An in-situ infection detection sensor coating for urinary catheters

Multifaceted Hydrogel Scaffolds: Bridging the Gap between Biomedical Needs and Environmental Sustainability

Hydrogels are dynamically evolving 3D networks composed of hydrophilic polymer scaffolds with significant applications in the healthcare and environmental sectors. Notably, protein-based hydrogels mimic the extracellular matrix, promoting cell adhesion. Further enhancing cell proliferation within these scaffolds are matrix-metalloproteinase-triggered amino acid motifs. Integration of cell-friendly modules like peptides and proteins expands hydrogel functionality. These exceptional properties position hydrogels for diverse applications, including biomedicine, biosensors, environmental remediation, and the food industry. Despite significant progress, there is ongoing research to optimize hydrogels for biomedical and environmental applications further. Engineering novel hydrogels with favorable characteristics is crucial for regulating tissue architecture and facilitating ecological remediation. This review explores the synthesis, physicochemical properties, and biological implications of various hydrogel types and their extensive applications in biomedicine and environmental sectors. It elaborates on their potential applications, bridging the gap between advancements in the healthcare sector and solutions for environmental issues.

A comprehensive status update on modification of foley catheter to combat catheter-associated urinary tract infections and microbial biofilms

Present-day healthcare employs several types of invasive devices, including urinary catheters, to improve medical wellness, the clinical outcome of disease, and the quality of patient life. Among urinary catheters, the Foley catheter is most commonly used in patients for bladder drainage and collection of urine. Although such devices are very useful for patients who cannot empty their bladder for various reasons, they also expose patients to catheter-associated urinary tract infections (CAUTIs). Catheter provides an ideal surface for bacterial colonization and biofilm formation, resulting in persistent bacterial infection and severe complications. Hence, rigorous efforts have been made to develop catheters that harbour antimicrobial and anti-fouling properties to resist colonization by bacterial pathogens. In this regard, catheter modification by surface functionalization, impregnation, blending, or coating with antibiotics, bioactive compounds, and nanoformulations have proved to be effective in controlling biofilm formation. This review attempts to illustrate the complications associated with indwelling Foley catheters, primarily focussing on challenges in fighting CAUTI, catheter colonization, and biofilm formation. In this review, we also collate scientific literature on catheter modification using antibiotics, plant bioactive components, bacteriophages, nanoparticles, and studies demonstrating their efficacy through in vitro and in vivo testing.

Green-Synthesized Silver Nanoparticles in the Prevention of Multidrug-Resistant Proteus mirabilis Infection and Incrustation of Urinary Catheters BioAgNPs Against P. mirabilis Infection

This study aimed to assess the activity of AgNPs biosynthesized by Fusarium oxysporum (bio-AgNPs) against multidrug-resistant uropathogenic Proteus mirabilis, and to assess the antibacterial activity of catheters coated with bio-AgNPs. Broth microdilution and time-kill kinetics assays were used to determine the antibacterial activity of bio-AgNPs. Catheters were coated with two (2C) and three (3C) bio-AgNPs layers using polydopamine as crosslinker. Catheters were challenged with urine inoculated with P. mirabilis to assess the anti-incrustation activity. MIC was found to be 62.5 µmol l-1, causing total loss of viability after 4 h and bio-AgNPs inhibited biofilm formation by 76.4%. Catheters 2C and 3C avoided incrustation for 13 and 20 days, respectively, and reduced biofilm formation by more than 98%, while the pristine catheter was encrusted on the first day. These results provide evidence for the use of bio-AgNPs as a potential alternative to combat of multidrug-resistant P. mirabilis infections.

Recent Advances in Pharmaceutical Approaches of Antimicrobial Agents for Selective Delivery in Various Administration Routes

Globally, the increase of pathogenic bacteria with antibiotic-resistant characteristics has become a critical challenge in medical treatment. The misuse of conventional antibiotics to treat an infectious disease often results in increased resistance and a scarcity of effective antimicrobials to be used in the future against the organisms. Here, we discuss the rise of antimicrobial resistance (AMR) and the need to combat it through the discovery of new synthetic or naturally occurring antibacterial compounds, as well as insights into the application of various drug delivery approaches delivered via various routes compared to conventional delivery systems. AMR-related infectious diseases are also discussed, as is the efficiency of various delivery systems. Future considerations in developing highly effective antimicrobial delivery devices to address antibiotic resistance are also presented here, especially on the smart delivery system of antibiotics.

A comprehensive review on hydrogel materials in urology: Problems, methods, and new opportunities

Hydrogel materials provide an extremely promising group of materials that can find an increasingly wide range of use in treating urinary system conditions due to their unique properties. The present review describes achievements to date in terms of the use and development prospects of hydrogel materials applications in the treatment and reconstruction of the urinary system organs, which among others include: hydrogel systems of intravesical drug delivery, ureteral stents design, treatment of vesicoureteral reflux, urinary bladder and urethral defects reconstruction, design of modern urinary catheters and also solutions applied in urinary incontinence therapy (Figure 4). In addition, hydrogel materials find increasingly growing applications in the construction of educational simulation models of organs and specific conditions of the urinary system, which enable the education of medical personnel. Numerous research efforts are underway to expand the existing treatment methods and reconstruction of the urinary system based on hydrogel materials. After conducting the further necessary research, many of the innovative solutions developed to date have high application potential.

