Antimicrobial films obtained from latex particles functionalized with quaternized block copolymers

Incorporation of Poly(Itaconic Acid) with Quaternized Thiazole Groups on Gelatin-Based Films for Antimicrobial-Active Food Packaging

Poly(itaconic acid) (PIA) was synthesized via conventional radical polymerization. Then, functionalization of PIA was carried out by an esterification reaction with the heterocyclic groups of 1,3-thiazole and posterior quaternization by N-alkylation reaction with iodomethane. The modifications were confirmed by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H-NMR), as well as ζ-potential measurements. Their antimicrobial activity was tested against different Gram-negative and Gram-positive bacteria. After characterization, the resulting polymers were incorporated into gelatin with oxidized starch and glycerol as film adjuvants, and dopamine as crosslinking agent, to develop antimicrobial-active films. The addition of quaternized polymers not only improved the mechanical properties of gelatin formulations, but also decreased the solution absorption capacity during the swelling process. However, the incorporation of synthesized polymers increased the deformation at break values and the water vapor permeability of films. The antioxidant capacity of films was confirmed by radical scavenging ability and, additionally, those films exhibited antimicrobial activity. Therefore, these films can be considered as good candidates for active packaging, ensuring a constant concentration of the active compound on the surface of the food, increasing products' shelf-life and reducing the environmental impact generated by plastics of petrochemical origin.

Chemical Hydrogels Bearing Thiazolium Groups with a Broad Spectrum of Antimicrobial Behavior

Several hydrogels based on 2-hydroxyethyl methacrylate and a methacrylic monomer containing a thiazole group in its lateral chain have been prepared by thermal polymerization at 60 °C in water solution varying the chemical composition of the gels. The posterior quaternization of the thiazole groups with methyl iodine has rendered positively charged hydrogels with potential antimicrobial activity. This modification has been structurally characterized by infrared spectroscopy, whereas the thermal stability of all hydrogels has been studied by thermal degradation in inert atmosphere. The swelling behavior in distilled water and the rheology of the different hydrogels have been analyzed as a function of 2-(4-methylthiazol-5-yl)ethyl methacrylate (MTA) monomer content as well as its methylation. Finally, the active character of hydrogels against Gram-positive and Gram-negative bacteria and fungi has been evaluated, revealing excellent antimicrobial activity against all tested microorganisms. The methylated hydrogels could be used as potential materials for wound healing or contact lens applications.

Microbicidal Dispersions and Coatings from Hybrid Nanoparticles of Poly (Methyl Methacrylate), Poly (Diallyl Dimethyl Ammonium) Chloride, Lipids, and Surfactants

Hybrid and antimicrobial nanoparticles (NPs) of poly (methyl methacrylate) (PMMA) in the presence of poly (diallyl dimethyl ammonium) chloride (PDDA) were previously obtained by emulsion polymerization in absence of surfactant with low conversion. In the presence of amphiphiles such as cetyl trimethyl ammonium bromide (CTAB), dioctadecyl dimethyl ammonium bromide (DODAB) or soybean lecithin, we found that conversion increased substantially. In this work, the effect of the amphiphiles on the NPs core-shell structure and on the antimicrobial activity of the NPs was evaluated. NPs dispersions casted on silicon wafers, glass coverslips or polystyrene substrates were also used to obtain antimicrobial coatings. Methods for characterizing the dispersions and coatings were based on scanning electron microscopy, dynamic light scattering, determination of thickness, rugosity, and wettability for the coatings and determination of colony-forming unities (log CFU/mL) of microbia after 1 h interaction with the coatings or dispersions. The amphiphiles used during PMMA/PDDA/amphiphile NPs synthesis reduced the thickness of the NPs PDDA shell surrounding each particle. The antimicrobial activity of the dispersions and coatings were due to PDDA-the amphiphiles were either washed out by dialysis or remained in the PMMA polymeric core of the NPs. The most active NPs and coatings were those of PMMA/PDDA/CTAB-the corresponding coatings showed the highest rugosity and total surface area to interact with the microbes. The dispersions and coatings obtained by casting of the NPs dispersions onto silicon wafers were hydrophilic and exhibited microbicidal activity against Escherichia coli, Staphylococcus aureus, and Candida albicans. In addition, a major effect of reduction in particle size revealed the suitability of nanometric and cationic NPs (sizes below 100 nm) represented by PMMA/PDDA/CTAB NPs to yield maximal microbicidal activity from films and dispersions against all microbia tested. The reduction of cell viability by coatings and dispersions amounted to 6-8 logs from [PDDA] ≥ minimal microbicidal concentration.

