Co-immobilization of cellobiose dehydrogenase and deoxyribonuclease I on chitosan nanoparticles against fungal/bacterial polymicrobial biofilms targeting both biofilm matrix and microorganisms

Nanoformulations for dismantling fungal biofilms: The latest arsenals of antifungal therapy

Globally, fungal infections have evolved as a strenuous challenge for clinicians, particularly in patients with compromised immunity in intensive care units. Fungal co-infection in Covid-19 patients has made the situation more formidable for healthcare practitioners. Surface adhered fungal population known as biofilm often develop at the diseased site to elicit antifungal tolerance and recalcitrant traits. Thus, an innovative strategy is required to impede/eradicate developed biofilm and avoid the formation of new colonies. The development of nanocomposite-based antibiofilm solutions is the most appropriate way to withstand and dismantle biofilm structures. Nanocomposites can be utilized as a drug delivery medium and for fabrication of anti-biofilm surfaces capable to resist fungal colonization. In this context, the present review comprehensively described different forms of nanocomposites and mode of their action against fungal biofilms. Amongst various nanocomposites, efficacy of metal/organic nanoparticles and nanofibers are particularly emphasized to highlight their role in the pursuit of antibiofilm strategies. Further, the inevitable concern of nanotoxicology has also been introduced and discussed with the exigent need of addressing it while developing nano-based therapies. Further, a list of FDA-approved nano-based antifungal formulations for therapeutic usage available to date has been described. Collectively, the review highlights the potential, scope, and future of nanocomposite-based antibiofilm therapeutics to address the fungal biofilm management issue.

Synergistic and antibiofilm activity of DNase I and glucose oxidase loaded chitosan nanoparticles against dual-species biofilms of Listeria monocytogenes and Salmonella

Salmonella and Listeria monocytogenes are two of the most common foodborne pathogens in the food industry. They form dual-species biofilms, which have a higher sensitivity to antimicrobial treatment and a greater microbial adhesion. In this experiment, we loaded DNase I and glucose oxidase (GOX) on chitosan nanoparticles (CSNPs) to explore their inhibitory effects on and disruption of dual-species biofilms of Salmonella enterica and L. monocytogenes. Transmission electron microscopy (TEM) showed that CSNP-DNase-GOX and CSNPs were spherical in shape. CSNP-DNase-GOX was shifted and altered compared to the infrared peaks of CSNPs. CSNPs loaded with DNase I and GOX showed an increase in the particle size and an alteration in the polydispersity index (PDI) and the zeta potential. Compared to free DNase I or GOX, DNase I and GOX loaded on CSNPs had higher stability at different temperatures. CSNP-DNase-GOX was more effective in inhibiting dual-species biofilms than CSNP-GOX. Scanning electron microscopy (SEM) and fluorescence microscopy were used to observe the structure of the biofilm, which further illustrated that CSNP-DNase-GOX disrupted the dual-species biofilms of S. enterica and L. monocytogenes.

Surface display system of Bacillus subtilis: A promising approach for improving the stability and applications of cellobiose dehydrogenase

Cellobiose dehydrogenase (CDH) plays a crucial role in lignocellulose degradation and bioelectrochemical industries, making it highly in demand. However, the production and purification of CDH through fungal heterologous expression methods is time-consuming, costly, and challenging. In this study, we successfully displayed Pycnoporus sanguineus CDH (psCDH) on the surface of Bacillus subtilis spores for the first time. Enzymatic characterization revealed that spore surface display enhanced the tolerance of psCDH to high temperature (80 °C) and low pH levels (3.5) compared to free psCDH. Furthermore, we found that glycerol, lactic acid, and malic acid promoted the activity of immobilized spore-displayed psCDH; glycerol has a more significant stimulating effect, increasing the activity from 16.86 ± 1.27 U/mL to 46.26 ± 3.25 U/mL. After four reuse cycles, the psCDH immobilized with spores retained 48% of its initial activity, demonstrating a substantial recovery rate. In conclusion, the spore display system, relying on cotG, enables the expression and immobilization of CDH while enhancing its resistance to adverse conditions. This system demonstrates efficient enzyme recovery and reuse. This approach provides a novel method and strategy for the immobilization and stability enhancement of CDH.

Anti-Biofilm Strategies: A Focused Review on Innovative Approaches

Biofilm (BF) can give rise to systemic infections, prolonged hospitalization times, and, in the worst case, death. This review aims to provide an overview of recent strategies for the prevention and destruction of pathogenic BFs. First, the main phases of the life cycle of BF and maturation will be described to identify potential targets for anti-BF approaches. Then, an approach acting on bacterial adhesion, quorum sensing (QS), and the extracellular polymeric substance (EPS) matrix will be introduced and discussed. Finally, bacteriophage-mediated strategies will be presented as innovative approaches against BF inhibition/destruction.

Biofilm therapy for chronic wounds

Chronic wounds have been a major factor of serious harm to global public health. At present, it is known that almost all chronic wounds contain biofilms, which seriously hinder the healing process. Removal of biofilms can effectively promote the healing of chronic wounds. As the study of wound biofilms deepens, many new treatment methods have emerged, thus bringing revolutionary means for the treatment of chronic wound biofilm. This review summarizes various methods for the treatment of chronic wound biofilm worldwide to provide a theoretical summary and practical basis for the selection of suitable wound biofilm treatment methods in clinical practice.

