Capture and Release of Cancer Cells Through Smart Bioelectronics

Noninvasive collection of target cells such as circulating tumor cells (CTCs) is crucial for biology and medicine research. Conventional methods of cell collection are often complex, requiring either size-dependent sorting or invasive enzymatic reactions. Here, we show the development of a functional polymer film, which combines the thermoresponsive poly(N-isopropylacrylamide) and the conducting poly(3,4-ethylenedioxythiopene)/poly(styrene sulfonate), and its use for the capture and release of CTCs. When coated onto microfabricated gold electrodes, the proposed polymer films are capable of noninvasively capturing and controllably releasing cells while, at the same time, monitoring these processes with conventional electrical measurements.

Microfluidics and materials for smart water monitoring: A review

Water quality monitoring of drinking, waste, fresh and seawaters is of great importance to ensure safety and wellbeing for humans, fauna and flora. Researchers are developing robust water monitoring microfluidic devices but, the delivery of a cost-effective, commercially available platform has not yet been achieved. Conventional water monitoring is mainly based on laboratory instruments or sophisticated and expensive handheld probes for on-site analysis, both requiring trained personnel and being time-consuming. As an alternative, microfluidics has emerged as a powerful tool with the capacity to replace conventional analytical systems. Nevertheless, microfluidic devices largely use conventional pumps and valves for operation and electronics for sensing, that increment the dimensions and cost of the final platforms, reducing their commercialization perspectives. In this review, we critically analyze the characteristics of conventional microfluidic devices for water monitoring, focusing on different water sources (drinking, waste, fresh and seawaters), and their application in commercial products. Moreover, we introduce the revolutionary concept of using functional materials such as hydrogels, poly(ionic liquid) hydrogels and ionogels as alternatives to conventional fluidic handling and sensing tools, for water monitoring in microfluidic devices.

An electroactive and thermo-responsive material for the capture and release of cells

Non-invasive collection of target cells is crucial for research in biology and medicine. In this work, we combine a thermo-responsive material, poly(N-isopropylacrylamide), with an electroactive material, poly(3,4-ethylene-dioxythiopene):poly(styrene sulfonate), to generate a smart and conductive copolymer for the label-free and non-invasive detection of the capture and release of cells on gold electrodes by electrochemical impedance spectroscopy. The copolymer is functionalized with fibronectin to capture tumor cells, and undergoes a conformational change in response to temperature, causing the release of cells. Simultaneously, the copolymer acts as a sensor, monitoring the capture and release of cancer cells by electrochemical impedance spectroscopy. This platform has the potential to play a role in top-notch label-free electrical monitoring of human cells in clinical settings.

Efficacy of several additives to modulate the phase behavior of biomedical polymers: A comprehensive and comparative outlook

Several new classes of polymeric materials are being introduced with unique properties. Thermoresponsive polymers (TRPs) are one of the most fascinating and emerging class of biomaterials in biomedical research. The design of TRPs with good response to temperature and its ability to exhibit coil to globular transition behavior near to physiological temperature made them more promising materials in the field of biomaterials and biomedicines. Instead of numerous studies on TRPs, the mechanistic interplay among several additives and TRPs is still not understood clearly and completely. The lack of complete understanding of biomolecular interactions of various additives with TRPs is limiting their applications in interdisciplinary science as well as pharmaceutical industry. There is a great need to provide a collective and comprehensive information of various additives and their behavior on widely accepted biopolymers, TRPs such as poly(N-isopropylacrylamide) (PNIPAM), poly(vinyl methyl ether) (PVME), poly(N-vinylcaprolactum) (PVCL) and poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (PEG-PPG-PEG) in aqueous solution. Obviously, as the literature on the influence of various additives on TRPs is very vast, therefore we focus our review only on these four selected TRPs. Additives such as polyols, methylamines, surfactants and denaturants basically made the significant changes in water structure associated to polymer via their entropy variation which is the direct influence of their directly or indirectly binding abilities. Eventually, this review addresses a brief overview of the most recent literature of applications based phase behavior of four selected TRPs in response to external stimuli. The work enhances the knowledge for use of TRPs in the advanced development of drug delivery system and in many more pharmaceutical applications. These kinds of studies provide powerful impact in exploring the utility range of polymeric materials in various field of science.

