Recycling and 3D-Printing Biodegradable Membranes for Gas Separation-toward a Membrane Circular Economy.

Polymer membranes employed in gas separation play a pivotal role in advancing environmental sustainability, energy production, and gas purification technologies. Despite their significance, the current design and manufacturing of these membranes lack cradle-to-cradle approaches, contributing to plastic waste pollution. This study explores emerging solutions, including the use of biodegradable biopolymers such as polyhydroxybutyrate (PHB) and membrane recycling, with a focus on the specific impact of mechanical recycling on the performance of biodegradable gas separation membranes. This research represents the first systematic exploration of recycling biodegradable membranes for gas separation. Demonstrating that PHB membranes can be recycled and remanufactured without solvents using hot-melt extrusion and 3D printing, the research highlights PHB's promising performance in developing more sustainable CO2 separations, despite an increase in gas permeability with successive recycling steps due to reduced polymer molecular weight. The study emphasizes the excellent thermal, chemical, and mechanical stability of PHB membranes, albeit with a marginal reduction in gas selectivity upon recycling. However, limitations in PHB's molecular weight affecting extrudability and processability restrict the recycling to three cycles. Anticipating that this study will serve as a foundational exploration, we foresee more sophisticated recycling studies for gas separation membranes, paving the way for a circular economy in future membrane technologies.

Advances in screening and diagnostic lab-on-chip tools for gynaecological cancers - a review.

Gynaecological cancers are a major global health concern due to the lack of effective screening programmes for ovarian and endometrial cancer, for example, and variable access to vaccination and screening tests for cervical cancer in many countries. Recent research on portable and cost-effective lab-on-a-chip (LoC) technologies show promise for mass screening and diagnostic procedures for gynaecological cancers. However, most LoCs for gynaecological cancer are still in development, with a need to establish and clinically validate factors such as the type of biomarker, sample and method of detection, before patient use. Multiplex approaches, detecting a panel of gynaecological biomarkers in a single LoC, offer potential for more reliable diagnosis. This review highlights the current research on LoCs for gynaecological cancer screening and diagnosis, emphasizing the need for further research and validation prior to their widespread adoption in clinical practice.

Antimicrobial releasing hydrogel forming microneedles.

Hydrogel-forming microneedle arrays as a technique for transdermal drug delivery show promise as an alternative to traditional drug delivery methods. In this work, hydrogel-forming microneedles have been created with effective, controlled delivery of amoxicillin and vancomycin within comparable therapeutic ranges to that of oral delivered antibiotics. Fabrication using reusable 3D printed master templates enabled quick and low-cost hydrogel microneedle manufacturing through micro-molding. By 3D printing at a tilt angle of 45° the resolution of the microneedle tip was improved by double (from ca. 64 µm down to 23 µm). Amoxicillin and vancomycin were encapsulated within the hydrogel's polymeric network through a unique room temperature swell/deswell drug loading method within minutes, eliminating the need for an external drug reservoir. The hydrogel-forming microneedle mechanical strength was maintained, and successful penetration of porcine skin grafts observed with negligible damage to the needles or surrounding skin morphology. Hydrogel swell rate was tailored by altering the crosslinking density, resulting in controlled antimicrobial release for an applicable delivered dosage. The potent antimicrobial properties of the antibiotic-loaded hydrogel-forming microneedles against both Escherichia coli and Staphylococcus aureus, highlights the beneficial use of hydrogel-forming microneedles towards the minimally invasive transdermal drug delivery of antibiotics.

Fabrication of a Lactate-Specific Molecularly Imprinted Polymer toward Disease Detection.

The development of sensitive and selective robust sensor materials for targeted biomarker detection aims to contribute to self-health monitoring and management. Molecularly imprinted polymeric (MIP) materials can perform as biomimetic recognition elements via tailored routes of synthesis for specific target analyte extraction and/or detection. In this work, a sensitive- and selective-lactate MIP has been developed utilizing methacrylic acid and ethylene glycol dimethacrylate as the functional monomer and cross-linker, respectively. The sensitivity of the as-synthesized imprinted species was evaluated by determining the target analyte retention, imprinting factor, and selectivity adsorption of up to 63.5%, 6.86, and 0.82, respectively. MIP selectivity elucidated the imprinting mechanism between the functional monomers and target analyte lactate, further experimentally evidenced by using structurally competitive analytes malic acid and sodium 2-hydroxybutyrate, where retentions of 22.6 and 25.2%, respectively, were observed. Understanding the specific intermolecular mechanisms of both the template analyte and structural interferents with the MIP enables experimentalists to make informed decisions regarding monomer-target and porogen selections and possible sites of interaction for improved molecular imprinting. This imprinting system highlights the potential to be further developed into artificial receptor sensor materials for the detection of disease.

