Development of Antimicrobial and Antifouling Universal Coating via Rapid Deposition of Polydopamine and Zwitterionization

Natural biopolymers in the fabrication and coating of ureteral stent: An overview

Ureteral stents are indwelling medical devices that are most commonly used in treating different urinary tract complications like ureteral obstruction, kidney stones, and strictures, and allow normal urine flow from the kidney to the bladder. Tremendous work has been done in ureteral stent technology to meet the clinical demands, however, till-date a gold standard material for ureteral stents has not yet been developed. Many materials such as metal, and synthetic polymers have been published, however, the role of natural biopolymers has not yet been summarized and discussed. There is no detailed review published to explain the role of natural biopolymers in ureteral stent technology. This is the first review that explains and summarizes the role of natural polymer in ureter stent technology. In this review alginate and chitosan polymers are discussed in detail in the fabrications and coating of ureteral stents. It was summarized that alginate polymer alone or in combination with other polymers have been successfully used by many researchers for the manufacturing of ureteral stents with satisfactory results in vitro, in vivo, and clinical trials. However, alginate is rarely used to coat the surface of ureteral stent. On the other hand, only two reports are available on chitosan polymers for the manufacturing of ureteral stents, however, chitosan is largely used to coat the existing ureteral stents owing to their good antibacterial characteristics. Coating procedures can inhibit encrustation and biofilm formation. Nevertheless, the lack of antibacterial efficiency and inadequate coating limit their applications, however, natural biopolymers like chitosan showed significant promises in coating. Overall, the renewable nature, abundant, biocompatible, and biodegradable potential of natural polymer can be established with significant aspects as the ideal ureteral stent. To fully utilize the potential of the natural biopolymers in the ureteral stent design or coatings, an in-depth study is required to understand and identify their performance both in vitro and in vivo in the urinary tract.

Smart self-defensive coatings with bacteria-triggered antimicrobial response for medical devices

Bacterial colonization and biofilm formation on medical devices represent one of the most urgent and critical challenges in modern healthcare. These issues not only pose serious threats to patient health by increasing the risk of infections but also exert a considerable economic burden on national healthcare systems due to prolonged hospital stays and additional treatments. To address this challenge, there is a need for smart, customized biomaterials for medical device fabrication, particularly through the development of surface modification strategies that prevent bacterial adhesion and the growth of mature biofilms. This review explores three bioinspired approaches through which antibacterial and antiadhesive coatings can be engineered to exhibit smart, stimuli-responsive features. This responsiveness is greatly valuable as it provides the coatings with a controlled, on-demand antibacterial response that is activated only in the presence of bacteria, functioning as self-defensive coatings. Such coatings can be designed to release antibacterial agents or change their surface properties/conformation in response to specific stimuli, like changes in pH, temperature, or the presence of bacterial enzymes. This targeted approach minimizes the risk of developing antibiotic resistance and reduces the need for continuous, high-dose antibacterial treatments, thereby preserving the natural microbiome and further reducing healthcare costs. The final part of the review reports a critical analysis highlighting the potential improvements and future evolutions regarding antimicrobial self-defensive coatings and their validation.

Polydopamine Applications in Biomedicine and Environmental Science

This manuscript explores the multifaceted applications of polydopamine (PDA) across various scientific and industrial domains. It covers the chemical aspects of PDA and its potential in bone tissue engineering, implant enhancements, cancer treatment, and nanotechnology. The manuscript investigates PDA's roles in tissue engineering, cell culture technologies, surface modifications, drug delivery systems, and sensing techniques. Additionally, it highlights PDA's contributions to microfabrication, nanoengineering, and environmental applications. Through detailed testing and assessment, the study identifies limitations in PDA-related research, such as synthesis complexity, incomplete mechanistic understanding, and biocompatibility variability. It also proposes future research directions aimed at improving synthesis techniques, expanding biomedical applications, and enhancing sensing technologies to optimize PDA's efficacy and scalability.

