Novel antimicrobial polyethylene composites prepared by metallocenic in situ polymerization with TiO2 -based nanoparticles

Surface modification of TiO2 nanoparticles with organic molecules and their biological applications

In recent years, titanium(IV) dioxide nanoparticles (TiO₂NPs) have shown promising potential in various biological applications such as antimicrobials, drug delivery, photodynamic therapy, biosensors, and tissue engineering. For employing TiO₂NPs in these fields, their nanosurface must be coated or conjugated with organic and/or inorganic agents. This modification can improve their stability, photochemical properties, biocompatibility, and even surface area for further conjugation with other molecules such as drugs, targeting molecules, polymers, etc. This review describes the organic-based modification of TiO₂NPs and their potential applications in the mentioned biological fields. In the first part of this review, around 75 recent publications (2017-2022) are mentioned on the common TiO₂NP modifiers including organosilanes, polymers, small molecules, and hydrogels, which improve the photochemical features of TiO₂NPs. In the second part of this review, we presented 149 recent papers (2020-2022) about the use of modified TiO₂NPs in biological applications, in which specific bioactive modifiers are introduced in this part with their advantages. In this review, the following information is presented: (1) the common organic modifiers for TiO₂NPs, (2) biologically important modifiers and their benefits, and (3) recent publications on biological studies on the modified TiO₂NPs with their achievements. This review shows the paramount significance of the organic-based modification of TiO₂NPs to enhance their biological effectiveness, paving the way toward the development of advanced TiO₂-based nanomaterials in nanomedicine.

Synthesis, Characterization, and Optimization Studies of Polycaprolactone/Polylactic Acid/Titanium Dioxide Nanoparticle/Orange Essential Oil Membranes for Biomedical Applications

The development of scaffolds for cell regeneration has increased because they must have adequate biocompatibility and mechanical properties to be applied in tissue engineering. In this sense, incorporating nanofillers or essential oils has allowed new architectures to promote cell proliferation and regeneration of new tissue. With this goal, we prepared four membranes based on polylactic acid (PLA), polycaprolactone (PCL), titanium dioxide nanoparticles (TiO₂-NPs), and orange essential oil (OEO) by the drop-casting method. The preparation of TiO₂-NPs followed the sol-gel process with spherical morphology and an average size of 13.39 nm ± 2.28 nm. The results show how the TiO₂-NP properties predominate over the crystallization processes, reflected in the decreasing crystallinity percentage from 5.2% to 0.6% in the membranes. On the other hand, when OEO and TiO₂-NPs are introduced into a membrane, they act synergistically due to the inclusion of highly conjugated thermostable molecules and the thermal properties of TiO₂-NPs. Finally, incorporating OEO and TiO₂-NPs promotes tissue regeneration due to the decrease in inflammatory infiltrate and the appearance of connective tissue. These results demonstrate the great potential for biomedical applications of the membranes prepared.

Synergic Effect of TiO2 Filler on the Mechanical Properties of Polymer Nanocomposites

Nanocomposites with polymer matrix offer excellent opportunities to explore new functionalities beyond those of conventional materials. TiO₂, as a reinforcement agent in polymeric nanocomposites, is a viable strategy that significantly enhanced their mechanical properties. The size of the filler plays an essential role in determining the mechanical properties of the nanocomposite. A defining feature of polymer nanocomposites is that the small size of the fillers leads to an increase in the interfacial area compared to traditional composites. The interfacial area generates a significant volume fraction of interfacial polymer, with properties different from the bulk polymer even at low loadings of the nanofiller. This review aims to provide specific guidelines on the correlations between the structures of TiO₂ nanocomposites with polymeric matrix and their mechanical properties. The correlations will be established and explained based on interfaces realized between the polymer matrix and inorganic filler. The paper focuses on the influence of the composition parameters (type of polymeric matrix, TiO₂ filler with surface modified/unmodified, additives) and technological parameters (processing methods, temperature, time, pressure) on the mechanical strength of TiO₂ nanocomposites with the polymeric matrix.

Cytotoxicity and DNA damage evaluation of TiO2 and ZnO nanoparticles. Uptake in lung cells in culture

The cytotoxicity and DNA damage of titanium dioxide and zinc oxide nanoparticles (TiO₂ and ZnO NPs) have been studied in a human lung carcinoma cell line (A549) after 24 h exposure. TiO₂ and ZnO NPs had mean diameters of 12.9 ± 2.8 and 24.1 ± 8.0 nm, respectively. ZnO NPs reduced cell viability from 250 μg/mL, increasing reactive oxygen species (ROS) and decreased GSH/GSSG ratio. The comet assay detected DNA damage from 50 μg/mL. TiO₂ NPs induced cytotoxicity and DNA damage from 50 to 100 μg/mL, respectively, along with a decrease of the GSH/GSSG ratio. Both particles were found inside the cells, within membrane-bound vesicles. The internalization mechanism is promoted partially by caveolae-mediated endocytosis and, in the case of TiO₂ NPs, also by macropinocytosis.

