Bioinspired Asymmetric Polypyrrole Membranes with Enhanced Photothermal Conversion for Highly Efficient Solar Evaporation.

Solar-driven interfacial evaporation (SDIE) has attracted great attention by offering a zero-carbon-emission solution for clean water production. The manipulation of the surface structure of the evaporator markedly promotes the enhancement of light capture and the improvement of evaporation performance. Herein, inspired by seedless lotus pod, a flexible pristine polypyrrole (PPy) membrane with macro/micro-bubble and nanotube asymmetric structure is fabricated through template-assisted interfacial polymerization. The macro- and micro-hierarchical structure of the open bubbles enable multiple reflections inner and among the bubble cavities for enhanced light trapping and omnidirectional photothermal conversion. In addition, the multilevel structure (macro/micro/nano) of the asymmetric PPy (PPy-A) membrane induces water evaporation in the form of clusters, leading to a reduction of water evaporation enthalpy. The PPy-A membranes achieve a full-spectrum light absorption of 96.3% and high evaporation rate of 2.03 kg m-2  h-1 under 1 sun. Long-term stable desalination is also verified with PPy-A membranes by applying one-way water channel. This study demonstrates the feasibility of pristine PPy membranes in SDIE applications, providing guidelines for modulation of the evaporator topologies toward high-efficient solar evaporation.

A multifunctional surgical suture with electroactivity assisted by oligochitosan/gelatin-tannic acid for promoting skin wound healing and controlling scar proliferation.

Surgical wound closure is accomplished most frequently with sutures, optimally proceeding rapidly and without complication. However, surgical sutures can trigger foreign body reactions and incite abnormal collagen deposition. Sustained inflammation can result in abnormal wound healing with hypertrophic scar formation. Therefore, evolution of suture material to inhibit inflammation and scar formation is of great clinical significance. In the present study, commercial 3-0 PPDO [poly(p-dioxanone)] suture was used as the base material and modified by adding two layers: a drug-loaded layer and an electroactive layer. The former layer was curcumin (Cur) encapsulated by PLGA [poly (lactic-co-glycolic acid)] and the latter layer was composed of oligochitosan-gelatin/tannic acid/polypyrrole (OCS-GE/TA/PPy). The multifunctional sutures, named S@LC@CGTP, had desirable sustained-drug release properties in vitro where Cur could be released for 8 days due to the action of PLGA. The three-dimensional network structure of OCS-GE/TA ensured S@LC@CGTP against surface cracking and maintained electrical. Furthermore, using an in vivo experiment, S@LC@CGTP could attenuate inflammation and promote scar-free wound healing according to suppression of infiltrating inflammatory cells, down-regulation of TGF-ß1 and collagen type I expression, and improved collagen arrangement. Cumulatively, we indicated that S@LC@CGTP suture material has great potential to facilitate optimal, nearly scarless healing of surgical incisions.

Turning waste into valuables: In situ deposition of polypyrrole on the obsolete mask for Cr(VI) removal and desalination.

The global mask consumption has been exacerbated because of the coronavirus disease 2019 (COVID-19) pandemic. Simultaneously, the traditional mask disposal methods (incineration and landfill) have caused serious environmental pollution and waste of resources. Herein, a simple and green mass-production method has been proposed to recycle carbon protective mask (CPM) into the carbon protective mask/polydopamine/polypyrrole (CPM/PDA/PPy) composite by in situ polymerization of PPy. The CPM/PDA/PPy composite was used for the removal of Cr(VI) and salt ions to produce clean water. The synergistic effect of PPy and the CPM improved the removal capability of Cr(VI). The CPM/PDA/PPy composite provided high adsorption capacity (358.68 mg g-1) and economic value (811.42 mg $-1). Consequently, the CPM/PDA/PPy (cathode) was combined with MnO2 (anode) for desalination in CDI cells, demonstrated excellent desalination capacity (26.65 mg g-1) and ultrafast salt adsorption rate (6.96 mg g-1 min-1), which was higher than conventional CDI cells. Our work proposes a new low-carbon strategy to recycle discarded masks and demonstrates their utilization in Cr(VI) removal and seawater desalination.

Conductive fibers for biomedical applications.

