Droplet-based microfluidics: an efficient high-throughput portable system for cell encapsulation

One of the goals of tissue engineering and regenerative medicine is restoring primary living tissue function by manufacturing a 3D microenvironment. One of the main challenges is protecting implanted non-autologous cells or tissues from the host immune system. Cell encapsulation has emerged as a promising technique for this purpose. It involves entrapping cells in biocompatible and semi-permeable microcarriers made from natural or synthetic polymers that regulate the release of cellular secretions. In recent years, droplet-based microfluidic systems have emerged as powerful tools for cell encapsulation in tissue engineering and regenerative medicine. These systems offer precise control over droplet size, composition, and functionality, allowing for creating of microenvironments that closely mimic native tissue. Droplet-based microfluidic systems have extensive applications in biotechnology, medical diagnosis, and drug discovery. This review summarises the recent developments in droplet-based microfluidic systems and cell encapsulation techniques, as well as their applications, advantages, and challenges in biology and medicine. The integration of these technologies has the potential to revolutionise tissue engineering and regenerative medicine by providing a precise and controlled microenvironment for cell growth and differentiation. By overcoming the immune system's challenges and enabling the release of cellular secretions, these technologies hold great promise for the future of regenerative medicine.

Light-Driven Spatiotemporal Pickering Emulsion Droplet Manipulation Enabled by Plasmonic Hybrid Microgels

The past decades have witnessed the development of various stimuli-responsive materials with tailored functionalities, enabling droplet manipulation through external force fields. Among different strategies, light exhibits excellent flexibility for contactless control of droplets, particularly in three-dimensional space. Here, we present a facile synthesis of plasmonic hybrid microgels based on the electrostatic heterocoagulation between cationic microgels and anionic Au nanoparticles. The hybrid microgels are effective stabilizers of oil-in-water Pickering emulsions. In addition, the laser irradiation on Au nanoparticles creats a "cascade effect" to thermally responsive microgels, which triggers a change in microgel wettability, resulting in microgel desorption and emulsion destabilization. More importantly, the localized heating generated by a focused laser induces the generation of a vapor bubble inside oil droplets, leading to the formation of a novel air-in-oil-in-water (A/O/W) emulsion. These A/O/W droplets are able to mimic natural microswimmers in an aqueous environment by tracking the motion of a laser spot, thus achieving on-demand droplet merging and chemical communication between isolated droplets. Such proposed systems are expected to extend the applications of microgel-stabilized Pickering emulsions for substance transport, programmed release and controlled catalytic reactions.

Biodegradable redox sensitive chitosan based microgels for potential agriculture application

In this work, we report redox sensitive, 2,3-dihydroxybenzoic acid (DH) functionalized chitosan/stearic acid microgels (DH-ChSt MGs) for controlled delivery of insecticide and capturing of heavy metal ions. DH-ChSt MGs (≈146 nm) are prepared by disulfide crosslinking of SH functionalized chitosan and stearic acid rendering them biodegradable. DH-ChSt MGs exhibit high loading (≈8 %) and encapsulation (≈85 %) efficiency for imidacloprid insecticide, and offer its prolonged release (≈75 % after 133 h) under reducing conditions. Functionalization with DH provides enhanced foliar adhesion on pea leaves. DH-ChSt MGs also bind Fe³⁺ very efficiently due to the strong chelation of Fe³⁺ by DH, offering the opportunity of supplying Fe³⁺ nutrient for plant care. MTT assay results using different cells confirm that DH-ChSt MGs are nontoxic up to the experimental concentration of 120 μg/mL. Additionally, reduced DH-ChSt MGs having free thiol groups are also capable of binding heavy metal ions, thus presenting the reported formulation as a promising platform for agriculture application.

