Influence of Dialysis Membranes on Clinical Outcomes: From History to Innovation

Comparative Study of Autogenic and Allogenic Chondrocyte Transplants on Polyethersulfone Scaffolds for Cartilage Regeneration

The aim of this study was to evaluate the chondrogenic potential of chondrocyte transplants cultured in vitro on polyethersulfone (PES) membranes. Forty-eight rabbits (96 knee joints) were used in the project. The synthetic, macro-porous PES membranes were used as scaffolds. Fragments of articular cartilage were harvested from non-weight-bearing areas of the joints of the animals. Chondrocytes were isolated and then cultivated on PES scaffolds for 3 weeks. The animals were divided into four groups. All the lesions in the articular cartilage were full thickness defects. In Group I, autogenic chondrocytes on PES membranes were transplanted into the defect area; in Group II, allogenic chondrocytes on PES membranes were transplanted into the defect area; in Group III, pure PES membranes were transplanted into the defect area; and in Group IV, lesions were left untreated. Half of the animals from each group were terminated after 8 weeks, and the remaining half were terminated 12 weeks postoperatively. The samples underwent macroscopic evaluation using the Brittberg scale and microscopic evaluation using the O'Driscoll scale. The best regeneration was observed in Groups II and I. In Group I, the results were achieved with two surgeries, while in Group II, only one operation was needed. This indicates that allogenic chondrocytes do not require two surgeries, highlighting the importance of further in vivo studies to better understand this advantage. The success of the study and the desired properties of PES scaffolds are attributed mainly to the presence of sulfonic groups in the structure of the material. These groups, similar to chondroitin sulfate, which naturally occurs in hyaline cartilage, likely enable mutual affinity between the scaffold and cells and promote scaffold colonization by the cells.

In vitro modelling of intramuscular injection site events

INTRODUCTION

Intramuscular (IM) injections deliver a plethora of drugs. The majority of IM-related literature details dissolution and/or pharmacokinetic (PK) studies, using methods with limited assessments of post-injection events that can impact drug fate, and absorption parameters. Food and Drug Association guidelines no longer require preclinical in vivo modeling in the U.S.A. Preclinical animal models fail to correlate with clinical outcomes, highlighting the need to study, and understand, IM drug fate in vitro using bespoke models emulating human IM sites. Post-IM injection events, i.e. underlying processes that influence PK outcomes, remain unacknowledged, complicating the application of in vitro methods in preclinical drug development. Understanding such events could guide approaches to predict and modulate IM drug fate in humans.

AREAS COVERED

This article reviews challenges in biorelevant IM site modeling (i.e. modeling drug fate outcomes), the value of technologies available for developing IM injectables, methods for studying drug fate, and technologies for training in performing IM administrations. PubMed, Web-of-Science, and Lens databases provided papers published between 2014 and 2024.

EXPERT OPINION

IM drug research is expanding what injectable therapeutics can achieve. However, post-injection events that influence PK outcomes remain poorly understood. Until addressed, advances in IM drug development will not realize their full potential.

Advances in Multifunctional Electronic Catheters for Precise and Intelligent Diagnosis and Therapy in Minimally Invasive Surgery

The advent of catheter-based minimally invasive surgical instruments has provided an effective means of diagnosing and treating human disease. However, conventional medical catheter devices are limited in functionalities, hindering their ability to gather tissue information or perform precise treatment during surgery. Recently, electronic catheters have integrated various sensing and therapeutic technologies through micro/nanoelectronics, expanding their capabilities. As micro/nanoelectronic devices become more miniaturized, flexible, and stable, electronic surgical catheters are evolving from simple tools to multiplexed sensing and theranostics for surgical applications. The review on multifunctional electronic surgical catheters is lacking and thus is not conducive to the reader's comprehensive understanding of the development trend in this field. This review covers the advances in multifunctional electronic catheters for precise and intelligent diagnosis and therapy in minimally invasive surgery. It starts with the summary of clinical minimally invasive surgical instruments, followed by the background of current clinical catheter devices for sensing and therapeutic applications. Next, intelligent electronic catheters with integrated electronic components are reviewed in terms of electronic catheters for diagnosis, therapy, and multifunctional applications. It highlights the present status and development potential of catheter-based minimally invasive surgical devices, while also illustrating several significant challenges that remain to be overcome.

Copper oxide(I) nanoparticle-modified cellulose acetate membranes with enhanced antibacterial and antifouling properties

Cellulose acetate membranes exhibit a potential to be applied in hemodialysis. However, their performance is limited by membrane fouling and a lack of antibacterial properties. In this research, copper oxide (I) nanoparticles were fabricated in situ into a cellulose acetate matrix in the presence of polyvinylpyrrolidone (pore-forming agent) and sulfobetaine (stabilising agent) to reduce the leakage of copper ions from nano-enhanced membranes. The influence of nanoparticles on the membrane structure and their antibacterial and antifouling properties were investigated. The results showed that incorporating Cu2O NPs imparted significant antibacterial properties against Staphylococcus aureus and fouling resistance under physiological conditions. The Cu2O NPs-modified membrane could pave the way for potential dialysis applications.