Bioelectricity has been stated as a key factor in regulating cell activity and tissue function in electroactive tissues. Thus, various biomedical electronic constructs have been developed to interfere with cell behaviors to promote tissue regeneration, or to interface with cells or tissue/organ surfaces to acquire physiological status via electrical signals. Benefiting from the outstanding advantages of flexibility, structural diversity, customizable mechanical properties, and tunable distribution of conductive components, conductive fibers are able to avoid the damage-inducing mechanical mismatch between the construct and the biological environment, in return to ensure stable functioning of such constructs during physiological deformation. Herein, this review starts by presenting current fabrication technologies of conductive fibers including wet spinning, microfluidic spinning, electrospinning and 3D printing as well as surface modification on fibers and fiber assemblies. To provide an update on the biomedical applications of conductive fibers and fiber assemblies, we further elaborate conductive fibrous constructs utilized in tissue engineering and regeneration, implantable healthcare bioelectronics, and wearable healthcare bioelectronics. To conclude, current challenges and future perspectives of biomedical electronic constructs built by conductive fibers are discussed.

Maple Leaf Inspired Conductive Fiber with Hierarchical Wrinkles for Highly Stretchable and Integratable Electronics.

Stretchable and durable conductors are significant to the development of wearable devices, robots, human-machine interfaces, and other artificial intelligence products. However, the desirable strain-insensitive conductivity and low hysteresis are restricted by the failure of stretchable structures and mismatch of mechanical properties (rigid conductive layer and elastic core substrate) under large deformation. Here, based on the principles of fractal geometry, a stretchable conductive fiber with hierarchical wrinkles inspired by the unique shape of the maple leaf was fabricated by combining surface modification, interfacial polymerization, and improved prestrain finishing methods to break through this dilemma. The shape and size of wrinkles predicted by buckling analysis via the finite element method fit well with that of actual wrinkles (30-80 µm of macro wrinkles and 4-6 µm of micro wrinkles) on the fabricated fiber. Such hierarchically wrinkled conductive fiber (HWCF) exhibited not only excellent strain-insensitive conductivity denoted by the relative resistance change ΔR/R0 = 0.66 with R0 the original resistance and ΔR the change of resistance after the concrete strain reaching up to 600%, but also low hysteresis (0.04) calculated by the difference in area between stretching and releasing curve of the ΔR/R0 strain under 300% strain and long-term durability (>1000 stretching-releasing cycles). Furthermore, the elastic conductive fiber with such a bionic structure design can be applied as highly stretchable electrical circuits for illumination and monitors for the human motion under large strains through tiny and rapid resistance changes as well. Such a smart biomimetic material holds great prospects in the field of stretchable electronics.

A honeybee stinger-inspired self-interlocking microneedle patch and its application in myocardial infarction treatment.

Weak tissue adhesion remains a major challenge in clinical translation of microneedle patches. Mimicking the structural features of honeybee stingers, stiff polymeric microneedles with unidirectionally backward-facing barbs were fabricated and embedded into various elastomer films to produce self-interlocking microneedle patches. The spirality of the barbing pattern was adjusted to increase interlocking efficiency. In addition, the micro-bleeding caused by microneedle puncturing adhered the porous surface of the patch substrate to the target tissue via coagulation. In the demonstrative application of myocardial infarction treatment, the bioinspired microneedle patches firmly fixed on challenging beating hearts, significantly reduced cardiac wall stress and strain in the infarct, and maintained left ventricular function and morphology. In addition, the microneedle patch was minimally invasively implanted onto beating porcine heart in 10 minutes, free of sutures and adhesives. Therefore, the honeybee stinger-inspired microneedles could provide an adaptive and convenient means to implant patches for various medical applications. STATEMENT OF SIGNIFICANCE: Adhesion between tissue and microneedle patches with smooth microneedles is usually weak. We introduce a novel barbing method of fabricating unidirectionally backward facing barbs with controllable spirality on the microneedles on microneedle patches. The microneedle patches self-interlock on mechanically dynamic beating hearts, similar to honeybee stingers. The micro-bleeding and coagulation on the porous surface provide additional adhesion force. The microneedle patches attenuate left ventricular remodeling via mechanical support and are compatible with minimally invasive implantation.

Flexible and easy-handling pristine polypyrrole membranes with bayberry-like vesicle structure for enhanced Cr(VI) removal from aqueous solution.