Modeling Tunable Fracture in Hydrogel Shell Structures for Biomedical Applications

Hydrogels are nowadays widely used in various biomedical applications, and show great potential for the making of devices such as biosensors, drug- delivery vectors, carriers, or matrices for cell cultures in tissue engineering, etc. In these applications, due to the irregular complex surface of the human body or its organs/structures, the devices are often designed with a small thickness, and are required to be flexible when attached to biological surfaces. The devices will deform as driven by human motion and under external loading. In terms of mechanical modeling, most of these devices can be abstracted as shells. In this paper, we propose a mixed graph-finite element method (FEM) phase field approach to model the fracture of curved shells composed of hydrogels, for biomedical applications. We present herein examples for the fracture of a wearable biosensor, a membrane-coated drug, and a matrix for a cell culture, each made of a hydrogel. Used in combination with experimental material testing, our method opens a new pathway to the efficient modeling of fracture in biomedical devices with surfaces of arbitrary curvature, helping in the design of devices with tunable fracture properties.

A review on urinary tract infections diagnostic methods: Laboratory-based and point-of-care approaches

Urinary tract infections (UTIs) are among the most common infectious diseases worldwide. This type of infections can be healthcare-associated or community-acquired and affects millions of people every year. Different diagnostic procedures are available to detect pathogens in urine and they can be divided into two main categories: laboratory-based and point-of-care (POC) detection techniques. Traditional methodologies are often time-consuming, thus, achieving a rapid and accurate identification of pathogens is a challenging feature that has been pursued by many research groups and companies operating in this area. The purpose of this review is to compare and highlight advantages and disadvantages of the traditional and currently most used detection methods, as well as the emerging POC approaches and the relevant advances in on-site detection of pathogens´ mechanisms, suitable to be adapted to UTI diagnosis. Lately, the commercially available UTI self-testing kits and devices are helping in the diagnosis of urinary infections as patients or care givers are able to perform the test, easily and comfortably at home and, upon the result, decide when to attend an appointment/Urgent Health Care Unit.

Nanomedicine-based strategies to improve treatment of cutaneous leishmaniasis

Nanomedicine strategies were first adapted and successfully translated to clinical application for diseases, such as cancer and diabetes. These strategies would no doubt benefit unmet diseases needs as in the case of leishmaniasis. The latter causes skin sores in the cutaneous form and affects internal organs in the visceral form. Treatment of cutaneous leishmaniasis (CL) aims at accelerating wound healing, reducing scarring and cosmetic morbidity, preventing parasite transmission and relapse. Unfortunately, available treatments show only suboptimal effectiveness and none of them were designed specifically for this disease condition. Tissue regeneration using nano-based devices coupled with drug delivery are currently being used in clinic to address diabetic wounds. Thus, in this review, we analyse the current treatment options and attempt to critically analyse the use of nanomedicine-based strategies to address CL wounds in view of achieving scarless wound healing, targeting secondary bacterial infection and lowering drug toxicity.

Optimisation of a lozenge-based sensor for detecting impending blockage of urinary catheters

Catheter-associated urinary tract infections resulting from urease-positive microorganisms are more likely to cause a urinary catheter blockage owing to the urease activity of the microbes. Catheter blockage can be dangerous and increases the risk of severe infections, such as sepsis. Ureases, a virulence factor in Proteus mirabilis, cause an increase in urine pH - leading to blockage. An optimised biosensor "lozenge" is presented here, which is able to detect impending catheter blockage. This lozenge has been optimised to allow easy manufacture and commercialisation. It functions as a sensor in a physiologically representative model of a catheterised urinary tract, providing 6.7 h warning prior to catheter blockage. The lozenge is stable in healthy human urine and can be sterilized for clinical use by ethylene oxide. Clinically, the lozenge will provide a visible indication of impending catheter blockage, enabling quicker clinical intervention and thus reducing the morbidity and mortality associated with blockage.

Shaping Macromolecules for Sensing Applications—From Polymer Hydrogels to Foldamers

Sensors are tools for detecting, recognizing, and recording signals from the surrounding environment. They provide measurable information on chemical or physical changes, and thus are widely used in diagnosis, environment monitoring, food quality checks, or process control. Polymers are versatile materials that find a broad range of applications in sensory devices for the biomedical sector and beyond. Sensory materials are expected to exhibit a measurable change of properties in the presence of an analyte or a stimulus, characterized by high sensitivity and selectivity of the signal. Signal parameters can be tuned by material features connected with the restriction of macromolecule shape by crosslinking or folding. Gels are crosslinked, three-dimensional networks that can form cavities of different sizes and forms, which can be adapted to trap particular analytes. A higher level of structural control can be achieved by foldamers, which are macromolecules that can attain well-defined conformation in solution. By increasing control over the three-dimensional structure, we can improve the selectivity of polymer materials, which is one of the crucial requirements for sensors. Here, we discuss various examples of polymer gels and foldamer-based sensor systems. We have classified and described applied polymer materials and used sensing techniques. Finally, we deliberated the necessity and potential of further exploration of the field towards the increased selectivity of sensory devices.

