Thermoresponsive nanodevices in biomedical applications

Nanogel-Mediated antigen delivery: Biocompatibility, immunogenicity, and potential for tailored vaccine design across species

Nanotechnology has emerged as a promising avenue for enhancing the efficacy of vaccine delivery systems. This study investigates the utilization of nanogels as carriers for the model antigen ovalbumin, with a focus on in vivo assessments in equine and murine models. Nanogels, owing to their biocompatibility and tunable physicochemical properties, offer a versatile platform for efficient antigen encapsulation and controlled release. The encapsulation efficiency and physicochemical characteristics of ovalbumin-loaded nanogels were comprehensively characterized. In vitro biocompatibility was evaluated, finding excellent properties of these nanogels. In vivo evaluations were conducted on both equine and murine subjects, assessing immunogenicity through antibody and splenic cell response. Furthermore, the study propose the potential use of nanogels in tailoring immune responses through the modulation of antigen release kinetics. The results obtained in the in vitro assays showed an increase in the uptake of nanogels by APCs compared to free antigen (OVA). In mice, an absence of inflammatory response in the inoculation site was observed, without systemic damage in the evaluated organs. In addition, non-significant humoral response was found nor cellular proliferation and proinflammatory cytokine production, compared with a traditional adjuvant as aluminum hydroxide, in both animal models. These findings allow further insights into nanogel-based delivery systems and offer valuable insights into their application in various animal models. In conclusion, this research establishes the utility of nanogels as effective carriers for antigens-based vaccines, with interesting biocompatibility properties and highly taken affinity by antigen-presenting cells, without inducing inflammation at the injection site. The study underscores the potential of nanogel technology in revolutionizing vaccine design and highlights the importance of tailored approaches for diverse target species.

Biopolymer-Based Nanogel Approach in Drug Delivery: Basic Concept and Current Developments

Due to their increased surface area, extent of swelling and active substance-loading capacity and flexibility, nanogels made from natural and synthetic polymers have gained significant interest in scientific and industrial areas. In particular, the customized design and implementation of nontoxic, biocompatible, and biodegradable micro/nano carriers makes their usage very feasible for a range of biomedical applications, including drug delivery, tissue engineering, and bioimaging. The design and application methodologies of nanogels are outlined in this review. Additionally, the most recent advancements in nanogel biomedical applications are discussed, with particular emphasis on applications for the delivery of drugs and biomolecules.

Polyelectrolyte-multivalent molecule complexes: physicochemical properties and applications

The complexation of polyelectrolytes with other oppositely charged structures gives rise to a great variety of functional materials with potential applications in a wide spectrum of technological fields. Depending on the assembly conditions, polyelectrolyte complexes can acquire different macroscopic configurations such as dense precipitates, nanosized colloids and liquid coacervates. In the past 50 years, much progress has been achieved to understand the principles behind the phase separation induced by the interaction of two oppositely charged polyelectrolytes in aqueous solutions, especially for symmetric systems (systems in which both polyions have similar molecular weight and concentration). However, in recent years, the complexation of polyelectrolytes with alternative building blocks such as small charged molecules (multivalent inorganic species, oligopeptides, and oligoamines, among others) has gained attention in different areas. In this review, we discuss the physicochemical characteristics of the complexes formed by polyelectrolytes and multivalent small molecules, putting a special emphasis on their similarities with the well-known polycation-polyanion complexes. In addition, we analyze the potential of these complexes to act as versatile functional platforms in various technological fields, such as biomedicine and advanced materials engineering.

Photo-Programmed Deformations in Rigid Liquid Crystalline Polymers Triggered by Body Temperature

Deformations triggered by body heat are desirable in the context of shape-morphing applications because, under the majority of circumstances, the human body maintains a higher temperature than that of its surroundings. However, at present, this bioenergy-triggered action is primarily limited to soft polymeric networks. Thus, herein, the programming of body temperature-triggered deformations into rigid azobenzene-containing liquid crystalline polymers (azo-LCPs) with a glass-transition temperature of 100 °C is demonstrated. To achieve this, a mechano-assisted photo-programming strategy is used to create a metastable state with room-temperature stable residual stress, which is induced by the isomerization of azobenzene. The programmed rigid azo-LCP can undergo large-amplitude body temperature-triggered shape changes within minutes and can be regenerated without any performance degradation. By changing the programming photomasks and irradiation conditions employed, various 2D to 3D shape-morphing architectures, including folded clips, inch-worm structures, spiral structures, and snap-through motions are achieved. When programmed with polarized light, the proposed strategy results in domain-selective activation, generating designed characteristics in multi-domain azo-LCPs. The reported strategy is therefore expected to broaden the applications of azo-LCPs in the fields of biomedical and flexible microelectronic devices.

