cancer cell lines. The synthetized compounds showed the formation of luminescent aggregates with diameter in the range 60 - 700 nm and proved excellent biocompatibility on normal cells [4]. A concentration dependent cytotoxicity against four cancer cell lines was noticed for the PEGylated phenothiazine containing an ester unit and against two cancer cell for direct PEGylated phenothiazine. In vivo anti-tumor investigations are in progress.

Acknowledgements:

This work was supported by the Romanian National Authority for Scientific Research MEN – UEFISCDI (grant number PN-III-P1-1.2-PCCDI2017-0569, no. 10PCCDI/2018).

References

[1] B. Varga, Á. Csonka, A Csonka, J Molnár, L. Amaral, G. Spengler, Possible biological and clinical applications of phenothiazines, Anticancer Res. 2017 37(11), 5983-5993, doi: 10.21873/invivo.11746.

[2] I. J.Al-Busaidi, A. Haque, N. K. Al Rasbi, M. S. Khan, Phenothiazine-based derivatives for optoelectronic applications: A review, Synthetic Met. 2019 257, 116189,

[3] S. Ahmadian, V. Panahi-Azar, M. A. A. Fakhree, W. E. Acree, Jr., A. Jouyban, J. Chem. Eng. Data. 2011 56, 4352–4355, doi: org/10.1021/je2001649.

[4] S. Cibotaru, A. I. Sandu, D. Belei, L. Marin, Mater. Sci. Eng. C. 2020 116, 111216, doi: org/10.1016/j.msec.2020.111216

The electrospinning, a facile, ecological and efficient technique from production cost view, was applied to yield chitosan (CS) nanofibers with sub-micrometric diameter which preserved the intrinsic properties of chitosan such as biocompatibility, lack of toxicity and good therapeutics activity (anti-microbial, anti-fungus, anti-tumor, anti-viral and anti-cholesterolemic activity) with potential for a large variety of applications [1-6].

The aim of this study was to prepare chitosan-based nanofibers functionalized with 2-formylfenilboronic acid by the imination reaction in heterogenous medium, in order to obtain biodegradable, biocompatible and antimicrobial bandages for burn wound healing applications. The aldehyde has been chosen due to its antifungal and antibiofilm properties demonstrated when it was combined with chitosan [7].

The preparation of the proposed fibers was realized in 3 steps. First, CS/PEO fibers were electrospun form a blend solution of CS/PEO (weight ratio of 2/1) in 80% acetic acid using an Inovenso electrospinning apparatus with a rotary collector, when applied the following parameters: voltage equal with 7 kV, tip to collector distance 10 cm, flow rate 0.4 ml/h, collector rotation speed 800 RPM, the process being realized at room conditions. The obtained material was neutralized using an aqueous solution of 5% NaOH to remove the residual acetic acid and then it was washed with ultra-pure water to remove the PEO, in order to obtain pure chitosan nanofibers. Further, the chitosan nanofibers were reacted with 2-folmylphenylboronic acid in different conditions to obtain a series of materials with different substitution degrees. The as obtained imine functionalized fibers were morphologically characterized by scanning electron microscopy and polarized optical microscopy. The imination reaction and the substitution degree were monitored by FT-IR and ¹H-RMN spectroscopy. The presence of the imine units was also evidenced by thermo-gravimetrical analysis, by variation of the degradation temperature. The water adsorption capacity was investigated by dynamic vapor sorption (DVS) technique and the antimicrobial activity was screened against different bacterial and fungal strains. It was established that the substitution degree influences the water sorption capacity of the fibers and the antimicrobial activity, the best results being obtained against staphylococcus aureus, candida albicans and aspergillus brasiliensis. It was concluded that as prepared materials keep a high potential for wound healing applications.

Acknowledgements

This work was supported by the Romanian National Authority for Scientific Research MEN – UEFISCDI (grant number PN-III-P1-1.2-PCCDI2017-0569, no. 10PCCDI/2018).

