Development, Testing, and Thermoforming of Thermoplastics Reinforced with Surface-Modified Aramid Fibers for Cover of Electronic Parts in Small Unmanned Aerial Vehicles Using 3D-Printed Molds.

This paper presents the development, characterization, and testing of PP/PE-g-MA composites with 10 and 15 wt% surface-modified aramid fibers, and aluminum-based pigment, as covers for a small drone body for collision protection. The successful fiber surface modification with SiO2 by the sol-gel method using TEOS was confirmed by FTIR, SEM, and EDS analyses. The composites were characterized by FTIR and SEM analyses and surface energy and water contact angle measurements and tested in terms of tensile, flexural, impact, and thermal properties. The materials exhibited hydrophobic character and compact and uniform morphostructures, with increased surface energy with fiber content owed to improved adhesion between modified fibers and the matrix. Compared to the control sample, composites with modified fibers showed an increase by 20% in tensile strength, and 36-52% in the modulus, and an increase by 26-33% in flexural strength and 30-47% in the modulus, with higher values at room temperature. Impact resistance of modified fiber composites showed an increase by 20-40% compared to the control sample, due to improved interaction between SiO2-modified fibers and maleic anhydride, which inhibits crack formation, allowing higher energies' absorption. The composites were vacuum-thermoformed on 3D-printed molds as a two-part cover for the body of a drone, successfully withstanding the flight test.

Antimicrobial Packaging for Plum Tomatoes Based on ZnO Modified Low-Density Polyethylene.

Food safety and quality are major concerns in the food industry. Despite numerous studies, polyethylene remains one of the most used materials for packaging due to industry reluctance to invest in new technologies and equipment. Therefore, modifications to the current materials are easier to implement than adopting whole new solutions. Antibacterial activity can be induced in low-density polyethylene films only by adding antimicrobial agents. ZnO nanoparticles are well known for their strong antimicrobial activity, coupled with low toxicity and UV shielding capability. These characteristics recommend ZnO for the food industry. By incorporating such safe and dependable antimicrobial agents in the polyethylene matrix, we have obtained composite films able to inhibit microorganisms' growth that can be used as packaging materials. Here we report the obtaining of highly homogenous composite films with up to 5% ZnO by a melt mixing process at 150 °C for 10 min. The composite films present good transparency in the visible domain, permitting consumers to visualize the food, but have good UV barrier properties. The composite films exhibit good antimicrobial and antibiofilm activity from the lowest ZnO composition (1%), against both Gram-positive and Gram-negative bacterial strains. The homogenous dispersion of ZnO nanoparticles into the polyethylene matrix was assessed by Fourier transform infrared microscopy and scanning electron microscopy. The optimal mechanical barrier properties were obtained for composition with 3% ZnO. The thermal analysis indicates that the addition of ZnO nanoparticles has increased thermal stability by more than 100 °C. The UV-Vis spectra indicate a low transmittance in the UV domain, lower than 5%, making the films suitable for blocking photo-oxidation processes. The obtained films proved to be efficient packaging films, successfully preserving plum (Rome) tomatoes for up to 14 days.

The Use of Additive Manufacturing Techniques in the Development of Polymeric Molds: A Review.

The continuous growth of additive manufacturing in worldwide industrial and research fields is driven by its main feature which allows the customization of items according to the customers' requirements and limitations. There is an expanding competitiveness in the product development sector as well as applicative research that serves special-use domains. Besides the direct use of additive manufacturing in the production of final products, 3D printing is a viable solution that can help manufacturers and researchers produce their support tooling devices (such as molds and dies) more efficiently, in terms of design complexity and flexibility, timeframe, costs, and material consumption reduction as well as functionality and quality enhancements. The compatibility of the features of 3D printing of molds with the requirements of low-volume production and individual-use customized items development makes this class of techniques extremely attractive to a multitude of areas. This review paper presents a synthesis of the use of 3D-printed polymeric molds in the main applications where molds exhibit a major role, from industrially oriented ones (injection, casting, thermoforming, vacuum forming, composite fabrication) to research or single-use oriented ones (tissue engineering, biomedicine, soft lithography), with an emphasis on the benefits of using 3D-printed polymeric molds, compared to traditional tooling.

