A biostable, anti-fouling zwitterionic polyurethane-urea based on PDMS for use in blood-contacting medical devices

Improving the hemocompatibility of a porohyperelastic layered vascular graft using luminal reversal microflows

Vascular graft thrombosis is a long-standing clinical problem. A myriad of efforts have been devoted to reducing thrombus formation following bypass surgery. Researchers have primarily taken a chemical approach to engineer and modify surfaces, seeking to make them more suitable for blood contacting applications. Using mechanical forces and surface topology to prevent thrombus formation has recently gained more attention. In this study, we have designed a bilayered porous vascular graft capable of repelling platelets and destabilizing absorbed protein layers from the luminal surface. During systole, fluid penetrates through the graft wall and is subsequently ejected from the wall into the luminal space (Luminal Reversal Flow - LRF), pushing platelets away from the surface during diastole. In-vitro hemocompatibility tests were conducted to compare platelet deposition in high LRF grafts with low LRF grafts. Graft material properties were determined and utilized in a porohyperelastic (PHE) finite element model to computationally predict the LRF generation in each graft type. Hemocompatibility testing showed significantly lower platelet deposition values in high versus low LRF generating grafts (median±IQR = 5,708 ± 987 and 23,039 ± 3,310 platelets per mm2, respectively, p=0.032). SEM imaging of the luminal surface of both graft types confirmed the quantitative blood test results. The computational simulations of high and low LRF generating grafts resulted in LRF values of -10.06 μm/s and -2.87 μm/s, respectively. These analyses show that a 250% increase in LRF is associated with a 75.2% decrease in platelet deposition. PHE vascular grafts with high LRF have the potential to improve anti-thrombogenicity and reduce thrombus-related post-procedure complications. Additional research is required to overcome the limitations of current graft fabrication technologies that further enhance LRF generation.

Functional Zwitterionic Polyurethanes: State-of-the-Art Review

Recent advancements in bioengineering and medical devices have been greatly influenced and dominated by synthetic polymers, particularly polyurethanes (PUs). PUs offer customizable mechanical properties and long-term stability, but their inherent hydrophobic nature poses challenges in practically biological application processes, such as interface high friction, strong protein adsorption, and thrombosis. To address these issues, surface modifications of PUs for generating functionally hydrophilic layers have received widespread attention, but the durability of generated surface functionality is poor due to irreversible mechanical wear or biodegradation. As a result, numerous researchers have investigated bulk modification techniques to incorporate zwitterionic polymers or groups onto the main or side chains of PUs, thereby improving their hydrophilicity and biocompatibility. This comprehensive review presents an extensive overview of notable zwitterionic PUs (ZPUs), including those based on phosphorylcholine, sulfobetaine, and carboxybetaine. The review explores their wide range of biomedical applications, from blood-contacting devices to antibacterial coatings, fouling-resistant marine coatings, separation membranes, lubricated surfaces, and shape memory and self-healing materials. Lastly, the review summarizes the challenges and future prospects of ZPUs in biological applications.

Reusable Zwitterionic Porous Organic Polymers for Bilirubin Removal in Serum

Herein, we report a straightforward strategy to construct reusable, hemocompatible, and highly efficient bilirubin adsorbents by installing zwitterionic modules into a porous organic polymer (POP) for hemoperfusion application. Three types of zwitterions with different amounts are used to evaluate their impacts on the characteristics of POPs, including carboxybetaine methacrylate (CB), sulfobetaine methacrylate (SB), and 2-methacryloyloxyethyl phosphorylcholine (MPC). Results show that zwitterions can improve hemocompatibility, hydrophilicity, and bilirubin uptake of the POP. Among all zwitterionic POPs, POP-CB-40% exhibits the best bilirubin uptake, ∼46.5 times enhancement compared with the non-zwitterionic POP in 100% serum. This enhancement can be attributed to the improved hydrophilicity and protein resistance ability in biological solutions. More importantly, the reusability test shows that POP-CB-40% maintains ∼99% of bilirubin uptake capacity at fifth recycling in 100% serum. Findings in this work provide a guideline for the design of biocompatible and efficient POP-based bilirubin adsorbents for hemoperfusion therapy.