Mesoporous Silica and Oligo (Ethylene Glycol) Methacrylates-Based Dual-Responsive Hybrid Nanogels

Polymeric-inorganic hybrid nanomaterials have emerged as novel multifunctional platforms because they combine the intrinsic characteristics of both materials with unexpected properties that arise from synergistic effects. In this work, hybrid nanogels based on mesoporous silica nanoparticles, oligo (ethylene glycol) methacrylates, and acidic moieties were developed employing ultrasound-assisted free radical precipitation/dispersion polymerization. Chemical structure was characterized by infrared spectroscopy and nuclear magnetic resonance. Hydrodynamic diameters at different temperatures were determined by dynamic light scattering, and cloud point temperatures were determined by turbidimetry. Cell viability in fibroblast (NIH 3T3) and human prostate cancer (LNCaP) cell lines were studied by a standard colorimetric assay. The synthetic approach allows covalent bonding between the organic and inorganic components. The composition of the polymeric structure of hybrid nanogels was optimized to incorporate high percentages of acidic co-monomer, maintaining homogeneous nanosized distribution, achieving appropriate volume phase transition temperature values for biomedical applications, and remarkable pH response. The cytotoxicity assays show that cell viability was above 80% even at the highest nanogel concentration. Finally, we demonstrated the successful cell inhibition when they were treated with camptothecin-loaded hybrid nanogels.

Aggressive strategies for regenerating intervertebral discs: stimulus-responsive composite hydrogels from single to multiscale delivery systems

As our research on the physiopathology of intervertebral disc degeneration (IVD degeneration, IVDD) has advanced and tissue engineering has rapidly evolved, cell-, biomolecule- and nucleic acid-based hydrogel grafting strategies have been widely investigated for their ability to overcome the harsh microenvironment of IVDD. However, such single delivery systems suffer from excessive external dimensions, difficult performance control, the need for surgical implantation, and difficulty in eliminating degradation products. Stimulus-responsive composite hydrogels have good biocompatibility and controllable mechanical properties and can undergo solution-gel phase transition under certain conditions. Their combination with ready-to-use particles to form a multiscale delivery system may be a breakthrough for regenerative IVD strategies. In this paper, we focus on summarizing the progress of research on the stimulus response mechanisms of regenerative IVD-related biomaterials and their design as macro-, micro- and nanoparticles. Finally, we discuss multi-scale delivery systems as bioinks for bio-3D printing technology for customizing personalized artificial IVDs, which promises to take IVD regenerative strategies to new heights.

A hybrid thermoresponsive plasmonic nanogel designed for NIR-mediated chemotherapy

Temperature-trigger chemotherapy is one of the state-of-the-art anti-tumoral strategies in nanomedicine. However, this strategy is in close relationship with the effect of the temperature in the tumor tissue. With high temperatures, the ablation of the tumor tissue can hinder a correct chemotherapy approximation. On the other hand, with moderate temperatures a negative vascularization that promotes the tumor growing is produced and competes with the chemotherapeutic effects. We have constructed one nanogel system composed of a thermoresponsive polymer cross-linked by plasmonic gold nanoparticles (AuNPs) for temperature-trigger chemotherapy. Doxorubicin loaded in the porous interior of the nanogel is released when the thermoresponsive network of the nanogel collapses due to the heat generated by the AuNPs upon near infra-red light irradiation. The hybrid nanogel system has been tested in vitro and in vivo, where it was observed that the temperatures reached in the in vivo NIR irradiation have an undesired effect on the inhibition of the tumor growth while the drug loaded systems considerably reduced the tumor sizes. This study shows the importance of design in temperature triggered antitumoral systems, where lower temperatures usually reached in practical situations due to light attenuation produced by the tissue can be positively utilized for enhancing the antitumoral effect of loaded drugs in the system.

Nanocarriers for Skin Applications: Where Do We Stand?