References:

1. Ohkawa, K., Cha, D., Kim, H., Nishida, A., & Yamamoto, H. (2004). Electrospinning of Chitosan. Macromolecular Rapid Communications 25(18): 1600–1605.
2. Jeon, Y. J., Kim, S. K. (2000). Production of chitooligosaccharides using ultrafiltration membrane reactor and their antibacterial activity. Carbohydrate Polymers 41: 133–141.
3. Jeon, Y. J., Kim, S. K. (2002) Antitumor activity of chisan oligosaccharides produced in an ultra-filtration membrane reactor system. Journal of Microbiology and Biotechnology 12: 503–507.
4. Hirano, S., Nagao, N. (1989). Effects of chitosan, pectic acid, lysozyme and chitinase on the growth of several phytopathogens. Agricultural and Biological Chemistry 53: 3065–3066.
5. Chirkov, S. N. (2002). The Antiviral Activity of Chitosan (Review). Applied Biochemistry and Microbiology 38(1): 1–8.
6. Sugano, M., Yoshida, K., Hashimoto, M., Enomoto, K., Hirano, S. (1992). Hypocholesterolemic activity of partially hydrolyzed chitosan in rats. In: Brine, C. J., Sandford, P. A., Zikakis, J. P. (Ed.) Advances in chitin and chitosan. Elsevier, London, pp. 472–478
7. Ailincai D., Marin L., Morariu S., Mares M., Bostanaru A. C., Pinteala M., Simionescu B. C., M. Barboiu (2016). Dual crosslinked iminoboronate-chitosan hydrogels with strong antifungal activity against Candida planktonic yeasts and biofilms, Carbohydrate Polymers 152: 306-316.

Microplastics are formed by the degradation of plastic wastes under the action of physicochemical mechanisms in environment, and they are contaminants of emerging concern that have been received considerable attention in recent years due to their adverse impact on living organisms and the environment. However, research on the aging characteristics and mechanism of microplastics is limited. For example, common polymers exposed to the environment are adversely affected by solar radiation (primarily ultraviolet (UV) UV-B), which initiates photooxidative degradation. Thus, exposure to ultraviolet UV radiation may provoke significant degradation of their structure since it results in breaking of the polymer chains, produces free radical and reduces their molecular weight, causing though the deterioration of their mechanical properties after an unpredictable time. In the present study, to improve understanding of aging process of microplastics, four of the most widely used polymers covering a wide spectrum of applications, due to their excellent chemical inertness and high processability in the present study, such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP) and polystyrene (PS) in the form of thin films were exposed to UV radiation at 254 nm with constant temperature (25 °C) and constant relative humidity (50%) for several times. After exposure, the films were removed from the chamber (after 5, 10, 20, 30, 45 and 60 days of radiation) and UV irradiation influence was evaluated by using FTIR (Fourier-Transform Infrared) Spectroscopy, DSC (Differential Scanning Calorimetry) measurements, XRD (X-Ray Diffraction), Py-GC/MS (Pyrolysis-Gas Chromatography/Mass Spectroscopy), SEM (Scanning Electron Microscopy), while their mechanical properties were also evaluated. From FTIR spectroscopy it was found that new carbonyl, vinyl, and hydroxyl/hydroxyperoxide groups were formed during UV exposure, while XRD, DSC and mechanical measurements boosted the obvious effect of UV irradiation in their crystalline, thermal and mechanical properties. SEM micrographs revealed the significant morphological alterations at the irradiated samples, due to the appearance of defects and holes at their surface, revealing extended decomposition after just 30 days of UV exposure. Finally, the mechanism of thermal degradation of the four polymers before and after UV exposure was studied by Py-GC/MS.

Acknowledgments
This research was financially supported by the Greek Ministry of Development and Investments (General Secretariat for Research and Technology) through the research project “Intergovernmental International Scientific and Technological Innovation-Cooperation. Joint declaration of Science and Technology Cooperation between China and Greece” (Grant no: T7ΔKI-00220).