Antifouling Properties of Amine-Oxide-Containing Zwitterionic Polymers

Biofouling due to nonspecific proteins or cells on the material surfaces is a major challenge in a range of applications such as biosensors, medical devices, and implants. Even though poly(ethylene glycol) (PEG) has become the most widely used stealth material in medical and pharmaceutical products, the number of reported cases of PEG-triggered rare allergic responses continues to increase in the past decades. Herein, a new type of antifouling material poly(amine oxide) (PAO) has been evaluated as an alternative to overcome nonspecific foulant adsorption and impart comparable biocompatibility. Alkyl-substituted PAO containing diethyl, dibutyl, and dihexyl substituents are prepared, and their solution properties are studied. Photoreactive copolymers containing benzophenone as the photo-cross-linker are prepared by reversible addition-fragmentation chain-transfer polymerization and fully characterized by gel permeation chromatography and dynamic light scattering. Then, these water-soluble polymers are anchored onto a silicon wafer with the aid of UV irradiation. By evaluating the fouling resistance properties of these modified surfaces against various types of foulants, protein adsorption and bacterial attachment assays show that the cross-linked PAO-modified surface can efficiently inhibit biofouling. Furthermore, human blood cell adhesion experiments demonstrate that our PAO polymer could be used as a novel surface modifier for biomedical devices.

Progress in Photocurable 3D Printing of Photosensitive Polyurethane: A Review

In recent years, as a class of advanced additive manufacturing (AM) technology, photocurable 3D printing has gained increasing attention. Based on its outstanding printing efficiency and molding accuracy, it is employed in various fields, such as industrial manufacturing, biomedical, soft robotics, electronic sensors. Photocurable 3D printing is a molding technology based on the principle of area-selective curing of photopolymerization reaction. At present, the main printing material suitable for this technology is the photosensitive resin, a composite mixture consisting of a photosensitive prepolymer, reactive monomer, photoinitiator, and other additives. As the technique research deepens and its application gets more developed, the design of printing materials suitable for different applications is becoming the hotspot. Specifically, these materials not only can be photocured but also have excellent properties, such as elasticity, tear resistance, fatigue resistance. Photosensitive polyurethanes can endow photocured resin with desirable performance due to their unique molecular structure including the inherent alternating soft and hard segments, and microphase separation. For this reason, this review summarizes and comments on the research and application progress of photocurable 3D printing of photosensitive polyurethanes, analyzing the advantages and shortcomings of this technology, also offering an outlook on this rapid development direction.

Magnetically assisted soft milli-tools for occluded lumen morphology detection

Methodologies based on intravascular imaging have revolutionized the diagnosis and treatment of endovascular diseases. However, current methods are limited in detecting, i.e., visualizing and crossing, complicated occluded vessels. Therefore, we propose a miniature soft tool comprising a magnet-assisted active deformation segment (ADS) and a fluid drag-driven segment (FDS) to visualize and cross the occlusions with various morphologies. First, via soft-bodied deformation and interaction, the ADS could visualize the structure details of partial occlusions with features as small as 0.5 millimeters. Then, by leveraging the fluidic drag from the pulsatile flow, the FDS could automatically detect an entry point selectively from severe occlusions with complicated microchannels whose diameters are down to 0.2 millimeters. The functions have been validated in both biologically relevant phantoms and organs ex vivo. This soft tool could help enhance the efficacy of minimally invasive medicine for the diagnosis and treatment of occlusions in various circulatory systems.

Challenge of material haemocompatibility for microfluidic blood-contacting applications

Biological applications of microfluidics technology is beginning to expand beyond the original focus of diagnostics, analytics and organ-on-chip devices. There is a growing interest in the development of microfluidic devices for therapeutic treatments, such as extra-corporeal haemodialysis and oxygenation. However, the great potential in this area comes with great challenges. Haemocompatibility of materials has long been a concern for blood-contacting medical devices, and microfluidic devices are no exception. The small channel size, high surface area to volume ratio and dynamic conditions integral to microchannels contribute to the blood-material interactions. This review will begin by describing features of microfluidic technology with a focus on blood-contacting applications. Material haemocompatibility will be discussed in the context of interactions with blood components, from the initial absorption of plasma proteins to the activation of cells and factors, and the contribution of these interactions to the coagulation cascade and thrombogenesis. Reference will be made to the testing requirements for medical devices in contact with blood, set out by International Standards in ISO 10993-4. Finally, we will review the techniques for improving microfluidic channel haemocompatibility through material surface modifications-including bioactive and biopassive coatings-and future directions.

