Contact Active Antimicrobial Surfaces Research Articles

Preparation and characterization of poly(lactic acid)-based contact-active antimicrobial surfaces

Preparation and characterization of poly(lactic acid)-based contact-active antimicrobial surfaces

A Synthetic Overview of Preparation Protocols of Nonmetallic, Contact-Active Antimicrobial Quaternary Surfaces on Polymer Substrates.

Antibacterial surfaces have been researched for more than 30 years and remain highly desirable. In particular, there is an interest in providing antimicrobial properties to commodity plastics, because these, in their native state, are excellent substrates for pathogens to adhere and proliferate on. Therefore, efficient strategies for converting surfaces of commodity plastics into contact-active antimicrobial surfaces are of significant interest. Many systems have been prepared and tested for their efficacy. Here, the synthetic approaches to such active surfaces are reviewed, with the restriction to only include systems with tested antibacterial properties. The review focuses on the synthetic approach to surface functionalization of the most common materials used and tested for biomedical applications, which effectively has limited the study to quaternary materials. For future developments in the field, it is evident that there is a need for development of simple methods that permit scalable production of active surfaces. Furthermore, in terms of efficacy, there is an outstanding concern of a lack of universal antimicrobial action as well as rapid deactivation of the antibacterial effect through surface fouling.

Constructing a Contact-Active Antimicrobial Surface Based on Quarternized Amphiphilic Carbonaceous Particles against Biofilms.

Although contact-active antimicrobial surfaces (CAASs) are efficient, persistent, and safe in inhibiting bacterial adhesion and biofilm formation and much more desirable for applications in the fields ranging from industry to medical devices than others, the intrinsic defects, such as time and cost consumption and uncertainty in the stable immobilization of biocides, of previously established strategies affect their scaling-up preparations. Herein, a CAAS containing amphiphilic carbonaceous particles (ACPs), quarternized polyethyleneimine (QPEI), and thermoplastic polyurethane (TPU) was constructed by a carrier dispersion strategy. Its procedures included the immobilization of QPEI onto ACPs (ACPs-QPEI) and the incorporation of these modified particles into TPU. Its contact-medicated biocidal activity and other properties mentioned above were confirmed by in vitro/in vivo studies. As a crucial component of this surface, ACPs-QPEI showed good amphiphilic nature and strong antimicrobial activity. Its uniform incorporation not only endowed the TPU membrane with strong antimicrobial activity but also enlarged its strength and hydrophilicity at a proper dosage range. Its lethal dosages for 106 cfu mL-1 of Staphylococcus aureus, Escherichia coli, Candida albicans, and MRSA were all below 0.1 mg mL-1. Their amphiphilic nature would enable them to be compatible with different polarities of polymers theoretically, which means that much more CAASs could be prepared using this antimicrobial filler. The strategy was facile and feasible and might open an avenue for CAAS construction and applications.

In vitro evaluation of contact-active antibacterial efficacy of Ti-Al-V alloys coated with the antimicrobial agent PHMB

Immobilized polycationic substances on biomaterial surfaces kill adhering bacteria upon contact and are considered a promising non-antibiotic alternative. Unfortunately, there is no generally accepted in vitro method for quantitatively evaluating the antibacterial efficacy of contact-active non-leachable antimicrobial surfaces. Moreover, guidelines of generally accepted international industrial standards do not reflect the basic principle of bacterial contamination and/or are performed in the presence of a solid covering material. Therefore, in the present study, six bacterial adherence tests on non-porous surfaces with no covering material were compared with respect to their efficacy and reproducibility, as well as to evaluate the bactericidal contact-killing of relevant device-associated slime-producing bacteria using antimicrobially coated Ti6Al4V surfaces with positively-charged poly(hexamethylene biguanide) hydrochloride (PHMB). After direct bacterial inoculation to simulate a perioperative infection, non-leaching PHMB reacts bactericidally against the slime-producing bacteria Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa after surface contact. The 6-h drop technique was found to be a suitable method to quantitatively evaluate contact-active antibacterial surfaces. Adjunctively, however, damage of bacterial membrane integrity should be confirmed by LIVE/DEAD staining and the presence of non-leaching agents. Statement of SignificanceUnintentional perioperative bacterial adhesion to implant surfaces can generate biomaterial-associated infections. Adhered bacteria produce biofilms that protect them from antibiotic attack, which may be complicated by possible antibiotic resistance. Polycationic surfaces can prevent such unwanted biofilm formation by killing bacteria upon initial contact. Unfortunately, no reliable in vitro methods exist to evaluate the efficacy of contact-active antimicrobial surfaces. In this study, we show that the 6-h drop technique may be a suitable method to evaluate positively-charged contact-killing surfaces. Identification of suitable screening assays for evaluating the bactericidal efficacy of non-leachable antimicrobial agents will greatly improve this newly developing field as a prophylactic alternative to postoperative treatment of implant-associated infections by antibiotics.