Health and safety issues should be addressed during the development and investigation of the industrial processes. In order to develop a sustainable process and fully evaluate its benefits and drawbacks for its optimization, it is crucial to determine its impact on the surrounding environment. This study aimed to assess the emission of volatile organic compounds during the modification of lignocellulosic fillers with passive dosimetry. Two types of processes were investigated: diisocyanate treatment of commercial lignocellulosic fillers in a batch mixer and thermo-mechanical treatment of brewers’ spent grain using a twin-screw extruder. The presence of multiple terpenes and terpenoids was detected during the processing of fillers. The main compounds detected during modification were camphene, 3-carene, limonene, α-pinene, and cymenes. These compounds can show the irritating and allergic character, according to the Globally Harmonized System of Classification and Labelling of Chemicals, as well as NFPA 704: Standard System for the Identification of the Hazards of Materials for Emergency Response. Some of them are also characterized by relatively low values of flash point, even below 40 °C. Therefore, their emissions during the modification of cellulose materials should be carefully monitored, and proper precautions need to be taken.

Over the last years, the trend associated with the incorporation of materials from renewable resources into polymer technology is getting significantly more vital. Researchers are trying to transfer the properties of natural raw materials into the polymer world. Therefore, different natural materials are more often investigated as potential additives for polymers. Such an effect is noted for the coffee industry by-products, such as coffee silverskin. Because of the relatively high contents of compounds showing antioxidant activity, such as caffeine, polyphenols, tannins, or melanoidins, this by-product could be considered not only as a filler, but also as a potential modifier for polymer materials. Its antioxidant activity is comparable to commercially available antioxidants applied in polymer technology. Therefore, in the presented paper, we examined the influence of the coffee silverskin (from 1 to 20 wt%) on the thermal and mechanical performance of polyethylene-based composites. Moreover, materials were subjected to accelerated aging tests in the UV chamber, which revealed that coffee silverskin could inhibit the photodegradation of the polymer matrix. Therefore, this by-product should be considered as an exciting alternative for the conventional lignocellulosic fillers, which could provide additional features to polymer composites.

Coffee silverskin is one of the by-products generated by the coffee industry. Although it is not the most burdensome one, because it stands only for ~4.2 wt% of coffee, it seems like an auspicious raw material for industrial processes. Coffee silverskin is characterized by a relatively low moisture content of ~5-7%, so it often does not require quite energy-consuming drying processes. The chemical composition of coffee silverskin, as well as other renewable materials, may be significantly affected by its type and origin, in this case, plant Coffea. Nevertheless, due to high fiber content, it could be considered as exciting material for the manufacturing of wood polymer composites. At the same time, it contains noticeable amounts of proteins, which may provide additional features to polymer composites. However, what is most important is the high content of antioxidants, which could noticeably enhance their lifetime by inhibition of the oxidation reactions. In the presented paper, attempts of coffee silverskin incorporation into different polymer matrices were summarized and discussed. Moreover, potential future trends in this area of research were proposed.

During the past few years, the production of biodegradable polymeric materials from renewable sources has gained extended attention in both academic and industrial fields. It is a promising approach to solve a number of problems connected with increasing pollution and energy shortage caused by the petroleum consumption. Focusing on this eco-friendly approach, aliphatic polyesters are of great interest due to their wide spectrum of potential applications and sustainability. Among this group segmented block copolymers exhibit a broad range of advantageous features as they can be produced using monomers from biomass feedstock. These copolymers consist of different types of sequences with different properties and distinct transition temperatures, thus being capable of forming hard and soft segments. Hard segments are responsible for the dimensional, thermal and mechanical stability of the polymer while the soft segments are designed to impart the elasticity to the polymer. Herein, biodegradable poly(butylene succinate-co-dilinoleic succinate) (PBS-DLS) copolymers with 70:30 (wt%) ratio of hard to soft segments were successfully synthesized using Candida antarctica lipase B (CAL-B) as a biocatalyst. During two-step synthesis in diphenyl ether, biobased succinate was polymerized with renewable 1,4 – butanediol and dimer linoleic diol to obtain “green” copolyesters as sustainable alternative to petroleum-based materials. Structure-properties relationships were discussed by investigating the number average molecular weight, chemical structure, crystalline behavior and thermal transition temperatures. Moreover, cytotoxicity test using mouse fibroblast cells L929 were performed on extracts of obtained PBS-DLS materials indicating excellent biocompatibility in vitro.