Properties of active packaging of PLA-PCL film integrated with chitosan as an antibacterial agent and syzygium cumini seed extract as an antioxidant agent

Active packaging is becoming increasingly significant in the food industry. The present study aims to explore the use of Syzygium Cumini Seed Extract (SCSE) as an antioxidant and chitosan as an antibacterial agent to produce active packaging based on polylactic acid (PLA), poly ε-caprolactone (PCL), and polyethylene glycol (PEG) blend. Using advanced characterization techniques, active packaging (PLA/PCL/PEG) incorporating with 0.5 g chitosan-0.5 mL SCSE was evaluated for its mechanical, physical, structural, and antibacterial-antioxidant properties. The addition of chitosan-SCSE caused an 18.57 % increase in tensile strength and decreased the Water Vapor Transmission Rate (WVTR) by up to 52 %, whereas smooth surface microscopy indicated good compatibility between polymers and active agents. Active packaging incorporating chitosan-SCSE reduced 96.66 % of Gram-positive bacteria Staphylococcus aureus and 73.98 % of Gram-negative bacteria, Escherichia coli. During 15 days of storage, the active packaging was able to slow the increase in Total Volatile Basic Nitrogen (TVBN) in beef and prevent the decrease in vitamin C contents in pineapple.

Extracellular matrix-degrading enzymes as a biofilm control strategy for food-related microorganisms

Biofilm is one of the major problems in food industries and is difficult to be removed or prevented by conventional sanitizers. In this review, we discussed the extracellular matrix-degrading enzymes as a strategy to control biofilms of foodborne pathogenic and food-contaminating bacteria. The biofilms can be degraded by using the enzymes targeting proteins, polysaccharides, extracellular DNA, or lipids which mainly constitute the extracellular polymeric substances of biofilms. However, the efficacy of enzymes varies by the growth medium, bacterial species, strains, or counterpart microorganisms due to a high variation in the composition of extracellular polymeric substances. Several studies demonstrated that the combined treatment using conventional sanitizers or multiple enzymes can synergistically enhance the biofilm removal efficacies. In this review, the application of the immobilized enzymes on solid substrates is also discussed as a potential strategy to prevent biofilm formation on food contact surfaces.

Staphylococcus aureus microbial biofilms degradation using cellobiose dehydrogenase from Thermothelomyces thermophilus M77

This work reports biochemical characterization of Thermothelomyces thermophilus cellobiose dehydrogenase (TthCDHIIa) and its application as an antimicrobial and antibiofilm agent. We demonstrate that TthCDHIIa is thermostable in different ionic solutions and is capable of oxidizing multiple mono and oligosaccharide substrates and to continuously produce H2O2. Kinetics measurements depict the enzyme catalytic characteristics consistent with an Ascomycota class II CDH. Our structural analyses show that TthCDHIIa substrate binding pocket is spacious enough to accommodate larger cello and xylooligosaccharides. We also reveal that TthCDHIIa supplemented with cellobiose reduces the viability of S. aureus ATCC 25923 up to 32 % in a planktonic growth model and also inhibits its biofilm growth on 62.5 %. Furthermore, TthCDHIIa eradicates preformed S. aureus biofilms via H2O2 oxidative degradation of the biofilm matrix, making these bacteria considerably more susceptible to gentamicin and tetracycline.

Biomaterials with antifungal strategies to fight oral infections

Oral fungal infections pose a threat to human health and increase the economic burden of oral diseases by prolonging and complicating treatment. A cost-effective strategy is to try to prevent these infections from happening in the first place. With this purpose, biomaterials with antifungal properties are a crucial element to overcome fungal infections in the oral cavity. In this review, we go through different kinds of biomaterials and coatings that can be used to functionalize them. We also review their potential as a therapeutic approach in addition to prophylaxis, by going through traditional and alternative antifungal compounds, e.g., essential oils, that could be incorporated in them, to enhance their efficacy against fungal pathogens. We aim to highlight the potential of these technologies and propose questions that need to be addressed in prospective research. Finally, we intend to concatenate the key aspects and technologies on the use of biomaterials in oral health, to create an easy to find summary of the current state-of-the-art for researchers in the field.

Recent progress in nanozymes for the treatment of diabetic wounds

The slow healing of diabetic wounds has seriously affected human health. Meanwhile, the open wounds are susceptible to bacterial infection. Clinical therapeutic methods such as antibiotic therapy, insulin treatment, and surgical debridement have made great achievements in the treatment of diabetic wounds. However, drug-resistant bacteria will develop after long-term use of antibiotics, resulting in decreased efficacy. To improve the therapeutic effect, increasing drug concentration is a common strategy in clinical practice, but it also brings serious side effects. In addition, hyperglycemia control or surgical debridement can easily bring negative effects to patients, such as hypoglycemia or damage of normal tissue. Therefore, it is essential to develop novel therapeutic strategies to effectively promote diabetic wound healing. In recent years, nanozyme-based diabetic wound therapeutic systems have received extensive attention because they possess the advantages of nanomaterials and natural enzymes. For example, nanozymes have the advantages of a small size and a high surface area to volume ratio, which can enhance the tissue penetration of nanozymes and increase the reactive active sites. Moreover, compared with natural enzymes, nanozymes have more stable catalytic activity, lower production cost, and stronger operability. In this review, we first reviewed the basic characteristics of diabetic wounds and then elaborated on the catalytic mechanism and action principle of different types of nanozymes in diabetic wounds from three aspects: controlling bacterial infection, controlling hyperglycemia, and relieving inflammation. Finally, the challenges, prospects and future implementation of nanozymes for diabetic wound healing are outlined.