Skin penetration of active molecules for treatment of diverse diseases is a major field of research owing to the advantages associated with the skin like easy accessibility, reduced systemic-derived side effects, and increased therapeutic efficacy. Despite these advantages, dermal drug delivery is generally challenging due to the low skin permeability of therapeutics. Although various methods have been developed to improve skin penetration and permeation of therapeutics, they are usually aggressive and could lead to irreversible damage to the stratum corneum. Nanosized carrier systems represent an alternative approach for current technologies, with minimal damage to the natural barrier function of skin. In this Review, the use of nanoparticles to deliver drug molecules, genetic material, and vaccines into the skin is discussed. In addition, nanotoxicology studies and the recent clinical development of nanoparticles are highlighted to shed light on their potential to undergo market translation.

Hydrogels Classification According to the Physical or Chemical Interactions and as Stimuli-Sensitive Materials

Hydrogels are attractive biomaterials with favorable characteristics due to their water uptake capacity. However, hydrogel properties are determined by the cross-linking degree and nature, the tacticity, and the crystallinity of the polymer. These biomaterials can be sorted out according to the internal structure and by their response to external factors. In this case, the internal interaction can be reversible when the internal chains are led by physicochemical interactions. These physical hydrogels can be synthesized through several techniques such as crystallization, amphiphilic copolymers, charge interactions, hydrogen bonds, stereo-complexing, and protein interactions. In contrast, the internal interaction can be irreversible through covalent cross-linking. Synthesized hydrogels by chemical interactions present a high cross-linking density and are employed using graft copolymerization, reactive functional groups, and enzymatic methods. Moreover, specific smart hydrogels have also been denoted by their external response, pH, temperature, electric, light, and enzyme. This review deeply details the type of hydrogel, either the internal structure or the external response. Furthermore, we detail some of the main applications of these hydrogels in the biomedicine field, such as drug delivery systems, scaffolds for tissue engineering, actuators, biosensors, and many other applications.

DNA Based and Stimuli-Responsive Smart Nanocarrier for Diagnosis and Treatment of Cancer: Applications and Challenges

The rapid development of multidrug co-delivery and nano-medicines has made spontaneous progress in tumor treatment and diagnosis. DNA is a unique biological molecule that can be tailored and molded into various nanostructures. The addition of ligands or stimuli-responsive elements enables DNA nanostructures to mediate highly targeted drug delivery to the cancer cells. Smart DNA nanostructures, owing to their various shapes, sizes, geometry, sequences, and characteristics, have various modes of cellular internalization and final disposition. On the other hand, functionalized DNA nanocarriers have specific receptor-mediated uptake, and most of these ligand anchored nanostructures able to escape lysosomal degradation. DNA-based and stimuli responsive nano-carrier systems are the latest advancement in cancer targeting. The data exploration from various studies demonstrated that the DNA nanostructure and stimuli responsive drug delivery systems are perfect tools to overcome the problems existing in the cancer treatment including toxicity and compromised drug efficacy. In this light, the review summarized the insights about various types of DNA nanostructures and stimuli responsive nanocarrier systems applications for diagnosis and treatment of cancer.

A review of stimuli-responsive polymeric micelles for tumor-targeted delivery of curcumin

Despite a potential drug with multiple pharmacological activities, curcumin has disadvantages of the poor water solubility, rapid metabolism, low bioavailability, which considerably limit its clinical application. Currently, polymeric micelles (PMs) have gained widespread concern due to their advantageous physical and chemical properties, easy preparation, and biocompatibility. They can be used to improve drug solubility, prolong blood circulation time, and allow passive targeted drug delivery to tumor through enhanced penetration and retention effect. Moreover, studies focused on tumor microenvironment offer alternatives to design stimulus-responsive smart PMs based on low pH, high levels of glutathione, altered enzyme expression, increased reactive oxygen species production, and hypoxia. There are various external stimuli, such as light, ultrasound, and temperature. These endogenous/exogenous stimuli can be used for the research of intelligent micelles. Intelligent PMs can effectively load curcumin with improved solubility, and intelligently respond to release the drug at a controlled rate at targeted sites such as tumors to avoid early release, which markedly improves the bioavailability of curcumin. The present review is aimed to discuss and summarize recent developments in research of curcumin-loaded intelligent PMs based on endogenous and exogenous stimuli, and facilitates the development of novel delivery systems for future research.