Telechelic biocidal poly(2-oxazoline)s and polycations

Antimicrobial polymers are an important alternative to low molecular weight antibiotics and biocides. While most of such polymers are controlled in their activity by the nature of the backbone, telechelic biocidal polymers are controlled by their end groups. Here, polymers - mostly poly(2-alkyl-2-oxazoline)s - with a biocidal quaternary ammonium end group are discussed regarding their activity, the satellite group effect, and their application in contact-active antimicrobial surfaces and materials. Also the control of other end group functions, such as antibiotics and the end group effects on polycations are discussed.

Formation of contact active antimicrobial surfaces by covalent grafting of quaternary ammonium compounds.

Different synthetic strategies for the formation of contact active antimicrobial materials utilizing covalent linkage of quaternary ammonium compounds (QACs) were reviewed. There is a demand to find methods that will prevent bacterial fouling without the release of antimicrobial agents, because biocides cause environment pollution and promote the development of bacteria resistance mechanisms. The contact active antimicrobial surfaces may provide a useful tool for this purpose. The covalent surface grafting of QACs seems to be a feasible and promising approach for the formation of safe and effective antimicrobial materials that could be utilized for medical devices, food industry, water treatment systems and other applications. This manuscript reviews covalent attachment of QACs to form contact active antimicrobial materials based on glass, metals, synthetic and natural polymers. The review emphasizes the description of different synthetic methods that are used for the covalent linkage. Direct covalent linkage of QACs to the material surfaces, a linkage via auxiliary nanoparticles (NPs), or spacers, controlled radical polymerization techniques and a linkage to pre-activated surfaces are discussed. The physico-chemical properties and biological activity of the modified surfaces are also described. This review does not cover non-covalent grafting of QACs and incorporation of QACs into a bulk material.

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.

Natural active molecule chemical grafting on the surface of microfibrillated cellulose for fabrication of contact active antimicrobial surfaces

In this work, a naturally occurring phenyl isothiocyanate (PITC) molecule was covalently bonded to the surface of microfibrillated cellulose (MFC) to prepare contact active antimicrobial surfaces based on presently used materials. A preliminary comparative study was carried out on the reactivity of the hydroxyl group of cellulose and lignin compounds with phenyl isothiocyanate. Classical second order reaction kinetics was established between the hydroxyl containing model alcohol compounds and phenyl isothiocyanate with the conversion up to 80% in 20min. X-ray diffraction and scanning electron microscopy (SEM) were utilized to monitor the change in crystallinity and morphology of the surface after grafting. Further, the successful immobilization of isothiocyanate was confirmed after grafting with contact angle measurements, Fourier transform infrared spectroscopy (FTIR) and presence of sulfur by elemental analysis. Antibacterial activity was investigated against gram positive bacteria, Staphylococcus aureus and Bacillus subtilis, in dynamic and static experimental conditions. The PITC grafted MFC did not exhibit a bactericidal activity in dynamic condition, however, a very strong activity (complete killing) was revealed under static condition with 3.5 log initial CFU. These findings may help in the establishment of new and safe strategy for the preparation of antimicrobial contact surfaces for packaging applications.

Surface cationized cellulose nanofibrils for the production of contact active antimicrobial surfaces

In the last decade, a new fiber pretreatment has been proposed to make easy cellulose fibrillation into microfibrils. In this context, different surface cationized MFC was prepared by optimizing the experimental parameters for cellulose fibers pretreatment before fibrillation. All MFCs were characterized by conductometric titration to establish degree of substitution, field emission gun scanning electron microscopy (FEG-SEM), atomic force microscopy (AFM) and optical microscopy assessed the effect of pretreatment on the morphology of the ensuing MFCs. Antibacterial activities of neat and cationized MFC samples were investigated against Gram positive bacteria (Bacillus subtilis, Staphylococcus aureus) and Gram negative bacteria (Escherichia coli). The CATMFC sample at DS greater than 0.18 displayed promising results with antibacterial properties without any leaching of quaternary ammonium into the environment. This work proved the potential of cationic MFCs with specific DS for contact active antimicrobial surface applications in active food packaging, medical packaging or in health and cosmetic field.