Polypyrrole has been extensively explored for Cr(VI) removal from wastewater towing to the advantages of superior performance, low cost, facile synthesis, and high environmental stability. However, the unsatisfactory adsorption capacity and complicated process of adsorbent separation from aqueous solutions remain a huge challenge, limiting its practical application. Herein, a flexible PPy membrane with bayberry-like vesicle structures (PPy-B) was prepared via template-assisted interfacial polymerization. It was found that sodium sulfosalicylate not only improved the flexibility and strength of the PPy-B membrane for easy-handling but also participated in the polymerization of PPy as a dopant to improve the specific surface area and doping level for increasing adsorption sites. Benefiting from these, the easy-handling PPy-B membrane exhibited a high adsorption capacity (586.90-682.50 mg/g at 298-318 K), a high reusability (five adsorption-desorption cycles), and a high ultimate adsorption capacity after adsorption-desorption cycles until membrane failure (1174.86 mg/g at 298 K). The proposed mechanisms of the enhanced Cr(VI) removal involve electrostatic adsorption, reduction, and ion exchange. This flexible PPy membrane therefore shows attractive advantages in wastewater treatment.

Conductive biomaterials for cardiac repair: A review.

Myocardial infarction (MI) is one of the fatal diseases in humans. Its incidence is constantly increasing annually all over the world. The problem is accompanied by the limited regenerative capacity of cardiomyocytes, yielding fibrous scar tissue formation. The propagation of electrical impulses in such tissue is severely hampered, negatively influencing the normal heart pumping function. Thus, reconstruction of the internal cardiac electrical connection is currently a major concern of myocardial repair. Conductive biomaterials with or without cell loading were extensively investigated to address this problem. This article introduces a detailed overview of the recent progress in conductive biomaterials and fabrication methods of conductive scaffolds for cardiac repair. After that, the advances in myocardial tissue construction in vitro by the restoration of intercellular communication and simulation of the dynamic electrophysiological environment are systematically reviewed. Furthermore, the latest trend in the study of cardiac repair in vivo using various conductive patches is summarized. Finally, we discuss the achievements and shortcomings of the existing conductive biomaterials and the properties of an ideal conductive patch for myocardial repair. We hope this review will help readers understand the importance and usefulness of conductive biomaterials in cardiac repair and inspire researchers to design and develop new conductive patches to meet the clinical requirements. STATEMENT OF SIGNIFICANCE: After myocardial infarction, the infarcted myocardial area is gradually replaced by heterogeneous fibrous tissue with inferior conduction properties, resulting in arrhythmia and heart remodeling. Conductive biomaterials have been extensively adopted to solve the problem. Summarizing the relevant literature, this review presents an overview of the types and fabrication methods of conductive biomaterials, and focally discusses the recent advances in myocardial tissue construction in vitro and myocardial repair in vivo, which is rarely covered in previous reviews. As well, the deficiencies of the existing conductive patches and their construction strategies for myocardial repair are discussed as well as the improving directions. Confidently, the readers of this review would appreciate advantages and current limitations of conductive biomaterials/patches in cardiac repair.

Chitosan/gelatin-tannic acid decorated porous tape suture with multifunctionality for tendon healing.

The inferior tendon healing after surgery is inextricably linked to the surgical suture. Poor load transfer along the suture often results in a high tendon re-tear rate. Besides, the severe inflammation and infection induced by sutures even cause a second surgery. Herein, to alleviate the above-mentioned issues, a multifunctional suture was fabricated by decorating chitosan/gelatin-tannic acid (CS/GE-TA) on the porous tape suture. The porous tape suture ensured the required mechanical properties and sufficient space for tissue integration. Compared to the pristine suture, the CS/GE-TA decorated suture (TA100) presented a 332% increase in pull-out force from the tendon, indicating potentially decreased re-tear rates. Meanwhile, TA100 showed superior anti-inflammatory and antibacterial performances. In vivo experiments further proved that TA100 could not only reduce inflammatory action but also facilitate collagen deposition and blood vessel formation. These results indicate that the multifunctional sutures are promising candidates for accelerating tendon healing.

Influence of polyethylene terephthalate/ polyamide (PET/PA) bilayer structure on physical and strength-related properties of superpressure angioplasty balloons.

