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ISSN : 1226-0088(Print)
ISSN : 2288-7253(Online)
Membrane Journal Vol.32 No.1 pp.23-32
DOI : https://doi.org/10.14579/MEMBRANE_JOURNAL.2022.32.1.23

Membrane Containing Biocidal Material for Reduced Biofilm Formation: A Review

Soohyun Son*, Rajkumar Patel**†
*Life Science and Biotechnology Department (LSBT), Underwood Division (UD), Underwood International College, Yonsei University, Seoul 03722, South Korea
**Energy and Environmental Science and Engineering (EESE), Integrated Science and Engineering Division (ISED), Underwood International College, Yonsei University, Incheon 21983, South Korea
†Corresponding author(e-mail: rajkumar@yonsei.ac.kr; http://orcid.org/0000-0002-3820-141X)
February 15, 2022 ; February 22, 2022 ; February 22, 2022

Abstract


Bacteria grow biofilm on various surface such as separation membrane, food packaging film and biomedical device. Growth of biofilm is associated with the formation of a complex structure of exopolysaccharides. Effect of antibacterial effect reduce drastically once the biofilm developed due to the difficulties in mass transport of antimicrobial agent. In order to enhance the antibacterial activity, surface of the membrane is modified, coated or immobilized with functional materials with biocidal properties. One of the idea is to introduce positive charge on the membrane surface by the presence of quaternary ammonium group which might displace divalent metal ion such as magnesium or calcium present in the bacteria cell wall. Efficacy of cell membrane disruption depends on the mobility of the agents available directly on the surface environment. In this review, various biocidal agents like quaternary ammonium group, helamine or zwitter ion containing membrane are discussed.


biocidal membrane , biofilm , antibacterial , zwitterion

미생물막 형성을 막기 위한 살균 물질 함유 막: 총설

손 수 현*, 라즈쿠마 파텔**†
*연세대학교 언더우드학부 생명과학공학과
**연세대학교 언더우드학부 융합과학공학부 에너지환경융합전공

초록


세균은 분리막, 식품 포장 필름 및 바이오 의료 기기와 같은 다양한 미생물 막의 표면 위에서 자란다. 미생물 막 의 성장은 엑소폴리사카라이드의 복잡한 구조 형성과 밀접한 관련이 있다. 미생물 막이 항균제의 대량 수송의 어려움으로 성 장하게 될 경우 항균효과는 급격하게 감소한다. 항균 활동을 활성화하기 위해서 막의 표면은 살균 특성이 있는 기능성 물질 들로 변형, 코팅 또는 고정한다. 한 가지 아이디어는 막 표면에 양전하 이온을 도입하는 것이다. 양전하 이온인 4차 암모늄 그룹의 존재는 마그네슘이나 칼슘같이 세균 세포벽에 존재하는 2가 금속이온을 대체할 수 있다. 세포막 파괴의 효능은 표면 환경에서 사용 가능한 작용제들의 이동성에 달려있다. 이 리뷰에서는 4차 암모늄 그룹, 헬라민(helamine), 쌍성이온(zwitter ion)과 같이 여러 살생물제를 포함하고 있는 막들을 다룬다.


    1. Introduction

    Health of human is at high risk due to bacteria triggered infectious disease. Bacterial growth can be controlled by coating the membrane surface by antimicrobial agent. Quaternary ammonium salt (QAS) function as a biocidal entity which can be grafted to the polymer chain present or can the small units can be coated on the surface[1-3]. Cell membrane of the bacteria can be ruptured by immobilized QAS, in which case mobility might be slow. Silver nanoparticles immobilized on to quaternary ammonium group rupture the cell wall by leaching from the host surface.

    Growing industrialization and unusual weather condition leads to scarcity of clean water. Desalination of sea water is another source to generate clean water. Reverse osmosis (RO) is well established separation technology for desalination in which biofouling of membrane is critical problem. Thin film nanocomposite membrane (TFNC) membrane prepared by interfacial polymerization in which nanoparticles are incorporated on the active layer which acts as antibacterial agents [4-9]. In order to extend the self-life of the antibiofouling membrane nanoparticles are immobilized with cationic functional group on the membrane surface.

    Similar to quaternized group zwitterionic polymer possess antibacterial properties in which both cationic and anionic centers are present. Presence of these group on the membrane surface prevent the adhesion of extracellular polymeric substance, which is the origination point of biofilm formation and microbial activity[10-13]. Presence of electrostatic interaction between the ionic groups and cell membrane as well as hydrophobicity of the long polymeric chain induce attraction leads to the instability of bacteria membrane surface. In this review, antifouling properties by quaternized group, nanoparticles and zwitterionic group are discussed. Fig. 1.