Multiplexed detection and differentiation of bacterial enzymes and bacteria by color-encoded sensor hydrogels

We report on the fabrication and characterization of color-encoded chitosan hydrogels for the rapid, sensitive and specific detection of bacterial enzymes as well as the selective detection of a set of tested bacteria through characteristic enzyme reactions. These patterned sensor hydrogels are functionalized with three different colorimetric enzyme substrates affording the multiplexed detection and differentiation of α-glucosidase, β-galactosidase and β-glucuronidase. The limits of detection of the hydrogels for an observation time of 60 min using a conventional microplate reader correspond to concentrations of 0.2, 3.4 and 4.5 nM of these enzymes, respectively. Based on their different enzyme expression patterns, Staphylococcus aureus strain RN4220, methicillin-resistant S. aureus (MRSA) strain N315, both producing α-glucosidase, but not β-glucuronidase and β-galactosidase, Escherichia coli strain DH5α, producing β-glucuronidase and α-glucosidase, but not β-galactosidase, and the enterohemorrhagic E. coli (EHEC) strain E32511, producing β-galactosidase, but none of the other two enzymes, can be reliably and rapidly distinguished from each other. These results confirm the applicability of enzyme sensing hydrogels for the detection and discrimination of specific enzymes to facilitate differentiation of bacterial strains. Patterned hydrogels thus possess the potential to be further refined as detection units of a multiplexed format to identify certain bacteria for future application in point-of-care microbiological diagnostics in food safety and medical settings.

Broad spectrum antimicrobial PDMS-based biomaterial for catheter fabrication

Background

In addition to the widespread use of antibiotics in healthcare settings, the current COVID-19 pandemic has escalated the emergence of antibiotic resistance. Nosocomial infections among hospitalized patients is a leading site for such resistant microbial colonization due to prolonged use of invasive devices and antibiotics in therapies. Invasive medical devices, especially catheters, are prone to infections that could accelerate the development of resistant microbes. Often, catheters - particularly urinary catheters - are prone to high infection rates. Antibiotic-coated catheters can reduce infection rates and although commercially available, are limited in efficacy and choices.

Methods

Herein, a novel and facile method to fabricate PMDS-based biomaterial for the development of antimicrobial eluting catheters is presented. Silicone based organic polymer polydimethylsiloxane (PDMS) was used to prepare a biomaterial containing novel polymeric imidazolium antimicrobial compound.

Results

It was found that the PDMS-based biomaterials could eradicate microbial colonization even after 60 days in culture with continuous microbial challenge, be recycled over multiple uses, stored at room temperature for long-term usage and importantly is biocompatible.

Conclusion

The PDMS-based biomaterial displayed biocidal functionality on microbes of clinical origin, which form major threats in hospital acquired infections.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s40824-021-00235-5.

Novel Phage-Derived Depolymerase with Activity against Proteus mirabilis Biofilms

The adherence of Proteus mirabilis to the surface of urinary catheters leads to colonization and eventual blockage of the catheter lumen by unique crystalline biofilms produced by these opportunistic pathogens, making P. mirabilis one of the leading causes of catheter-associated urinary tract infections. The Proteus biofilms reduce efficiency of antibiotic-based treatment, which in turn increases the risk of antibiotic resistance development. Bacteriophages and their enzymes have recently become investigated as alternative treatment options. In this study, a novel Proteus bacteriophage (vB_PmiS_PM-CJR) was isolated from an environmental sample and fully characterized. The phage displayed depolymerase activity and the subsequent genome analysis revealed the presence of a pectate lyase domain in its tail spike protein. The protein was heterologously expressed and purified; the ability of the purified tail spike to degrade Proteus biofilms was tested. We showed that the application of the tail spike protein was able to reduce the adherence of bacterial biofilm to plastic pegs in a MBEC (minimum biofilm eradication concentration) assay and improve the survival of Galleria mellonella larvae infected with Proteus mirabilis. Our study is the first to successfully isolate and characterize a biofilm depolymerase from a Proteus phage, demonstrating the potential of this group of enzymes in treatment of Proteus infections.

Potential strategies to prevent encrustations on urinary stents and catheters - thinking outside the box: a European network of multidisciplinary research to improve urinary stents (ENIUS) initiative

Introduction: Urinary stents have been around for the last 4 decades, urinary catheters even longer. They are associated with infections, encrustation, migration, and patient discomfort. Research efforts to improve them have shifted onto molecular and cellular levels. ENIUS brought together translational scientists to improve urinary implants and reduce morbidity.Methods & materials: A working group within the ENIUS network was tasked with assessing future research lines for the improvement of urinary implants.Topics were researched systematically using Embase and PubMed databases. Clinicaltrials.gov was consulted for ongoing trials.Areas covered: Relevant topics were coatings with antibodies, enzymes, biomimetics, bioactive nano-coats, antisense molecules, and engineered tissue. Further, pH sensors, biodegradable metals, bactericidal bacteriophages, nonpathogenic uropathogens, enhanced ureteric peristalsis, electrical charges, and ultrasound to prevent stent encrustations were addressed.Expert opinion: All research lines addressed in this paper seem viable and promising. Some of them have been around for decades but are yet to proceed to clinical application (i.e. tissue engineering). Others are very recent and, at least in urology, still only conceptual (i.e. antisense molecules). Perhaps the most important learning point resulting from this pan-European multidisciplinary effort is that collaboration between all stakeholders is not only fruitful but also truly essential.