Development of biomaterial surfaces with and without microbial nanosegments

Abstract Infections by microorganisms are a major problem in public health throughout the world. Artificial materials, including biomedical goods, inherently lack defense against microbial development. Therefore, microbial cells can adhere on any type of artificial surface, particularly in a moist environment, and start to multiply to form a huge population. In this review, we will discuss a strategy for designing antimicrobial polymers and antimicrobial surfaces. Generally, there are five types of antimicrobial polymers: (a) polymeric biocides, (b) biocidal polymers, (c) biocide-releasing polymers, (d) bioactive oligopeptides, and (e) antimicrobial surfaces. Antimicrobial surfaces preventing the growth of microorganisms are a promising method to inhibit the spread of microbial infections. The antimicrobial surfaces can reject the attachment of microbes and/or kill microbes in the vicinity and can be designed to kill microbes on contact. It is recommended that the material surface not release biocidal substances, therefore preventing exhaustion of biocide release to kill microbes. Furthermore, the antimicrobial surfaces are desired to be nontoxic to human cells. The development of contact-active antimicrobial surfaces by grafting antimicrobial nanosegments onto the material surface will be an important topic in the future.

Air-ozonolysis to generate contact active antimicrobial surfaces: Activation of polyethylene and polystyrene followed by covalent graft of quaternary ammonium salts

Air-ozonolysis was revealed as an accessible and effective approach for surface activation and further functionalization of hydrocarbon polymers. Antimicrobial contact active polyethylene (PE) and polystyrene (PS) were designed by generation on their surfaces OH-functional groups and covalent graft of dimethyloctadecyl [3-(trimethoxysilyl) propyl] ammonium chloride (C18-TSA) quaternary ammonium salt. The shortened analog, trimethyl [3-(trimethoxysilyl) propyl] ammonium chloride (C1-TSA), was also covalently attached to the activated PE and PS surfaces. X-ray photoelectron spectroscopy (XPS) and FTIR confirmed the surface modifications. Scanning electron (SEM) and confocal microscopy were utilized to monitor surface morphology and bacteria interactions. The antimicrobial effect of the C18-TSA grafted polymer surfaces was demonstrated on Gram-negative and Gram-positive bacteria species including human pathogen, Salmonella enterica. The shorter C1-TSA grafted polymers did not demonstrate bactericidal activity, suggesting the critical role of the alkyl chain length. The described strategy may establish a new general and safe platform for future development and application of contact active antimicrobial polymers.

Durable contact active antimicrobial materials formed by a one-step covalent modification of polyvinyl alcohol, cellulose and glass surfaces

In this work we have applied a direct covalent linkage of quaternary ammonium salts (QAS) to prepare a series of contact active antimicrobial surfaces based on widely utilized materials. Formation of antimicrobial polyvinyl alcohol (PVA-QAS), cellulose (cellulose-QAS) and glass (glass-QAS) surfaces was achieved by one step synthesis with no auxiliary linkers. The X-ray photoelectron spectroscopy (XPS) revealed tridentate binding mode of the antimicrobial agent. The antimicrobial activity of the prepared materials was tested on Bacillus cereus, Alicyclobacillus acidoterrestris, Escherichia coli and Pseudomonas aeruginosa. Active site density of the modified materials was examined and found to correlate with their antimicrobial activity. Stability studies at different pH values and temperatures confirmed that the linkage of the bioactive moiety to the surface is robust and resistant to a range of pH and temperatures. Prolonged long-term effectiveness of the contact active materials was demonstrated by their repeated usage, without loss of the antimicrobial efficacy.

Antimicrobial Polymers in Solution and on Surfaces: Overview and Functional Principles

The control of microbial infections is a very important issue in modern society. In general there are two ways to stop microbes from infecting humans or deteriorating materials—disinfection and antimicrobial surfaces. The first is usually realized by disinfectants, which are a considerable environmental pollution problem and also support the development of resistant microbial strains. Antimicrobial surfaces are usually designed by impregnation of materials with biocides that are released into the surroundings whereupon microbes are killed. Antimicrobial polymers are the up and coming new class of disinfectants, which can be used even as an alternative to antibiotics in some cases. Interestingly, antimicrobial polymers can be tethered to surfaces without losing their biological activity, which enables the design of surfaces that kill microbes without releasing biocides. The present review considers the working mechanisms of antimicrobial polymers and of contact-active antimicrobial surfaces based on examples of recent research as well as on multifunctional antimicrobial materials.