The population growth and the limited reservoir of fossil resources have ignited the attention of scientific communities and entrepreneurs to produce alternative products with raw-materials from renewable sources. In this work, proteins derived from the recycling of waste textiles were studied as raw-material in the synthesis of thermosetting polymers of phenolic type (phenol-formaldehyde resins) suitable for use as adhesives in the production of wood-based panels. The physical, thermal, and morphological properties of the thermosetting polymers were investigated. For comparison reasons, a typical phenol-formaldehyde (PF) resin was also presented in this study. In detail, the chemical bonds between raw-materials and PF resins were verified with Fourier Transform Infrared spectroscopy (FTIR). The curing performance and thermal stability of the thermosetting PF resins were studied with Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA), respectively. Wood-based panels were prepared and tested at a lab scale following a simulation of the industrial practice. Optical Microscope and Scanning Electron Microscopy (SEM) were applied for the study of the interaction between PF resins and woodchips at the lab scale. It was found that the resins were successfully prepared. The maximum curing temperature of the experimental resins was shifted to higher values than the control PF. According to the TGA results, the protein-based resins seem to lose mass with a lower rate, which denotes that they are more thermally stable than a typical PF resin. It can be concluded that protein from waste textiles can effectively replace part of the petrochemical phenol in the PF resin synthesis, thereby increasing the bio-content of the PF resin and making them more friendly to the environment.

Poly(alkylene 2,5 furan-dicarboxylate)s (PAFs) belong in a relatively new class of bio-based polyester prepared from renewable resources aiming at use in food packaging applications, owing to their excellent mechanical and gas barrier performance. Both properties are severely connected to crystallinity. Thus, the enhancement of the latter is attempted here by the in situ introduction in the PAF matrices of a variety of inorganic nanofillers, graphene nanoplatelets, carbon and halloysite nanotubes, nanoclays and silica nanoparticles. The nanofillers are used in the bulk/initial state as well as upon surface modifications, moreover, in the forms of mixtures and hybrid particles. For the structural and crystallization investigation, we employ the following combination of techniques Fourier transform infra-red spectroscopy, calorimetry, X-ray diffraction, polarized optical microscopy and broadband dielectric spectroscopy. The direct effects of the fillers on the rate and the amount of crystallization are correlated with the semicrystalline morphology, with molecular mobility and, in some cases, with the mechanical performance. The employed fillers facilitate crystallization acting as additional nuclei, with the strength of this facilitation increasing systematically with the aspect ratio of the fillers. Contrariwise, upon surface modification and development of strong polymer-particle interactions the nucleation action is hindered, which is demonstrated in PAFs for the first time. Overall the results suggest that such materials serve quite well as tailor-made nanocomposites for targeted applications.

Active compounds of plants are of great interest for biomedical use. Cat’s claw (Uncaria tomentosa) is a woody vine plant from the Peruvian rainforest known for its anti-inflammatory, anti-arthritic and anti-asthmatic properties. Meanwhile, aloe vera (Aloe barbadensis) is a plant commonly used for wound healing and skin hydration.

In this study, we elaborated microparticles from an emulsion made of alginate solutions with aloe vera gel or cat’s claw extract and poloxamer 407 as a stabilizing agent with ultrasound. Then, tri-dimensional membranes were obtained by solvent evaporation and, finally, crosslinked in a calcium chloride solution to improve their mechanical properties.

The 27 to 33 µm-thick membranes showed a porous surface on a scanning electron microscope (SEM) which is significantly different to membranes with no microparticles. The contact angle of water on the membranes showed an increase in hydrophilicity due to the use of aloe vera gel. Furthermore, the presence of aloe vera also improved water absorption in an acetate buffer (pH 5.5) at 37.5˚C. Finally, the presence of cat’s claw extract in the microparticles significantly enhanced radical scavenging, which was measured by ABTS decoloration assay, in comparison to tri-dimensional alginate membranes with no active compounds.