Metal Nanomaterials and Hydrolytic Enzyme-Based Formulations for Improved Antifungal Activity

Active research of metal-containing compounds and enzymes as effective antifungal agents is currently being conducted due to the growing antifungal resistance problem. Metals are attracting special attention due to the wide variety of ligands that can be used for them, including chemically synthesized and naturally obtained variants as a result of the so-called "green synthesis". The main mechanism of the antifungal action of metals is the triggering of the generation and accumulation of reactive oxygen species (ROS). Further action of ROS on various biomolecules is nonspecific. Various hydrolytic enzymes (glucanases and proteases), in turn, exhibit antifungal properties by affecting the structural elements of fungal cells (cell walls, membranes), fungal quorum sensing molecules, fungal own protective agents (mycotoxins and antibiotics), and proteins responsible for the adhesion and formation of stable, highly concentrated populations in the form of biofilms. A wide substrate range of enzymes allows the use of various mechanisms of their antifungal actions. In this review, we discuss the prospects of combining two different types of antifungal agents (metals and enzymes) against mycelial fungi and yeast cells. Special attention is paid to the possible influence of metals on the activity of the enzymes and the possible effects of proteins on the antifungal activity of metal-containing compounds.

Understanding bacterial biofilms: From definition to treatment strategies

Bacterial biofilms are complex microbial communities encased in extracellular polymeric substances. Their formation is a multi-step process. Biofilms are a significant problem in treating bacterial infections and are one of the main reasons for the persistence of infections. They can exhibit increased resistance to classical antibiotics and cause disease through device-related and non-device (tissue) -associated infections, posing a severe threat to global health issues. Therefore, early detection and search for new and alternative treatments are essential for treating and suppressing biofilm-associated infections. In this paper, we systematically reviewed the formation of bacterial biofilms, associated infections, detection methods, and potential treatment strategies, aiming to provide researchers with the latest progress in the detection and treatment of bacterial biofilms.

Targeted pH-responsive chitosan nanogels with Tanshinone IIA for enhancing the antibacterial/anti-biofilm efficacy

Persistent bacterial infection caused by biofilms is one of the most serious problems that threatened human health. The development of antibacterial agents remains a challenge to penetrate biofilm and effectively treat the underlying bacterial infection. In the current study, chitosan-based nanogels were developed for encapsulating the Tanshinone IIA (TA) to enhance the antibacterial and anti-biofilm efficacy against Streptococcus mutans (S. mutans). The as-prepared nanogels (TA@CS) displayed excellent encapsulation efficiency (91.41 ± 0.11 %), uniform particle sizes (393.97 ± 13.92 nm), and enhanced positive potential (42.27 ± 1.25 mV). After being coated with CS, the stability of TA under light and other harsh environments was greatly improved. In addition, TA@CS displayed pH responsiveness, allowing it to selectively release more TA in acidic conditions. Furthermore, the positively charged TA@CS were equipped to target negatively charged biofilm surfaces and efficiently penetrate through biofilm barriers, making it promising for remarkable anti-biofilm activity. More importantly, when TA was encapsulated into CS nanogels, the antibacterial activity of TA was enhanced at least 4-fold. Meanwhile, TA@CS inhibited 72 % of biofilm formation at 500 μg/mL. The results demonstrated that the nanogels constituted CS and TA had antibacterial/anti-biofilm properties with synergistic enhanced effects, which will benefit pharmaceutical, food, and other fields.

Nanomaterials and Coatings for Managing Antibiotic-Resistant Biofilms

Biofilms are a global health concern responsible for 65 to 80% of the total number of acute and persistent nosocomial infections, which lead to prolonged hospitalization and a huge economic burden to the healthcare systems. Biofilms are organized assemblages of surface-bound cells, which are enclosed in a self-produced extracellular polymer matrix (EPM) of polysaccharides, nucleic acids, lipids, and proteins. The EPM holds the pathogens together and provides a functional environment, enabling adhesion to living and non-living surfaces, mechanical stability, next to enhanced tolerance to host immune responses and conventional antibiotics compared to free-floating cells. Furthermore, the close proximity of cells in biofilms facilitates the horizontal transfer of genes, which is responsible for the development of antibiotic resistance. Given the growing number and impact of resistant bacteria, there is an urgent need to design novel strategies in order to outsmart bacterial evolutionary mechanisms. Antibiotic-free approaches that attenuate virulence through interruption of quorum sensing, prevent adhesion via EPM degradation, or kill pathogens by novel mechanisms that are less likely to cause resistance have gained considerable attention in the war against biofilm infections. Thereby, nanoformulation offers significant advantages due to the enhanced antibacterial efficacy and better penetration into the biofilm compared to bulk therapeutics of the same composition. This review highlights the latest developments in the field of nanoformulated quorum-quenching actives, antiadhesives, and bactericides, and their use as colloid suspensions and coatings on medical devices to reduce the incidence of biofilm-related infections.