Hydrogels and Their Role in Biosensing Applications

Hydrogels play an important role in the field of biomedical research and diagnostic medicine. They are emerging as a powerful tool in the context of bioanalytical assays and biosensing. In this context, this review gives an overview of different hydrogels and the role they adopt in a range of applications. Not only are hydrogels beneficial for the immobilization and embedding of biomolecules, but they are also used as responsive material, as wearable devices, or as functional material. In particular, the scientific and technical progress during the last decade is discussed. The newest hydrogel types, their synthesis, and many applications are presented. Advantages and performance improvements are described, along with their limitations.

The recent advances in surface antibacterial strategies for biomedical catheters

As one of the most common hospital-acquired infections, catheter-related infections (CRIs) which are caused by microbial colonization lead to increasing morbidity and mortality of patients and life threat for medical staffs. In this case, a variety of efforts have been made to design functional materials to limit bacterial colonization and biofilm formation. In this review, we focus on the recent advances in surface modification strategies of biomedical catheters used to prevent CRIs. The tests for the evaluation of the performances of modified catheters are listed. Future prospects of surface antibacterial strategies for biomedical catheters are also outlined.

Hydrogel-Based Technologies for the Diagnosis of Skin Pathology

Hydrogels, swellable hydrophilic polymer networks fabricated through chemical cross-linking or physical entanglement are increasingly utilized in various biomedical applications over the past few decades. Hydrogel-based microparticles, dressings and microneedle patches have been explored to achieve safe, sustained and on-demand therapeutic purposes toward numerous skin pathologies, through incorporation of stimuli-responsive moieties and therapeutic agents. More recently, these platforms are expanded to fulfill the diagnostic and monitoring role. Herein, the development of hydrogel technology to achieve diagnosis and monitoring of pathological skin conditions are highlighted, with proteins, nucleic acids, metabolites, and reactive species employed as target biomarkers, among others. The scope of this review includes the characteristics of hydrogel materials, its fabrication procedures, examples of diagnostic studies, as well as discussion pertaining clinical translation of hydrogel systems.

Implantable Medical Devices and Tissue Engineering: An Overview of Manufacturing Processes and the Use of Polymeric Matrices for Manufacturing and Coating their Surfaces

Medical devices are important diagnosis and therapy tools for several diseases which include a wide range of products. Technological advances in this area have been proposed to reduce adverse complication incidences. New technologies and manufacturing processes, as well as the development of new materials or medical devices with modified surface and the use of biodegradable polymeric devices such as a substrate for cell culture in the field of tissue engineering, have attracted considerable attention in recent years by the scientific community intended to produce medical devices with superior properties and morphology. This review article focused on implantable devices, addresses the major advances in the biomedical field related to the devices manufacture processes such as 3D printing and hot melting extrusion, and the use of polymer matrices composed of copolymers, blends, nanocomposites or grafted with antiproliferative drugs for manufacturing and/or coating the devices surface.

Time-Resolved Dynamics of Struvite Crystallization: Insights from the Macroscopic to Molecular Scale

The crystallization of magnesium ammonium phosphate hexahydrate (struvite) often occurs under conditions of fluid flow, yet the dynamics of struvite growth under these relevant environments has not been previously reported. In this study, we use a microfluidic device to evaluate the anisotropic growth of struvite crystals at variable flow rates and solution supersaturation. We show that bulk crystallization under quiescent conditions yields irreproducible data owing to the propensity of struvite to adopt defects in its crystal lattice, as well as fluctuations in pH that markedly impact crystal growth rates. Studies in microfluidic channels allow for time-resolved analysis of seeded growth along all three principle crystallographic directions and under highly controlled environments. After having first identified flow rates that differentiate diffusion and reaction limited growth regimes, we operated solely in the latter regime to extract the kinetic rates of struvite growth along the [100], [010], and [001] directions. In situ atomic force microscopy was used to obtain molecular level details of surface growth mechanisms. Our findings reveal a classical pathway of crystallization by monomer addition with the expected transition from growth by screw dislocations at low supersaturation to that of two-dimensional layer generation and spreading at high supersaturation. Collectively, these studies present a platform for assessing struvite crystallization under flow conditions and demonstrate how this approach is superior to measurements under quiescent conditions.

Innovations in indwelling urethral catheterisation

The indwelling urethral catheter remains an integral part of contemporary medical care, despite its significant design shortcomings. Urethral catheterisation is responsible for well-recognised complications including catheter-associated urinary tract infection (CAUTI), catheter-associated urethral injury (CAUI), catheter blockage, and bladder mucosal irritation. In this narrative review, we provide an update on current innovations in urethral catheter design, aimed at safeguarding against these complications. There is an obvious need to improve catheter technology and urologists should support the translation of innovations into clinical practice.