Thermoresponsive Poly(N-Isopropylacrylamide-co-Dimethylaminoethyl Methacrylate) Microgel Aqueous Dispersions with Potential Antimicrobial Properties

The work herein describes the preparation of thermoresponsive microgels with potential antimicrobial properties. Most of the work performed so far regarding microgels with antimicrobial activity, deals with the ability of microgels to carry and release antibiotics or antimicrobial agents (antimicrobial peptides). The originality of this work lies in the possibility of developing intrinsic antimicrobial microgels by copolymerization of the well-known thermoresponsive monomer, N-isopropylacrylamide (NIPAM) with dimethylaminoethyl methacrylate (DMAEMA), a water-soluble monomer, to form microgels via precipitation polymerization (radical polymerization). Due to the presence of a tertiary amine in the DMAEMA comonomer, microgels can be modified by N-alkylation reaction with methyl and butyl iodide. This quaternization confers positive charges to the microgel surfaces and thus the potential antimicrobial activity. The effect of DMAEMA content and its quaternization with both, methyl and butyl iodide is evaluated in terms of thermal and surface charge properties, as well as in the microgel size and viscoelastic behavior. Finally, a preliminary study of the antimicrobial activity against different microorganisms is also performed in terms of minimum inhibitory concentration (MIC). From this study we determined that in contrast with butylated microgels, methylated ones show potential antimicrobial activity and good physical properties besides of maintaining microgel thermo-responsiveness.

Antimicrobial Porous Surfaces Prepared by Breath Figures Approach

Herein, efficient antimicrobial porous surfaces were prepared by breath figures approach from polymer solutions containing low content of block copolymers with high positive charge density. In brief, those block copolymers, which were used as additives, are composed of a polystyrene segment and a large antimicrobial block bearing flexible side chain with 1,3-thiazolium and 1,2,3-triazolium groups, PS54-b-PTTBM-M44, PS54-b-PTTBM-B44, having different alkyl groups, methyl or butyl, respectively. The antimicrobial block copolymers were blended with commercial polystyrene in very low proportions, from 3 to 9 wt %, and solubilized in THF. From these solutions, ordered porous films functionalized with antimicrobial cationic copolymers were fabricated, and the influence of alkylating agent and the amount of copolymer in the blend was investigated. Narrow pore size distribution was obtained for all the samples with pore diameters between 5 and 11 µm. The size of the pore decreased as the hydrophilicity of the system increased; thus, either as the content of copolymer was augmented in the blend or as the copolymers were quaternized with methyl iodide. The resulting porous polystyrene surfaces functionalized with low content of antimicrobial copolymers exhibited remarkable antibacterial efficiencies against Gram positive bacteria Staphylococcus aureus, and Candida parapsilosis fungi as microbial models.

Self-Assembled Antimicrobial Nanomaterials

Nanotechnology came to stay improving the quality of human life by reducing environmental contamination of earth and water with pathogens. This review discusses how self-assembled antimicrobial nanomaterials can contribute to maintain humans, their water and their environment inside safe boundaries to human life even though some of these nanomaterials display an overt toxicity. At the core of their strategic use, the self-assembled antimicrobial nanomaterials exhibit optimal and biomimetic organization leading to activity at low doses of their toxic components. Antimicrobial bilayer fragments, bilayer-covered or multilayered nanoparticles, functionalized inorganic or organic polymeric materials, coatings and hydrogels disclose their potential for environmental and public health applications in this review.

Tailoring Macromolecular Structure of Cationic Polymers towards Efficient Contact Active Antimicrobial Surfaces

The aim of this work is the preparation of contact active antimicrobial films by blending copolymers with quaternary ammonium salts and polyacrylonitrile as matrix material. A series of copolymers based on acrylonitrile and methacrylic monomers with quaternizable groups were designed with the purpose of investigating the influence of their chemical and structural characteristics on the antimicrobial activity of these surfaces. The biocide activity of these systems was studied against different microorganisms, such as the Gram-positive bacteria Staphylococcus aureus and the Gram-negative bacteria Pseudomona aeruginosa and the yeast Candida parapsilosis. The results confirmed that parameters such as flexibility and polarity of the antimicrobial polymers immobilized on the surfaces strongly affect the efficiency against microorganisms. In contrast to the behavior of copolymers in water solution, when they are tethered to the surface, the active cationic groups are less accessible and then, the mobility of the side chain is critical for a good contact with the microorganism. Blend films composed of copolymers with high positive charge density and chain mobility present up to a more than 99.999% killing efficiency against the studied microorganisms.