BACKGROUND: Percutaneous transluminal coronary angioplasty (PTCA), including balloon angioplasty, is a standard clinical invasive treatment for coronary artery disease. The coronary lesion with calcification is difficult to dilate and the prevention of balloon failure is especially important. OBJECTIVE: A novel superpressure balloon was fabricated with bilayered structure of polyethylene terephthalate (PET) and PA12 (polyamide). METHODS: The structures of bilayer balloon were adjusted to achieve overall excellent performance. Physicochemical, thermal and mechanical properties of bilayer balloons were characterized by X-ray diffraction, differential scanning calorimeter, hydraulic tester and theoretical simulation. RESULTS: Compared with pure PA12 and PET balloons, PA12 outer layer: PET inner layer balloon with layer ratio of 3:7 shows the highest burst stress and relatively low compliance due to an increase in crystallinity and orientation. CONCLUSIONS: The produced bilayer balloon proved to possess a small folding dimension thanks to its ultrathin bilayer structure, which is good for crossing cramped vessels. We believe these optimally fabricated bilayer balloons are proved to provide attractive opportunities for preparation, performance enhancement, and practical applications of super-pressure balloon catheters and cryoablation balloons, that will significantly promote the development of percutaneous transluminal coronary angioplasty for clinical applications.

Design of Electro-Thermal Glove with Sensor Function for Raynaud's Phenomenon Patients.

Raynaud's phenomenon (RP) is a disease that mainly affects human fingertips during cold weather. It is difficult to treat this disease using medicine, apart from keeping the body in a warm environment. In this research, conductive knitted fabrics were fabricated to help relax the vessels of the patient's fingertips by providing proper heat, and also serving as a sensor to detect finger motion after relaxation of the blood vessels of patients. Four different structures, termed plain, purl, interlock, and rib were produced using conductive silver/PE (polyethylene) yarn and wool yarn, with a computerized flat knitting machine. The effect of knitted structure on the electro-thermal behavior, sensitivity, and stability of resistance change (∆R/R) under different tensile forces was investigated. By comprehensive comparison, the purl structure was identified as the preferred structure for the heating glove for RP patients, owing to superior electro-thermal behavior. Additionally, the purl structure had a greater capacity to detect different motions with stable resistance change. This potential electro-thermal glove could be used for functional, as well as aesthetic (fashion) purposes, and could be worn at any time and occasion with complete comfort.

A biocompatible polypyrrole membrane for biomedical applications.

Polypyrrole (PPy) is the most widely investigated electrically conductive biomaterial. However, because of its intrinsic rigidity, PPy has only been used either in the form of a composite or a thin coating. This work presents a pure and soft PPy membrane that is synergically reinforced with the electrospun polyurethane (PU) and poly-l-lactic acid (PLLA) fibers. This particular reinforcement not only renders the originally rather fragile PPy membrane easy to manipulate, it also prevents the membrane from deformation in an aqueous environment. Peel and mechanical tests confirmed the strong adhesion of the fibers and the significantly increased tensile strength of the reinforced membrane. Surface electrical conductivity and long-term electrical stability were tested, showing that these properties were not affected by the reinforcement. Surface morphology and chemistry were analyzed with scanning electron spectroscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). Material thermal stability was investigated with thermogravimetric analysis (TGA). Finally, the adhesion and proliferation of human skin keratinocytes on the membrane were assessed by Hoechst staining and the methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay. In conclusion, this membrane proves to be the first PPy-based soft conductive biomaterial that can be practically used. Its electrical conductivity and cytocompatibility promise a wide range of biomedical applications.

Limb salvage after aneurysmal degeneration of a cryopreserved vein allograft: Searching the autologous veins of the arm is worth the effort.

CLINICAL DATA: We hereby report a case of limb salvage involving a 64-year-old man who was hospitalized with ischemic foot ulcers for two months. Endarterectomy with patching and stenting of the left iliofemoral artery failed. A composite bypass of two segments of the endarterectomized superficial femoral artery and a cryopreserved saphenous vein graft was implanted one week later. On day 4 postoperatively, an infection (Staphylococcus epidermidis and Pseudomonas aeruginosa) was treated empirically with antibiotics. Four months later, the femoro-tibial bypass thrombosed and the patency was restored by thrombolysis. The aneurysmal cryopreserved vein was excised. Iterative complications followed and final success was attained after implantation of autologous cephalic and basilic veins. Four years later, this femoro-tibial is still patent. PATHOLOGICAL ANALYSES: After a gross observation, the explant was dissected and the most significant sections were processed for histology, followed by analyses in scanning electron microscopy, light microscopy and transmission electron microscopy. RESULTS: The explanted specimen showed a smooth flow surface proximally but a severe distortion distally, with an accumulation of poorly organized mural thrombi. The wall of the arterialized vein was accompanied with an important inflammatory reaction. The degradation of the collagen structure was evidenced in TEM. The fibrils of collagen were still individualized but were fragmented and did not display parallelly. The regular banding was preserved. The presence of Pseudomonas aeruginosa was shown inside the wall of the homologous vein. COMMENTS: In case of sepsis, the most aggressive antibiotic treatments cannot fully eliminate the bacteremic colonizations within the wall of an alternative conduit. The cephalic and basilic autologous veins are proved to be preferable in absence of the autologous saphenous vein. The amputation was prevented and four years later the bypass is still patent. This is an outstanding result based upon the comorbidities of the patient. The most aggressive harvesting shall be recommended. This patient represented a considerable challenge and the clinical result is highly gratifying: the search for the autologous cephalic and basilic veins proved to be worth the effort.