    2. Membrane with Quaternary Group

    Cationic polymer with quaternary –oniums group acts as antimicrobial agent[14]. A recent mechanism named “phospholipid sponge effect” proposes that the positive charge on the polymeric chain interact with negatively charged phospholipid on the cell membrane of the bacteria resulting in their agglomeration on the polymer surface. As a result, there is disruption of cell wall and bacterial death. Polyethylenimine (PEI) was modified by irradiation to prepare N,N-dodecyl methyl-co-N, Nmethylbenzophenone methyl quaternary PEI (DMBQPEI). Fig. 2 represent the phospholipid sponge effect.

    The crosslink density of the modified PEI was tuned to further confirm the sponge effect mechanism. Crosslink density of the polymer was checked by quantitative nanomechnical mapping. When the crosslink density of the quaternary polymer was increased, antibacterial activity reduced which indicates that the sterically hindrance in the interaction of cationic group with the anionic phospholipid present on the cell surface. Modified PEI with lower crosslink density are highly effective towards killing of S. aureus and E. Coli.

    Haresco et al. synthesized new poly(dopamine-sulfobetaine methacrylate) [P(DA-SBMA)] nanoparticles via aza-Michael addition and oxidative polymerization[15]. Those particles were embedded into polyamide layers of the thin film nanocomposite (TFN) membranes which is prepared by interfacial polymerization. FTIR and SEM illustrated successful crafting of the membrane containing P(DA-SBMA) particles. The resulting TFN membrane had improved hydrophilicity, having negatively charged surface. The optimal activity was exhibited by the TFN membrane with weight ratio [P(DA-SBMA)/TMC] of 0.55, providing pure water flux of 73.11 ± 6.73 L m-2 h-1 and salt flux of 64.21 ± 3.94 L m-2 h-1 with salt rejection of 98.20%. It also showed excellent fouling resistance, exhibiting high flux recovery rate of 99.53% after the exposure to BSA (protein). P(DA-SBMA) particles successfully improved the performance of thin-film nanocomposite membranes.

    Ma et al. crafted SBMA@EVOH nanofibrous membrane by reacting Poly(vinyl alcohol-co-ethylene) (EVOH) with BPTCD (3,3’,4,4’-benzophenonetetracaboxylic dianhydride) and a zwitterionic monomer [2-(methacryloyloxy) ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA) [16]. The resulting SBMA@EVOH NFMs performed manageable biocidal activity through constant reactive oxygen species (ROS) generation or by storing photoactivity under UV light and releasing ROS in the dark condition. SBMA moieties added antifouling properties to the NFMs, minimizing bacterial adhesion. The combination of biocidal and bacterial anti-adhesion prop-erty makes SBMA@EVOH NFMs inhibit microbial contaminations and biofilm formation, making the membranes suitable for various applications.

    Zhang et al. reported antiviral nanofibrous membrane which is applied for bioprotection[17] (Fig. 2 & 3). Various polyvinyl alcohol-co-polyethylene (PVA-co-PE) based modified nanofiber membrane were fabricated by electrospinning prcess. Those bio protective nanofirous membrane (RNM) maintain biocidal performance under light and easily release reactive oxygen species (ROS) in dark conditions, allowing consistent biocidal activity. Under dark conditions, the synthesized BDCA-RNM membrane killed 6 log colony forming unit of L.innocua and E.Coli in 120 minutes, exhibiting effective contact- killing activity. The antibacterial performance under light conditions was similar to that of the dark conditions. The RNMs also showed high filtration performance and robust structure, allowing it to be effectively employed for bioprotective purposes.

    Antifouling thin film composite membrane was prepared by grafting of long polymer chain containing ionic end groups[18]. Macroinitiator was generated on the thin film composite membrane surface by mussel- inspired method in which catechol chemistry was used in dopamine. Then it was further linked to antifouling zwitterionic polymer brushes and QAS polymer brushes through surface initiated activators regenerated by electron transfer−atom transfer radical polymerization (ARGET-ARTP). The synthetic scheme is represented in Fig. 5.

    The resulting membrane is a dual functioning membrane that exhibits resistance towards biocontaminant adhesion and degradation of the biocontaminants. The chemical force microscopy and protein/bacterial adhesion tests results illustrate fine antimicrobial activity and low biofouling propensity, showing great potential to be applied to water purification and desalination through reverse osmosis process.

    Yi et al. demonstrated a photoactive membrane for dye degradation by modifying the silk-derived nanofibrous membrane with 3,3’,4,4’-benzophenone tetracarboxylic dianhydride (BDSNM)[19]. Synthesis scheme is presented in Fig. 6.