Recent Nanotechnologies to Overcome the Bacterial Biofilm Matrix Barriers

Bacterial biofilm-related infectious diseases severely influence human health. Under typical situations, pathogens can colonize inert or biological surfaces and form biofilms. Biofilms are functional aggregates that coat bacteria with extracellular polymeric substances (EPS). The main reason for the failure of biofilm infection treatment is the low permeability and enrichment of therapeutic agents within the biofilm, which results from the particular features of biofilm matrix barriers such as negatively charged biofilm components and highly viscous compact EPS structures. Hence, developing novel therapeutic strategies with enhanced biofilm penetrability is crucial. Herein, the current progress of nanotechnology methods to improve therapeutic agents' penetrability against biofilm matrix, such as regulating material morphology and surface properties, utilizing the physical penetration of nano/micromotors or microneedle patches, and equipping nanoparticles with EPS degradation enzymes or signal molecules, is first summarized. Finally, the challenges, perspectives, and future implementations of engineered delivery systems to manage biofilm infections are presented in detail.

Engineered organic nanoparticles to combat biofilms

Biofilms are colonies of microorganisms that are embedded in autocrine extracellular polymeric substances (EPS), imparting antibiotic resistance and recalcitrant bacterial infection. Nanoparticles (NPs) can enhance the biofilm inhibition and eradication of delivered antibiotics. This is mainly because of enhanced EPS penetration and a high local drug concentration. As we discuss here, novel strategies are being developed to further enhance the antibiofilm capacity of NPs, including size optimization, surface modification, stimuli-triggered release, and combined strategies. Thus, NPs represent an effective and promising approach to combat biofilms.

Combination of Enzymes with Materials to Give Them Antimicrobial Features: Modern Trends and Perspectives

Multidrug-resistant bacteria form serious problems in many areas, including medicine and the food industry. At the same time, great interest is shown in the transfer or enhancement of antimicrobial properties to various materials by modifying them with enzymes. The use of enzymes in biomaterials with antimicrobial properties is important because enzymes can be used as the main active components providing antimicrobial properties of functionalized composite biomaterials, or can serve as enhancers of the antimicrobial action of certain substances (antibiotics, antimicrobial peptides, metal nanoparticles, etc.) against cells of various microorganisms. Enzymes can simultaneously widen the spectrum of antimicrobial activity of biomaterials. This review presents the most promising enzymes recently used for the production of antibacterial materials, namely hydrolases and oxidoreductases. Computer modeling plays an important role in finding the most effective combinations between enzymes and antimicrobial compounds, revealing their possible interactions. The range of materials that can be functionalized using enzymes looks diverse. The physicochemical characteristics and functionalization methods of the materials have a significant impact on the activity of enzymes. In this context, fibrous materials are of particular interest. The purpose of this review is to analyze the current state of the art in this area.

Candida albicans biofilms: antifungal resistance, immune evasion, and emerging therapeutic strategies

Candida albicans is a fungal pathogen that can form biofilms on medical devices and host tissue, resulting in serious, life-threatening infections. These fungal biofilms are inherently resistant to traditional antifungal therapies and the host immune system; therefore, biofilm-associated infections are a huge clinical challenge. This review summarizes the most important insights into C. albicans biofilm-associated antifungal drug resistance mechanisms and immune evasion strategies. In addtion, this review also discusses the strategies for antifungal drug use to combat these processes, providing further evidence for novel drugs research and clinical therapies.

Nanocarriers for combating biofilms: advantages and challenges

Bacterial biofilms are highly resistant to antibiotics and pose a great threat to human and animal health. The control and removal of bacterial biofilms have become an important topic in the field of bacterial infectious diseases. Nanocarriers show great anti-biofilm potential because of their small particle size and strong permeability. In this review, the advantages of nanocarriers for combating biofilms are analyzed. Nanocarriers can act on all stages of bacterial biofilm formation and diffusion. They can improve the scavenging effect of biofilm by targeting biofilm, destroying extracellular polymeric substances, and enhancing the biofilm permeability of antimicrobial substances. Nanocarriers can also improve the antibacterial ability of antimicrobial drugs against bacteria in biofilm by protecting the loaded drugs and controlling the release of antimicrobial substances. Additionally, we emphasize the challenges faced in using nanocarrier formulations and translating them from a preclinical level to the clinical setting.