Gold Half-Shell-Coated Paclitaxel-Loaded PLGA Nanoparticles for the Targeted Chemo-Photothermal Treatment of Cancer

Conventional cancer therapies suffer from nonspecificity, drug resistance, and a poor bioavailability, which trigger severe side effects. To overcome these disadvantages, in this study, we designed and evaluated the in vitro potential of paclitaxel-loaded, PLGA-gold, half-shell nanoparticles (PTX-PLGA/Au-HS NPs) conjugated with cyclo(Arg-Gly-Asp-Phe-Lys) (cyRGDfk) as a targeted chemo-photothermal therapy system in HeLa and MDA-MB-231 cancer cells. A TEM analysis confirmed the successful gold half-shell structure formation. High-performance liquid chromatography showed an encapsulation efficiency of the paclitaxel inside nanoparticles of more than 90%. In the release study, an initial burst release of about 20% in the first 24 h was observed, followed by a sustained drug release for a period as long as 10 days, reaching values of about 92% and 49% for NPs with and without near infrared laser irradiation. In in vitro cell internalization studies, targeted nanoparticles showed a higher accumulation than nontargeted nanoparticles, possibly through a specific interaction of the cyRGDfk with their homologous receptors, the ανβ3 y ανβ5 integrins on the cell surface. Compared with chemotherapy or photothermal treatment alone, the combined treatment demonstrated a synergistic effect, reducing the cell viability to 23% for the HeLa cells and 31% for the MDA-MB-231 cells. Thus, our results indicate that these multifuncional nanoparticles can be considered to be a promising targeted chemo-photothermal therapy system against cancer.

Dextran/eudragit S-100 based redox sensitive nanoparticles for colorectal cancer therapy

Herein, we present disulfide crosslinked dextran/eudragit S-100 nanoparticles (DEEU NPs) (≈55 nm) for colorectal cancer treatment. These redox environment sensitive DEEU NPs are synthesized by simple oxidation of thiolated polymers in air. This approach allows avoiding the use of any additional chemical crosslinker. These DEEU NPs have high encapsulation efficiency for the doxorubicin (DOX) model drug (≈95%). The prepared DEEU NPs are redox sensitive owing to disulfide units and exhibit ≈80% DOX release in the reducing environment of GSH. Additionally, DOX-DEEU NPs display enhanced cytotoxicity for HCT116 cancer cells as compared to free DOX. Annexin V staining results also support the higher anticancer efficiency of DOX-DEEU NPs via induction of apoptosis. In vivo biodistribution results demonstrate that DEEU NPs can remain in the colon region for up to 24 hours. These results indicate that DEEU NPs can act as a promising platform for colorectal cancer treatment.

Biodegradable dual stimuli responsive alginate based microgels for controlled agrochemicals release and soil remediation

To meet the growing food demand of increasing world population while reducing the harmful environmental effects of agrochemicals, development of smart nanoformulation is of prime importance. Herein, dual stimuli responsive alginate based microgels (OAlgDP MGs) (≈160 nm) are developed for controlled release of agrochemicals and soil remediation. These microgels are prepared using octyl amine functionalized alginate which is crosslinked by 3, 3'-dithiopropionohydrazide crosslinker providing both hydrazone and disulfide bonds in microgels network. OAlgDP MGs are further loaded with hydrophobic diuron herbicide displaying ≈85 % encapsulation efficiency. Sustained release of diuron is obtained in 2 mM GSH (≈100 % after 380 h) and at pH 5 (≈72 % after 240 h). Furthermore, OAlgDP MGs are nontoxic up to 150 μg/mL against HEK293T cells while their reduced form is capable of capturing the heavy metal ions (Cu²⁺ and Hg²⁺) showing the potential of the developed system for moving toward sustainable agriculture.

Swift catalytic reduction of hazardous pollutants by new generation microgels

In this manuscript, we report for the first time a new generation microgel synthesis without using any divinyl functionalized cross-linker. A new generation less crosslinked microgel structure has been achieved by optimizing the amount of N-hydroxy methyl acrylamide (NHMA) and using a fixed amount of styrene (St), acrylic acid (AA) and N-vinyl pyrrolidone (NVP) via a free radical emulsion solution polymerization technique. Poly(NHMA) works as a hydrophilic as well as a crosslinking agent. Furthermore, microgels have been upgraded into a composite by incorporation of Ag nanoparticles for catalytic reduction applications. Microgels and their composites have been characterized by EDAX, FT-IR, particle size analyzer, SEM, TEM, TGA, UV-vis spectroscopy and XRD. Methylene blue (MB) dye and p-nitrophenol (PNP) were chosen as model hazardous pollutants for catalytic reduction applications. Microgels efficiently adsorb both pollutants over the surface and microgel_Ag composites dramatically reduced both pollutants in the non-toxic form at room temperature by using smaller doses of NaBH₄.