Probing of local polarity in poly(methyl methacrylate) with the charge transfer transition in Nile red

The permittivity of polymers and its spatial distribution play a crucial role in the behavior of thin films, such as those used, e.g., as sensor coatings. In an attempt to develop a conclusive approach to determine these quantities, the polarity of the model polymer poly(methyl methacrylate) (PMMA) in 600 nm thin films on a glass support was probed by the energy of the charge transfer transition in the oxazine dye Nile red (NR) at 25 °C. The absorption and fluorescence spectra of NR were observed to shift to the red with increasing solvent polarity, because of the intramolecular charge transfer character of the optical transition. New types of solvatochromic plots of emission frequency against absorption frequency and vice versa afforded the Onsager radius-free estimation of the ground and excited states dipole moment ratio. With this approach the values of these dipole moments of 11.97 D and 18.30–19.16 D, respectively, were obtained for NR. An effective local dielectric constant of 5.9–8.3 for PMMA thin films was calculated from the solvatochromic plot and the fluorescence maximum of NR observed in the PMMA films. The fluorescence band of NR in the rigid PMMA films shifted to the red by 130 cm⁻¹ with increasing excitation wavelength from 470 to 540 nm, while in a series of liquids the position of the emission maximum of NR remained constant within same range of the excitation wavelength. It is concluded that the fluorescence spectrum of NR in PMMA undergoes inhomogeneous broadening due to different surroundings of NR molecules in the ground state and slow sub-glass transition (T_g) relaxations in PMMA.

An In Vitro Bladder Model for Studying Catheter-Associated Urinary Tract Infection and Associated Analysis of Biofilms

Urethral catheters are among the most widely used medical devices, applied to manage a wide range of conditions in hospital, community, and care home settings. In long-term catheterized individuals, infection with Proteus mirabilis frequently complicates the care of patients owing to formation of extensive crystalline biofilms. Here we describe the use of an in vitro bladder model of the catheterized urinary tract and associated analyses to study P. mirabilis crystalline biofilm formation. The model originally described by Stickler et al. (1999, 310:494-501, Methods Enzymol) replicates a complete sterile closed drainage system as used in clinical practice, and permits formation of biofilms directly on catheters under conditions representative of those encountered in vivo. Models may be used to replicate either established infection or early stage colonization, and we describe a range of associated methods for quantification and visualization of biofilms formed on catheters. These methods are also easily adapted to study catheter-associated biofilm formation by other urinary tract pathogens.

Bacterial biofilm formation on indwelling urethral catheters

Urethral catheters are the most commonly deployed medical devices and used to manage a wide range of conditions in both hospital and community care settings. The use of long-term catheterization, where the catheter remains in place for a period >28 days remains common, and the care of these patients is often undermined by the acquisition of infections and formation of biofilms on catheter surfaces. Particular problems arise from colonization with urease-producing species such as Proteus mirabilis, which form unusual crystalline biofilms that encrust catheter surfaces and block urine flow. Encrustation and blockage often lead to a range of serious clinical complications and emergency hospital referrals in long-term catheterized patients. Here we review current understanding of bacterial biofilm formation on urethral catheters, with a focus on crystalline biofilm formation by P. mirabilis, as well as approaches that may be used to control biofilm formation on these devices. SIGNIFICANCE AND IMPACT OF THE STUDY: Urinary catheters are the most commonly used medical devices in many healthcare systems, but their use predisposes to infection and provide ideal conditions for bacterial biofilm formation. Patients managed by long-term urethral catheterization are particularly vulnerable to biofilm-related infections, with crystalline biofilm formation by urease producing species frequently leading to catheter blockage and other serious clinical complications. This review considers current knowledge regarding biofilm formation on urethral catheters, and possible strategies for their control.

Evaluating Efficacy of Antimicrobial and Antifouling Materials for Urinary Tract Medical Devices: Challenges and Recommendations

In Europe, the mean incidence of urinary tract infections in intensive care units is 1.1 per 1000 patient-days. Of these cases, catheter-associated urinary tract infections (CAUTI) account for 98%. In total, CAUTI in hospitals is estimated to give additional health-care costs of £1-2.5 billion in the United Kingdom alone. This is in sharp contrast to the low cost of urinary catheters and emphasizes the need for innovative products that reduce the incidence rate of CAUTI. Ureteral stents and other urinary-tract devices suffer similar problems. Antimicrobial strategies are being developed, however, the evaluation of their efficacy is very challenging. This review aims to provide considerations and recommendations covering all relevant aspects of antimicrobial material testing, including surface characterization, biocompatibility, cytotoxicity, in vitro and in vivo tests, microbial strain selection, and hydrodynamic conditions, all in the perspective of complying to the complex pathology of device-associated urinary tract infection. The recommendations should be on the basis of standard assays to be developed which would enable comparisons of results obtained in different research labs both in industry and in academia, as well as provide industry and academia with tools to assess the antimicrobial properties for urinary tract devices in a reliable way.