Hurdle technology using encapsulated enzymes and essential oils to fight bacterial biofilms

Biofilm formation on abiotic surfaces has become a major public health concern because of the serious problems they can cause in various fields. Biofilm cells are extremely resistant to stressful conditions, because of their complex structure impedes antimicrobial penetration to deep-seated cells. The increased resistance of biofilm to currently applied control strategies underscores the urgent need for new alternative and/or supplemental eradication approaches. The combination of two or more methods, known as Hurdle technology, offers an excellent option for the highly effective control of biofilms. In this perspective, the use of functional enzymes combined with biosourced antimicrobial such as essential oil (EO) is a promising alternative anti-biofilm approach. However, these natural antibiofilm agents can be damaged by severe environmental conditions and lose their activity. The microencapsulation of enzymes and EOs is a promising new technology for enhancing their stability and improving their biological activity. This review article highlights the problems related to biofilm in various fields, and the use of encapsulated enzymes with essential oils as antibiofilm agents. KEY POINTS: • Problems associated with biofilms in the food and medical sectors and their subsequent risks on health and food quality. • Hurdle technology using enzymes and essential oils is a promising strategy for an efficient biofilms control. • The microencapsulation of enzymes and essential oils ensures their stability and improves their biological activities.

Recent Advances and Opportunities in the Study of Candida albicans Polymicrobial Biofilms

It is well known that the opportunistic pathogenic yeast, Candida albicans, can form polymicrobial biofilms with a variety of bacteria, both in vitro and in vivo, and that these polymicrobial biofilms can impact the course and management of disease. Although specific interactions are often described as either synergistic or antagonistic, this may be an oversimplification. Polymicrobial biofilms are complex two-way interacting communities, regulated by inter-domain (inter-kingdom) signaling and various molecular mechanisms. This review article will highlight advances over the last six years (2016-2021) regarding the unique biology of polymicrobial biofilms formed by C. albicans and bacteria, including regulation of their formation. In addition, some of the consequences of these interactions, such as the influence of co-existence on antimicrobial susceptibility and virulence, will be discussed. Since the aim of this knowledge is to inform possible alternative treatment options, recent studies on the discovery of novel anti-biofilm compounds will also be included. Throughout, an attempt will be made to identify ongoing challenges in this area.

DNase enhances photodynamic therapy against fluconazole-resistant Candida albicans biofilms

OBJECTIVE

This study evaluated the effectiveness of DNase I combined with antimicrobial photodynamic therapy, mediated by Photodithazine^® and light-emitting diode light, against biofilms formed by a fluconazole-resistant Candida albicans strain (ATCC 96901) and two clinical isolates (R14 and R70).

MATERIALS AND METHODS

Biofilms were grown for 48 h and exposed to DNase for 5 min, followed by application of a photosensitizer (P) and light (L), either singly or combined (P+L+, P-L+, P+L-, P-L-, P-L-DNase, P+L+DNase, P+L-DNase, and P-L+DNase; n = 12). Biofilm analysis included quantification of extracellular matrix components (water-soluble and insoluble proteins and polysaccharides, and extracellular DNA), and biomass (total and insoluble), as well as enumeration of colony-forming units. The data were analyzed using three-way analysis of variance with Bonferroni's post-hoc test.

RESULTS

The DNase treatment combined with aPDT showed a reduction of 1.92, 1.65, and 1.29 log₁₀ of cell viability compared with untreated controls for ATCC 96901, R14, and R70 strains, respectively. It also reduced extracellular matrix contents of water-soluble polysaccharides (36.3%) and extracellular DNA (72.3%), as well as insoluble biomass content (43.3%).

CONCLUSION

The three strains showed similar behavior when treated with DNase, and the extracellular matrix components were affected, improving the effectiveness of antimicrobial photodynamic therapy.

Nanoparticle, a promising therapeutic strategy for the treatment of infective endocarditis

Infective endocarditis (IE) has been recognized as a biofilm-related disease caused by pathogenic microorganisms, such as bacteria and fungi that invade and damage the heart valves and endocardium. There are many difficulties and challenges in the antimicrobial treatment of IE, including multi-drug resistant pathogens, large dose of drug administration with following side effects, and poor prognosis. For the past few years, the development of nanotechnology has promoted the use of nanoparticles as antimicrobial nano-pharmaceuticals or novel drug delivery systems (NDDS) in antimicrobial therapy for chronic infections and biofilm-related infectious disease as these molecules exhibit several advantages. Therefore, nanoparticles have a potential role to play in solving problems in the treatment of IE, including improving antimicrobial activity, increasing drug bioavailability, minimizing frequency of drug administration, and preventing side effects. In this article, we review the latest advances in nanoparticles against drug-resistant bacteria in biofilm and recommends nanoparticles as an alternative strategy to the antibiotic treatment of IE.

Immobilized enzymes as potent antibiofilm agent

Biofilm has been a point of concern in hospitals and various industries. They not only cause various chronic infections but are also responsible for the degradation of various medical appliances. Since the last decade, various alternate strategies are being adopted to combat the biofilm formed on various biotic and abiotic surfaces. The use of enzymes as a potent anti-fouling agent is proved to be of utmost importance as the enzymes can inhibit biofilm formation in an eco-friendly and cost-effective way. The physical and chemical immobilization of the enzyme not only leads to the improvement of thermostability and reusability of the enzyme, but also gains better efficiency of biofilm removal. Immobilization of amylase, cellobiohydrolase, pectinase, subtilisin A and β-N-acetyl-glucosaminidase (DspB) are proved to be most effective in inhibition of biofilm formation and removal of matured biofilm than their free forms. Hence, these immobilized enzymes provide greater eradication of biofilm formed on various surfaces and are coming up to be the potent antibiofilm agent.