A Biocompatible, pH-Sensitive, and Magnetically Separable Superparamagnetic Hydrogel Nanocomposite as an Efficient Platform for the Removal of Cationic Dyes in Wastewater Treatment

A series of environment-friendly cationic dye adsorbents, namely, pH-sensitive superparamagnetic hydrogel nanocomposite AA-VSA-P/SPIONs systems with different concentrations of superparamagnetic iron oxide nanoparticles (SPIONs; 1.2, 3.2, and 5.2 wt %), was synthesized by free-radical polymerization reaction using two pH-sensitive monomers, acrylic acid (AA) and vinylsulfonic acid (VSA), in an optimum ratio, in the presence of presynthesized SPIONs. The structural properties, thermal stability, and chemical configuration of AA-VSA-P/SPIONs systems with different weight percentages of SPIONs were characterized by XRD, TGA, Raman spectroscopy, and FTIR spectroscopy. The systems show substantial efficiency as dye adsorbents for removing cationic dyes (MB dye) from aqueous solution in neutral to alkaline medium. Further, these systems exhibit easy magnetic separation capabilities from aqueous solutions after dye adsorption, even for a very low weight percentage of SPIONs. The adsorption kinetics, mechanism, and isotherms of these systems were evaluated. The study suggests consistency with the pseudo-second-order kinetic model, following an intraparticle diffusion mechanism, where the heterogeneous surface of the system having different activation energies for adsorption plays the crucial role in dye adsorption via chemisorption for higher pH medium, which was further substantiated by excellent data fit with the Freundlich isotherm model. Biocompatibility and regeneration-ability studies establish the environment-friendliness and cost effectivity of the system.

Janus nanoparticles: an efficient intelligent modern nanostructure for eradicating cancer

In the modern age, the struggle to generate appropriate bio-based materials and nano-scaled colloidal particulates for developed application domains, has already resulted in remarkable attempts in the advancement of regulated size and shape, anisotropy, and characteristics of nanostructures. The bottom-up development strategies of components are among the most important science areas throughout nanotechnology, in which the designed building blocks are often utilized to generate novel structures by random self-assembly. In biomedical applications, Janus nanoparticles (JNPs) are necessary. This is due to their effective stimulus-responsive properties, tunable structure, biocompatibility, containing two surfaces with various hydrophobic characteristics and distinct functional groups. Featuring two parts with differing hydrophobicity has been the most critical aspect of the Janus amphiphilic particles. Development of JNPs has been afforded, using imaging agents (e.g. gold (AU) for photoacoustic imaging processing (PAI), silver for surface-enhanced Raman scattering (SERS), and Fe₃O₄ and MnO₂ to magnetic resonance imaging (MRI)). It is also to be mentioned that a number of other properties become salient - properties such as integration imaging factors into JNPs (like quantum dots, fluorescent dyes), multiple imaging methods for screening and diagnosis application can indeed be accomplished. Janus nanostructures have been promising platforms for bioengineering as therapeutic carriers, drug delivery vehicles, and biosensor equipment; they may also be employed for the transport of bioactive hydrophilic and hydrophobic materials. The main production approaches and major advancement of JNPs in the biomedical sector and cancer therapy will be described in this paper.