Tuning of volume phase transition for poly(N-isopropylacrylamide) ionogels by copolymerization with solvatophilic monomers

Ionogels are crosslinked polymer networks that swell in ionic liquids (ILs) and exhibit high conductivity and chemical stability. Combined with a representative thermally responsive polymer, poly(N-isopropylacrylamide) (PNIPAm), previously studied ionogels fulfilled the requirements for smart responsive materials, but their transition temperature in hydrophobic ILs exceeded that which could be used for practical applications. In this study, we prepared transition temperature tunable ionogels via copolymerization of NIPAm with solvatophilic N,N'-diethylacrylamide (NDEAm). The hydrophobic diethyl moiety in NDEAm promoted ionogel solvatophilicity toward the IL, resulting in a larger swelling ratio, lower volume phase transition temperature, and narrower transition range with increase in NDEAm content in the prepared ionogels. Based on these fundamental observations, ionogels that exhibit a volume phase transition near room temperature were prepared. We also studied the swelling and deswelling kinetics of the prepared ionogels, revealing that the deswelling rate is much slower than swelling due to the formation of a dense skin layer on the ionogel surface.

Influence of additives on thermoresponsive polymers in aqueous media: a case study of poly(N-isopropylacrylamide)

Thermoresponsive polymers (TRPs) in different solvent media have been studied over a long period and are important from both scientific and technical points of view.

Mechanically Tunable, Readily Processable Ion Gels by Self-Assembly of Block Copolymers in Ionic Liquids

Room temperature ionic liquids are of great interest for many advanced applications, due to the combination of attractive physical properties with essentially unlimited tunability of chemical structure. High chemical and thermal stability, favorable ionic conductivity, and complete nonvolatility are just some of the most important physical characteristics that make ionic liquids promising candidates for emerging technologies. Examples include separation membranes, actuators, polymer gel electrolytes, supercapacitors, ion batteries, fuel cell membranes, sensors, printable plastic electronics, and flexible displays. However, in these and other applications, it is essential to solidify the ionic liquid, while retaining the liquid state properties of interest. A broadly applicable solidification strategy relies on gelation by addition of suitable triblock copolymers with the ABA architecture, producing ion gels or ionogels. In this paradigm, the A end blocks are immiscible with the ionic liquid, and consequently self-assemble into micellar cores, while some fraction of the well-solvated B midblocks bridge between micelles, forming a percolating network. The chemical structures of the A and B repeat units, the molar mass of the blocks, and the concentration of the copolymer in the ionic liquid are all independently tunable to attain desired property combinations. In particular, the modulus of the resulting ion gel can be readily varied between 100 Pa and 1 MPa, with little sacrifice of the transport properties of the ionic liquid, such as ionic conductivity or gas diffusivity. Suitable A blocks can impart thermoreversible gelation (with solidification either on heating or cooling) or even photoreversible gelation. By virtue of the nonvolatility of ionic liquids, a wide range of processing strategies can be employed directly to prepare ion gels in thin or thick film forms, including solvent casting, spin coating, aerosol jet printing, photopatterning, and transfer printing. For higher modulus ion gels it is even possible to employ a manual "cut and stick" strategy for easy device fabrication. Ion gels prepared from common triblock copolymers, for example, with A = polystyrene and B = poly(ethylene oxide) or poly(methyl methacrylate), in imidazolium based ionic liquids provide exceptional performance in membranes for separating CO₂ from N₂ or CH₄. The same materials also are the best available gate dielectrics for printed plastic electronics, because their high capacitance endows organic transistors with milliamp output currents for sub-1 V applied bias, with switching speeds that can go well beyond 100 kHz, while being amenable to large area roll-to-roll printing. Incorporation of well-designed electroluminescent (e.g., Ru(bpy)₃-based) or electrochromic (e.g., viologen-based) moieties into ion gels held between transparent electrodes yields flexible color displays operating with sub-1 V dc inputs.

Poly(Ionic Liquid) Semi-Interpenetrating Network Multi-Responsive Hydrogels

Herein we describe poly(ionic liquid) hydrogel actuators that are capable of responding to multiple stimuli, namely temperature, ionic strength and white light irradiation. Using two starting materials, a crosslinked poly ionic liquid (PIL) and a linear poly(N-isopropylacrylamide-co-spiropyran-co-acrylic acid), several semi-interpenetrating (sIPN) hydrogels were synthesised. The dimensions of hydrogels discs were measured before and after applying the stimuli, to quantify their response. Samples composed of 100% crosslinked PIL alone showed an average area reduction value of ~53% when the temperature was raised from 20 °C to 70 °C, ~24% when immersed in 1% w/w NaF salt solution and no observable photo-response. In comparison, sIPNs containing 300% w/w linear polymer showed an average area reduction of ~45% when the temperature was raised from 20 °C to 70 °C, ~36% when immersed in 1% NaF w/w salt solution and ~10% after 30 min exposure to white light irradiation, respectively. Moreover, by varying the content of the linear component, fine-control over the photo-, thermo- and salt response, swelling-deswelling rate and mechanical properties of the resulting sIPN was achieved.

