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1. Grafting polysiloxane onto ultrafiltration membranes to optimize surface energy and mitigate fouling

   https://doi.org/10.1039/D0SM00551G  

   Tran, Thien; Chen, Xiaoyi; Doshi, Sarthak; Stafford, Christopher M.; Lin, Haiqing (June 2020, Soft Matter)

   null (Ed.)

   Conventional approaches to mitigate fouling of membrane surfaces impart hydrophilicity to the membrane surface, which increases the water of hydration and fluidity near the surface. By contrast, we demonstrate here that tuning the membrane surface energy close to that of the dispersive component of water surface tension (21.8 mN m −1 ) can also improve the antifouling properties of the membrane. Specifically, ultrafiltration (UF) membranes were first modified using polydopamine (PDA) followed by grafting of amine-terminated polysiloxane (PSi-NH 2 ). For example, with 2 g L −1 PSi-NH 2 coating solution, the obtained coating layer contains 53% by mass fraction PSi-NH 2 and exhibits a total surface energy of 21 mN m −1 , decreasing the adsorption of bovine serum albumin by 44% compared to the unmodified membrane. When challenged with 1 g L −1 sodium alginate in a constant-flux crossflow system, the PSi-NH 2 -grafted membrane exhibits a 70% lower fouling rate than the pristine membrane at a water flux of 110 L (m 2 h) −1 and good stability when cleaned with NaOH solutions. 

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2. Porous Silicon on Paper: A Platform for Quantitative Rapid Diagnostic Tests

   https://doi.org/10.1021/acsami.4c18940  

   An, Huijin; Ward, Simon J; Layouni, Rabeb; Laibinis, Paul E; Locke, Andrea K; Weiss, Sharon M (January 2025, ACS Applied Materials & Interfaces)

   Porous silicon (PSi) thin films on silicon substrates have been extensively investigated in the context of biosensing applications, particularly for achieving label-free optical detection of a wide range of analytes. However, mass transport challenges have made it difficult for these biosensors to achieve rapid response times and low detection limits. In this work, we introduce an approach for improving the efficiency of molecule transport in PSi by using open-ended PSi membranes atop paper substrates in a flow-through sensor scheme. The paper substrate provides structural support as well as an efficient means of draining solutions from the PSi membrane without the use of an external pump and microfluidic channels. Distinct changes in the reflectance properties of the PSi membrane are measured when molecules are captured in the membrane. A concentration dependent response of the sensor for protein detection is demonstrated. Factors influencing the interaction time of molecules in the PSi membrane and the drying time of the membrane, which directly affect the detection sensitivity and overall testing time, are discussed. The demonstrated performance of the PSi-on-paper sensor establishes the feasibility of a platform for low-cost rapid diagnostic tests with a highly sensitive, quantitative readout. 

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3. Antifouling Activity of Bottlebrush Network Hydrogels

   https://doi.org/10.1021/acsabm.5c00291  

   Chiang, Meng-Chen; Clarke, Brandon R; Tew, Gregory N; Schiffman, Jessica D (April 2025, ACS Applied Bio Materials)

   Mitigating the attachment of microorganisms to polymer biomaterials is critical for preventing hospital-acquired infections. Two chemical strategies to mitigate fouling include fabricating fouling-resistant surfaces, which typically present hydrophilic polymers, such as polyethylene glycol (PEG), or creating fouling-release surfaces, which are generally hydrophobic featuring polydimethylsiloxane (PDMS). Despite the demonstrated promise of employing PEG or PDMS, amphiphilic PEG/PDMS copolymer materials remain understudied. Here, for the first time, we investigated if phase-separated amphiphilic copolymers confounded microbial adhesion. We used bottlebrush amphiphilic PEG/PDMS co-networks and homopolymer networks to study bacterial adhesion across a library of gels (ϕPEG = 0.00, 0.21, 0.40, 0.55, 0.80, and 1.00). Hydrated atomic force microscopy measurements revealed that most of the gels had low surface roughness, less than 5 nm, and an elastic modulus of ∼80 kPa. Interestingly, the surface roughness and elastic modulus of the ϕPEG = 0.40 gel were twice as high as those of the other gels due to the presence of crystalline domains, as confirmed using polarized optical microscopy on the hydrated gel. The interactions of these six well-characterized gels with bacteria were determined using Escherichia coli K12 MG1655 and Staphylococcus aureus SH1000. The attachment of both microbes decreased by at least 60% on all polymer gels versus the glass controls. S. aureus adhesion peaked on the ϕPEG = 0.40, likely due to its increased elastic modulus, consistent with previous literature demonstrating that modulus impacts microbial adhesion. These findings suggest that hydrophilic, hydrophobic, and amphiphilic biomaterials effectively resist the early attachment of Gram-negative and Gram-positive microorganisms, providing guidance for the design of next-generation antifouling surfaces. 