Polymeric Biocomposite Based on Thermoplastic Polyurethane (TPU) and Protein and Elastomeric Waste Mixture.

Polymeric biocomposites based on TPU/recycled TPUW/mixed leather and SBR rubber waste unmodified/modified with polydimethylsiloxane/PE-g-MA in different percentages were made via the mixing technique on a Plasti-Corder Brabender mixer with an internal capacity of 350 cm3. The waste, which came from the shoe industry, was cryogenically ground with the help of a cryogenic cyclone mill at micrometric sizes and different speeds. For the tests, standard plates of 150 × 150 × 2 mm were obtained in a laboratory-scale hydraulic press via the method of compression between its plates, with well-established parameters. The biocomposites were tested physico-mechanically and rheologically (MFI) according to the standards in force on polymer-specific equipment, also via FT-IR spectroscopy and microscopy, as well as via differential scanning calorimetry-DSC. Following the tests carried out, according to the standard for use in the footwear industry, at least two samples present optimal values (of interest) suitable for use in the footwear industry by injection or pressing in forming moulds.

Mechanical Properties and Equilibrium Swelling Characteristics of Some Polymer Composites Based on Ethylene Propylene Diene Terpolymer (EPDM) Reinforced with Hemp Fibers.

EPDM/hemp fiber composites with fiber loading of 0-20 phr were prepared by the blending technique on a laboratory electrically heated roller mill. Test specimens were obtained by vulcanization using a laboratory hydraulic press. The elastomer crosslinking and the chemical modification of the hemp fiber surface were achieved by a radical reaction mechanism initiated by di(tert-butylperoxyisopropyl)benzene. The influence of the fiber loading on the mechanical properties, gel fraction, swelling ratio and crosslink degree was investigated. The gel fraction, crosslink density and rubber-hemp fiber interaction were evaluated based on equilibrium solvent-swelling measurements using the Flory-Rehner relation and Kraus and Lorenz-Park equations. The morphology of the EPDM/hemp fiber composites was analyzed by scanning electron microscopy. The water absorption increases as the hemp fiber loading increases.

Radiation Processing and Characterization of Some Ethylene-propylene-diene Terpolymer/Butyl (Halobutyl) Rubber/Nanosilica Composites.

Composites based on ethylene-propylene-diene terpolymer (EPDM), butyl/halobutyl rubber and nanosilica were prepared by melt mixing and subjected to different doses of electron beam irradiation. The effect of irradiation dose on the mechanical properties, morphology, glass transition temperature, thermal stability and water uptake was investigated. The efficiency of the crosslinking by electron beam irradiation was analyzed by Charlesby-Pinner parameter evaluation and crosslink density measurements. The scanning electron microscopy data showed a good dispersion of nanosilica in the rubber matrix. An improvement in hardness and 100% modulus was revealed by increasing irradiation dose up to 150 kGy. The interaction between polymer matrix and nanosilica was analyzed using the Kraus equation. Additionally, these results indicated that the mechanical properties, surface characteristics, and water uptake were dependent on crosslink characteristics.

Hybrid Magnetic Nanostructures For Cancer Diagnosis And Therapy.

Cancer is the second disease in the world from the point of view of mortality. The conventional routes of treatment were found to be not sufficient and thus alternative ways are imposed. The use of hybrid, magnetic nanostructures is a promising way for simultaneous targeted diagnosis and treatment of various types of cancer. For this reason, the development of core@shell structures was found to be an efficient way to develop stable, biocompatible, non-toxic carriers with shell-dependent internalization capacity in cancer cells. So, the multicomponent approach can be the most suitable way to assure the multifunctionality of these nanostructures to achieve the desired/necessary properties. The in vivo stability is mostly assured by the coating of the magnetic core with various polymers (including polyethylene glycol, silica etc.), while the targeting capacity is mostly assured by the decoration of these nanostructures with folic acid. Unfortunately, there are also some limitations related to the multilayered approach. For instance, the increasing of the thickness of layers leads to a decrease the magnetic properties, (hyperthermia and guiding ability in the magnetic field, for instance), the outer shell should contain the targeting molecules (as well as the agents helping the internalization into the cancer cells), etc.

Manufacturing nanostructured chitosan-based 2D sheets with prolonged antimicrobial activity.