Self-Assembly of Shark Scale-Patterned Tunable Superhydrophobic/Antifouling Structures with Visual Color Response

The stacked riblet-like shark scales, also known as dermal denticles, allow them to control the boundary layer flow over the skin and to reduce interactions with any biomaterial attached, which guide the design of antifouling coatings. Interestingly, shark scales are with a wide variation in geometry both across species and body locations, thereby displaying diversified antifouling capabilities. Inspired by the multifarious denticles, a stretchable shark scale-patterned silica hollow sphere colloidal crystal/polyperfluoroether acrylate-polyurethane acrylate composite film is engineered through a scalable self-assembly approach. Upon stretching, the patterned photonic crystals feature different short-term antibacterial and long-term anti-biofilm performances with a distinguished color response under varied elongation ratios. To gain a better understanding, the dependence of elongation ratio on antiwetting behaviors, antifouling performances, and structural color changes has also been investigated in this research.

Urushiol-Based Benzoxazine Containing Sulfobetaine Groups for Sustainable Marine Antifouling Applications

Benzoxazine resins are new thermosetting resins with excellent thermal stability, mechanical properties, and a flexible molecular design, demonstrating promise for applications in marine antifouling coatings. However, designing a multifunctional green benzoxazine resin-derived antifouling coating that combines resistance to biological protein adhesion, a high antibacterial rate, and low algal adhesion is still challenging. In this study, a high-performance coating with a low environmental impact was synthesized using urushiol-based benzoxazine containing tertiary amines as the precursor, and a sulfobetaine moiety into the benzoxazine group was introduced. This sulfobetaine-functionalized urushiol-based polybenzoxazine coating (poly(U-ea/sb)) was capable of clearly killing marine biofouling bacteria adhered to the coating surface and significantly resisting protein attachment. poly(U-ea/sb) exhibited an antibacterial rate of 99.99% against common Gram negative bacteria (e.g., Escherichia coli and Vibrio alginolyticus) and Gram positive bacteria (e.g., Staphylococcus aureus and Bacillus sp.), with >99% its algal inhibition activity, and it effectively prevented microbial adherence. Here, a dual-function crosslinkable zwitterionic polymer, which used an "offensive-defensive" tactic to improve the antifouling characteristics of the coating was presented. This simple, economic, and feasible strategy provides new ideas for the development of green marine antifouling coating materials with excellent performance.

Synthesis and characterization of low surface energy thermoplastic polyurethane elastomers based on polydimethylsiloxane

Organosilicon modified polyurethane elastomers (Si-MTPUs) were synthesized in order to improve the anti-graffiti property of thermoplastic polyurethane elastomers (TPUs). Si-MTPUs were prepared from polydimethylsiloxane (PDMS) and polytetramethylene glycol (PTMG) as mixed soft segment, 1,4-butanediol (BDO) and imidazole salt ionic liquid N-glyceryl-N-methyl imidazolium chloride ([MIM_l,g]Cl) used as chain extender, and 4,4'-dicyclohexylmethane diisocyanate (HMDI). The structure, thermal stability, mechanical properties and physical crosslinking density of Si-MTPUs were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetry analysis (TGA), mechanical test and low field nuclear magnetic resonance. Surface energy and water absorption were characterized by static contact angle test and water resistance test, and anti-graffiti and self-cleaning properties were characterized with water, milk, ink, lipstick, oily markers and spray paint. It was found that the mechanical properties of Si-MTPU-10 with the content of PDMS 10 wt% were optimized, with a maximum tensile strength of 32.3 MPa and elongation at break of 656%. Surface energy reached the minimum value of 23.1 mN m^-1 with the best anti-graffiti performance, which no longer decreased with the increase of PDMS contents. This work provides novel idea and strategy for the preparation of low surface energy TPUs.