Coordination-driven robust antibacterial coatings using catechol-conjugated carboxymethyl chitosan

To prevent bacterial contamination on solid surfaces, a simple yet efficient antibacterial coating was developed in a substrate-independent manner by using the catechol-conjugated carboxymethyl chitosan (CMC-DOPA). The CMC-DOPA was firstly synthesized via an aza-Michael reaction with methyl acrylate and the subsequent acyl substitution with dopamine. The coating strategy consists of spin-coating-assisted deposition of CMC-DOPA on polydopamine-coated substrates and coordination-driven crosslinks between catechol groups and Fe3+ ions in sequence, producing the multilayered CMC-DOPA films. The film thickness was controllable depending on the concentration of CMC-DOPA. Compared to bare controls, the CMC-DOPA-coated substrates reduced the bacterial adhesion by up to 99.8 % and 96.2 % for E. coli and S. aureus, respectively. It is demonstrated that the CMC-DOPA coating can be a robust antibacterial coating across various pH environments, inhibiting bacterial adhesion by 78.7 %, 95.1 %, and 93.2 %, respectively, compared to the control, even after 7 days of acidic, physiological, and alkaline pH treatment. The current coating approach could be applied to various substrates including silicon dioxide, titanium dioxide, and polyurethane. Given its simple and versatile coating capability, we think that the coordination-driven CMC-DOPA coating could be useful for various medical devices and implants.

Betainization of Polydopamine/Polyethylenimine Coating for Universal Zwitterionization

Biofoulants can adhere to multiple surfaces, degrading the performance of medical devices and industrial facilities and/or causing nosocomial infection. The surface immobilization of zwitterionic materials can prevent the initial attachment of the foulants but lacks extensive implementation. Herein, we propose a facile, universal, two-step surface modification strategy to improve fouling resistance. In the first step, the substrates were immersed in a codeposition solution containing dopamine and branched polyethylenimine (PEI) to form a "primer" layer (PDA/PEI). In the second step, the primer layers were treated with 1,3-propane sultone to betainize primary/secondary/tertiary amine moieties of PEI, generating zwitterions on substrates. After betainization, PS-grafted PDA/PEI (PDA/PEI/S) via a ring-opening alkylation reaction manifested changes in wettability. X-ray photoelectron spectroscopy revealed the presence of zwitterionic moieties on the PDA/PEI/S surfaces. Further investigations using ellipsometry and atomic force microscopy were conducted to scrutinize the relation among the PEI content, film thickness, primer stability, and betainization. As a result, zwitterion-decorated substrates prepared under optimal conditions can exhibit high resistance against bacterial fouling, achieving a 98.5% reduction in bacterial attachment. In addition, the method shows a substrate-independent property, capable of successfully applying it on organic and inorganic substrates. Finally, the newly developed approach shows excellent biocompatibility, displaying no significant difference compared with blank control samples. Overall, we envision that the facile surface modification strategy can further promote the preparation of zwitterion-decorated materials in the future.

Substrate-independent and widely applicable deposition of antibacterial coatings

Antibacterial coatings are regarded as a necessary tool to prevent implant-related infections. Substrate-independent and widely applicable coating techniques are gaining significant interest to synthesize different types of antibacterial films, which can be relevant from a fundamental and application-oriented perspective. Plasma polymer- and polydopamine-based antibacterial coatings represent the most widely studied and versatile approaches among these coating techniques. Both single- and dual-functional antibacterial coatings can be fabricated with these approaches and a variety of dual-functional antibacterial coating strategies can still be explored in future work. These coatings can potentially be used for a wide range of different implants (material, shape, and size). However, for most implants, significantly more fundamental knowledge needs to be gained before these coatings can find real-life use.