The purpose of this study was to synthesize, characterize and test the antimicrobial and antifungal activity of chitosan-based hydrogels containing metal (silver - Ag) and oxide (zinc oxide - ZnO) nanoparticles (NPs) but also natural compounds such as usnic acid (UA). The two-dimensional (2D) sheets were obtained by electrospinning technique, with the aim to produce multifunctional wound dressing with regenerative and even anti-infective roles. The most important advantages of the electrospinning technique are related to the possibility of obtaining fibers with controlled morphology, usually having high specific surface and water and air penetration and the possibility of functionalizing these fibers and nets depending on the desired application. These advantages make it possible to use electrospinning for a wide range of biomedical applications, such as tissue engineering, controlled release, implantology, wound healing, and more. The obtained composite materials were characterized by infrared (IR) spectroscopy and scanning electron microscopy (SEM) and tested against common pathogens: Pseudomonas aeruginosa (Gram-negative staining), Staphylococcus aureus (Gram-positive staining) and Candida albicans (fungus).

Applications of mesoporous silica in biosensing and controlled release of insulin.

The development of new oral insulin delivery systems could bring significant benefits to insulin-dependent patients due to the simplicity of the method, avoidance of pain caused by parenteral administration and maintenance of optimal therapeutic levels for a longer period. However, administration of such therapeutic proteins orally remains a challenge because insulin (Ins) is a very sensitive molecule and can be easily degraded under the existing pH conditions in the stomach and intestines. Moreover, due to the large size of insulin, intestinal epithelium permeability is very low. This could be improved by immobilizing insulin in the mesoporous silica pores (MSN), acting as a shield to protect the molecule integrity from the proteolytic degradation existing in the stomach and upper part of the small intestine. Due to the high adsorption capacity of insulin, biocompatibility, ease of functionalization with various organic and/or inorganic groups, high mechanical and chemical resistance, adjustable pore size and volume, MSN is considered an ideal candidate for the development of controlled release systems that are sensitive to various stimuli (pH, temperature) as well as to glucose. Modifying MSN surfaces by coating with various mucoadhesive polymers (chitosan, alginate, etc.) will also facilitate interaction with the intestinal mucus and improve intestinal retention time. Moreover, the development of glucose-responsive systems for achieving MSN-based self-regulated insulin delivery, decorated with various components serving as sensors - glucose oxidase (GODx) and phenylboronic acid (PBA) that can control the insulin dosage, avoiding overdose leading to serious hypoglycemia. MSN have also been tested for application as biosensors for glucose monitoring.

Advances in Drug Delivery Systems, from 0 to 3D superstructures.

BACKGROUND: Nanomedicine is currently exploited for manufacturing therapeutic DDS and treatments protocols for various diseases and disorders. To obtain DDS, different types of materials are used, from organic to inorganic, polar to non-polar, micro to nanomaterials from 0D to 3D structured materials, respectively. Many of these materials were extensively studied and reviewed in the literature. OBJECTIVE: The objectives of this review is to make a clear overview on drug delivery systems depending several aspects related to delivery mechanisms, the type of supports, the active agents ant the potential applications in the prevention or treatment of various diseases. RESULTS: Following aspects are extensively debated: synthesis issues, characteristics and potential uses of 0, 1, 2 and 3D drug delivery systems according to their nature and applications. These systems can be can be tailored according to the delivery mechanism (0-3D delivery) as well as by using more active agents, with more therapeutic activity or same activity but with different mechanisms of action. The size and morphology of the drug delivery system is essential, especially when talking about the internalization into the tumor cells while the mobility is especially dependent on the size. The influence of the nature of the supports and their polarity was extensively studied during the last decades, as well as the importance of the porosity and pore size, but only limited papers are devoted to the holistic analysis of the dimensionality of the support and the ways of delivering the active agents. CONCLUSION: This review is devoted to a holistic insight into the drug delivery systems, from a new, only marginally studied point of view, meaning the dimensionality of the drug delivery systems and the characteristics of the delivery.

Extended release of vitamins from magnetite loaded polyanionic polymeric beads.

Here we explore a novel approach of increasing the release duration of folic and ascorbic acid from magnetite entrapped into calcium-alginate beads. Synthesis and characterization of magnetite-vitamins complexes are reported. The magnetite-vitamins complexes were characterized by FT-IR, XRD, SEM, BET and DTA-TG. Also calcium-alginate magnetic beads were prepared by dripping a mixture of sodium alginate with magnetite-vitamins complexes into calcium chloride solution. Extended release profile of the two experimental models was evaluated and quantified by UV-vis.