Zwitterionic Polysulfobetaine Coating and Antiplatelet Liposomes Reduce Fouling in Artificial Lung Circuits

The artificial lung has provided life-saving support for pulmonary disease patients and recently afforded patients with severe cases of COVID-19 better prognostic outcomes. While it addresses a critical medical need, reducing the risk of clotting inside the device remains challenging. Herein, a two-step surface coating process of the lung circuit using Zwitterionic polysulfobetaine methacrylate is evaluated for its nonspecific protein antifouling activity. It is hypothesized that similarly applied coatings on materials integrated (IT) or nonintegrated (NIT) into the circuit will yield similar antifouling activity. The effects of human plasma preconditioned with nitric oxide-loaded liposome on platelet (plt) fouling are also evaluated. Fibrinogen antifouling activities in coated fibers are similar in the IT and NIT groups. It however decreases in coated polycarbonate (PC) in the IT group. Also, plt antifouling activity in coated fibers is similar in the IT and NIT groups and is lower in coated PC and Tygon in the IT group compared to the NIT group. Coating process optimization in the IT lung circuit may help address difference in the coating appearance of outer and inner fiber bundle fibers, and the NO-liposome significantly reduces (86%) plt fouling on fibers indicating its potential use for blood anticoagulation.

Stability and Thrombogenicity Analysis of Collagen/Carbon Nanotube Nanocomposite Coatings Using a Reversible Microfluidic Device

Currently, the development of stable and antithrombogenic coatings for cardiovascular implants is socially important. This is especially important for coatings exposed to high shear stress from flowing blood, such as those on ventricular assist devices. A method of layer-by-layer formation of nanocomposite coatings based on multi-walled carbon nanotubes (MWCNT) in a collagen matrix is proposed. A reversible microfluidic device with a wide range of flow shear stresses has been developed for hemodynamic experiments. The dependence of the resistance on the presence of a cross-linking agent for collagen chains in the composition of the coating was demonstrated. Optical profilometry determined that collagen/c-MWCNT and collagen/c-MWCNT/glutaraldehyde coatings obtained sufficiently high resistance to high shear stress flow. However, the collagen/c-MWCNT/glutaraldehyde coating was almost twice as resistant to a phosphate-buffered solution flow. A reversible microfluidic device made it possible to assess the level of thrombogenicity of the coatings by the level of blood albumin protein adhesion to the coatings. Raman spectroscopy demonstrated that the adhesion of albumin to collagen/c-MWCNT and collagen/c-MWCNT/glutaraldehyde coatings is 1.7 and 1.4 times lower than the adhesion of protein to a titanium surface, widely used for ventricular assist devices. Scanning electron microscopy and energy dispersive spectroscopy determined that blood protein was least detected on the collagen/c-MWCNT coating, which contained no cross-linking agent, including in comparison with the titanium surface. Thus, a reversible microfluidic device is suitable for preliminary testing of the resistance and thrombogenicity of various coatings and membranes, and nanocomposite coatings based on collagen and c-MWCNT are suitable candidates for the development of cardiovascular devices.

Piranha solution treatment: A facile method for improving the antithrombotic ability and regulating smooth muscle cell growth on blood contact materials

Blood contact materials require strong anti-fouling capabilities to avoid thrombus formation. Recently, TiO2-based photocatalytic antithrombotic treatment has gained focus. Nevertheless, this method is restricted to titanium materials with photocatalytic abilities. This study offers an alternative solution that can be applied to a broader range of materials: piranha solution treatment. Our findings revealed that the free radicals generated by the treatment effectively altered the surface physicochemical properties of various inorganic materials, enhancing their surface hydrophilicity and oxidizing organic contaminants, thus improving their antithrombotic properties. Additionally, the treatment resulted in contrasting effects on the cellular affinity of SS and TiO2. While it significantly reduced the adhesion and proliferation of SMCs on SS surfaces, it significantly enhanced these on TiO2 surfaces. These observations suggested that the impact of the piranha solution treatment on the cellular affinity of biomaterials was closely tied to the intrinsic properties of the materials. Thus, materials suitable for piranha solution treatment could be selected based on the functional requirements of implantable medical devices. In conclusion, the broad applicability of piranha solution surface modification technology in both blood-contact and bone implant materials highlights its promising prospects.