Environmental Liquid Cell Technique for Improved Electron Microscopic Imaging of Soft Matter in Solution

Liquid-phase transmission electron microscopy is a technique for simultaneous imaging of the structure and dynamics of specimens in a liquid environment. The conventional sample geometry consists of a liquid layer tightly sandwiched between two Si3N4 windows with a nominal spacing on the order of 0.5 μm. We describe a variation of the conventional approach, wherein the Si3N4 windows are separated by a 10-μm-thick spacer, thus providing room for gas flow inside the liquid specimen enclosure. Adjusting the pressure and flow speed of humid air inside this environmental liquid cell (ELC) creates a stable liquid layer of controllable thickness on the bottom window, thus facilitating high-resolution observations of low mass-thickness contrast objects at low electron doses. We demonstrate controllable liquid thicknesses in the range 160 ± 34 to 340 ± 71 nm resulting in corresponding edge resolutions of 0.8 ± 0.06 to 1.7 ± 0.8 nm as measured for immersed gold nanoparticles. Liquid layer thickness 40 ± 8 nm allowed imaging of low-contrast polystyrene particles. Hydration effects in the ELC have been studied using poly-N-isopropylacrylamide nanogels with a silica core. Therefore, ELC can be a suitable tool for in situ investigations of liquid specimens.

Galvanic Replacement as a Synthetic Tool for the Construction of Anisotropic Magnetoplasmonic Nanocomposites with Synergistic Phototransducing and Magnetic Properties

Magnetoplasmonic nanomaterials, which combine light and magnetic field responsiveness in an advantageous manner, are attractive candidates for bio-nanoapplications. However, the synthetic access to such hybrid particles has been limited by the incompatibility of the iron- and gold-based lattices. In this work, we provide the first insights into a new synthetic strategy for developing magnetoplasmonic anisotropic nanocomposites with prominent phototransducing properties. In our approach, magnetic nanocubes based on an alloy of iron oxide, zinc, and silver were constructed. In a key second stage, the galvanic replacement of silver with gold atoms yielded satellite-like magnetoplasmonic anisotropic structures. Superior magnetic and photoconverting properties were observed for the novel magnetoplasmonic nanocomposites when compared with the pure parent structures. Moreover, the synergy between the magnetic and optical stimuli was examined, showing shape-dependent contributions in the magnetization experiments. More importantly, an excellent cell ablation capability upon laser irradiation was observed for the magnetoplasmonic nanocomposites compared to the pure magnetic or plasmonic controls. Further demonstration of these novel theragnostic agents as MRI contrast agents is also reported even during the light-irradiation event. Thus, the described particles showed promising properties for bioapplications emerging from the novel synthetic methodology.

Bottom-Up Approach to Assess the Molecular Structure of Aqueous Poly(N-Isopropylacrylamide) at Room Temperature via Infrared Spectroscopy

The structure of poly(N-isopropylacrylamide) (PNIPAM) in solution is still an unresolved topic. Here, the PNIPAM structure in water was investigated using a bottom-up approach, involving the monomer, dimer, and trimer, and a combination of infrared (IR) spectroscopies as well as molecular dynamics simulations. The experiments show that the monomer and oligomers exhibit a broad and asymmetric amide I band with two underlying transitions, while PNIPAM presents the same major transitions and a minor one. Analysis of the 2D IR spectra and theoretical modeling of the amide I band indicates that the two transitions of the monomer do not have the same molecular origin as the oligomers and the polymer. In the monomer, the two bands originate from the ultrafast rotation of its ethyl group, which leads to different solvation structures for the various rotational conformers. In the case of the oligomers, the asymmetry and splitting of the amide I band is caused by the vibrational coupling among adjacent amide side chains. Moreover, it is deduced from the simulations that the oligomers have three distinct backbone conformations for neighboring amides. In particular, two of the backbone conformations have a closed and compact structure, while in the third, the backbone is open and elongated. The bottom-up approach allowed us to infer that such backbone conformations exist in PNIPAM as well. Consequently, the two major amide I transitions of the polymer are also assigned to split amide I transitions resulting from the vibrationally coupled nearest-neighboring amides. In contrast, the additional minor transition observed in PNIPAM is assigned to unsolvated amide units of the polymer. The proposed molecular model successfully describes that PNIPAM amide I band changes with temperature in terms of its molecular structure. This new model strongly suggests that PNIPAM does not have a completely random backbone structure, but has distinct backbone conformers between neighboring amides.