Recent Developments in Multifunctional Antimicrobial Surfaces and Applications toward Advanced Nitric Oxide-Based Biomaterials

Implant-associated infections arising from biofilm development are known to have detrimental effects with compromised quality of life for the patients, implying a progressing issue in healthcare. It has been a struggle for more than 50 years for the biomaterials field to achieve long-term success of medical implants by discouraging bacterial and protein adhesion without adversely affecting the surrounding tissue and cell functions. However, the rate of infections associated with medical devices is continuously escalating because of the intricate nature of bacterial biofilms, antibiotic resistance, and the lack of ability of monofunctional antibacterial materials to prevent the colonization of bacteria on the device surface. For this reason, many current strategies are focused on the development of novel antibacterial surfaces with dual antimicrobial functionality. These surfaces are based on the combination of two components into one system that can eradicate attached bacteria (antibiotics, peptides, nitric oxide, ammonium salts, light, etc.) and also resist or release adhesion of bacteria (hydrophilic polymers, zwitterionic, antiadhesive, topography, bioinspired surfaces, etc.). This review aims to outline the progress made in the field of biomedical engineering and biomaterials for the development of multifunctional antibacterial biomedical devices. Additionally, principles for material design and fabrication are highlighted using characteristic examples, with a special focus on combinational nitric oxide-releasing biomedical interfaces. A brief perspective on future research directions for engineering of dual-function antibacterial surfaces is also presented.

Polydopamine, harness of the antibacterial potentials-A review

Antibiotic resistance is one of the major causes of morbidity and mortality, triggered by the adhesion of microbes and to some extent the formation of biofilms. This condition has been quite challenging in the health and industrial sector. Conditions and processes required to foil these infectious and resistance are of much concern. The synthesis of PDA material, inspired by the Mytilus edulis foot protein (MEFP)5 possesses unique characteristics that allow for, adhesion, photothermal therapy, synergistic effects with other materials, biocompatibility process, etc. Therefore, their usage holds great potential for dealing with both the infectious nature and the antibiotic resistance processes. Hence, this review provides an overview of the mechanism involved in accomplishing and eradicating bacteria, the recently harnessed antibacterial effect of the PDA through other properties they possess, a way forward in tapping the benefit embedded in the PDA, and the future perspective.

A two-step bioluminescence assay for optimizing antibacterial coating of hollow-fiber membranes with polydopamine in an integrative approach

Pure-water filtration membranes are often fouled by bacterial biofilms. Antibacterial coatings for preventing biofilm formation on such membranes should not rely on leaching of inhibiting compounds but should only be effective on surface contact. Certified assays for antibacterial coatings do not sufficiently exclude leaching effects and involve nutrient-rich cultivation media that do not correspond to conditions in pure-water systems. In this study, a two-step bioluminescence assay was developed for optimizing an antibacterial coating of PES/PVP ultrafiltration hollow-fiber membranes with a polydopamine as a sustainable, bio-inspired material for preventing bacterial biofilm formation. In the first step, leaching of the antimicrobial coating was analyzed by a bioluminescence assay with supernatants generated by washing coated membranes. In the second step, bioluminescence of bacterial biofilms on coated and uncoated membranes was measured using a nutrient-poor medium resembling site-specific conditions. Based on this bioluminescence assay, an optimized protocol for the coating process could be established by acidic polymerization of dopamine using 2 g/L sodium periodate and 4 g/L dopamine at 40 °C for 20 min reaction time. With coatings produced in this way, bioluminescence was reduced on coated membranes only while the corresponding supernatants exhibited no inhibitory effects.

Antifouling PVC Catheters by Gamma Radiation-Induced Zwitterionic Polymer Grafting

In medical environments, polymeric surfaces tend to become contaminated, hindering the treatment and recovery from diseases. Biofouling-resistant materials, such as zwitterionic polymers, may mitigate this problem. In this work, the modification of PVC catheters with a binary graft of 4-vinylpyridine (4VP) and sulfobetaine methacrylate (SBMA) by the oxidative pre-irradiation method is proposed to develop pH-responsive catheters with an antifouling capacity. The ionizing radiation allowed us to overcome limitations in the synthesis associated with the monomer characteristics. In addition, the grafted materials showed a considerable increase in their hydrophilic character and antifouling capacity, significantly decreasing the protein adsorption compared to the unmodified catheters. These materials have potential for the development of a combined antimicrobial and antifouling capabilities system to enhance prophylactic activity or even to help treat infections.