Chiroptical Elastomer Film Constructed by Chiral Helical Substituted Polyacetylene and Polydimethylsiloxane: Multiple Stimuli Responsivity and Chiral Amplification

Chiral and circularly polarized luminescence (CPL) materials with multiple stimuli responses have become a focus of attention. Meanwhile, elastomers have found substantial applications in a wide variety of fields. However, how to design and construct chiral elastomers, in particular CPL-active elastomers, still remains an academic challenge. In the present study, chiral helical substituted polyacetylene is chemically bonded with polydimethylsiloxane (PDMS) by hydrosilylation to form a chiroptically active elastomer. A CPL-active film was further fabricated by adding achiral fluorophores. Compared with the corresponding chiral helical polymer, the chiral films show much enhanced thermal stability in terms of chiroptical properties. The films also demonstrate reversible tunability in optical activity and CPL property when being subjected to a stretching-restoring process and exposed to a solvent like toluene. Further, noticeable chiral amplification is observed when the chiral PDMS film is superimposed with a pure PDMS film. This interesting finding is proposed to be due to the photoreflectivity of PDMS. This study provides an alternative strategy to exploit novel CPL-active elastomer materials with multiple stimuli responsivity and tunability, which may open up new opportunities for developing novel chiroptical devices.

"Built to Last": Plant-based Eco-friendly Durable Antibacterial Coatings

The demand for effective and long-term durable antibacterial surfaces has been ever-growing in the past decades. A wide variety of long-lasting antibacterial surfaces developed from release-killing, active-killing, and anti-fouling strategies have demonstrated the desired effectiveness and durability so far. Most of these successful designs were developed from toxic and fossil-based materials, which failed to comply with the green design criteria. Furthermore, the longevity of these surfaces remained an unaddressed challenge. Herein, we present a disruptive paradigm that emphasizes both eco-friendliness and long-lasting antibacterial properties. A bio-based active-killing essential oil, namely carvacrol, and nonfouling carboxybetaine zwitterionic moieties were combined and incorporated into a highly bio-based polyurethane (BPU). The long-lasting active-killing property for this antibacterial BPU coating was enabled through the extended release of the bounded carvacrol via hydrolysis in an aqueous environment and compared to unbound carvacrol by liquid infusion. Also, the release of carvacrol generates zwitterionic moieties to prevent further bacterial attachment at the release site, resulting in a "kill and defend" synergistic antibacterial function in the BPU. The kinetics of the extended-release property were investigated and compared with unbound carvacrol BPU coatings; unbound carvacrol infused into BPU was quickly exhausted after 2 days of immersion in water, while the extended-release surface exhibited a nearly constant release rate of ∼128 ng cm^-2 h^-1 even after 45 days. The in vitro antibacterial efficiency of the BPUs was quantitatively evaluated using the modified ISO standard for cross-laboratory comparison. As a result, approximately 98.9 and 98.7% of Escherichia coli and Staphylococcus aureus were eliminated from the coating surfaces, and only a negligible variance in the antibacterial efficiency was observed after 5 cycles of test. The feasibility for practical application was also demonstrated by challenging the BPU coatings in everyday settings. This "built-to-last" design theory provided insights for future development of greener antibacterial coatings with long-term performance.