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4. Bioinspired Zwitterionic Nanowires with Simultaneous Biofouling Reduction and Release

   https://doi.org/10.1002/smll.202400784  

   Wang, Jing; Macdonald, Brian; Cho, Tae H; Repetto, Taylor; Sun, Kai; Tuteja, Anish; Dasgupta, Neil P (June 2024, Small)

   Marine biofouling is a complex and dynamic process that significantly increases the carbon emissions from the maritime industry by increasing drag losses. However, there are no existing non‐toxic marine paints that can achieve both effective fouling reduction and efficient fouling release. Inspired by antifouling strategies in nature, herein, a superoleophobic zwitterionic nanowire coating with a nanostructured hydration layer is introduced, which exhibits simultaneous fouling reduction and release performance. The zwitterionic nanowires demonstrate >25% improvement in fouling reduction compared to state‐of‐the‐art antifouling nanostructures, and four times higher fouling‐release compared to conventional zwitterionic coatings. Fouling release is successfully achieved under a wall shear force that is four orders of magnitude lower than regular water jet cleaning. The mechanism of this simultaneous fouling reduction and release behavior is explored, and it is found that a combination of 1) a mechanical biocidal effect from the nanowire geometry, and 2) low interfacial adhesion resulting from the nanostructured hydration layer, are the major contributing factors. These findings provide insights into the design of nanostructured coatings with simultaneous fouling reduction and release. The newly established synthesis procedure for the zwitterionic nanowires opens new pathways for implementation as antifouling coatings in the maritime industry and biomedical devices. 

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5. Surfaces with antifouling-antimicrobial dual function via immobilization of lysozyme on zwitterionic polymer thin films

   https://doi.org/10.1039/D1TB02597J  

   Khlyustova, Alexandra; Kirsch, Mia; Ma, Xiaojing; Cheng, Yifan; Yang, Rong (April 2022, Journal of Materials Chemistry B)

   Due to the emergence of wide-spread infectious diseases, there is a heightened need for antimicrobial and/or antifouling coatings that can be used to prevent infection and transmission in a variety of applications, ranging from healthcare devices to public facilities. While antimicrobial coatings kill pathogenic bacteria upon contact with the surface, the antimicrobial function alone often lacks long-term effectiveness due to the accumulation of dead cells and their debris on the surface, thus reducing the performance of the coating over time. Therefore, it is desirable to develop coatings with the dual functions of antimicrobial efficacy and fouling resistance, in which antifouling coatings provide the added benefit of preventing the adhesion of dead cells and debris. Leveraging the outstanding antifouling properties of zwitterionic coatings, we synthesized copolymers with this antimicrobial-antifouling dual function by immobilizing lysozyme, a common antimicrobial enzyme, to the surface of a pyridinium-based zwitterionic copolymer. Specifically, poly(4-vinylpyridine- co -pentaflurophenyl methacrylate- co -divinyl benzene) [P(4VP-PFPMA-DVB)] thin films were synthesized by an all-dry vapor deposition technique, initiated Chemical Vapor Deposition, and derivatized using 1,3-propane sultone to obtain sulfobetaine moieties. Lysozyme, known to hydrolyze polysaccharides in the cell wall of Gram-positive bacteria, was immobilized by forming amide bonds with the copolymer coating via nucleophilic substitution of the pentafluorophenyl group. The antifouling and antibacterial performance of the novel lysozyme-zwitterionic coating was tested against Gram-positive Bacillus subtilis and Gram-negative Pseudomonas aeruginosa . A reduction in surface adhesion of 87% was achieved for P. aeruginosa , and of 75% for B. subtilis , when compared to a common poly(vinyl chloride) surface. The lysozyme-zwitterionic coating also deactivated 67% of surface-attached Gram-positive bacteria, B. subtilis . This novel dual-function material can produce anti -infection surfaces for medical devices and surgical tools, personal care products, and surfaces in public facilities. 

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