Two-layer Electrospun System Enabling Wound Exudate Management and Visual Infection Response

The spread of antimicrobial resistance calls for chronic wound management devices that can engage with the wound exudate and signal infection by prompt visual effects. Here, the manufacture of a two-layer fibrous device with independently-controlled exudate management capability and visual infection responsivity was investigated by sequential free surface electrospinning of poly(methyl methacrylate-co-methacrylic acid) (PMMA-co-MAA) and poly(acrylic acid) (PAA). By selecting wound pH as infection indicator, PMMA-co-MAA fibres were encapsulated with halochromic bromothymol blue (BTB) to trigger colour changes at infection-induced alkaline pH. Likewise, the exudate management capability was integrated via the synthesis of a thermally-crosslinked network in electrospun PAA layer. PMMA-co-MAA fibres revealed high BTB loading efficiency (>80 wt.%) and demonstrated prompt colour change and selective dye release at infected-like media (pH > 7). The synthesis of the thermally-crosslinked PAA network successfully enabled high water uptake (WU = 1291 ± 48 - 2369 ± 34 wt.%) and swelling index (SI = 272 ± 4 - 285 ± 3 a.%), in contrast to electrospun PAA controls. This dual device functionality was lost when the same building blocks were configured in a single-layer mesh of core-shell fibres, whereby significant BTB release (~70 wt.%) was measured even at acidic pH. This study therefore demonstrates how the fibrous configuration can be conveniently manipulated to trigger structure-induced functionalities critical to chronic wound management and monitoring.

Emerging vistas in theranostic medicine

Recent years have witnessed a paradigm shift in the focus of healthcare towards development of customized therapies which cater to the unmet needs in a myriad of disease areas such as cancer, infections, cardiovascular diseases, neurodegenerative disorders and inflammatory disorders. The term 'theranostic' refers to such multifunctional systems which combine the features of diagnosis and treatment in a single platform for superior control of the disease. Theranostic systems enable detection of disease, treatment and real time monitoring of the diseased tissue. Theranostic nanocarriers endowed with multiple features of imaging, targeting, and providing on-demand delivery of therapeutic agents have been designed for enhancement of therapeutic outcomes. Fabrication of theranostics involves utilization of materials having distinct properties for imaging, targeting, and programming drug release spatially and temporally. Although the field of theranostics has been widely researched and explored so far for treatment of different types of cancer, there have been considerable efforts in the past few years to extend its scope to other areas such as infections, neurodegenerative disorders and cardiovascular diseases. This review showcases the potential applications of theranostics in disease areas other than cancer. It also highlights the cardinal issues which need to be addressed for successful clinical translation of these theranostic tools.

Emerging medical and engineering strategies for the prevention of long-term indwelling catheter blockage

Urinary catheters have been used on an intermittent or indwelling basis for centuries, in order to relieve urinary retention and incontinence. Nevertheless, the use of urinary catheters in the clinical setting is fraught with complication, the most common of which is the development of nosocomial urinary tract infections, known as catheter-associated urinary tract infections. Infections of this nature are not only significant owing to their high incidence rate and subsequent economic burden but also to the severe medical consecutions that result. A range of techniques have been employed in recent years, utilising various technologies in attempts to counteract the perilous medical cascade following catheter blockage. This review will focus on the current advancement (within the last 10 years) in prevention of encrustation and blockage of long-term indwelling catheters both from engineering and medical perspectives, with particular emphasis on the importance of stimuli-responsive systems.

Innovating urinary catheter design: An introduction to the engineering challenge

Every day, people around the world rely on intermittent and indwelling urinary catheters to manage bladder dysfunction, but the potential or actual harm caused by these devices is well-recognised. Current catheter designs can cause urinary tract infection and septicaemia, bladder and urethral trauma and indwelling devices frequently become blocked. Furthermore, the devices can severely disrupt users' lives, limiting their daily activities and can be costly to manage for healthcare providers. Despite this, little significant design innovation has taken place in the last 80 years. In this article current catheter designs and their limitations are reviewed, common catheter-associated problems are outlined and areas of design ripe for improvement proposed. The potential to relieve the individual and economic burden of catheter use is high.

Development of an Infection-Responsive Fluorescent Sensor for the Early Detection of Urinary Catheter Blockage

Formation of crystalline biofilms following infection by Proteus mirabilis can lead to encrustation and blockage of long-term indwelling catheters, with serious clinical consequences. We describe a simple sensor, placed within the catheter drainage bag, to alert of impending blockage via a urinary color change. The pH-responsive sensor is a dual-layered polymeric "lozenge", able to release the self-quenching dye 5(6)-carboxyfluorescein in response to the alkaline urine generated by the expression of bacterial urease. Sensor performance was evaluated within a laboratory model of the catheterized urinary tract, infected with both urease positive and negative bacterial strains under conditions of established infection, achieving an average "early warning" of catheter blockage of 14.5 h. Signaling only occurred following infection with urease positive bacteria. Translation of these sensors into a clinical environment would allow appropriate intervention before the occurrence of catheter blockage, a problem for which there is currently no effective control method.