Biomimetic materials based on zwitterionic polymers toward human-friendly medical devices

This review summarizes recent research on the design of polymer material systems based on biomimetic concepts and reports on the medical devices that implement these systems. Biomolecules such as proteins, nucleic acids, and phospholipids, present in living organisms, play important roles in biological activities. These molecules are characterized by heterogenic nature with hydrophilicity and hydrophobicity, and a balance of positive and negative charges, which provide unique reaction fields, interfaces, and functionality. Incorporating these molecules into artificial systems is expected to advance material science considerably. This approach to material design is exceptionally practical for medical devices that are in contact with living organisms. Here, it is focused on zwitterionic polymers with intramolecularly balanced charges and introduce examples of their applications in medical devices. Their unique properties make these polymers potential surface modification materials to enhance the performance and safety of conventional medical devices. This review discusses these devices; moreover, new surface technologies have been summarized for developing human-friendly medical devices using zwitterionic polymers in the cardiovascular, cerebrovascular, orthopedic, and ophthalmology fields.

Adaptive wireless millirobotic locomotion into distal vasculature

Microcatheters have enabled diverse minimally invasive endovascular operations and notable health benefits compared with open surgeries. However, with tortuous routes far from the arterial puncture site, the distal vascular regions remain challenging for safe catheter access. Therefore, we propose a wireless stent-shaped magnetic soft robot to be deployed, actively navigated, used for medical functions, and retrieved in the example M4 segment of the middle cerebral artery. We investigate shape-adaptively controlled locomotion in phantoms emulating the physiological conditions here, where the lumen diameter shrinks from 1.5 mm to 1 mm, the radius of curvature of the tortuous lumen gets as small as 3 mm, the lumen bifurcation angle goes up to 120^°, and the pulsatile flow speed reaches up to 26 cm/s. The robot can also withstand the flow when the magnetic actuation is turned off. These locomotion capabilities are confirmed in porcine arteries ex vivo. Furthermore, variants of the robot could release the tissue plasminogen activator on-demand locally for thrombolysis and function as flow diverters, initiating promising therapies towards acute ischemic stroke, aneurysm, arteriovenous malformation, dural arteriovenous fistulas, and brain tumors. These functions should facilitate the robot’s usage in new distal endovascular operations.

Accessibility into the distal vascular systems to treat various diseases remains challenging using medical catheters. Here, Wang et al. demonstrate that a stent-shaped wireless magnetic soft robot enables adaptive locomotion and medical functions into these distal vascular regions.

Structure-Dependent Nontraditional Intrinsic Fluorescence of Aliphatic Hyperbranched Polyureas

The nontraditional intrinsic fluorescence (NTIF) of polymers containing heteroatoms has gained considerable attention due to its promising applications in label-free bioimaging. Aliphatic hyperbranched polyureas (aBPUs), which have recently shown great promise in the field of nanomedicine, bear controllable urea groups distributed on the branch points and thus are potential candidate luminogens. However, their NTIF properties and how their structures influence the NTIF properties have not been illustrated yet. Here, we addressed these issues by synthesizing a series of aBPUs with different degrees of branching (DBs) or different modifications. aBPUs exhibited an obvious NTIF phenomenon and with the increase of DBs, the NTIF enhanced as well. Chemical modifications either at the branching ends or in the interior of aBPUs could affect the NTIF performances, which were highly dependent on the types of modification. Disruption of the intra-/intermolecular hydrogen-bonding interactions decreased the NTIF. In addition, poly(ethylene glycol) (PEG)-modified aBPUs could self-assemble into nanospheres, and the formation of nanoassembly led to 89% enhancement on NTIF compared with the homogeneous solution of aBPUs-PEG in dimethylformamide (DMF). Finally, aBPUs-PEG nanoassembly demonstrated a capability in realizing label-free material imaging in vitro. These results shed light on the rational design of the polymer structures to achieve desired fluorescence with unconventional luminophores.

Biodegradable polyurethane scaffolds in regenerative medicine: Clinical translation review