Preparation of Copolymer-Based Nanoparticles with Broad-Spectrum Antimicrobial Activity

Polyacrylate and guanidine-based nanoparticles which involve acrylate monomers and glycidyl methacrylate modified oligo-guanidine were prepared by a seeded semi-continuous emulsion polymerization. The results from transmission electron microscope and dynamic light scattering measurements showed that the nanoparticles were spherical in shape and the particle size was in the range of 80⁻130 nm. Antimicrobial experiments were performed with two types of bacteria, Gram-negative (Escherichia coli, ATCC 8739) and Gram-positive (Staphylococcus aureus, ATCC 6538). The as-synthesized cationic nanoparticles exhibited effective antimicrobial activities on Escherichia coli and Staphylococcus aureus with the minimal inhibitory concentrations at 8 μg/mL and 4 μg/mL, respectively. The mechanism of action of the resulted nanoparticles against these bacteria was revealed by the scanning electron microscopic observation. In addition, the films consisting of latex nanoparticles are non-leaching antimicrobial materials with excellent antimicrobial activity, which indicates the polymers could preserve their antimicrobial activity for long-term effectiveness.

Antimicrobial Polymers in the Nano-World

Infections are one of the main concerns of our era due to antibiotic-resistant infections and the increasing costs in the health-care sector. Within this context, antimicrobial polymers present a great alternative to combat these problems since their mechanisms of action differ from those of antibiotics. Therefore, the microorganisms' resistance to these polymeric materials is avoided. Antimicrobial polymers are not only applied in the health-care sector, they are also used in many other areas. This review presents different strategies that combine nanoscience and nanotechnology in the polymer world to combat contaminations from bacteria, fungi or algae. It focuses on the most relevant areas of application of these materials, viz. health, food, agriculture, and textiles.

“Leaching or not leaching”: an alternative approach to antimicrobial materials via copolymers containing crown ethers as active groups

New copolymers containing MMA and 18C6 crown-ether pendants, with or without a PEG arm, were synthesized to check if sequestering structural alkali-earth ions from the bacterial outer membrane (OM) may lead to bacterial death.

Polymeric Quaternary Ammonium-Containing Coatings with Potential Dual Contact-Based and Release-Based Antimicrobial Activity

In the present work, reactive blending of copolymers with complementary functional groups was applied to control their antimicrobial activity and antifouling action in real conditions. For this purpose, two series of copolymers, poly(4-vinylbenzyl chloride-co-acrylic acid), P(VBC-co-AAx), and poly(sodium 4-styrenesulfonate-co-glycidyl methacrylate), P(SSNa-co-GMAx), were synthesized via free radical copolymerization and further modified by the incorporation of biocidal units either covalently (4-vinyl benzyl dimethylhexadecylammonium chloride, VBCHAM) or electrostatically bound (cetyltrimethylammonium 4-styrenesulfonate, SSAmC₁₆). The cross-linking reaction of the carboxylic group of acrylic acid (AA) with the epoxide group of glycidyl methacrylate (GMA) of these two series of reactive antimicrobial copolymers was explored in blends obtained through solution casting after curing at various temperatures. The combined results from the ATR-FTIR characterization of the membranes, solubility tests, turbidimetry, and TEM suggest that the reaction occurs already at 80 °C, leading mostly to graft samples, while at higher curing temperatures (120 or 150 °C) insoluble cross-linked samples are usually obtained. Controlled release experiments of selected membranes were performed in pure water and aqueous 1 M NaCl solutions for a period of two months. The released material was followed through gravimetry and TOC/TN measurements, while the evolution of the integrity and the morphology of the membranes were followed visually and through SEM, respectively. Antimicrobial tests also revealed that the cross-linked membranes presented strong antimicrobial activity against S. aureus and P. aeruginosa. Finally, a specific blend combination was applied on aquaculture nets and cured at 80 °C. The modified nets, emerged in the sea for 15 and 35 days, exhibited high antifouling action as compared to blank nets.

Synthesis of antimicrobial block copolymers bearing immobilized bacteriostatic groups

Antimicrobial block copolymers bearing covalently bonded quaternized ammonium groups were synthesized through atom transfer radical polymerization (ATRP). Moreover, a new class of antimicrobial block copolymers were designed combining two types of biocide incorporation into one system (both contact-based and release-based mechanisms).