Substrate-independent adsorption of nanoparticles as anti-biofilm coatings

Healthcare-associated infections are common causes of morbidity and mortality. Advanced nanotechnology provides a means of overcoming this problem, but it remains challenging to develop universal coating strategies for decorating antimicrobial nanomaterials onto various clinical devices. In this paper, we propose a general silane-based method for immobilizing monolayer metal nanoparticle (NP) arrays onto any type of substrate surface-especially for a diverse range of clinical implantable devices. The surface silanization was achieved simply through the adsorption of N¹-(3-trimethoxysilylpropyl)diethylenetriamine (TMS), regardless of the material (polymer, metal, oxide) or morphology (flat, curved, textured) of the substrate, with no need for pretreatment or expensive instrumentation. Monolayers of various nanostructures (Ag, Au, and hollow Au NPs) were then decorated rapidly onto the TMS-treated substrates, thereby further functionalizing their surfaces. In particular, immobilization of the Ag NPs resulted in excellent anti-biofilm efficacy against three clinically life-threatening pathogens: Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus. Sustained release of Ag⁺ ions led to durable inhibition of bacterial attachment for up to 28 days. Studies with NIH3T3 fibroblasts revealed that the Ag NP arrays displayed no cytotoxicity toward mammalian cells. Overall, this universal coating process appears to be an innovative method for the surface-functionalization of diverse materials and devices employed in the fields of energy, sensing, and medicine-especially to prevent healthcare-associated infections arising from the use of clinical implantable devices in hospitals.

Cationic Alternating Polypeptide Fixed on Polyurethane at Multiple Sites for Excellent Antibacterial and Antifouling Properties

Bacterial infection and blockage are severe problems for polyurethane (PU) catheters and there is an urgent demand for surface-functionalized polyurethane. Herein, a cationic alternating copolymer comprising allyl-substituted ornithine and glycine (allyl-substituted poly(Orn-alter-Gly)) with abundant carbon-carbon double bond functional groups (C═C) is designed. Polyurethane is prepared with a large quantity of C═C groups (PU-D), and different amounts of allyl-substituted poly(Orn-alter-Gly) are grafted onto the PU-D surface (PU-D-2%AMPs and PU-D-20%AMPs) via the C═C functional groups. The chemical structures of the allyl-substituted poly(Orn-alter-Gly) and polyurethane samples (PU, PU-D, PU-D-2%AMPs, and PU-D-20%AMPs) are characterized and the results reveal that allyl-substituted poly(Orn-alter-Gly) is decorated on the polyurethane. PU-D-20%AMPs shows excellent antibacterial activity against Escherichia coli, Enterococcus faecalis, and Staphylococcus aureus because of the high surface potential caused by cationic allyl-substituted poly(Orn-alter-Gly), and it also exhibits excellent long-term antibacterial activity and antibiofilm properties. PU-D-20%AMPs also has excellent antifouling properties because the cationic copolymer is fixed at multiple reactive sites, thus avoiding the formation of movable long chain brush. A strong surface hydration barrier is also formed to prevent adsorption of proteins and ions, and in vivo experiments reveal excellent biocompatibility. This flexible strategy to prepare dual-functional polyurethane surfaces with antibacterial and antifouling properties has large potential in biomedical implants.