    BDSNM could store photoactive activity and release reactive oxygen species (ROS). The resulting BDSNM displayed large surface area of 13.8 m2g-1, rapid ROS production, fine diameter of 129 nm, superhydrophilicity, and excellent degradation capacity for reactive red 195 by more than 99.9999% within 30 min. Its efficiency is intact for up to five cycles. This silk membrane with outstanding photoactive capacity can help further application for decoloration of dyes by photoactive membranes.

    3. Halamine Containing Membrane

    Bai et al. demonstrated an effective way of synthesizing N-Halamine containing polymers having antibacterial properties[20]. Through electrospinning, nanofiber of polymethylmethacrylic acid (PMMA) containing N-halamine was prepared, which has antibacterial activity against E. coli and S. aureus. Fig. 7 represents the antibacterial properties of the nanofiber membrane.

    The antibacterial mechanism of PMMA fibers carrying N-halamine can be attributed to both contact killing and release killing. It was also revealed to continue antibacterial activity performance for 5 recycle tests. The synthesis provides an easy strategy to fabricate N-halamines, yet the PMMA fibers despite being adaptive to electrospinning, are not rigid and flexible enough for practical application, thus requiring further research.

    Si et al. reported a new efficient mode of disinfecting water in attempt to solve conventional water disinfection issues[21]. Those included chemically intensive methods, biofouling, and irrevocable consumption of disinfectants, ultimately limiting the practical use to treat real-life contaminated water. The idea is to construct biocidal, replenishable nanofibrous membrane architectures by incorporating N-halamine antimicrobial agent with electrospun biocidal nanofibrous (BNF) membranes (BNF). Fig. 8 represent the scheme diagram of nanofiber membrane fabrication.

    The synthesis employed solvent-free melt radical graft polymerization to bond N-halamine moieties covalently and uniformly to the polymers, and electrospinning the nanofibrous membrane. In combination with rigidity and the high flux of the nanofibrous architecture (10,000 L m-2 h-1), N-halamine contents allowed easy chlorination of the BNF membrane, allowing BNF membranes to effectively reduce 6 log Colony Forming Unit of pathogenic E. coli in 10 minutes of contact time. This proves BNF membranes are much practical to disinfect the real-life contaminated water compared to traditional methods, in the way that not only its biocidal activity is rechargeable but also having robust, high flux membrane structure allowing direct filtration of water.

    4. Zwitterionic Containing Membrane

    A mussle-inspired nanofiltration membrane was prepared for wastewater treatment process. Dopamine was rapidly deposited and polymerized onto zwitterionic polymer (SBMA) by generation of hydroxyl free radical in the CuSO4/H2O2 complex to prepare PDA/SBMA membrane[22]. The resulting RD-1S membrane with 2mg/mL PDA and 2mg/mL SBMA showed optimum surface property. The separation capability of the crafted membrane showed low salt rejection and high dye rejection. Pure water flux of the membrane is 27.4 L m-2 h-1 bar-1. RD-1S membrane further exhibited excellent anti-fouling performance considering both fouling resistance reversibility and anti-bacterial activity through co-existence of chelated copper and SBMA.

    Liu et al. prepared polyzwitterionic brush by ATRP on TFC membrane to construct a profoundly antifouling membrane[23]. The membrane characterization revealed that the thick coverage of polyzwitterionic brushes reduced the roughness and increased hydrophilicity and water affinity of the surface. Such characterization can be attributed to increased antifouling property of the membrane since it minimized the surface area available for the interaction between the foulant (1 order less of interaction than original TFC membrane) and the membrane and allowed formation of concentrated hydration layer, acting as an energetic barrier towards foulant absorption. The polyzwitterionic brushes on TFC-PSBMA (poly(sulfobetaine methacrylate)) membrane also prevented calcium-ion induced fouling due to their coverage of the shielding carboxylic groups that existed on the original TFC membrane. The water flux experiment showed that after 500 mL of feed solution permeated, TFC membrane had 25% decline in flux while TFC-PSBMA had only experienced decline of 15%. Although the antifouling mechanisms are typically effective at early stages of fouling, the polyzwitterionic coated TFC membrane remarkably delayed fouling compared to the original TFC membrane. With TFC-PSBMA, it is possible to maintain transport properties while controlling organic antifouling, thus applicable in various industrial fields.

    Zhao et al. demonstrated antifouling membranes with amphiphilic surfaces by incorporating hydrophilic poly(ethylene oxide) (PEO) and low surface energy polydimethylsiloxane (PDMS)[24]. PEO was employed for fouling-resistance through prevention of biofoulant absorption and PDMS was used to release absorbed biofoulants. The surface features of the membrane were determined through FTIR, XPS, and water contact angle measurement. The resulting surfaces of the membrane had high antifouling performance compared to the control polyethersulfone (PES) membrane against bovine serum albumin (BSA), sodium alginate (SA), and yeast. The crafted membrane had rejection of >99.5%, 98%, and 100% against BSA, SA, and yeast respectively. The membrane also exhibited significant decrease of the decline in both irreversible and reversible flux upon shear flow, and near 100% flux recovery ratio for bio-separation.