Antimicrobial coatings based on chitosan to prevent implant-associated infections: A systematic review

Despite the advancements in material science and surgical techniques, the incidence of implant-associated infections (IAIs) has increased significantly. IAIs are mainly caused by microbial adhesion and biofilm formation on implant surfaces. In this study, we aimed to evaluate and critically discuss the antimicrobial efficacy of chitosan-based coatings to prevent the occurrence of IAIs. For this purpose, a PRISMA-oriented systematic review was conducted based on predefined criteria and forty studies were selected for qualitative analysis. Results indicated that chitosan (CS) association with enzymes and antimicrobial peptides improves its antimicrobial activity and extends its use in a broad range of physiological conditions. Likewise, CS association with polymers resulted in enhanced antimicrobial and anti-adhesive coatings with desirable properties, such as biocompatibility and durability, for implantable medical devices (IMDs). These findings can assist researchers in the design of new CS coatings for application in IMDs.

Multienzyme nanoassemblies: from rational design to biomedical applications

Multienzyme nanoassemblies (MENAs) that combine the functions of several enzymes into one entity have attracted widespread research interest due to their improved enzymatic performance and great potential for multiple applications. Considerable progress has been made to design and fabricate MENAs in recent years. This review begins with an introduction of the up-to-date strategies in designing MENAs, mainly including substrate channeling, compartmentalization and control of enzyme stoichiometry. The desirable properties that endow MENAs with important applications are also discussed in detail. Then, the recent advances in utilizing MENAs in the biomedical field are reviewed, with a particular focus on biosensing, tumor therapy, antioxidant and drug delivery. Finally, the challenges and perspectives for development of versatile MENAs are summarized.

Current progress and prospects of organic nanoparticles against bacterial biofilm

Biofilm plays a vital role in the pathogenicity and resistance of bacteria, and is an important problem to be settled urgently in the treatment of bacterial diseases. Exploring effective strategies to control bacterial biofilm has become a hot research topic. Compared to other measures, organic nanomaterials have shown greater prospects in overcoming the problems of bacterial biofilms due to their unique properties. In order to explore more effective organic nanomaterials against biofilms, we used relevant keywords to search for related published publications on the Web of Science . On the basis of these searched publications, this review firstly summarized the properties, formulation, harmness, and treatment challenges of biofilm. Secondly, the current progress of organic nanomaterials against bacterial biofilm and its possible anti-biofilm mechanisms (e.g., reducing the adhesion of biofilms, enhancing the permeability of antimicrobial agents, maintaining drug stability, fighting against biofilm using specific actions) was analyzed. Thirdly, the influences on the anti-biofilm efficacy of organic nanomaterials were discussed from nanoparticles and biofilm characteristics. Finally, the challenges and prospects of organic nanoparticles against biofilm were concluded. This review may help researchers to realize the progress and challenges of nanoparticles against biofilm and thus help to design more efficient organic nanomaterial to fight against biofilms.

Magnetic combi CLEA for inhibition of bacterial biofilm: A green approach

In the present study different enzymes (α- amylase, trypsin, cellulase, horse-radish peroxidase and pectinex ultra clear) were studied for bacterial biofilm inhibition and Pectinex ultra clear showed best inhibition. So, m-combi-CLEA of Pectinex ultra clear was developed by cross linked enzyme aggregate (CLEA) formation on APTES (3-aminopropyltriethoxysilane) modified iron oxide nanoparticles. Different parameters were optimized and it was observed that 0.4 mg/ml of protein (containing 25 U/mg cellulase activity), 0.5 mg/ml BSA and 10 mM glutaraldehyde when incubated for 3 h gives 100% enzyme activity using ethanol as the precipitant. The CLEA formed were thermally more stable as compared to free enzyme. m-combi-CLEA of Pectinex ultra clear shows 75-78% biofilm inhibition of E. coli and S. aureus. Furthermore, m-combi-CLEA can be reused till 4 cycles with same efficiency. The carbohydrate contents of E. coli biofilm decreased from 64.629 μg to 6.23 μg and for S. aureus biofilm, it decreased from 58.46 μg to 5.52 μg when treated with m-combi CLEA in comparison to untreated biofilms. FTIR, darkfield illumination Fluorescence Microscopy, and Scanning Electron Microscopy was further used for characterization.

Approaches for the inhibition and elimination of microbial biofilms using macromolecular agents

Biofilms are complex three-dimensional structures formed at interfaces by the vast majority of bacteria and fungi. These robust communities have an important detrimental impact on a wide range of industries and other facets of our daily lives, yet their removal is challenging owing to the high tolerance of biofilms towards conventional antimicrobial agents. This key issue has driven an urgent search for new innovative antibiofilm materials. Amongst these emerging approaches are highly promising materials that employ aqueous-soluble macromolecules, including peptides, proteins, synthetic polymers, and nanomaterials thereof, which exhibit a range of functionalities that can inhibit biofilm formation or detach and destroy organisms residing within established biofilms. In this Review, we outline the progress made in inhibiting and removing biofilms using macromolecular approaches, including a spotlight on cutting-edge materials that respond to environmental stimuli for "on-demand" antibiofilm activity, as well as synergistic multi-action antibiofilm materials. We also highlight materials that imitate and harness naturally derived species to achieve new and improved biomimetic and biohybrid antibiofilm materials. Finally, we share some speculative insights into possible future directions for this exciting and highly significant field of research.