Rapid Assembly of Infection-Resistant Coatings: Screening and Identification of Antimicrobial Peptides Works in Cooperation with an Antifouling Background

Bacterial adhesion and the succeeding biofilm formation onto surfaces are responsible for implant- and device-associated infections. Bifunctional coatings integrating both nonfouling components and antimicrobial peptides (AMPs) are a promising approach to develop potent antibiofilm coatings. However, the current approaches and chemistry for such coatings are time-consuming and dependent on substrates and involve a multistep process. Also, the information is limited on the influence of the coating structure or its components on the antibiofilm activity of such AMP-based coatings. Here, we report a new strategy to rapidly assemble a stable, potent, and substrate-independent AMP-based antibiofilm coating in a nonfouling background. The coating structure allowed for the screening of AMPs in a relevant nonfouling background to identify optimal peptide combinations that work in cooperation to generate potent antibiofilm activity. The structure of the coating was changed by altering the organization of the hydrophilic polymer chains within the coatings. The coatings were thoroughly characterized using various surface analytical techniques and correlated with the efficiency to prevent biofilm formation against diverse bacteria. The coating method that allowed the conjugation of AMPs without altering the steric protection ability of hydrophilic polymer structure results in a bifunctional surface coating with excellent antibiofilm activity. In contrast, the conjugation of AMPs directly to the hydrophilic polymer chains resulted in a surface with poor antibiofilm activity and increased adhesion of bacteria. Using this coating approach, we further established a new screening method and identified a set of potent surface-tethered AMPs with high activity. The success of this new peptide screening and coating method is demonstrated using a clinically relevant mouse infection model to prevent catheter-associated urinary tract infection (CAUTI).

Facile fabrication of antibacterial and antiviral perhydrolase-polydopamine composite coatings

In situ generation of antibacterial and antiviral agents by harnessing the catalytic activity of enzymes on surfaces provides an effective eco-friendly approach for disinfection. The perhydrolase (AcT) from Mycobacterium smegmatis catalyzes the perhydrolysis of acetate esters to generate the potent disinfectant, peracetic acid (PAA). In the presence of AcT and its two substrates, propylene glycol diacetate and H₂O₂, sufficient and continuous PAA is generated over an extended time to kill a wide range of bacteria with the enzyme dissolved in aqueous buffer. For extended self-disinfection, however, active and stable AcT bound onto or incorporated into a surface coating is necessary. In the current study, an active, stable and reusable AcT-based coating was developed by incorporating AcT into a polydopamine (PDA) matrix in a single step, thereby forming a biocatalytic composite onto a variety of surfaces. The resulting AcT-PDA composite coatings on glass, metal and epoxy surfaces yielded up to 7-log reduction of Gram-positive and Gram-negative bacteria when in contact with the biocatalytic coating. This composite coating also possessed potent antiviral activity, and dramatically reduced the infectivity of a SARS-CoV-2 pseudovirus within minutes. The single-step approach enables rapid and facile fabrication of enzyme-based disinfectant composite coatings with high activity and stability, which enables reuse following surface washing. As a result, this enzyme-polymer composite technique may serve as a general strategy for preparing antibacterial and antiviral surfaces for applications in health care and common infrastructure safety, such as in schools, the workplace, transportation, etc.

Sulfobetaine Hydrogels with a Complex Multilength-Scale Hierarchical Structure

Hydrogels with a hierarchical structure were prepared from a new highly water-soluble crosslinker N,N,N',N'-tetramethyl-N,N'-bis(2-ethylmethacrylate)-propyl-1,3-diammonium dibromide and from the sulfobetaine monomer 2-(N-3-sulfopropyl-N,N-dimethyl ammonium)ethyl methacrylate. The free radical polymerization of the two compounds is rapid and yields near-transparent hydrogels with sizes up to 5 cm in diameter. Rheology shows a clear correlation between the monomer-to-crosslinker ratio and the storage and loss moduli of the hydrogels. Cryo-scanning electron microscopy, low-field nuclear magnetic resonance (NMR) spectroscopy, and small-angle X-ray scattering show that the gels have a hierarchical structure with features spanning the nanometer to the sub-millimeter scale. The NMR study is challenged by the marked inhomogeneity of the gels and the complex chemical structure of the sulfobetaine monomer. NMR spectroscopy shows how these complications can be addressed via a novel fitting approach that considers the mobility gradient along the side chain of methacrylate-based monomers.