Cross-Linking of Sugar-Derived Polyethers and Boronic Acids for Renewable, Self-Healing, and Single-Ion Conducting Organogel Polymer Electrolytes.

This report describes the synthesis and characterization of organogels by reaction of a diol-containing polyether, derived from the sugar d-xylose, with 1,4-phenylenediboronic acid (PDBA). The cross-linked materials were analyzed by infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), scanning electron microscopy (FE-SEM), and rheology. The rheological material properties could be tuned: gel or viscoelastic behavior depended on the concentration of polymer, and mechanical stiffness increased with the amount of PDBA cross-linker. Organogels demonstrated self-healing capabilities and recovered their storage and loss moduli instantaneously after application and subsequent strain release. Lithiated organogels were synthesized through incorporation of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) into the cross-linked matrix. These lithium-borate polymer gels showed a high ionic conductivity value of up to 3.71 × 10-3 S cm-1 at 25 °C, high lithium transference numbers (t + = 0.88-0.92), and electrochemical stability (4.51 V). The gels were compatible with lithium-metal electrodes, showing stable polarization profiles in plating/stripping tests. This system provides a promising platform for the production of self-healing gel polymer electrolytes (GPEs) derived from renewable feedstocks for battery applications.

Conductive Polymer-Coated 3D Printed Microneedles: Biocompatible Platforms for Minimally Invasive Biosensing Interfaces.

Conductive polymeric microneedle (MN) arrays as biointerface materials show promise for the minimally invasive monitoring of analytes in biodevices and wearables. There is increasing interest in microneedles as electrodes for biosensing, but efforts have been limited to metallic substrates, which lack biological stability and are associated with high manufacturing costs and laborious fabrication methods, which create translational barriers. In this work, additive manufacturing, which provides the user with design flexibility and upscale manufacturing, is employed to fabricate acrylic-based microneedle devices. These microneedle devices are used as platforms to produce intrinsically-conductive, polymer-based surfaces based on polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). These entirely polymer-based solid microneedle arrays act as dry conductive electrodes while omitting the requirement of a metallic seed layer. Two distinct coating methods of 3D-printed solid microneedles, in situ polymerization and drop casting, enable conductive functionality. The microneedle arrays penetrate ex vivo porcine skin grafts without compromising conductivity or microneedle morphology and demonstrate coating durability over multiple penetration cycles. The non-cytotoxic nature of the conductive microneedles is evaluated using human fibroblast cells. The proposed fabrication strategy offers a compelling approach to manufacturing polymer-based conductive microneedle surfaces that can be further exploited as platforms for biosensing.

Molecularly imprinted polymers in diagnostics: accessing analytes in biofluids.

Bio-applied molecularly imprinted polymers (MIPs) are biomimetic materials with tailor-made synthetic recognition sites, mimicking biological counterparts known for their sensitive and selective analyte detection. MIPs, specifically designed for biomarker analysis within biofluids, have the potential to significantly aid patient diagnostics at the point-of-care, enabling self-health monitoring and management. Recent research in this field, facilitated by the hybridisation of materials science and biology, has developed and utilised a variety of different polymerisation synthesis methods tailored to the bio-application of MIPs. This review evaluates the principles of molecular imprinting for disease diagnostics, including recent progress in integrated MIP-sensor technologies for high-affinity analyte detection in complex biofluids from serum and saliva to cerebrospinal fluid, sweat, urine, nasopharyngeal fluid, and tears. The work highlights the state-of-the-art in the progression of MIP-sensor technologies' translation into commercially available sensors and their potential contribution to disease detection systems in healthcare settings.

Development of a high sensitivity RT-PCR assay for detection of SARS-CoV-2 in individual and pooled nasopharyngeal samples.

