A step-wise self-assembly approach in preparation of multi-responsive poly(styrene-co-methyl methacrylate) nanoparticles containing spiropyran

A ratiometric fluorescent probe based on spiropyran in situ switching for tracking dynamic changes of lysosomal autophagy and anticounterfeiting

Autophagy is the controlled breakdown of cellular components that dysfunctional or nonessential, and the decomposition products are further recycled and synthesized for the normal physiological activities of cells. Lysosomal autophagy has been implicated in cancer, neurological disorders, Parkinson's disease, etc. Therefore, it is necessary to develop a fluorescent probe that can clearly describe the process of lysosomal autophagy. However, there are currently limited fluorescent probes for ratiometric monitoring of the autophagic process in dual channels. To solve this problem, a fluorescent probe based on spiropyran with lysosomal targeting and pH response for ratiometric monitoring the autophagy process of lysosomes were designed. The sensitive response of the probe to pH in vitro was verified by UV and fluorescence spectrum tests. Meanwhile, the probe demonstrated the ability to monitor the intracellular pH fluctuations. In addition, the application of Lyso-SD in the field of anti-counterfeiting has been proposed based on the obvious photoluminescence ability of Lyso-SD under UV irradiation.

RAFT-mediated polymerization-induced self-assembly (RAFT-PISA): current status and future directions

Polymerization-induced self-assembly (PISA) combines polymerization and self-assembly in a single step with distinct efficiency that has set it apart from the conventional solution self-assembly processes. PISA holds great promise for large-scale production, not only because of its efficient process for producing nano/micro-particles with high solid content, but also thanks to the facile control over the particle size and morphology. Since its invention, many research groups around the world have developed new and creative approaches to broaden the scope of PISA initiations, morphologies and applications, etc. The growing interest in PISA is certainly reflected in the increasing number of publications over the past few years, and in this review, we aim to summarize these recent advances in the emerging aspects of RAFT-mediated PISA. These include (1) non-thermal initiation processes, such as photo-, enzyme-, redox- and ultrasound-initiation; the achievements of (2) high-order structures, (3) hybrid materials and (4) stimuli-responsive nano-objects by design and adopting new monomers and new processes; (5) the efforts in the realization of upscale production by utilization of high throughput technologies, and finally the (6) applications of current PISA nano-objects in different fields and (7) its future directions.

Photoluminescent Nanoinks with Multilevel Security for Quick Authentication of Encoded Optical Tags by Sunlight: Effective Physicochemical Parameters on Responsivity, Printability, and Brightness

Investigation of developed photoactive security inks and anticounterfeiting technologies in recent years indicates significant challenges for future of this research area, such as increase of security, fast responsivity, and facile authentication. Here, amine-functionalized latex nanoparticles were synthesized by emulsion copolymerization of methyl methacrylate (MMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA). Size of the latex nanoparticles was increased as a function of poly(dimethylaminoethyl acrylate) (PDMAEMA) contents, and also a decrease of particle size was obtained in response to an increase of temperature from 25 to 70 °C, above the lower critical solution temperature (LCST) of PDMAEMA. Surface physical modification of the functional latex nanoparticle with spiropyran photoswitches led to the development of anticounterfeiting nanoinks that have multilevel security and photochromic/fluorescence properties with a higher intensity and also brightness. The photoluminescent nanoinks were made of spiropyran latex nanoparticles and used for printing of the encoded optical security tags on cellulosic papers and banknotes. The results displayed that an increase of the particle size above 100 nm and an increase of the PDMAEMA contents led to a remarkable decrease of printability, fluorescent emission, brightness, intensity of photochromism, and also resolution of the printed security tags. As a significant advantage of the developed security inks, the printed security tags could be authenticated easily and fast upon sunlight irradiation by means of photochromism. The responsivity of encoded tags from the invisible to visible state is immediate upon sunlight irradiation for some seconds, whose intensity of coloration is appropriate and detectable clearly by naked eyes. The security anticounterfeiting inks based on spiropyran with multilevel security have been reported for the first time for applying in printing of encoded security tags on cellulosic papers, banknotes, and other documents, where the printed marks are detectable on sunlight exposure.