Chemical and physical Chitosan modification for designing enzymatic industrial biocatalysts: How to choose the best strategy?

Chitosan is one of the most abundant natural polymer worldwide, and due to its inherent characteristics, its use in industrial processes has been extensively explored. Because it is biodegradable, biocompatible, non-toxic, hydrophilic, cheap, and has good physical-chemical stability, it is seen as an excellent alternative for the replacement of synthetic materials in the search for more sustainable production methodologies. Thus being, a possible biotechnological application of Chitosan is as a direct support for enzyme immobilization. However, its applicability is quite specific, and to overcome this issue, alternative pretreatments are required, such as chemical and physical modifications to its structure, enabling its use in a wider array of applications. This review aims to present the topic in detail, by exploring and discussing methods of employment of Chitosan in enzymatic immobilization processes with various enzymes, presenting its advantages and disadvantages, as well as listing possible chemical modifications and combinations with other compounds for formulating an ideal support for this purpose. First, we will present Chitosan emphasizing its characteristics that allow its use as enzyme support. Furthermore, we will discuss possible physicochemical modifications that can be made to Chitosan, mentioning the improvements obtained in each process. These discussions will enable a comprehensive comparison between, and an informed choice of, the best technologies concerning enzyme immobilization and the application conditions of the biocatalyst.

Akim A, Chong PP. Approaches for Mitigating Microbial Biofilm-Related Drug Resistance: A Focus on Micro- and Nanotechnologies

Biofilms play an essential role in chronic and healthcare-associated infections and are more resistant to antimicrobials compared to their planktonic counterparts due to their (1) physiological state, (2) cell density, (3) quorum sensing abilities, (4) presence of extracellular matrix, (5) upregulation of drug efflux pumps, (6) point mutation and overexpression of resistance genes, and (7) presence of persister cells. The genes involved and their implications in antimicrobial resistance are well defined for bacterial biofilms but are understudied in fungal biofilms. Potential therapeutics for biofilm mitigation that have been reported include (1) antimicrobial photodynamic therapy, (2) antimicrobial lock therapy, (3) antimicrobial peptides, (4) electrical methods, and (5) antimicrobial coatings. These approaches exhibit promising characteristics for addressing the impending crisis of antimicrobial resistance (AMR). Recently, advances in the micro- and nanotechnology field have propelled the development of novel biomaterials and approaches to combat biofilms either independently, in combination or as antimicrobial delivery systems. In this review, we will summarize the general principles of clinically important microbial biofilm formation with a focus on fungal biofilms. We will delve into the details of some novel micro- and nanotechnology approaches that have been developed to combat biofilms and the possibility of utilizing them in a clinical setting.

Novel Approaches to Combat Medical Device-Associated BioFilms

Biofilms are aggregates formed as a protective survival state by microorganisms to adapt to the environment and can be resistant to antimicrobial agents and host immune responses due to chemical or physical diffusion barriers, modified nutrient environments, suppression of the growth rate within biofilms, and the genetic adaptation of cells within biofilms. With the widespread use of medical devices, medical device-associated biofilms continue to pose a serious threat to human health, and these biofilms have become the most important source of nosocomial infections. However, traditional antimicrobial agents cannot completely eliminate medical device-associated biofilms. New strategies for the treatment of these biofilms and targeting biofilm infections are urgently required. Several novel approaches have been developed and identified as effective and promising treatments. In this review, we briefly summarize the challenges associated with the treatment of medical device-associated biofilm infections and highlight the latest promising approaches aimed at preventing or eradicating these biofilms.

Microbial Interkingdom Biofilms and the Quest for Novel Therapeutic Strategies

Fungal and bacterial species interact with each other within polymicrobial biofilm communities in various niches of the human body. Interactions between these species can greatly affect human health and disease. Diseases caused by polymicrobial biofilms pose a major challenge in clinical settings because of their enhanced virulence and increased drug tolerance. Therefore, different approaches are being explored to treat fungal-bacterial biofilm infections. This review focuses on the main mechanisms involved in polymicrobial drug tolerance and the implications of the polymicrobial nature for the therapeutic treatment by highlighting clinically relevant fungal-bacterial interactions. Furthermore, innovative treatment strategies which specifically target polymicrobial biofilms are discussed.

Biofilms and nanoparticles: applications in agriculture

A profound need to explore eco-friendly methods to practice sustainable agriculture leads to the research and exploration of plant growth-promoting rhizobacteria (PGPRs). Biofilms are assemblages of microbial communities within a self-secreted exopolymeric matrix, adhering to different biotic and abiotic surfaces and performing a variety of desired and undesired functions. Biofilm formation by PGPRs is governed by effective root colonization of the host plant in providing plant growth promotion and stress management. Biofilms can also provide a suitable environment for the synthesis and entrapment of nanoparticles. Together, nanoparticles and PGPRs may contribute towards biocontrol and crop management. This review discusses the significance of biofilms in agriculture and their confluence with different types of nanoparticles for plant protection and improved crop production.