Revealing the NIR-triggered chemotherapy therapeutic window of magnetic and thermoresponsive nanogels

The combination of magnetic nanoparticles and thermoresponsive nanogels represents an appealing strategy for the development of theranostic probes. These hybrid nanocarriers present several advantages such as outstanding properties for guided therapy, magnetic resonance imaging, and triggered release of encapsulated cargoes. Most magnetic thermoresponsive nanogels are built with strategies that comprise a physical interaction of particles with the polymeric network or the covalent attachment of a single particle to the linear polymer. Herein, we report a facile synthetic approach for the synthesis of magnetic and thermoresponsive nanogels that allows the controlled incorporation of multiple superparamagnetic inorganic cores as covalent cross-linkers. An ultrasonication-assisted precipitation-polymerization afforded nanogels with sizes in the nanometric range and similar magnetization and light transduction properties compared to the discrete magnetic nanoparticles. The theranostic capability of these nanocarriers was further investigated both in vitro and in vivo. In vivo experiments demonstrated the capacity of these materials as nanocarriers for near-infrared (NIR) triggered chemotherapy and highlighted the relevance of the correct concentration/dose in this antitumoral modality to achieve a superior therapeutic efficacy.

Advancement in nanogel formulations provides controlled drug release

Nanogels are currently considered as promising nanosized drug delivery carriers. Nanogels are made of a crosslinked polymeric network which could encapsulate both hydrophilic and hydrophobic drugs due to their tunable nature. The ability of nanogels to control drug release is vastly described in the literature and researchers are consistently improving the control of drug release from nanogel by designing new polymers having specific sensitivity to a chemical or physical stimulus. In this review, we briefly discuss the definition of nanogels, their release profiles, their specific gel-based characteristics and the pathways of dug release from nanogels. We have focused on the stimuli responsive nanogels and their release profile. This compilation opens the window for understanding the influence of chemical composition and design of various nanogel on their release in the presence and absence of corresponding stimuli such as temperature, pH, enzymes and others. The uniqueness of this review is that it highlights the data of release profiles in terms of the different nanogel composition and triggers. It also points the high potential of nanogels in the list of candidates for drug delivery systems, thanks to their properties regarding drug encapsulation and release, combined advantages of nano-size and swelling characteristics of hydrogel.

Insulin-induced conformational transition of fluorescent copolymers: a perspective of self-assembly between protein and micellar solutions of smart copolymers

Synthesizing and understanding phase transition behavior of novel block copolymers is very crucial for fabricating next generation of smart materials with foreseeable applications. In this regard, we synthesized three random (r) copolymers of poly(N-vinyl-caprolactam) (PVCL) and poly(2-dimethyl amino ethyl methacrylate) (PDMAEMA) with varying percentages of each block and characterized them using nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) patterns, time-resolved fluorescence spectroscopy, and atomic force microscopy (AFM). Synthesized copolymers i.e. PVCL₃₀-PDMAEMA₇₀, PVCL₅₀-PDMAEMA₅₀ and PVCL₇₀-PDMAEMA₃₀ have fluorescence properties, which were confirmed by time-resolved fluorescence spectra and emission spectra, and emission bands were observed at ∼310, ∼435 and ∼424 nm, respectively. The fluorescence lifetime for PVCL₅₀-PDMAEMA₅₀ is larger than those of the other two copolymers suggesting a slow decay of the excited state. The copolymers have spherical geometry as micelles, which were confirmed by TEM. We observed patterned arrangement of micelles and the arranged micelles appear to be pentagon in shape, creating space in between the arranged micelles; however, for PVCL₅₀-PDMAEMA₅₀, the arranged micelles do not form any particular shape. The thermal phase transition of PVCL-r-PDMAEMA in aqueous solution was studied by differential scanning calorimetry and thermal fluorescence spectroscopy. In order to design a biomimetic polymer for bio-specific applications and to understand novel concepts towards polymer-protein interactions, we studied the effect of insulin on lower critical solution temperature (LCST) of PVCL-r-PDMAEMA using multiple sophisticated techniques. The LCST is finely tuned by incorporation of two blocks with various block compositions and the value falls within the range of human body temperature, making PVCL₅₀-PDMAEMA₅₀ a highly compatible material for bio-medical and bio-material applications. Insulin forms a self-assembly with the monomers of PVCL-r-PDMAEMA, which leads to enhancing the micellar aggregates and the eventual decrease in the LCST of the diblock copolymer aqueous solution. The present study provides new insights into insulin-copolymer interactions and can be used for self-assembling nanocarriers and designing protein resistance surfaces.