Achieving enhanced solid-state photochromism and mechanochromism by introducing a rigid steric hindrance group

For photochromic molecules, effective isomerization usually requires conformational freedom, which is usually unavailable under solvent-free conditions. In this work, we report a new method, which can realize the reversible switching of spiropyran molecules by introducing a rigid aromatic ring group and this method can provide the required free volume to transform from a closed-ring to an open-ring form. This new molecule can quickly change color in the solid state under ultraviolet light, and can be erased after being heated at 60 °C for about 5 minutes. Furthermore, this new compound presents mechanochromicity when a mechanical force is applied. What is more, it can be used for at least 30 cycles of print-erase operations without apparent fatigue. This new molecule exhibits improved photochromic and anti-fatigue properties in the solid state, which can promote its application in both ultraviolet printing and anti-counterfeiting materials.

Impact of Poly (Styrene-Acrylic Acid) Latex Nanoparticles on Colorectal and Cervical Cancer Cells

Polymer nanoparticles are a promising approach for cancer treatment and detection, due to their biocompatibility, biodegradability, targeting capabilities, capacity for drug loading and long blood circulation time. This study aims to evaluate the impact of poly (styrene–acrylic acid) latex particles on colorectal and cervical cancer cells for anti-tumor efficiency. Latex particles were synthesized by a surfactant-free radical emulsion polymerization process and the obtained polymer particles were characterized in terms of size, size distribution, morphology using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and electrokinetic property (i.e., zeta potential). Human colorectal and cervical cancer, and normal cell lines, were then treated with different concentrations of poly (styrene–acrylic acid) latex particles. The cell morphology changes were pointed out using an optical microscope and the nanoparticles’ (NPs) cell cytotoxicity was evaluated using MTT assay. The obtained results showed that poly (styrene–acrylic acid) latex particles are effective against colorectal and cervical cancer cells if treated with an appropriate particle concentration for 48 h. In addition, it showed that normal cells are the least affected by this treatment. This indicates that these NPs are safe as a drug delivery carrier when used at a low concentration.

Chitosan nanobeads loaded with Biginelli hybrids as cell-selective toxicity systems with a homogeneous distribution of the cell cycle in cancer treatment

Tetrahydropyrimidines are a class of azaheterocycles, also called Biginelli hybrids (obtained from the Biginelli reaction), that have attracted an enormous interest in the medicinal chemistry community in recent years, due to a broad biological activity, such as anticancer, antiviral, anti-inflammatory, antidiabetic, antituberculosis activities, etc. According to SciFinder®, more than 70 000 different Biginelli-like compounds have been covered in publications. However, although the Biginelli reaction can yield a large number of compounds with a broad range of activities, none of them have been captured in a carrier. In this study, chitosan-based (Ch) nanoparticles (NPs) containing three different molecules (Biginelli hybrids) were developed and tested for the first time as simple and promising vehicles for anticancer Biginelli-based drugs. The key features of NPs, such as size, surface morphology, drug encapsulation efficiency, and in vitro release were systematically investigated. Rather weak cell selectivity of pure Biginelli hybrids (A–C) to selected cancer cell lines has improved and this has been accompanied with two-to-four times stronger cytotoxic effect of A–C loaded Ch NPs, with a triple reduction in toxicity to healthy cells (MRC-5). It has been observed that the examined NPs induce apoptosis. The cell cycle analysis has confirmed the influence of A-loaded Ch (A-Ch), B-loaded Ch (B-Ch), and C-loaded Ch (C-Ch) on the cell cycle distribution, which was homogenously affected. This is the difference with regard to the effect of A, B, and C on the cell cycle. It has been established that the increased selectivity and antitumor activity of NPs are related to the presence of the carrier.

Chitosan nanoparticles containing tetrahydropyrimidines were developed and tested for the first time as simple and promising vehicles for anticancer Biginelli-based drugs.