Early explorations of tissue engineering and regenerative medicine concepts commonly utilized simple polyesters such as polyglycolide, polylactide, and their copolymers as scaffolds. These biomaterials were deemed clinically acceptable, readily accessible, and provided processability and a generally known biological response. With experience and refinement of approaches, greater control of material properties and integrated bioactivity has received emphasis and a broadened palette of synthetic biomaterials has been employed. Biodegradable polyurethanes (PUs) have emerged as an attractive option for synthetic scaffolds in a variety of tissue applications because of their flexibility in molecular design and ability to fulfill mechanical property objectives, particularly in soft tissue applications. Biodegradable PUs are highly customizable based on their composition and processability to impart tailored mechanical and degradation behavior. Additionally, bioactive agents can be readily incorporated into these scaffolds to drive a desired biological response. Enthusiasm for biodegradable PU scaffolds has soared in recent years, leading to rapid growth in the literature documenting novel PU chemistries, scaffold designs, mechanical properties, and aspects of biocompatibility. Despite the enthusiasm in the field, there are still few examples of biodegradable PU scaffolds that have achieved regulatory approval and routine clinical use. However, there is a growing literature where biodegradable PU scaffolds are being specifically developed for a wide range of pathologies and where relevant pre-clinical models are being employed. The purpose of this review is first to highlight examples of clinically used biodegradable PU scaffolds, and then to summarize the growing body of reports on pre-clinical applications of biodegradable PU scaffolds.

Thermoplastic zwitterionic elastomer with critical antifouling properties

Thermoplastic elastomers are widely used in the medical industry for advanced medical and healthcare products, helping millions of patients achieve a better quality of life. Yet, microbial contamination and material-associated biofilms on devices remain a critical challenge because it is challenging for currently available materials to provide critical antifouling properties, thermoplasticity, and elastic properties simultaneously. We developed a highly flexible zwitterionic thermoplastic polyurethane with critical antifouling properties. A series of poly((diethanolamine ethyl acetate)-co-poly(tetrahydrofuran)-co-(1,6-diisocyanatohexane)) (PCB-PTHFUs) were synthesized. The PCB-PTHFUs exhibit a breaking strain of more than 400%, a high resistance to fibroblast cells for 24 h, and the excellent ability to prevent biofilm formation for up to three weeks. This study lays a foundation for clarifying the structure-function relationships of zwitterionic polymers. This thermoplastic PCB-PTHFU platform, with its unmatched antifouling properties and high elasticity, has potential for implanted medical devices and a broad spectrum of applications that suffer from biofouling, such as material-associated infection.

PDMS-Zwitterionic Hybrid for Facile, Antifouling Microfluidic Device Fabrication

Poly(dimethylsiloxane) (PDMS) has been used in a wide range of biomedical devices and medical research due to its biostability, cytocompatibility, gas permeability, and optical properties. Yet, some properties of PDMS create critical limitations, particularly fouling through protein and cell adhesion. In this study, a diallyl-terminated sulfobetaine (SB-diallyl) molecule was synthesized and then directly mixed with a commercial PDMS base (Sylgard 184) and curing agent to produce a zwitterionic group-bearing PDMS (PDMS-SB) hybrid that does not require a complex or an additional surface modification process for the desired end product. In vitro examination of antifouling behavior following exposure to fresh ovine blood showed a significant reduction in platelet deposition for the PDMS-SB hybrid surface compared to that of a PDMS control (p < 0.05, n = 5). The manufacturability via soft lithography using the synthesized polymers was found to be comparable to that for unmodified PDMS. Bonding via O₂ plasma treatment was confirmed, and the strength was measured and again found to be comparable to the control. PDMS-SB microfluidic devices were successfully fabricated and showed improved blood compatibility that could reduce channel occlusion due to clot formation relative to PDMS control devices. Further, gas (CO₂) transfer through a PDMS-SB hybrid membrane was also tested with a proof-of-concept microchannel device and shown to be comparable to that through the PDMS control.

Unprecedented Strength Polysiloxane-Based Polyurethane for 3D Printing and Shape Memory

Thermoplastic polysiloxane-based polyurethane (Si-TPU) has been attracting a great deal of attention because of the dual advantages of polysiloxane and polyurethane. However, the strength of Si-TPU with a traditional structure is low, and improvement is urgently needed for diverse applications. Herein, we design a polysiloxane-based soft segment (SS) with two urethane groups at the end of the polysiloxane chain, and then we prepare a series of Si-TPUs through a designed SS, isophorone diisocyanate and 1,4-butanediol. Such structural design improves the polarity of the SS and endows more regular hydrogen bonds to the polymer molecular chain. As a result, the prepared Si-TPUs exhibit a good microphase separation structure, unprecedentedly high strength, repeatable processing, noncytotoxicity, shape memory properties, and three-dimensional printing capabilities. Moreover, a maximum tensile strength of Si-TPUs can reach 20.3 MPa, exceeding that of other existing Si-based polymer materials. Si-TPUs show great potential for biomedical applications.