    5. Conclusions

    Membrane fouling by bacteria is sever problem which can be tackle by different kind of modification. Functional group or nanoparticle with antibacterial properties need to be embedded or immobilized on the membrane process before biofilm formation. Cationic polymer with antibacterial properties dissolved in sol-ution exchange the divalent cation and disrupt the bacterial cell wall and death. Immobilized polymer brush with quaternary ammonium cation on the polymeric membrane surface are as effective as dissolved cationic polymeric solution. This mechanism is proved by the phospholipid sponge effect in which it showed that the cationic group interact with anionic phospholipid group on the bacterial wall and it agglomerate on the long chain hydrophobic polymer brush leading to cell wall rupture and death. In this review, three different groups such as quaternary ammonium, helamine and zwitterion are discussed.

    Figures

    MEMBRANE_JOURNAL-32-1-23_F1.gif

    Schematic diagram of classification of classification of the review.

    MEMBRANE_JOURNAL-32-1-23_F2.gif

    Illustration of How the Cross-Linking Density of DMBQPEI Networks Influences the Antimicrobial Efficiency Based on the Phospholipid Sponge Effect (Reproduced with permission from Gao et al., 14, Copyright 2017, American Chemical Society).

    MEMBRANE_JOURNAL-32-1-23_F3.gif

    Design, structure, and biocidal function of RNMs. (A) Chemical structure of BA-RNM, BD-RNM, CA-RNM, and BDCA-RNM. (B) Microscopic architecture of various RNM samples. (C) Optical photograph of the BDCA-RNM sample. (D) Schematic demonstration of the biocidal functions of RNMs by releasing ROS. (E) Jablonski diagrams representing the singlet excitation and following ISC to triplet. (F) Proposed mechanism for the photoactive and photo-storable biocidal cycles (Reproduced from Zhang et al., 17, American Association for the Advancement of Science).

    MEMBRANE_JOURNAL-32-1-23_F4.gif

    Antibacterial and antiviral properties of BDCA-RNM.(A and B) Bactericidal activity against E. coli and L. innocua of BDCA-RNM under daylight irradiation (A) and charged BDCA-RNM under dark conditions (B). (C and D) Five cycle antibacterial test of BDCA-RNMs under daylight irradiation (C) and charged BDCA-RNMs under dark conditions (D). (E to L) Morphology (E to H) and live/dead bacterial viability assay (I to L) of E. coli and L. innocua cells in contact with control membranes and BDCA-RNM with 1-hour daylight irradiation. (M and N) Measurement of the leakage of nucleic acid (M) and proteins (N) from E. coli and L. innocua cells. (O and P) Biocidal assay against T7 phage for BDCA-RNM under daylight irradiation (O) and charged BDCA-RNM under dark conditions (P) (Reproduced from Zhang et al., 17, American Association for the Advancement of Science).

    MEMBRANE_JOURNAL-32-1-23_F5.gif

    Illustration of the structure of dual-functional block polymer brushes on a TFC membrane for integrated antifouling strategy (a) and surface-initiated ARGET-ATRP synthesis of the poly(SBMA-b-MTAC) from the TFC membrane (b). The initiator BiBB (1) is coupled with dopamine (2) for immobilization onto the surface of the TFC membrane in pH 8.5 Tris buffer (Reproduced with permission from Ye et al., 18, Copyright 2015, American Chemical Society).

    MEMBRANE_JOURNAL-32-1-23_F6.gif

    Scheme of Design, Processing, and Degradation Functions of As-Prepared BDSNM (Reproduced with permission from Yi et al., 19, Copyright 2019, American Chemical Society).

    MEMBRANE_JOURNAL-32-1-23_F7.gif

    (A) Schematic illustration of dialysis test. (B) Oxidation–reduction reactions and (C) the corresponding color change involved in the iodometric/thiosulfate titration. (D) Antibacterial results of the dialysis test (Reproduced with permission from Bai et al., 20, Copyright 2016, American Chemical Society).

    MEMBRANE_JOURNAL-32-1-23_F8.gif

    (a) Scheme of the design, processing, and bactericidal functions of as-prepared BNF membranes. (b) Optical image of a BNF membrane on a large scale of 50 × 60 cm2. Microscopic nanofibrous architecture of (c) BNF-6, (d) BNF-8, and (e) BNF-10 membranes (Reproduced with permission from Si et al., 21, Copyright 2017, American Chemical Society).

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