Temperature-enabled reversible "On/Off" switch-like hazardous herbicide picloram voltammetric sensor in agricultural and environmental samples based on thermo-responsive PVCL-tethered MWCNT@Au catalyst

Picloram (PCR), a vastly utilized chlorinated herbicide, is very stable in water and soil with severe ecological and health impacts. It is necessary to establish a fast and highly sensitive technique for accurately detecting trace level PCR in agricultural and environmental samples. We employed a temperature-responsive poly(N-vinylcaprolactam)-tethered multiwalled carbon nanotubes (MWCNT-PVCL) decorated gold nanoparticles (Au@MWCNT-PVCL) catalyst on the electrochemical sensor for the sensitive "On/Off" switch-like detection of PCR. The effect of temperature-sensitive catalyst surface chemistry on electrocatalytic activity was scrutinized. Results showed that the hydrophilic surface of PVCL at 25 °C (<lower critical solution temperature (LCST)) extended to bury the electroactive sites of Au nanoparticles and MWCNT, and the PCR unable to pass over the PVCL to achieve electron exchange process, signifying the "Off" state. Surface wettability of the prepared Au@MWCNT-PVCL then spontaneously switched its hydrophilic to hydrophobic surface one at 40 °C (>LCST) that immensely upgraded PCR oxidation on the catalyst in the electrochemical reaction, signifying the "On" state. The detection of the Au@MWCNT-PVCL modified electrode ranged from 0.02-183 μM with a low detection limit (LOD) of 1.5 nM at 40 °C toward PCR. The proposed sensor was successfully used to detect PCR in real agricultural and environmental samples.

Physicochemical aspects of inorganic nanoparticles stabilized in N-vinyl caprolactam based microgels for various applications

The vinyl caprolactam (VCL) based microgel system has become the center of great attention due to its versatile properties. Copolymerization of VCL with an ionic monomer imparts pH responsive properties into the microgel system in addition to thermo-sensitivity. Stimuli responsive behavior of VCL-based microgels makes them prospective and appealing candidates for practical applications covering the fields of drug delivery, catalysis and optical devices. In the last few years, VCL-based microgels have been used as microreactors and stabilizers for the synthesis and stabilization of inorganic nanoparticles to obtain hybrid microgels. The present review article provides a summary of the present-day progress of fabrication, stabilization, categorization and analysis of VCL-based microgels and their hybrids with different morphologies. The stimuli responsive properties and applications of VCL-based hybrid microgels have been reviewed critically. The remaining problems which need to be addressed have been pointed out for further advancement in this field.

Inhalable hybrid nanocarriers for respiratory disorders

Rapid advancements in the field of drug delivery lead to increased use of inhalable formulations as they are cost effective, noninvasive, and targeted and have less systemic side effects and above all better patient compliance. Development of inhalable hybrid systems has offered manifold advantages to this area of drug delivery. Inclusion of polymer and lipid, inorganic and organic substances, and metallic nanoparticles all of them aim to achieve codelivery of drugs which are incompatible in single phase systems. The recent progress in nanotechnology has gained momentum toward delivery of siRNA and miRNA and vaccines to the targeted site. The present work is an attempt to compile all the hybrid and inhalable systems to give readers an overview toward this delivery system as much more work is needed in this field to achieve better resolution of inflammatory disorders.

Size-Tailored Biocompatible FePt Nanoparticles for Dual T1/T2 Magnetic Resonance Imaging Contrast Enhancement

The development of new contrast agents (CAs) for magnetic resonance imaging (MRI) is of high interest, especially because of the increased concerns of patient safety and quick clearance of clinically used gadolinium and iron oxide-based CAs, respectively. Here, a two-step synthesis of superparamagnetic water-soluble iron platinum (FePt) nanoparticles (NPs) with core sizes between 2 and 8 nm for use as CAs in MRI is reported. First, wet-chemical organometallic NPs are synthesized by thermal decomposition in the presence of stabilizing oleic acid and oleylamine. Second, the hydrophobic NPs are coated with an amphiphilic polymer and transferred into aqueous media. Their magnetization values and relaxation rates exceed those published for CAs already used for clinical application. Their saturation magnetization increases with the core size to approximately 82 A·m²/kg_Fe. For 8 nm NPs, the T₂ relaxivity of approximately 221 (mM·s)^-1 is 5 times larger than that for the ferumoxides, and for 6 nm NPs, the T₁ relaxivity of approximately 12 (mM·s)^-1 is slightly higher than that of ultrasmall gadolinium oxide NPs. The 6 nm FePt NPs are identified as excellent CAs for both T₁ and T₂ imaging. Most importantly, because of their coating, significantly low cytotoxicity is achieved. FePt NPs prove to be a promising alternative to gadolinium and iron oxide NPs showing high-quality CA characteristics for both T₁- and T₂-weighted images.