Functional Polymers and Polymer-Dye Composites for Food Sensing

The sensitive, safe, and portable detection of food spoilage is becoming unprecedentedly important because it is closely related to the public health and economic development, particularly given the globalization of food supply chain. However, the existing approaches for food monitoring are still limited to meet these requirements. To address this challenge, much research has been done to develop an ideal food sensor that can indicate food quality in real-time in a sensitive and reliable way. So far, many sensors such as time-temperature indicators, smart trademarks, colorimetric tags, electronic noses, and electronic tongues, have been developed and even commercialized. In this feature article, the recent progress of food sensors based on functional polymers, including the molecular design of polymer structures, sensing mechanisms, and relevant processing techniques to fabricate a variety of food sensor devices is reviewed.

Light-, temperature-, and pH-responsive micellar assemblies of spiropyran-initiated amphiphilic block copolymers: Kinetics of photochromism, responsiveness, and smart drug delivery

Multi-responsive polymer assemblies are a significant class of smart polymers with potential applications in drug-delivery and gen-delivery systems. Poly(dimethylaminoethyl methacrylate) (PDMAEMA) is among the most applicable multi-responsive polymers that changes its physical and chemical properties in response to temperature, pH, and CO₂. Herein, different types of light-, temperature-, pH-, and CO₂-responsive polymer assemblies were developed based on multi-responsive PDMAEMA and hydrophobic poly(methyl methacrylate) blocks. In addition, spiropyran was incorporated at the chain ends by using spiropyran-initiated atom transfer radical polymerization method. Novel smart drug-delivery systems were developed by self-assembly of these amphiphilic block copolymers to micellar morphologies in aqueous media. Dynamic light scattering results showed that size of the polymer assemblies changed in response to pH variations (from 5 to 9), temperature changes (above the lower critical solution temperature (LCST) of PDMAEMA), and also UV light irradiation (wavelength of 365 nm). The LCST of PPDMAEMA showed a shift from 53 to 60 °C after isomerization of the SP to MC form, as a result of increase of polarity and water-solubility. The PDMAEMA block results in responsivity of the prepared copolymer assemblies to CO₂, which display pH variation from 8-8.6 to 5-6 after 2 min of CO₂ gas bubbling. All the multi-responsive micellar polymer assemblies showed various loading capacities and release profiles, and the DOX release can be controlled by pH, temperature, and light. The release efficiency is reached to 60-85% at pH 5.3, 80-90% at temperatures higher than the LCST of PDMAEMA (60 °C), and also 90-100% under UV light irradiation after 48 h. In summary, the multi-responsive polymer assemblies based on amphiphilic block copolymers containing spiropyran chain end groups in the current study have potential applications in smart drug-delivery systems, and offer controlling over the drug-release by different triggers, such as light irradiation, pH variation, and temperature change. A very low concentration of spiropyran molecules (one per polymer chain) showed light-controlling of drug-release from the assemblies with high efficiencies.

Length of the Stabilizing Zwitterionic Poly(2-methacryloyloxyethyl phosphorycholine) Block Influences the Activity of the Conjugated Arsenic Drug in Drug-Directed Polymerization-Induced Self-Assembly Particles

We report on the synthesis of poly(2-methacryloyloxyethyl phosphorycholine-co-PENAO)-block-poly(methyl methacrylate) core-shell nanoparticles which carry different chain lengths of zwitterionic 2-methacryloyloxyethyl phosphorycholine (MPC) on a nanoparticle surface. The particles, 30-40 nm in size, were readily obtained by polymerization-induced self-assembly (PISA) of the corresponding arsenic-based MPC polymers as the stabilizer block and methyl methacrylate (MMA) as the core-forming block. Zwitterionic nanoparticles are ideal candidates for protein-repellent materials. Herein, we show how the decrease of zwitterionic chain lengths tunes the reactivity and cytotoxicity of the organoarsenical anticancer drug PENAO (4-(N-(S-penicillaminylacetyl)amino) phenylarsonous acid). More cytotoxic (5-fold) nanoparticles were obtained when the MPC chain lengths were condensed from 37 to 13 repeating units. To gain a better understanding of the behavior of the drug-directed PISA particles, small-angle neutron scattering (SANS) experiments were conducted, evidencing that having PENAO located in the hydrophilic building block indeed influences the physiochemical micelle structure in terms of core radius (r_core), SLD, shell thickness, and aggregation number.

The light-controlling of temperature-responsivity in stimuli-responsive polymers

Light-controlling of phase separation in temperature-responsive polymer solutions by using light-responsive materials for reversible controlling physical and chemical properties of the media with an out-of-system stimulus with tunable intensity.