Selective Discrimination of Key Enzymes of Pathogenic and Nonpathogenic Bacteria on Autonomously Reporting Shape-Encoded Hydrogel Patterns

This work reports on a new approach to rapidly and selectively detect and discriminate enzymes of pathogenic from those of nonpathogenic bacteria using a patterned autonomously reporting hydrogel on a transparent support, in which the selectivity has been encoded by the pattern shape to enable facile detection by a color change at one single wavelength. In particular, enzyme-responsive chitosan hydrogel layers that report the presence of the enzymes β-glucuronidase (β-Gus) and β-galactosidase (β-Gal), produced by the nonvirulent Escherichia coli K12 and the food-borne biosafety level 3 pathogen enterohemorrhagic E. coli, respectively, via the blue color of an indigo dye were patterned by two complementary strategies. The comparison of the functionalization of patterned chitosan patches on a solid support with two chromogenic substrates on one hand and the area-selective conjugation of the substrates on the other hand showed that the two characteristic enzymes could indeed be rapidly and selectively discriminated. The limits of detection of the highly stable sensing layers for an observation time of 60 min using a spectrophotometer correspond to enzyme concentrations of β-Gus and β-Gal of ≤5 and ≤3 nM, respectively, and to ≤62 and ≤33 nM for bare eye detection in nonoptimized sensor patches. These results confirm the applicability of this approach, which is compatible with the simple measurement of optical density at one single wavelength only as well as with parallel, multiplexed detection, to differentiate the enzymes secreted by a highly pathogenic E. coli from a nonpathogenic E. coli on the basis of specifically secreted enzymes. Hence, a general approach for the rapid and selective detection of enzymes of different bacterial species for potential applications in food safety as well as point-of-care microbiological diagnostics is described.

Biomodification Strategies for the Development of Antimicrobial Urinary Catheters: Overview and Advances

Microbial burden associated with medical devices poses serious health challenges and is accountable for an increased number of deaths leading to enormous medical costs. Catheter-associated urinary tract infections are the most common hospital-acquired infections with enhanced patient morbidity. Quite often, catheter-associated bacteriuria produces apparent adverse outcomes such as urosepsis and even death. Taking this into account, the methods to modify urinary catheters to control microbial infections with relevance to clinical drug resistance are systematically evaluated in this review. Technologies to restrict biofilm formation at initial stages by using functional nanomaterials are elucidated. The conventional methodology of using single therapeutic intervention for developing an antimicrobial catheter lacks clinically meaningful benefit. Therefore, catheter modification using naturally derived antimicrobials such as essential oils, curcumin, enzymes, and antimicrobial peptides in combination with synthetic antibiotics/nanoantibiotics is likely to exert sufficient inhibitory effect on uropathogens and is extensively discussed. Futuristic efforts in this area are projected here that demand clinical studies to address areas of uncertainty to avoid development of bacterial resistance to the new generation therapy with minimum discomfort to the patients.

Cateter urinário: o tempo de exposição e calibre podem influenciar na formação de biofilme?

Resumo Objetivo: Avaliar a influência do tempo de exposição e calibre na formação de biofilme em cateteres urinários de Foley (CUFs). Método: Pesquisa in vitro com amostras de fragmentos de CUFs em látex siliconizado de diferentes calibres (n° 14 e n° 16 Frenchs). A urina artificial foi confeccionada, inoculada com bactérias-padrão Staphylococcus aureus (ATCC 25923) e Pseudomonas aeruginosa (ATCC 27853) e incubada a 37 °C por 24 horas e 72 horas. As análises foram realizadas por meio de cultura (carga bacteriana) e microscopia eletrônica de varredura. Resultados: Não houve diferença na carga bacteriana dos biofilmes formados nas superfícies dos CUFs com relação aos diferentes calibres (p > 0,05). Por outro lado, o tempo de exposição (24 horas e 72 horas) foi o fator determinante para formação do biofilme de P. aeruginosa nos CUFs (p < 0,05). Conclusão: O tempo de exposição influenciou a formação do biofilme de P. aeruginosa nos CUFs, independentemente dos calibres.

User perspectives, preferences and priorities relating to products for managing bladder and bowel dysfunctions

A great many people of all ages around the world cannot fully control their bladder or bowel, or both. Either in the short or long term, they rely upon products and devices to manage the emptying of their bladders and bowels and to collect, absorb and contain leaked urine or faeces. The incontinence product market is large and growing, and ongoing developments in materials and technologies should lead to improvements in these products and devices. Engineers and designers who work in this field - or who plan to do so - need to recognise the breadth of factors that affect the effectiveness and acceptability of products. The primary functions of products for managing bladder and bowel dysfunctions are the collection and containment of urine or faeces - and the associated engineering and design challenges may be considered in terms of flow rates and volumes and methods of acquisition and containment. But products will fail if they do not take into account other factors, some of which relate less directly to these primary functions and some not at all. This article aims to highlight the product characteristics that are most important to the people who use them, and areas where user-centred innovation and development may lead to improvements.