A Comparative Study and Prediction of the Ex Vivo Permeation of Six Vaginally Administered Drugs across Five Artificial Membranes and Vaginal Tissue

The theoretical interpretation of the vaginal permeability phenomenon, the evaluation of the suitability of five artificial membranes, and the prediction of the behaviors of vaginal drugs were the main objectives of this study. Franz vertical diffusion cells and different validated HPLC methods were used to measure the permeability of six vaginally administered drugs (econazole, miconazole, metronidazole, clindamycin, lidocaine, and nonoxynol-9). This study was performed (in vitro) on different membranes of polyvinylidene fluoride (PVDF), plain cellulose or cellulose impregnated with isopropyl myristate (IPM), and cellulose combined with PVDF or IPM. The results were compared with those obtained from cow vaginal tissue (ex vivo), where cellulose was proven to be the best simulant. According to the permeability profiles (Papp), the water solubility of the drugs was considered a necessary criterion for their transport in the membranes or in the tissue, while the size was important for their penetration. Furthermore, it was found that polar compounds show clear superiority when penetrating cellulose or tissue, while non-polar ones show superiority when penetrating the lipophilic PVDF membrane. Finally, a successful attempt was made to predict the Papp values (|Papp-predPapp| < 0.005) of the six drugs under study based on a PLS (Partial Least Squares) in silico simulation model.

A chronic intermittent haemodialysis pig model for functional evaluation of dialysis membranes

Performance evaluation of new dialysis membranes is primarily performed in vitro, which can lead to differences in clinical results. Currently, data on dialysis membrane performance and safety are available only for haemodialysis patients. Herein, we aimed to establish an in vivo animal model of dialysis that could be extrapolated to humans. We created a bilateral nephrectomy pig model of renal failure, which placed a double-lumen catheter with the hub exposed dorsally. Haemodialysis was performed in the same manner as in humans, during which clinically relevant physiologic data were evaluated. Next, to evaluate the utility of this model, the biocompatibility of two kinds of membranes coated with or without vitamin E used in haemodiafiltration therapy were compared. Haemodialysis treatment was successfully performed in nephrectomized pigs under the same dialysis conditions (4 h per session, every other day, for 2 weeks). In accordance with human clinical data, regular dialysis alleviated renal failure in pigs. The vitamin E-coated membrane showed a significant reduction rate of advanced oxidation protein products during dialysis than non-coated membrane. In conclusion, this model mimics the pathophysiology and dialysis condition of patients undergoing haemodialysis. This dialysis treatment model of renal failure will be useful for evaluating the performance and safety of dialysis membranes.

Adsorption- and Displacement-Based Approaches for the Removal of Protein-Bound Uremic Toxins

End-stage renal disease (ESRD) patients rely on renal replacement therapies to survive. Hemodialysis (HD), the most widely applied treatment, is responsible for the removal of excess fluid and uremic toxins (UTs) from blood, particularly those with low molecular weight (MW < 500 Da). The development of high-flux membranes and more efficient treatment modes, such as hemodiafiltration, have resulted in improved removal rates of UTs in the middle molecular weight range. However, the concentrations of protein-bound uremic toxins (PBUTs) remain essentially untouched. Due to the high binding affinity to large proteins, such as albumin, PBUTs form large complexes (MW > 66 kDa) which are not removed during HD and their accumulation has been strongly associated with the increased morbidity and mortality of patients with ESRD. In this review, we describe adsorption- and displacement-based approaches currently being studied to enhance the removal of PBUTs. The development of mixed matrix membranes (MMMs) with selective adsorption properties, infusion of compounds capable of displacing UTs from their binding site on albumin, and competitive binding membranes show promising results, but the road to clinical application is still long, and further investigation is required.

Polymeric Membranes for Biomedical Applications

Polymeric membranes are selective materials used in a wide range of applications that require separation processes, from water filtration and purification to industrial separations. Because of these materials' remarkable properties, namely, selectivity, membranes are also used in a wide range of biomedical applications that require separations. Considering the fact that most organs (apart from the heart and brain) have separation processes associated with the physiological function (kidneys, lungs, intestines, stomach, etc.), technological solutions have been developed to replace the function of these organs with the help of polymer membranes. This review presents the main biomedical applications of polymer membranes, such as hemodialysis (for chronic kidney disease), membrane-based artificial oxygenators (for artificial lung), artificial liver, artificial pancreas, and membranes for osseointegration and drug delivery systems based on membranes.