SYNTHESIS AND APPLICATIONS OF Fe3O4/SiO2 CORE-SHELL MATERIALS.

Multifunctional nanoparticles based on magnetite/silica core-shell, consisting of iron oxides coated with silica matrix doped with fluorescent components such as organic dyes (fluorescein isothiocyanate - FITC, Rhodamine 6G) or quantum dots, have drawn remarkable attention in the last years. Due to the bi-functionality of these types of nanoparticles (simultaneously having magnetic and fluorescent properties), they are successfully used in highly efficient human stem cell labeling, magnetic carrier for photodynamic therapy, drug delivery, hyperthermia and other biomedical applications. Another application of core-shell-based nanoparticles, in which the silica is functionalized with aminosilanes, is for immobilization and separation of various biological entities such as proteins, antibodies, enzymes etc. as well as in environmental applications, as adsorbents for heavy metal ions. In vitro tests on human cancerous cells, such as A549 (human lung carcinoma), breast, human cervical cancer, THP-1 (human acute monocytic leukaemia) etc. , were conducted to assess the potential cytotoxic effects that may occur upon contact of nanoparticles with cancerous tissue. Results show that core-shell nanoparticles doped with cytostatics (cisplatin, doxorubicin, etc.), are easily adsorbed by affected tissue and in some cases lead to an inhibition of cell proliferation and induce cell death by apoptosis. The goal of this review is to summarize the advances in the field of core-shell materials, particularly those based on magnetite/silica with applicability in medicine and environmental protection. This paper briefly describes synthesis methods of silica-coated magnetite nanoparticles (Stöber method and microemulsion), the method of encapsulating functional groups based on aminosilanes in silica shell, as well as applications in medicine of these types of simple or modified nanoparticles for cancer therapy, MRI, biomarker immobilization, drug delivery, biocatalysis etc., and in environmental applications (removal of heavy metal ions and catalysis).

MAGNETIC CORE SHELL STRUCTURES: from 0D to 1D assembling.

Material research and development studies are focused on different techniques of bringing out nanomaterials with desired characteristics and properties. From the point of view of materials development, nowadays scientists are strongly focused on obtaining materials with predefined characteristics and properties. The morphology control seems to be a determinant factor and increasing attention is devoted to this aspect. At this moment it is possible to engineer the material's features by using different methods and materials combination for both medical and industrial applications. In the applications of chemistry and synthesis, biology, mechanics, optics solar cells and microelectronics tailoring the adjustable parameters of stoichiometry, chemical structure, shape and segregation are evaluated and opens new fields. Because of the magnetic features of nanoparticles and durable particle size, less than 100 nm, this study is aiming to describe their uses in practical applications. That's why the whole hydrodynamic magnetic core shell topic will be reviewed on this paper. Additionally, the properties acting in general sight in solid-state physics are utilized for material selection and for defining issue connecting the core, shell structure and their producing properties. Here, in the study of core/shell nanoparticle various physical and chemical synthesis routes and the effect of electrospun method are briefly discussed. Starting from a real void of the scientific literature, the existent data related to the 1D magnetic electrospun materials are reviewed. The perspectives in the medical, environmental or energetic sector is great and bring some real advantages related to the 0D core@shell structures because both mechanical and biological properties are dependent on the morphology of the materials.

Magnetite: from synthesis to applications.

In this review the synthesis, functionalization and some applications of magnetite nanoparticles (MNPs) were highlighted. It is our intention to highlight the correlations between the synthesis routes, related synthesis parameters, functionalization strategies and the properties expected for the materials containing MNPs. The uses of MNPs are strongly influenced by the properties of the materials. Therefore this review is trying to discuss the applications of the magnetite and magnetite based nanomaterials by taking into account all the factors that can influence the properties of the final materials and consequently their potential applications.

Mesoporous materials used in medicine and environmental applications.