Toward Designing of Anti-infective Hydrogels for Orthopedic Implants: From Lab to Clinic

An alarming increase in implant failure incidence due to microbial colonization on the administered orthopedic implants has become a horrifying threat to replacement surgeries and related health concerns. In essence, microbial adhesion and its subsequent biofilm formation, antibiotic resistance, and the host immune system's deficiency are the main culprits. An advanced class of biomaterials termed anti-infective hydrogel implant coatings are evolving to subdue these complications. On this account, this review provides an insight into the significance of anti-infective hydrogels for preventing orthopedic implant associated infections to improve the bone healing process. We briefly discuss the clinical course of implant failure, with a prime focus on orthopedic implants. We identify the different anti-infective coating strategies and hence several anti-infective agents which could be incorporated in the hydrogel matrix. The fundamental design criteria to be considered while fabricating anti-infective hydrogels for orthopedic implants will be discussed. We highlight the different hydrogel coatings based on the origin of the polymers involved in light of their antimicrobial efficacy. We summarize the relevant patents reported in the prevention of implant infections, including orthopedics. Finally, the challenges concerning the clinical translation of the aforesaid hydrogels are described, and considerable solutions for improved clinical practice and better future prospects are proposed.

Recent Advances in a Polydopamine-Mediated Antimicrobial Adhesion System

The drug resistance developed by bacteria during antibiotic treatment has been a call to action for researchers and scientists across the globe, as bacteria and fungi develop ever increasing resistance to current drugs. Innovative antimicrobial/antibacterial materials and coatings to combat such infections have become a priority, as many infections are caused by indwelling implants (e.g., catheters) as well as improving postsurgical function and outcomes. Pathogenic microorganisms that can exist either in planktonic form or as biofilms in water-carrying pipelines are one of the sources responsible for causing water-borne infections. To combat this, researchers have developed nanotextured surfaces with bactericidal properties mirroring the topographical features of some natural antibacterial materials. Protein-based adhesives, secreted by marine mussels, contain a catecholic amino acid, 3,4-dihydroxyphenylalanine (DOPA), which, in the presence of lysine amino acid, empowers with the ability to anchor them to various surfaces in both wet and saline habitats. Inspired by these features, a novel coating material derived from a catechol derivative, dopamine, known as polydopamine (PDA), has been designed and developed with the ability to adhere to almost all kinds of substrates. Looking at the immense potential of PDA, this review article offers an overview of the recent growth in the field of PDA and its derivatives, especially focusing the promising applications as antibacterial nanocoatings and discussing various antimicrobial mechanisms including reactive oxygen species-mediated antimicrobial properties.

A Glance at Antimicrobial Strategies to Prevent Catheter-Associated Medical Infections

Urinary and intravascular catheters are two of the most used invasive medical devices; however, microbial colonization of catheter surfaces is responsible for most healthcare-associated infections (HAIs). Several antimicrobial-coated catheters are available, but recurrent antibiotic therapy can decrease their potential activity against resistant bacterial strains. The aim of this Review is to question the actual effectiveness of currently used (coated) catheters and describe the progress and promise of alternative antimicrobial coatings. Different strategies have been reviewed with the common goal of preventing biofilm formation on catheters, including release-based approaches using antibiotics, antiseptics, nitric oxide, 5-fluorouracil, and silver as well as contact-killing approaches employing quaternary ammonium compounds, chitosan, antimicrobial peptides, and enzymes. All of these strategies have given proof of antimicrobial efficacy by modifying the physiology of pathogens or disrupting their structural integrity. The aim for synergistic approaches using multitarget processes and the combination of both antifouling and bactericidal properties holds potential for the near future. Despite intensive research in biofilm preventive strategies, laboratorial studies still present some limitations since experimental conditions usually are not the same and also differ from biological conditions encountered when the catheter is inserted in the human body. Consequently, in most cases, the efficacy data obtained from in vitro studies is not properly reflected in the clinical setting. Thus, further well-designed clinical trials and additional cytotoxicity studies are needed to prove the efficacy and safety of the developed antimicrobial strategies in the prevention of biofilm formation at catheter surfaces.