Construction and application of textile-based tissue engineering scaffolds: a review.

Tissue engineering (TE) provides a practicable method for tissue and organ repair or substitution. As the most important component of TE, a scaffold plays a critical role in providing a growing environment for cell proliferation and functional differentiation as well as good mechanical support. And the restorative effects are greatly dependent upon the nature of the scaffold including the composition, morphology, structure, and mechanical performance. Medical textiles have been widely employed in the clinic for a long time and are being extensively investigated as TE scaffolds. However, unfortunately, the advantages of textile technology cannot be fully exploited in tissue regeneration due to the ignoring of the diversity of fabric structures. Therefore, this review focuses on textile-based scaffolds, emphasizing the significance of the fabric design and the resultant characteristics of cell behavior and extracellular matrix reconstruction. The structure and mechanical behavior of the fabrics constructed by various textile techniques for different tissue repairs are summarized. Furthermore, the prospect of structural design in the TE scaffold preparation was anticipated, including profiled fibers and some unique and complex textile structures. Hopefully, the readers of this review would appreciate the importance of structural design of the scaffold and the usefulness of textile-based TE scaffolds in tissue regeneration.

Long-term anticoagulation and selective cells adhesion surface via combination of covalent grafting and layer by layer assembly.

Surface modification by long-term active component is essential for biocompatible polymers-based vascular grafts to prevent thrombus formation and reduce intimal hyperplasia. In this study, a simple approach was developed to immobilize bioactive heparin to the surface of ε-polycaprolactone (PCL) grafts through a two-step strategy combining covalent grafting and layer by layer assembly of polyelectrolytes. The performance of heparinized PCL was evaluated in vitro, including the release behavior of heparin, anticoagulation and different types of cells adhesion characteristic. A sustained-release of heparin was achieved by this immobilization strategy. Surface remaining heparin was up to 1.10 µg cm-2 on the modified PCL after release in vitro for 30 d. Specifically, the heparinized PCL has the long-term ability to prevent adhesion of blood cells and thrombus formation, and significantly inhibit the adhesion of smooth muscle cells. The two-step strategy provides a simple and general route to incorporate heparin on PCL graft surface. The surface heparinized PCL demonstrated in this work can be a useful material platform for biodegradable vascular stent graft.

Donkey pericardium compares favorably with commercial xenopericardia used in the manufacture of transcatheter heart valves.

Transcatheter aortic valve implantation (TAVI) has gained considerable acceptance in the past decade due to its lower risks than conventional open-heart surgery. However, the deformation and delamination of the leaflets during the crimping procedure have raised questions about the durability and long-term serviceability of the pericardium tissue from which the leaflets are made. The collagen architecture, wall thickness and mechanical properties of donkey pericardium were investigated to assess its suitability as an alternative material for the manufacture of heart valves. Coupons sampled from different locations of donkey pericardium were investigated. Bovine, equine, and porcine pericardium specimens served as controls. The donkey pericardium had a similar surface morphology to that of the control pericardia except for the wavy topology on both the fibrous and serous sides. The average thickness of donkey pericardium (ca. 120 µm) was significantly lower than that from bovine (375 µm) and equine (410 µm), but slightly higher than that from porcine (99 µm) specimens. The interlaced wavy collagen bundles in the pericardium were composed of collagen fibers about 100 nm in diameter. This unique structure ensures that the donkey pericardium has a comparable ultimate tensile strength (UTS) and a much higher failure strain than the commercial pericardia used for the manufacture of heart valves. The donkey pericardium has an organized wavy collagen bundle architecture similar to that of bovine pericardium and has a satisfactory UTS and high failure strain. The thin and strong donkey pericardium might be a good candidate valve leaflet material for TAVI.

Surface modification by assembling: a modular approach based on the match in nanostructures.