Mesoporous materials synthesized in the presence of templates, are commonly used for environment and medical applications. Due to the properties it holds, mesoporous silica nanoparticles is an excellent material for use in medical field, biomaterials, active principles delivery systems, enzyme immobilization and imaging. Their structure allows embedding large and small molecules, DNA adsorption and genetic transfer. Using mesoporous silica nanoparticles for delivery of bioactive molecules can protect them against degradation under physiological conditions, allow controlled drugs release and minimize side effects on healthy tissues. Cellular tests performed on mesoporous silica nanoparticles demonstrate that MSN's cytotoxicity is dependent on the size and concentration and suggests the use of larger size nanoparticles is optimal for medical applications. Mesoporous materials possess high biological compatibility, are non-toxic and can be easily modified by functionalizing the surface or inside the pores by grafting or co-condensation method. The structure, composition and pores size of this material can be optimized during synthesis by varying the stoichiometric reactants, reaction conditions, nature of the template's molecules or by functionalization method.

Antitumoral materials with regenerative function obtained using a layer-by-layer technique.

A layer-by layer technique was successfully used to obtain collagen/hydroxyapatite-magnetite-cisplatin (COLL/HAn-Fe3O4-CisPt, n=1-7) composite materials with a variable content of hydroxyapatite intended for use in the treatment of bone cancer. The main advantages of this system are the possibility of controlling the rate of delivery of cytostatic agents, the presence of collagen and hydroxyapatite to ensure more rapid healing of the injured bone tissue, and the potential for magnetite to be a passive antitumoral component that can be activated when an appropriate external electromagnetic field is applied. In vitro cytotoxicity assays performed on the COLL/HAn-Fe3O4-CisPt materials obtained using a layer-by layer method confirmed their antitumoral activity. Samples with a higher content of hydroxyapatite had more antitumoral activity because of their better absorption of cisplatin and consequently a higher amount of cisplatin being present in the matrices.

Multifunctional materials for bone cancer treatment.

The purpose of this review is to present the most recent findings in bone tissue engineering. Special attention is given to multifunctional materials based on collagen and collagen-hydroxyapatite composites used for skin and bone cancer treatments. The multi-functionality of these materials was obtained by adding to the base regenerative grafts proper components, such as ferrites (magnetite being the most important representative), cytostatics (cisplatin, carboplatin, vincristine, methotrexate, paclitaxel, doxorubicin), silver nanoparticles, antibiotics (anthracyclines, geldanamycin), and/or analgesics (ibuprofen, fentanyl). The suitability of complex systems for the intended applications was systematically analyzed. The developmental possibilities of multifunctional materials with regenerative and curative roles (antitumoral as well as pain management) in the field of skin and bone cancer treatment are discussed. It is worth mentioning that better materials are likely to be developed by combining conventional and unconventional experimental strategies.

Nanostructured biomaterials with antimicrobial properties.

The present review is intended to bring together the main advances in the field of nanostructured biomaterials with antimicrobial properties. It is generally accepted that the discovery of antibiotics was of great importance but, nowadays new antimicrobial agents are needed and/or their better administration routes. The limitation of the use of antibiotics is essential because of the following reasons: the excessive use of antibiotics leads to the development of antibiotic resistant microorganisms; there are some alternatives for many types of infections, many of these alternatives being less toxic and do not lead to antibiotic similar resistance. In compliance with the above presented, the use of antibiotic is recommended to be eliminated (when alternatives are available) or to be reduced by using combined therapy when possible or to administrate these drugs through targeted or loco-regional drug delivery systems.

Collagen-hydroxyapatite/cisplatin drug delivery systems for locoregional treatment of bone cancer.

In this paper, the synthesis and characterization of novel cisplatin-loaded collagen (COLL)/hydroxyapatite (HA) composite materials are presented. The composite materials were designed to obtain a COLL: HA weight ratio close to the bone composition. The content of embedded cisplatin was chosen to assure a concentration of cisplatin of 6 and 10 µM, respectively, into the culture media used in cell culture experiments. These cisplatin delivery systems were characterized by determining the physico-chemical properties of the composite material, the drug release process as well as their biological activity. Based on the in vitro data that showed the cytotoxic, anti-proliferative and anti-invasive activities of these multifunctional systems on G292 osteosarcoma cells in dependence on the cisplatin concentration released in culture medium, we conclude that the newly developed COLL/HA-cisplatin drug delivery system could be a feasible approach for locoregional chemotherapy of bone cancer.