Thermo-resistance of ESKAPE-panel pathogens, eradication and growth prevention of an infectious biofilm by photothermal, polydopamine-nanoparticles in vitro

Nanotechnology offers many novel infection-control strategies that may help prevent and treat antimicrobial-resistant bacterial infections. Here, we synthesized polydopamine, photothermal-nanoparticles (PDA-NPs) without further surface-functionalization to evaluate their potential with respect to biofilm-control. Most ESKAPE-panel pathogens in suspension with photothermal-nanoparticles showed three- to four-log-unit reductions upon Near-Infra-Red (NIR)-irradiation, but for enterococci only less than two-log unit reduction was observed. Exposure of existing Staphylococcus aureus biofilms to photothermal-nanoparticles followed by NIR-irradiation did not significantly kill biofilm-inhabitants. This indicates that the biofilm mode of growth poses a barrier to penetration of photothermal-nanoparticles, yielding dissipation of heat to the biofilm-surrounding rather than in its interior. Staphylococcal biofilm-growth in the presence of photothermal-nanoparticles could be significantly prevented after NIR-irradiation because PDA-NPs were incorporated in the biofilm and heat dissipated inside it. Thus, unmodified photothermal nanoparticles have potential for prophylactic infection-control, but data also constitute a warning for possible development of thermo-resistance in infectious pathogens.

Polydopamine-on-liposomes: stable nanoformulations, uniform coatings and superior antifouling performance

Polydopamine (PDA), a mussel-inspired synthetic polymer, affords biocompatible and antifouling coatings on a variety of surfaces. However, the traditional protocol of preparing PDA by polymerizing dopamine (DA) under basic conditions yields physically-unstable and non-uniform coatings that are prone to delamination and exhibit compromised antifouling performance in vivo. Here, we show that the high local pH in the vicinity of vesicular self-assemblies formed by a series of acetal-based cationic amphiphiles can be exploited to conveniently polymerise DA under physiological conditions in a gradual manner without requiring any external oxidant. Two of the four PDA-liposome nanoformulations viz. PDA-L1 and PDA-L2 turned out to be highly stable physically and resisted precipitation for more than a month while the other two formulations (PDA-L3 and PDA-L4) were less stable and formed visible precipitates with time. Further, the PDA-liposome formulations had significantly improved haemocompatibility compared to that of pristine liposomes. PDA-L1 formed highly uniform, nanostructured coatings on implants like catheter, cotton and bandages that did not delaminate even after a week of continuous incubation in simulated body fluid, or on exposure to pH change and presence of proteolytic enzymes. The PDA-L1 coated catheter implants resisted biofouling by both Gram-positive and Gram-negative bacteria in vitro and also had superior in vivo performance in mice vis-à-vis the implants coated with traditional base-polymerised PDA formulation (BP-PDA). Thus, these novel liposomal PDA nanoformulations significantly improve the practical utility of PDA-based coatings for antimicrobial applications.

Polydopamine Nanostructures as Biomaterials for Medical Applications

Polydopamine is a versatile and organic material that can be deposited as a conformal film with nanometer thickness on virtually any substrate. Much of the initial foundational work regarding polydopamine synthesis and processing was reported during the 2000s. Latter years have witnessed increasing interest and widespread adoption of polydopamine as a material for many applications including medicine. Conformal polydopamine coatings confer unique chemical and physical properties to many substrate materials including metals, ceramics, polymers, and beyond. Polydopamine-modified surfaces permit facile bioconjugation of many biomedical materials for potential use as bioadhesives, contrast agents, drug delivery systems, and protein-adsorption resistant interfaces. Polydopamine-based materials and interfaces may improve the performance of biomedical devices used in neurotechnology, diagnostics, and cardiovascular applications. This highlight article reviews recent advances in polydopamine processing capabilities. The use of polydopamine as a material in various biomedical applications is also discussed. Finally, challenges and opportunites in translating polydopamine for future biomedical technologies are summarized.