Quantitative co-immobilization of multiple bioactive proteins or diverse chemical moieties on a surface is challenging because of the competition among the reactants. In this work, a two-step method is proposed, in which each type of reactant is firstly grafted onto the surface of functional nanoparticles, and then these nanoparticles are mixed and cast onto a substrate that has an appropriate nano-topography to trap and immobilize the nanoparticles. This approach has two distinct advantages: (1) it avoids competition among reactants of different natures; (2) the nanoparticles prepared in the first step can be physically mixed at the desired quantity and time and with the desired type. To demonstrate the feasibility, human and bovine albumins as model molecules were covalently immobilized onto the surface of reactive polypyrrole (PPy) nanoparticles, separately; and then the two types of protein grafted particles were mixed at various ratios in aqueous solution and cast onto the nanotubular surface of a PPy membrane. On drying, the nanotubes on the membrane surface shrunk and "locked" the particles, forming a stable bifunctional surface. Considering the availability of a wide range of nanoparticles and the technical capability to construct nanostructured substrates, this strategy may provide a general solution to quantitatively immobilize multiple biomolecules or chemical moieties. In particular, the electrically conductive and multi-biofunctional flexible PPy membrane demonstrated in this work can be a useful material platform for biomedical applications such as multi-target biosensing and targeted electrical stimulation.

Polypyrrole as Electrically Conductive Biomaterials: Synthesis, Biofunctionalization, Potential Applications and Challenges.

Electrical phenomenon is ubiquitous in any biological system. However, most synthetic biomaterials are insulators to either electrical or ionic current. To mimic the electrical and ionic conductivities of natural tissues, electrically conductive polymers have been studied and are becoming a new class of biomaterials. This chapter focuses on polypyrrole, one of the most widely investigated synthetic and intrinsically conductive polymers. Polypyrrole is a heterocyclic polymer that is both electrically conductive and ionically active. It can be easily synthesized through electrochemical polymerization or oxidative polymerization. Because of its unique properties, polypyrrole has been studied for sensing, drug delivery, and actuation. Because of its good biocompatibility, it has been used to interface electrical elements and tissues, either for recording or stimulation purpose. Polypyrrole can also be chemically modified to carry functional groups and biomolecules, allowing both specific biological recognition and electrical stimulation. This chapter also discusses a unique soft polypyrrole membrane that can be easily used as biomaterials. Hopefully, the readers of this chapter would appreciate the importance of electrical conductivity for biomaterials and the usefulness of polypyrrole.

Conductive Polymer Waving in Liquid Nitrogen.

The poor mechanical properties and processability of pristine heterocyclic conductive polymers represent the most notable scientific and technological challenges that have greatly limited the application of these polymers. We report a soft and mechanically processable free-standing pristine polypyrrole (PPy) membrane (PPy-N) that is as soft in liquid nitrogen (-196 °C) as it is at room temperature, despite a glass transition temperature (Tg) above 100 °C. This PPy membrane also displays a highly attractive combination of properties, including mechanical processability, lightweight (9 g m-2), large surface area (14.5 m2 g-1), stable electrothermal behavior, amphiphilicity, excellent cytocompatibility, and easy synthesis, at virtually any size. This discovery demonstrates an approach to changing the mechanical property of heterocyclic conductive polymer with no chemical alterations or compounding and may enhance the development of inherently conducting polymers for applications in energy storage and biomedicine and as lightweight conducting and heating materials.

One-step reactivity-driven synthesis of core-shell structured electrically conducting particles for biomedical applications.

Electrically conductive and functional polymeric nanoparticles have significant potential in biomedical applications such as in sensing and stimulation. Polymeric core-shell particles are usually prepared either through a multiple-step process or by the design of amphiphilic macromolecules. Here we report a simple one-step and one-pot emulsion polymerization method to synthesize the core-shell structured electrically conducting polymer particles based on the difference in comonomer reactivity. The morphology and the surface and bulk chemistry of poly(pyrrole-co-(1-(2-carboxyethyl)pyrrole)) (PPy-co-PPyCOOH) particles formed at different reaction times were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and total elemental analysis. The particles were found to be formed by a shell composed of the less conductive but functional PPyCOOH homopolymer, and a core made of the PPy dominated PPy-co-PPyCOOH copolymer of high conductivity. Human serum albumin antibody (anti-HSA) as a model molecule was covalently immobilized onto the particle surface and proven to be reactive to HSA. A five-step schema based on a novel reactivity-driven mechanism was proposed to explain the formation of the core-shell structure. This new strategy therefore provides a simple and general route to prepare core-shell conductive particles with a functional surface, based on the reactivity of comonomers.