Nanomechanics and Nanorheology of Microgels at Interfaces

The review addresses nanomechanics and nanorheology of stimuli responsive microgels adsorbed at an interface. In order to measure the mechanical properties on a local scale, an atomic force microscope is used. The tip presents an indenter with a radius of curvature of a few 10 s of nm. Static indentation experiments and dynamic studies with an excited cantilever are presented. The effect of several internal and external parameters on the mechanical properties is reviewed. The focus is on the correlation between the swelling abilities of the gels and their mechanical properties. Several results are surprising and show that the relationship is not as simple as one might expect.

Functional Microgels: Recent Advances in Their Biomedical Applications

Here, a spotlight is shown on aqueous microgel particles which exhibit a great potential for various biomedical applications such as drug delivery, cell imaging, and tissue engineering. Herein, different synthetic methods to develop microgels with desirable functionality and properties along with degradable strategies to ensure their renal clearance are briefly presented. A special focus is given on the ability of microgels to respond to various stimuli such as temperature, pH, redox potential, magnetic field, light, etc., which helps not only to adjust their physical and chemical properties, and degradability on demand, but also the release of encapsulated bioactive molecules and thus making them suitable for drug delivery. Furthermore, recent developments in using the functional microgels for cell imaging and tissue regeneration are reviewed. The results reviewed here encourage the development of a new class of microgels which are able to intelligently perform in a complex biological environment. Finally, various challenges and possibilities are discussed in order to achieve their successful clinical use in future.

Stimuli-Responsive Microgels and Microgel-Based Systems: Advances in the Exploitation of Microgel Colloidal Properties and Their Interfacial Activity

In this paper, recent developments in the chemical design of functional microgels are summarized. A wide range of available synthetic methods allows the incorporation of various reactive groups, charges, or biological markers inside the microgel network, thus controlling the deformation and swelling degree of the resulting smart microgels. These microgels can respond to various stimuli, such as temperature, pH, light, electric field, etc. and can show unique deformation behavior at the interface. Due to their switchability and interfacial properties, these smart microgels are being extensively explored for various applications, such as antifouling coatings, cell encapsulation, catalysis, controlled drug delivery, and tissue engineering.

Tunable clustering of magnetic nanoparticles in microgels: enhanced magnetic relaxivity by modulation of network architecture

In the present work we used microgels as colloidal containers for the loading of hydrophobic magnetic nanoparticles using the solvent exchange method. We varied systematically two parameters: (i) the crosslinking degree of microgels (1-4.5 mol% crosslinker) and (ii) loading of hydrophobic magnetite nanoparticles (d = 7 nm) in microgels (2-10 wt%). The experimental data show that the interplay between these two parameters provides efficient control over the clustering of magnetic nanoparticles in the microgel structure. Transverse magnetization relaxation measurements indicate that the formation of nanoparticle clusters in microgels induces non-linear enhancement of the relaxivity with the increase of nanoparticle loading in microgels. The results suggest that the modulation of the microgel network architecture can be efficiently applied to trigger self-assembly processes inside microgels and design hybrid colloids with unusual morphologies and properties.

Nanofluidic chip for liquid TEM cell fabricated by parylene and silicon nitride direct bonding

Despite the importance of nanofluidic transmission electron microscope (TEM) chips, a simple fabrication method has yet to be developed due to the difficulty of wafer bonding techniques using a nanoscale thick bonding layer. We present a simple and robust wafer scale bonding technique using parylene as a bonding layer. A nanoscale thick parylene layer was deposited on a silicon nitride (SiN) wafer and patterned to construct nanofluidic channels. The patterned parylene layer was directly bonded to another SiN wafer by thermal surface activation and bonding, with a bonding strength of ∼3 MPa. Fourier transform infrared spectroscopy showed that carbon-oxygen bonds were generated by thermal activation. We demonstrated TEM imaging of gold nanoparticles suspended in liquid using the fabricated nanofluidic chip.