Bacterial adhesion properties of parylene C and D deposited on polydimethylsiloxane

Parylene, a widely used protective coating, has received significant attention in medical applications. In this study, the bacterial adhesion properties of parylene C and D coated on polydimethylsiloxane (PDMS) substrates,...

Recent Strategies to Develop Innovative Photosensitizers for Enhanced Photodynamic Therapy

This review presents a robust strategy to design photosensitizers (PSs) for various species. Photodynamic therapy (PDT) is a photochemical-based treatment approach that involves the use of light combined with a light-activated chemical, referred to as a PS. Attractively, PDT is one of the alternatives to conventional cancer treatment due to its noninvasive nature, high cure rates, and low side effects. PSs play an important factor in photoinduced reactive oxygen species (ROS) generation. Although the concept of photosensitizer-based photodynamic therapy has been widely adopted for clinical trials and bioimaging, until now, to our surprise, there has been no relevant review article on rational designs of organic PSs for PDT. Furthermore, most of published review articles in PDT focused on nanomaterials and nanotechnology based on traditional PSs. Therefore, this review aimed at reporting recent strategies to develop innovative organic photosensitizers for enhanced photodynamic therapy, with each example described in detail instead of providing only a general overview, as is typically done in previous reviews of PDT, to provide intuitive, vivid, and specific insights to the readers.

Quasicrystalline Coatings Exhibit Durable Low Interfacial Toughness with Ice

Ice accretion can adversely impact many engineering structures in commercial and residential sectors. Although there are many reports of low-ice-adhesion-strength materials, a scalable and durable deicing solution remains elusive, as ice detachment is dominated by interfacial toughness for large interfaces. In this work, durable metallic coatings based on Al-rich quasicrystalline alloys were prepared and applied on aluminum substrates using high-velocity oxyfuel thermal spray. X-ray diffraction patterns confirmed the quasicrystalline phases of the coating, and its large-scale deicing capability was studied by evaluating the coating's ice detachment mechanics using long lengths of ice. A toughness-controlled regime of interfacial fracture was observed for ice lengths longer than ∼2 cm, and a low shear strength of ∼30 kPa was achieved for a 20 cm ice length. The metallic coatings exhibited excellent ice repellency even after being abraded, scratched, heated, UV-irradiated, and exposed to chemical contaminations, demonstrating promising durability for real-world, large-scale ice removal.

Micellar Carriers of Active Substances Based on Amphiphilic PEG/PDMS Heterograft Copolymers: Synthesis and Biological Evaluation of Safe Use on Skin

Amphiphilic copolymers containing polydimethylsiloxane (PDMS) and polyethylene glycol methyl ether (MPEG) were obtained via an azide-alkyne cycloaddition reaction between alkyne-functionalized copolymer of MPEG methacrylate and azide-functionalized PDMS. “Click” reactions were carried out with an efficiency of 33–47% increasing grafting degrees. The grafted copolymers were able to carry out the micellization and encapsulation of active substances, such as vitamin C (VitC), ferulic acid (FA) and arginine (ARG) with drug loading content (DLC) in the range of 2–68% (VitC), and 51–89% (FA or ARG). In vitro release studies (phosphate buffer saline, PBS; pH = 7.4 or 5.5) demonstrated that the maximum release of active substances was mainly after 1–2 h. The permeability of released active substances through membrane mimicking skin evaluated by transdermal tests in Franz diffusion cells indicated slight diffusion into the solution (2–16%) and their remaining in the membrane. Studies on the selected carrier with FA showed no negative effect on cell viability, proliferation capacity or senescence, as well as cell apoptosis/necrosis differences or cell cycle interruption in comparison with control cells. These results indicated that the presented micellar systems are good candidates for carriers of cosmetic substances according to physicochemical characterization and biological studies.