The COVID-19 pandemic requires sensitive detection of the SARS-CoV-2 virus from samples to ensure accurate detection of infected patients, an essential component of effective national track and trace programs. Due to the scaling challenges of large sample numbers, sample pooling is an attractive solution to reduce both extraction and amplification reagent costs, if high sensitivity can be maintained. We demonstrate that the Erba Molecular ErbaMDx SARS-CoV-2 RT-PCR Kit (EM kit) delivers high sensitivity, achieving analytical detection of 5 copies/reaction SARS-CoV-2 genomic RNA, and 200 copies/mL SARS-CoV-2 inactivated virus spiked into nasopharyngeal swab (NP) samples and extracted through workflow. Furthermore, the EM Kit demonstrates high sensitivity in both pooled (1 in 5) and non-pooled NP samples when compared to an FDA Emergency Use Authorization approved assay, following published FDA guidelines. These findings demonstrate that the EM Kit is suitable for sample pooling, with minimal impact on assay performance. As the COVID-19 pandemic progresses, high sensitivity assays such as the EM Kit will have an important role in ensuring high throughput and sensitive testing using pooled samples can be maintained, delivering the most cost-effective sample extraction and amplification option for national test and trace programs.

Molecular diagnostics in the era of COVID-19.

As the COVID-19 pandemic continues to escalate globally and acquires new mutations, accurate diagnostic technologies continue to play a vital role in controlling and understanding the epidemiology of this disease. A plethora of technologies have enabled the diagnosis of individuals, informed clinical management, aided population-wide screening to determine transmission rates and identified cases within the wider community and high-risk settings. This review explores the application of molecular diagnostics technologies in controlling the spread of COVID-19, and the key factors that affect the sensitivity and specificity of the tests used.

Optimization of Cortisol-Selective Molecularly Imprinted Polymers Enabled by Molecular Dynamics Simulations.

Today, we heavily rely on technology and increasingly utilize it to monitor our own health. The identification of sensitive, accurate biosensors that are capable of real-time cortisol analysis is one important potential feature for these technologies to aid us in the maintenance of our physical and mental wellbeing. Detection and quantification of cortisol, a well-known stress biomarker present in sweat, offers a noninvasive and potentially real-time method for monitoring anxiety. Molecularly imprinted polymers are attractive candidates for cortisol recognition elements in such devices as they can selectively rebind a targeted template molecule. However, mechanisms of imprinting and subsequent rebinding depend on the choice and composition of the prepolymerization mixture where the molecular interactions between the template, functional monomer, cross-linker, and solvent molecules are not fully understood. Here, we report the synthesis and evaluation of a molecularly imprinted polymer selective for cortisol detection. Molecular dynamics simulations were used to investigate the interactions between all components in the prepolymerization mixture of the as-synthesized molecularly imprinted polymer. Varying the component ratio of the prepolymerization mixture indicates that the number of cross-linker molecules relative to the template impacts the quality of imprinting. It was determined that a component ratio of 1:6:30 of cortisol, methacrylic acid, and ethylene glycol dimethacrylate, respectively, yields the optimal theoretical complexation of cortisol for the polymeric systems investigated. Experimental synthesis and rebinding results demonstrate an imprinting factor of up to 6.45. The trends in cortisol affinity predicted by molecular dynamics simulations of the prepolymerization mixture were also corroborated through experimental analysis of those modeled molecularly imprinted compositions, demonstrating the predictive capabilities of these simulations.

Hydrogel-Forming Microneedles: Current Advancements and Future Trends.

In this focused progress review, the recent developments and trends of hydrogel-forming microneedles (HFMs) and potential future directions are presented. Previously, microneedles (solid, hollow, coated, and dissolving microneedles) have primarily been used to enhance the effectiveness of transdermal drug delivery to facilitate a wide range of applications such as vaccinations and antibiotic delivery. However, the recent trend in microneedle development has resulted in microneedles formed from hydrogels which have the ability to offer transdermal drug delivery and, due to the hydrogel swelling nature, passively extract interstitial fluid from the skin, meaning they have the potential to be used for biocompatible minimally invasive monitoring devices. Thus, in this review, these recent trends are highlighted, which consolidate microneedle design considerations, hydrogel formulations, fabrication processes, applications of HFMs and the potential future opportunities for utilizing HFMs for personalized healthcare monitoring and treatment.

Valorizing Plastic-Contaminated Waste Streams through the Catalytic Hydrothermal Processing of Polypropylene with Lignocellulose.