Effect of surfactants on the swelling behaviors of thermosensitive hydrogels: applicability of the generalized Langmuir isotherm

Herein, the surfactant effects on the thermosensitive swelling behaviors of nanometer-sized particle gels are investigated.

Solvato-morphologically controlled, reversible NIPAAm hydrogel photoactuators

Herein we demonstrate the ability to control the swelling and photo-induced shrinking kinetics of hydrogels by changing the polymerisation solvent.

Recent advances in polymeric micelles for anti-cancer drug delivery

Block co-polymeric micelles receive increased attention due to their ability to load therapeutics, deliver the cargo to the site of action, improve the pharmacokinetic of the loaded drug and reduce off-target cytotoxicity. While polymeric micelles can be developed with improved drug loading capabilities by modulating hydrophobicity and hydrophilicity of the micelle forming block co-polymers, they can also be successfully cancer targeted by surface modifying with tumor-homing ligands. However, maintenance of the integrity of the self-assembled system in the circulation and disassembly for drug release at the site of drug action remain a challenge. Therefore, stimuli-responsive polymeric micelles for on demand drug delivery with minimal off-target effect has been developed and extensively investigated to assess their sensitivity. This review focuses on discussing various polymeric micelles currently utilized for the delivery of chemotherapeutic drugs. Designs of various stimuli-sensitive micelles that are able to control drug release in response to specific stimuli, either endogenous or exogenous have been delineated.

Two-dimensional photonic crystal chemical and biomolecular sensors

We review recent progress in the development of two-dimensional (2-D) photonic crystal (PC) materials for chemical and biological sensing applications. Self-assembly methods were developed in our laboratory to fabricate 2-D particle array monolayers on mercury and water surfaces. These hexagonal arrays strongly forward Bragg diffract light to report on their array spacings. By embedding these 2-D arrays onto responsive hydrogel surfaces, 2-D PC sensing materials can be fabricated. The 2-D PC sensors utilize responsive polymer hydrogels that are chemically functionalized to show volume phase transitions in selective response to particular chemical species. Novel hydrogels were also developed in our laboratory by cross-linking proteins while preserving their native structures to maintain their selective binding affinities. The volume phase transitions swell or shrink the hydrogels, which alter their 2-D array spacings, and shift their diffraction wavelengths. These shifts can be visually detected or spectrally measured. These 2-D PC sensing materials have been used for the detection of many analytes, such as pH, surfactants, metal ions, proteins, anionic drugs, and ammonia. We are exploring the use of organogels that use low vapor pressure ionic liquids as their mobile phases for sensing atmospheric analytes.

Influence of imidazolium based green solvents on volume phase transition temperature of crosslinked poly(N-isopropylacrylamide-co-acrylic acid) hydrogel

The volume phase transition temperature (VPTT) of crosslinked poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM-co-AA) hydrogel in water in the presence of five imidazolium based ionic liquids (ILs) was studied. The VPTT of PNIPAM-co-AA hydrogel can be modulated to different extents by the addition of different amounts of ILs. The modulations in VPTT values can be attributed to the IL-induced alterations in hydrophobic, hydrophilic and hydrogen bonding interactions of PNIPAM-co-AA hydrogel with the neighboring solvent and molecular chains. The influence of ILs having a common cation, 1-butyl-3-methylimidazolium cation ([Bmim]) and different anions, such as iodide (I-), tetrafluoroborate (BF4-), chloride (Cl-), acetate (CH3COO-) and hydrogen sulfate (HSO4-), on the phase transition of PNIPAM-co-AA hydrogel was monitored by the aid of differential scanning calorimetry (DSC), dynamic light scattering (DLS) and Fourier transform infrared (FT-IR) spectroscopy. Furthermore, the interfacial properties between aqueous IL and polymer surface were scrutinized with the help of contact angle (CA) measurements. The overall specific ranking of ILs in preserving the hydration layer around the PNIPAM-co-AA hydrogel in water was [Bmim][I]>[Bmim][BF4]>[Bmim][Cl]>[Bmim][Ac]>[Bmim][HSO4]. The trend of these ILs followed the well-known Hofmeister series. Interestingly, the PNIPAM-co-AA hydrogel in water shows abnormal salting-out property in the presence of [Bmim][BF4] at higher concentration and this abnormal behavior can be explained based on the lack of sufficient binding sites on the macromolecule for higher number of [Bmim][BF4] at a higher concentration.