Light-Induced Aggregation and Disaggregation of Stimuli-Responsive Latex Particles Depending on Spiropyran Concentration: Kinetics of Photochromism and Investigation of Reversible Photopatterning

Light-controlling the physical and chemical properties of smart polymers by using photochromic compounds has been an interesting research subject. Incorporation of spiropyran (SP) on the surface of particles can induce photoswitchable aggregation/disaggregation to stimuli-responsive colloids. Herein, we developed a novel class of stimuli-responsive latex particles bearing SP with different contents (0, 0.5, 1, 3, and 5 wt %) by semicontinuous emulsifier-free emulsion copolymerization, which is able to change the particle size by light-induced aggregation/disaggregation in response to ultraviolet (UV) irradiation and visible light. The scanning electron microscopy images revealed the spherical morphology of the latex particles, with the size in the range of 400-900 nm. Light-induced aggregation and disaggregation of stimuli-responsive latex particles were investigated by dynamic light scattering and also confirmed by variation of transmittance during UV illumination time using ultraviolet-visible spectroscopy. The range of the light-induced shift in the particle size is about 200-600 nm (depending on the concentration of SP), where the reduction of transmittance upon UV irradiation (and conversely upon visible light) confirms the ability of latex particles for displaying reversible photoswitchable aggregation/disaggregation and also light-controlling the particle size. The kinetics of SP to merocyanine (MC) and MC to SP isomerizations were experimentally investigated and fitted by exponential equations. The photochromic latexes displayed remarkable photoswitchability and photofatigue resistant properties under alternating UV and visible light irradiation cycles. Additionally, these stimuli-responsive latexes displayed potential applications such as anticounterfeiting inks in erasable and rewritable writings on cellulosic papers for increasing safety in security documents.

Rewritable Anticounterfeiting Polymer Inks Based on Functionalized Stimuli-Responsive Latex Particles Containing Spiropyran Photoswitches: Reversible Photopatterning and Security Marking

Increase of safety in security documents by using anticounterfeiting inks based on fluorochromic and photochromic compounds has attracted a great deal of attention in the recent years. Herein, we developed novel functionalized stimuli-responsive latex particles containing spiropyran (1 wt %) by semicontinuous emulsifier-free emulsion polymerization, which are usable as anticounterfeiting inks for marking on security documents and also photopatterning on cellulosic papers. The size and morphology of the latex particles were characterized by scanning electron microscopy and dynamic light scattering and their functionality was characterized by Fourier-transform infrared spectroscopy. All the stimuli-responsive latexes are composed of spherical particles with different hydroxyl, epoxy, and carboxylic acid functional groups, and the size of the particles varies in the range of 400-900 nm. Additionally, the latex particles undergo a remarkable light-induced size variation (aggregation-disaggregation) upon UV illumination (365 nm), depending on the functional group type, as a result of π-π stacking interactions and also electrostatic attractions between the different particles. The photochromic behavior, kinetics of the SP ⇌ MC isomerization, photoswitchability, and photofatigue-resistant characteristics of the prepared latexes were extensively investigated. The results display that the photochromic behavior and SP ⇌ MC isomerization can significantly be influenced by the polar interactions between the functional groups and MC molecules. As a novel application, the prepared stimuli-responsive latexes were used as anticounterfeiting inks for writing on cellulosic paper and also security marking on several monies, where the written phrase displayed red fluorescence emission and coloration under and after UV illumination (365 nm), respectively. Additionally, the latexes were sprayed on cellulosic papers to prepare stimuli-responsive papers for investigation of their photopatterning ability under UV irradiation and different masking. The presence of functional groups and large particle sizes are the main effective factors for stabilization of the latex particles on cellulosic papers. This is the first report on application of functionalized stimuli-responsive latex particles containing spiropyran as anticounterfeiting inks for security marking and photopatterning on cellulosic papers, directly and without using further additives.

Thermo/pH dual-responsive core–shell particles for apatinib/doxorubicin controlled release: preparation, characterization and biodistribution

Schematic representation of the structure and functioning mechanism of DD particles.