Food waste is a promising resource for the production of fuels and chemicals. However, increasing plastic contamination has a large impact on the efficiency of conversion for the more established biological routes such as anaerobic digestion or fermentation. Here, we assessed a novel route through the hydrothermal liquefaction (HTL) of a model waste (pistachio hulls) and polypropylene (PP). Pure pistachio hulls gave a biocrude yield of 34% (w/w), though this reduced to 16% (w/w) on the addition of 50% PP in the mixture. The crude composition was a complex blend of phenolics, alkanes, carboxylic acids, and other oxygenates, which did not change substantially on the addition of PP. Pure PP does not breakdown at all under HTL conditions (350 °C, 15% solids loading), and even with biomass, there is only a small synergistic effect resulting in a conversion of 19% PP. This conversion was enhanced through using typical HTL catalysts including Fe, FeSO4·7H2O, MgSO4·H2O, ZnSO4·7H2O, ZSM-5, aluminosilicate, Y-zeolite, and Na2CO3; the conversion of PP reached a maximum of 38% with the aluminosilicate, for example. However, the PP almost exclusively broke down into a solid-phase product, with no enhancement of the biocrude fraction. The mechanism was explored, and with the addition of the radical scavenger butylated hydroxytoluene (BHT), the conversion of plastic reduced substantially, demonstrating that radical formation is necessary. As a result, the plastic conversion was enhanced to over 50% through the addition of the co-solvent and hydrogen donor, formic acid, and the radical donor, hydrogen peroxide. The addition of formic acid also changed the crude composition, including more carboxylic acids and oxygenated species than the conversion of the biomass alone; however, the majority of the carbon distributed to the volatile organic gas fraction producing an array of short-chain volatile hydrocarbons, which potentially could be repolymerized as a polyolefin or combined with the biocrude for further processing. Catalytic HTL was therefore shown to be a promising method for the valorization of polyolefins with biomass under typical HTL conditions.

Co-processing of common plastics with pistachio hulls via hydrothermal liquefaction.

Mixed, wet, plastic streams containing food waste residues are being increasingly collected at point of use, but are extremely challenging to recycle and are therefore largely sent to landfill. While a challenging waste problem, this also represents an underutilised feedstock, which could be co-processed with biomass, increasing the scope of products, easing out seasonal variation in biomass production and increasing the production capacity of a traditional biorefinery. One promising method of biomass conversion is hydrothermal liquefaction (HTL), where lignocellulosic residues are broken down in water at high temperatures and pressures to produce a bio-crude oil, a solid residue and an aqueous fertiliser. In this study, the co-processing of common plastic waste with pistachio hulls was assessed to investigate the suitability of the HTL approach. The HTL of pistachio hulls was undertaken at 350 °C over 15 and 60 min, with four commonly used plastics: polyethylene, polypropylene, PET and nylon-6, in blends of up to 20 wt% plastic to biomass. A novel FT-IR method was developed to estimate the conversion of plastics in the system, and the product phases were fully analysed. High yields of up to 35% bio-crude were achieved, and under optimal conditions, nylon-6 and PET were found to break down almost completely in the system. PET generated numerous products that distributed predominantly into the aqueous phase; the major decomposition product of nylon-6 was found to be the monomer ∊-caprolactam, also largely partitioning into the aqueous phase. The polyolefins were less reactive; a limited degree of decomposition formed oxidised products, which distributed into the bio-crude phase. This result represents a highly promising method for waste plastic valorisation.

Depleting Depletion: Maintaining Single-Walled Carbon Nanotube Dispersions after Graft-To Polymer Functionalization.

Grafting polymers onto single-walled carbon nanotubes (SWCNTs) usefully alters properties but does not typically yield stable, solvated species directly. Despite the expectation of steric stabilization, a damaging (re)dispersion step is usually necessary. Here, poly(vinyl acetate)s (PVAc's) of varying molecular weights are grafted to individualized, reduced SWCNTs at different concentrations to examine the extent of reaction and degree of solvation. The use of higher polymer concentrations leads to an increase in grafting ratio (weight fraction of grafted polymer relative to the SWCNT framework), approaching the limit of random sequentially adsorbed Flory "mushrooms" on the surface. However, at higher polymer concentrations, a larger percentage of SWCNTs precipitate during the reaction; an effect which is more significant for larger weight polymers. The precipitation is attributed to depletion interactions generated by ungrafted homopolymer overcoming Coulombic repulsion of adjacent like-charged SWCNTs; a simple model is proposed. Larger polymers and greater degrees of functionalization favor stable solvation, but larger and more concentrated homopolymers increase depletion aggregation. By using low concentrations (25 µM) of larger molecular weight PVAc (10 kDa), up to 65% of grafted SWCNTs were retained in solution (at 65 µg mL-1) directly after the reaction.

Thermochemical functionalisation of graphenes with minimal framework damage.