Formulation, stabilisation and encapsulation of bacteriophage for phage therapy

Against a backdrop of global antibiotic resistance and increasing awareness of the importance of the human microbiota, there has been resurgent interest in the potential use of bacteriophages for therapeutic purposes, known as phage therapy. A number of phage therapy phase I and II clinical trials have concluded, and shown phages don't present significant adverse safety concerns. These clinical trials used simple phage suspensions without any formulation and phage stability was of secondary concern. Phages have a limited stability in solution, and undergo a significant drop in phage titre during processing and storage which is unacceptable if phages are to become regulated pharmaceuticals, where stable dosage and well defined pharmacokinetics and pharmacodynamics are de rigueur. Animal studies have shown that the efficacy of phage therapy outcomes depend on the phage concentration (i.e. the dose) delivered at the site of infection, and their ability to target and kill bacteria, arresting bacterial growth and clearing the infection. In addition, in vitro and animal studies have shown the importance of using phage cocktails rather than single phage preparations to achieve better therapy outcomes. The in vivo reduction of phage concentration due to interactions with host antibodies or other clearance mechanisms may necessitate repeated dosing of phages, or sustained release approaches. Modelling of phage-bacterium population dynamics reinforces these points. Surprisingly little attention has been devoted to the effect of formulation on phage therapy outcomes, given the need for phage cocktails, where each phage within a cocktail may require significantly different formulation to retain a high enough infective dose. This review firstly looks at the clinical needs and challenges (informed through a review of key animal studies evaluating phage therapy) associated with treatment of acute and chronic infections and the drivers for phage encapsulation. An important driver for formulation and encapsulation is shelf life and storage of phage to ensure reproducible dosages. Other drivers include formulation of phage for encapsulation in micro- and nanoparticles for effective delivery, encapsulation in stimuli responsive systems for triggered controlled or sustained release at the targeted site of infection. Encapsulation of phage (e.g. in liposomes) may also be used to increase the circulation time of phage for treating systemic infections, for prophylactic treatment or to treat intracellular infections. We then proceed to document approaches used in the published literature on the formulation and stabilisation of phage for storage and encapsulation of bacteriophage in micro- and nanostructured materials using freeze drying (lyophilization), spray drying, in emulsions e.g. ointments, polymeric microparticles, nanoparticles and liposomes. As phage therapy moves forward towards Phase III clinical trials, the review concludes by looking at promising new approaches for micro- and nanoencapsulation of phages and how these may address gaps in the field.

Prevention of encrustation and blockage of urinary catheters by Proteus mirabilis via pH-triggered release of bacteriophage

The crystalline biofilms of Proteus mirabilis can seriously complicate the care of patients undergoing long-term indwelling urinary catheterisation. Expression of bacterial urease causes a significant increase in urinary pH, leading to the supersaturation and precipitation of struvite and apatite crystals. These crystals become lodged within the biofilm, resulting in the blockage of urine flow through the catheter. Here, we describe an infection-responsive surface coating for urinary catheters, which releases a therapeutic dose of bacteriophage in response to elevated urinary pH, in order to delay catheter blockage. The coating employs a dual-layered system comprising of a lower hydrogel 'reservoir' layer impregnated with bacteriophage, capped by a 'trigger' layer of the pH-responsive polymer poly(methyl methacrylate-co-methacrylic acid) (EUDRAGIT®S 100). Evaluation of prototype coatings using a clinically reflective in vitro bladder model system showed that catheter blockage time was doubled (13 h to 26 h (P < 0.05)) under conditions of established infection (10⁸ CFU ml^-1) in response to a 'burst-release' of bacteriophage (10⁸ PFU ml^-1). Coatings were stable both in the absence of infection, and in the presence of urease-negative bacteria. Quantitative and visual analysis of crystalline biofilm reduction show that bacteriophage constitute a promising strategy for the prevention of catheter blockage, a clinical problem for which there is currently no effective control method.

Advanced Nanobiomaterials: Vaccines, Diagnosis and Treatment of Infectious Diseases

The use of nanoparticles has contributed to many advances due to their important properties such as, size, shape or biocompatibility. The use of nanotechnology in medicine has great potential, especially in medical microbiology. Promising data show the possibility of shaping immune responses and fighting severe infections using synthetic materials. Different studies have suggested that the addition of synthetic nanoparticles in vaccines and immunotherapy will have a great impact on public health. On the other hand, antibiotic resistance is one of the major concerns worldwide; a recent report of the World Health Organization (WHO) states that antibiotic resistance could cause 300 million deaths by 2050. Nanomedicine offers an innovative tool for combating the high rates of resistance that we are fighting nowadays, by the development of both alternative therapeutic and prophylaxis approaches and also novel diagnosis methods. Early detection of infectious diseases is the key to a successful treatment and the new developed applications based on nanotechnology offer an increased sensibility and efficiency of the diagnosis. The aim of this review is to reveal and discuss the main advances made on the science of nanomaterials for the prevention, diagnosis and treatment of infectious diseases. Highlighting innovative approaches utilized to: (i) increasing the efficiency of vaccines; (ii) obtaining shuttle systems that require lower antibiotic concentrations; (iii) developing coating devices that inhibit microbial colonization and biofilm formation.