Mechanical and Antimicrobial Polyethylene Composites with CaO Nanoparticles

Low-density polyethylene composites containing different sizes of calcium oxide (CaO) nanoparticles were obtained by melt mixing. The CaO nanoparticles were synthesized by either the sol-gel or sonication methods, obtaining two different sizes: ca. 55 nm and 25 nm. These nanoparticles were used either as-synthesized or were modified organically on the surface with oleic acid (Mod-CaO), at concentrations of 3, 5, and 10 wt% in the polymer. The Mod-CaO nanoparticles of 25 nm can act as nucleating agents, increasing the polymer’s crystallinity. The Young’s Modulus increased with the Mod-CaO nanoparticles, rendering higher reinforcement effects with an increase as high as 36%. The reduction in Escherichia coli bacteria in the nanocomposites increased with the amount of CaO nanoparticles, the size reduction, and the surface modification. The highest antimicrobial behavior was found in the composites with a Mod-CaO of 25 nm, presenting a reduction of 99.99%. This strong antimicrobial effect can be associated with the release of the Ca²⁺ from the composites, as studied for the composite with 10 wt% nanoparticles. The ion release was dependent on the size of the nanoparticles and their surface modification. These findings show that CaO nanoparticles are an excellent alternative as an antimicrobial filler in polymer nanocomposites to be applied for food packaging or medical devices.

Synthesis of Chitosan Beads Incorporating Graphene Oxide/Titanium Dioxide Nanoparticles for In Vivo Studies

Scaffold development for cell regeneration has increased in recent years due to the high demand for more efficient and biocompatible materials. Nanomaterials have become a critical alternative for mechanical, thermal, and antimicrobial property reinforcement in several biopolymers. In this work, four different chitosan (CS) bead formulations crosslinked with glutaraldehyde (GLA), including titanium dioxide nanoparticles (TiO₂), and graphene oxide (GO) nanosheets, were prepared with potential biomedical applications in mind. The characterization of by FTIR spectroscopy, X-ray photoelectron spectroscopy (XRD), thermogravimetric analysis (TGA), energy-dispersive spectroscopy (EDS) and scanning electron microscopy (SEM), demonstrated an efficient preparation of nanocomposites, with nanoparticles well-dispersed in the polymer matrix. In vivo, subdermal implantation of the beads in Wistar rat′s tissue for 90 days showed a proper and complete healing process without any allergenic response to any of the formulations. Masson′s trichrome staining of the histological implanted tissues demonstrated the presence of a group of macrophage/histiocyte compatible cells, which indicates a high degree of biocompatibility of the beads. The materials were very stable under body conditions as the morphometry studies showed, but with low resorption percentages. These high stability beads could be used as biocompatible, resistant materials for long-term applications. The results presented in this study show the enormous potential of these chitosan nanocomposites in cell regeneration and biomedical applications.

Fungicides Films of Low-Density Polyethylene (LDPE)/Inclusion Complexes (Carvacrol and Cinnamaldehyde) Against Botrytis Cinerea

Low density polyethylene (LDPE) films were prepared with the incorporation of natural agents (carvacrol and trans-cinnamaldehyde) by the melting process. The co-precipitation method was used successfully to complex the carvacrol or trans-cinnamaldehyde with β-cyclodextrin (β-CD). The active compounds encapsulated in β-CD achieved ca. 90% encapsulation efficiency (E.E.). The inclusion complex studied by scanning electron microscopy (SEM) found particles of different sizes, ca. 4 μm. The active compounds were added directly (1 and 5 wt %) into the polymer matrix, yielding LDPE + carvacrol and LDPE + cinnamaldehyde films. The active compounds encapsulated in β-cyclodextrin (β-CD) were added to LDPE, yielding LDPE + β-CD-carvacrol and LDPE + β-CD-cinnamaldehyde films. The incorporation of carvacrol and trans-cinnamaldehyde, and their corresponding inclusion complexes with β-cyclodextrin, did not affect the thermal properties of LDPE. The microcapsules distributed in all polymer matrices had sizes of 5–20 μm as shown by scanning electron microscopy (SEM). In terms of mechanical properties, the polymers showed a slight decrease of Young’s modulus (12%) and yield stress compared (14%) to neat LDPE. This could be due to the essential oil acting as a plasticizer in the polymer matrix. The LDPE + carvacrol and LDPE + cinnamaldehyde films had the capacity to inhibit fungi by 99% compared to neat LDPE. The effectiveness against fungi of LDPE+β-CD + active agent was slower than by the direct incorporation of the essential oil in the LDPE in the same amount of active agent. The biocidal properties were related to the gradual release of active compound from the polymer. The results confirm the applicability of carvacrol, trans-cinnamaldehyde, and their corresponding inclusion complexes in active packaging, as well as their use in the food delivery industry.