We Are One: Multispecies Metabolism of a Biofilm Consortium and Their Treatment Strategies

The ecological and medical significance of bacterial biofilms have been well recognized. Biofilms are harder to control than their planktonic free-living counterparts and quite recently, the focus of the study has shifted to the multispecies consortia, which represent the vast majority of real-case infection scenarios. Studies have begun to explore the complex interspecies interactions within these biofilms. However, only little attention is currently given to the role of cellular metabolites in the cell-to-cell communication. The concentration gradients of metabolic substrates and products affect the spatial growth of bacteria in multispecies biofilm. This, if looked into more deeply, can lead to identification of potential therapies targeting the specific metabolites and hence the coordinated protection in the bacterial community. Herein, we review the interspecies communications, including their metabolic cross-talking, in multispecies biofilm, to signify the importance of such interactions on the initial formation and subsequent growth of these biofilms. Multispecies biofilms with their species heterogeneity are more resilient to antimicrobial agents than their single species biofilm counterparts and this characteristic is of particular interest when dealing with pathogenic bacteria. In this Review, we also discuss the treatment options available, to include current and emerging avenues to combat pathogenic multispecies biofilms in the clinical, environmental, as well as industrial settings.

Improvement of biodiesel production from palm oil by co-immobilization of Thermomyces lanuginosa lipase and Candida antarctica lipase B: Optimization using response surface methodology

Candida antarctica lipase B (CALB) and Thermomyces lanuginose lipase (TLL) were co-immobilized on epoxy functionalized silica gel via an isocyanide-based multicomponent reaction. The immobilization process was carried out in water (pH 7) at 25 °C, rapidly (3 h) resulting in high immobilization yields (100%) with a loading of 10 mg enzyme/g support. The immobilized preparations were used to produce biodiesel by transesterification of palm oil. In an optimization study, response surface methodology (RSM) and central composite rotatable design (CCRD) methods were used to study the effect of five independent factors including temperature, methanol to oil ratio, t-butanol concentration and CALB:TLL ratio on the yield of biodiesel production. The optimum combinations for the reaction were CALB:TLL ratio (2.1:1), t-butanol (45 wt%), temperature (47 °C), methanol: oil ratio (2.3). This resulted in a FAME yield of 94%, very close to the predicted value of 98%.

Innovative Strategies Toward the Disassembly of the EPS Matrix in Bacterial Biofilms

Bacterial biofilms represent a major concern at a worldwide level due to the high demand for implantable medical devices and the rising numbers of bacterial resistance. The complex structure of the extracellular polymeric substances (EPS) matrix plays a major role in this phenomenon, since it protects bacteria from antibiotics, avoiding drug penetration at bactericidal concentrations. Besides, this structure promotes bacterial cells to adopt a dormant lifestyle, becoming less susceptible to antibacterial agents. Currently, the available treatment for biofilm-related infections consists in the administration of conventional antibiotics at high doses for a long-term period. However, this treatment lacks efficiency against mature biofilms and for implant-associated biofilms it may be necessary to remove the medical device. Thus, biofilm-related infections represent an economical burden for the healthcare systems. New strategies focusing on the matrix are being highlighted as alternative therapies to eradicate biofilms. Here, we outline reported matrix disruptive agents, nanocarriers, and technologies, such as application of magnetic fields, photodynamic therapy, and ultrasounds, that have been under investigation to disrupt the EPS matrix of clinically relevant bacterial biofilms. In an ideal therapy, a synergistic effect between antibiotics and the explored innovated strategies is aimed to completely eradicate biofilms and avoid antimicrobial resistance phenomena.

Nanovectorized Microalgal Extracts to Fight Candida albicans and Cutibacterium acnes Biofilms: Impact of Dual-Species Conditions

Biofilm-related infections are a matter of concern especially because of the poor susceptibility of microorganisms to conventional antimicrobial agents. Innovative approaches are needed. The antibiofilm activity of extracts of cyanobacteria Arthrospira platensis, rich in free fatty acids, as well as of extract-loaded copper alginate-based nanocarriers, were studied on single- and dual-species biofilms of Candida albicans and Cutibacterium acnes. Their ability to inhibit the biofilm formation and to eradicate 24 h old biofilms was investigated. Concentrations of each species were evaluated using flow cytometry. Extracts prevented the growth of C. acnes single-species biofilms (inhibition > 75% at 0.2 mg/mL) but failed to inhibit preformed biofilms. Nanovectorised extracts reduced the growth of single-species C. albicans biofilms (inhibition > 43% at 0.2 mg/mL) while free extracts were weakly or not active. Nanovectorised extracts also inhibited preformed C. albicans biofilms by 55% to 77%, whereas the corresponding free extracts were not active. In conclusion, even if the studied nanocarrier systems displayed promising activity, especially against C. albicans, their efficacy against dual-species biofilms was limited. This study highlighted that working in such polymicrobial conditions can give a more objective view of the relevance of antibiofilm strategies by taking into account interspecies interactions that can offer additional protection to microbes.