Graphene and graphene nanoplatelets can be functionalised via a gas-phase thermochemical method; the approach is versatile, readily scalable, and avoids the introduction of additional defects by exploiting existing sites. Direct TEM imaging confirmed covalent modification of single layer graphene, without damaging the connectivity of the lattice, as supported by Raman spectrometry and AFM nano-indentation measurements of mechanical stiffness. The grafting methodology can also be applied to commercially-available bulk graphene nanoplatelets, as illustrated by the preparation of anionic, cationic, and non-ionic derivatives. Successful bulk functionalisation is evidenced by TGA, Raman, and XPS, as well as in dramatic changes in aqueous dispersability. Thermochemical functionalisation thus provides a facile approach to modify both graphene monolayers, and a wide range of graphene-related nanocarbons, using variants of simple CVD equipment.

Exploring Carbon Nanomaterial Diversity for Nucleation of Protein Crystals.

Controlling crystal nucleation is a crucial step in obtaining high quality protein crystals for structure determination by X-ray crystallography. Carbon nanomaterials (CNMs) including carbon nanotubes, graphene oxide, and carbon black provide a range of surface topographies, porosities and length scales; functionalisation with two different approaches, gas phase radical grafting and liquid phase reductive grafting, provide routes to a range of oligomer functionalised products. These grafted materials, combined with a range of controls, were used in a large-scale assessment of the effectiveness for protein crystal nucleation of 20 different carbon nanomaterials on five proteins. This study has allowed a direct comparison of the key characteristics of carbon-based nucleants: appropriate surface chemistry, porosity and/or roughness are required. The most effective solid system tested in this study, carbon black nanoparticles functionalised with poly(ethylene glycol) methyl ether of mean molecular weight 5000, provides a novel highly effective nucleant, that was able to induce crystal nucleation of four out of the five proteins tested at metastable conditions.

Reductively PEGylated carbon nanomaterials and their use to nucleate 3D protein crystals: a comparison of dimensionality.

A range of carbon nanomaterials, with varying dimensionality, were dispersed by a non-damaging and versatile chemical reduction route, and subsequently grafted by reaction with methoxy polyethylene glycol (mPEG) monobromides. The use of carbon nanomaterials with different geometries provides both a systematic comparison of surface modification chemistry and the opportunity to study factors affecting specific applications. Multi-walled carbon nanotubes, single-walled carbon nanotubes, graphite nanoplatelets, exfoliated few layer graphite and carbon black were functionalized with mPEG-Br, yielding grafting ratios relative to the nanocarbon framework between ca. 7 and 135 wt%; the products were characterised by Raman spectroscopy, TGA-MS, and electron microscopy. The functionalized materials were tested as nucleants by subjecting them to rigorous protein crystallization studies. Sparsely functionalized flat sheet geometries proved exceptionally effective at inducing crystallization of six proteins. This new class of nucleant, based on PEG grafted graphene-related materials, can be widely applied to promote the growth of 3D crystals suitable for X-ray crystallography. The association of the protein ferritin with functionalized exfoliated few layer graphite was directly visualized by transmission electron microscopy, illustrating the formation of ordered clusters of protein molecules critical to successful nucleation.

Study of fluid and transport properties of porous anodic aluminum membranes by dynamic atomic force microscopy.

Recent work on carbon nanotubes (CNT) has focused on their potential application in water treatment as a result of their predicted and observed enhanced flow rates. Recent work on the lesser-known porous anodic alumina membranes (PAAMs) has also shown flow enhancement, albeit at only a fraction of what has been observed in CNTs. Despite their potential applications, little research has been conducted on PAAMs' hydrodynamic properties, and in this Article we present experimental results and theoretical models that explore the fluid flow behavior around and through these membranes. The experiments were conducted using an atomic force microscope (AFM) that pushed a solid silica particle against PAAMs that were characterized with different pore diameters. Furthermore, the PAAMs were classified as either closed or open, with the latter allowing fluid to pass through. The theoretical model developed to describe the experimental data incorporates Derjaguin-Landau-Verwey-Overbeek (DLVO) effects, cantilever drag, and hydrodynamic forces. By using the slip boundary condition for the hydrodynamic forces, we were able to fit the model to experimental findings and also demonstrate that the difference between closed and open PAAMs was negligible. The slip lengths did not correspond to any physical feature of the PAAMs, but our model does provide a simple yet effective means of describing the hydrodynamics for not only PAAMs but for membranes in general.