Polysulfone Membranes Doped with Human Neutrophil Elastase Inhibitors: Assessment of Bioactivity and Biocompatibility

The use of polysulfone (PSU) hemodialysis (HD) membranes modified with bioactive compounds has gained relevance in chronic kidney disease (CKD) management. Compounds based on the 4-oxo-β-lactam scaffold have outstanding inhibitory ability and selectivity for human neutrophil elastase (HNE). The present work aimed to evaluate the bioactivity and biocompatibility of PSU-based HD membranes doped with HNE inhibitors (HNEIs). For this, two 4-oxo-β-lactam derivates (D4L-1 and D4L-2) synthesized in house were used, as well as a commercial HNEI (Sivelestat), for comparison purposes. Their HNE inhibition efficacy was evaluated in in vitro and ex vivo (incubations with human plasma) assay conditions. All biomaterials were bioactive and hemocompatible. The inhibitory capacity of the HNEIs and HNEI-PSU membranes in vitro was D4L-1 > D4L-2 > Sivelestat and D4L-2 > Sivelestat > D4L-1, respectively. In ex vivo conditions, both HNEIs and HNEI-PSU materials presented the same relative inhibitory ability (D4L-1 > D4L-2 > Sivelestat). The difference observed between in vitro and ex vivo conditions is most likely due to the inherent lipophilicity/hydrophobicity of each HNEI influencing their affinity and accessibility to HNE when trapped in the membrane. Compared to Sivelestat, both D4L-1 and D4L-2 (and the respective doped membranes) have more potent inhibition capabilities. In conclusion, this work reports the successful development of PSU membranes functionalized with HNEIs.

High-Throughput Preparation of Uncontaminated Graphene-Oxide Aqueous Dispersions with Antioxidant Properties by Semi-Automated Diffusion Dialysis

A semi-automated diffusion-dialysis purification procedure is proposed for the preparation of uncontaminated graphene oxide (GO) aqueous dispersions. The purification process is integrated with analytical-signal processing to control the purification degree online by several channels: oxidation-reduction potential, conductivity, and absorbance. This approach reduces the amounts of reagents for chemical treatment during dialysis. The total transition metal (Mn and Ti) content was reduced to a sub-ppb level (assessed by slurry nebulization in inductively coupled plasma optical atomic emission spectroscopy). Purified aqueous GO samples possess good stability for about a year with a zeta-potential of ca. -40 mV and a lateral size of ca. sub-µm. Purified GO samples showed increased antioxidant properties (up to five times compared to initial samples according to chemiluminometry by superoxide-radical (O₂^-) generated in situ from xanthine and xanthine oxidase with the lucigenin probe) and significantly decreased peroxidase-like activity (assessed by the H₂O₂-L-012 system).

Vitamin E (Alpha-Tocopherol) Metabolism and Nutrition in Chronic Kidney Disease

Vitamin E (alpha-tocopherol) is an essential micronutrient and fat-soluble antioxidant with proposed role in protecting tissues from uncontrolled lipid peroxidation. This vitamin has also important protein function and gene modulation effects. The metabolism of vitamin E depends on hepatic binding proteins that selectively retain food alpha-tocopherol for incorporation into nascent VLDL and tissue distribution together with esterified cholesterol and triglycerides. Chronic kidney disease (CKD) is a condition of oxidative stress and increased lipid peroxidation, that are associated with alterations of alpha-tocopherol metabolism and function. Specific changes have been reported for the levels of its enzymatic metabolites, including both short-chain and long-chain metabolites, the latter being endowed with regulatory functions on enzymatic and gene expression processes important for the metabolism of lipids and xenobiotics detoxification, as well as for the control of immune and inflammatory processes. Vitamin E therapy has been investigated in CKD using both oral vitamin E protocols and vitamin E-coated hemodialyzers, showing promising results in the secondary prevention of cardiovascular disease, as well as of immune and hematological complications. These therapeutic approaches are reviewed in the present article, together with a narrative excursus on the main findings indicating CKD as a condition of relative deficiency and impaired metabolism of vitamin E.

Biocompatibility of Surface-Modified Membranes for Chronic Hemodialysis Therapy

Hemodialysis is a life-sustaining therapy for millions of people worldwide. However, despite considerable technical and scientific improvements, results are still not fully satisfactory in terms of morbidity and mortality. The membrane contained in the hemodialyzer is undoubtedly the main determinant of the success and quality of hemodialysis therapy. Membrane properties influence solute removal and the interactions with blood components that define the membrane’s biocompatibility. Bioincompatibility is considered a potential contributor to several uremic complications. Thus, the development of more biocompatible polymers used as hemodialyzer membrane is of utmost importance for improving results and clinical patient outcomes. Many different surface-modified membranes for hemodialysis have been manufactured over recent years by varying approaches in the attempt to minimize blood incompatibility. Their main characteristics and clinical results in hemodialysis patients were reviewed in the present article.