Review of Recent Advances in Polylactic Acid/TiO2 Composites

Polylactic acid/titanium oxide (PLA/TiO2) composites as multifunctional materials have been studied extensively by couple of research groups owing to their outstanding mechanical, thermal, photocatalytic, and antimicrobial properties. This review describes the experimental approaches used to improve the compatibility of PLA/TiO2 composites. The mechanical, thermal, photocatalytic, and antimicrobial properties of PLA/TiO2 composites are discussed. The potential applications arising from the structural and functional properties of PLA/TiO2 composites were also reviewed. Finally, it is concluded that a deep understanding of the impacts of TiO2 filler with available improvement approaches in the dispersibility of this filler in the PLA matrix would be the key for the effective usage of PLA/TiO2 composites and to expand their suitability with worldwide application requirements.

The Quality Evaluation of Postharvest Strawberries Stored in Nano-Ag Packages at Refrigeration Temperature

Different percentages (0%, 1%, 5%, and 10%) of nano-Ag particles were added to polylactic acid (PLA) to make an active nanocomposite packaging film. Strawberries were packaged by the nanocomposite films and stored at 4 ± 1 °C for 10 days. The freshness of strawberries was assessed by regularly measuring the physicochemical properties of the strawberries in each packaging film. The difference in the freshness of strawberries was evaluated by determining the following parameter changes: weight loss, hardness, soluble solids, titratable acid, color, vitamin C, total phenol, free radical scavenging activity, peroxidase activity, and sensory evaluation. The results revealed that the active nanocomposite packaging film has better preservation effect when compared with pure PLA film. Its preservation effect is mainly reflected in the more effective reduction of vitamin C loss, delaying the decline of total phenols and 1-Diphenyl-2-picrylhydrazyl (DPPH) in strawberries. It also showed better physical properties. The results showed that the PLA nanocomposite packaging film could effectively preserve freshness of strawberries.

Polyethylene/silver-nanofiber composites: A material for antibacterial films

Silver nanofibers (Ag-Nfbs)~80nm in diameter were synthesized by hydrothermal treatment. The nanofibers (3 and 5wt%) were added in the initial feed together with the catalytic system. Polymerizations in an ethylene atmosphere were performed, yielding PE nanocomposites in situ with 3 and 5wt% content of Ag-Nfbs. The antibacterial effect of the silver-nanofiber composites was evaluated after incubation of Escherichia coli ATCC 25923 for 8h on their surface. Bacterial viability tests showed that the silver-nanofiber composites inhibited the growth of Escherichia coli ATCC 25923 by 88 and 56%. This behavior is attributed to increased silver ions release from the nanocomposite. TEM analysis showed that the antibacterial effect is associated with membrane disruption but not with changes in shape.

Bionanocomposites with enhanced antimicrobial activity and photodegradability based on low density polyethylene and nano TiO2/organoclay

Bionanocomposite materials with enhanced photodegradability and bactericidal activity, as well as improved gas barrier properties, were manufactured by incorporating silicate nanolayers into the structure of low density polyethylene (LDPE) filled with nano titanium dioxide (TiO2) via melt compounding. Effects of interfacial compatibilization upon developed microstructure were studied by incorporating maleated LDPE into the nanocomposites formulation. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and rheo-mechanical spectroscopy (RMS) techniques were conducted to characterize the microstructure of the nanocomposites. Interfacially compatibilized TiO2/organoclay (OC) based nanocomposites exhibited shorter induction time for the onset of photodegradation, and an acceptable inactivation of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) microbe cells upon UV light irradiation, indicating enhanced photoactivity of the hybridized TiO2/OC nanosystem. TiO2/OC-based nanocomposites exhibited increased melt viscosity and pseudo solid like characteristics in melt linear viscoelastic behavior. Moreover, TiO2/OC-based nanocomposites presented improved barrier properties, which make such materials applicable for packaging applications.