Understanding the elusive protein corona of thermoresponsive nanogels

Aim: We analyzed the protein corona of thermoresponsive, poly(N-isopropylacrylamide)- or poly(N-isopropylmethacrylamide)-based nanogels. Materials & methods: Traces of protein corona detected after incubation in human serum were characterized by proteomics and dynamic light scattering in undiluted serum. Results: Apolipoprotein B-100 and albumin were the main components of the protein coronae. For dendritic polyglycerol-poly(N-isopropylacrylamide) nanogels at 37°C, an increase in adsorbed immunoglobulin light chains was detected, followed by partially reversible nanogel aggregation. All nanogels in their hydrophilic state are colloidally stable in serum and bear a dysopsonin-rich protein corona. Conclusion: We observed strong changes in NG stability upon slight alterations in the composition of the protein coronae according to nanogel solvation state. Nanogels in their hydrophilic state possess safe protein coronae.

Design, Synthesis and Architectures of Hybrid Nanomaterials for Therapy and Diagnosis Applications

Hybrid nanomaterials based on inorganic nanoparticles and polymers are highly interesting structures since they combine synergistically the advantageous physical-chemical properties of both inorganic and polymeric components, providing superior functionality to the final material. These unique properties motivate the intensive study of these materials from a multidisciplinary view with the aim of finding novel applications in technological and biomedical fields. Choosing a specific synthetic methodology that allows for control over the surface composition and its architecture, enables not only the examination of the structure/property relationships, but, more importantly, the design of more efficient nanodevices for therapy and diagnosis in nanomedicine. The current review categorizes hybrid nanomaterials into three types of architectures: core-brush, hybrid nanogels, and core-shell. We focus on the analysis of the synthetic approaches that lead to the formation of each type of architecture. Furthermore, most recent advances in therapy and diagnosis applications and some inherent challenges of these materials are herein reviewed.

Temperature-Enhanced Follicular Penetration of Thermoresponsive Nanogels

Hair follicles can serve as an effective reservoir for dermal drug delivery upon the topical application of particulate substances. Here, the follicular penetration of an indodicarbocyanine-labelled thermoresponsive nanogel (189 nm) having a cloud point temperature of 34°C and linked via an acid-labile linker to the model drug indocarbocyanine was investigated. In total, 227 hair follicles of porcine ear skin were examined after topical application of the thermoresponsive nanogels at room temperature (21°C), physiological skin surface temperature (32°C) and core body temperature (37°C) for the follicular penetration depths of indodicarbocyanine and indocarbocyanine using confocal laser scanning microscopy. The results showed a significantly increased mean follicular penetration of the carrier to a depth of 298.8±85.8 μm after incubation at 37°C compared to samples incubated at 21°C and 32°C with mean follicular penetration depths of 202.7±81.7 μm and 219.4±52.9 μm, respectively (p<0.001). Possibly structural changes in the thermoresponsive nanogel induced by the increased incubation temperature led to an enhancement of follicular penetration. Therefore, thermoresponsive nanogels may be suitable for the temperature-enhanced penetration into the hair follicles under physiological conditions.

Optimizing Circulating Tumor Cells' Capture Efficiency of Magnetic Nanogels by Transferrin Decoration

Magnetic nanogels (MNGs) are designed to have all the required features for their use as highly efficient trapping materials in the challenging task of selectively capturing circulating tumor cells (CTCs) from the bloodstream. Advantageously, the discrimination of CTCs from hematological cells, which is a key factor in the capturing process, can be optimized by finely tuning the polymers used to link the targeting moiety to the MNG. We describe herein the relationship between the capturing efficiency of CTCs with overexpressed transferrin receptors and the different strategies on the polymer used as linker to decorate these MNGs with transferrin (Tf). Heterobifunctional polyethylene glycol (PEG) linkers with different molecular weights were coupled to Tf in different ratios. Optimal values over 80% CTC capture efficiency were obtained when 3 PEG linkers with a length of 8 ethylene glycol (EG) units were used, which reveals the important role of the linker in the design of a CTC-sorting system.

Thermoresponsive nanogels with film-forming ability

A one pot semibatch method was proposed for synthesizing poly(N-vinylcaprolactam)-based nanogels with particle coalescence ability.

Enhanced topical delivery of dexamethasone by β-cyclodextrin decorated thermoresponsive nanogels

Highly hydrophilic, responsive nanogels are attractive as potential systems for the topical delivery of bioactives encapsulated in their three-dimensional polymeric scaffold. Yet, these drug carrier systems suffer from drawbacks for efficient delivery of hydrophobic drugs. Addressing this, β-cyclodextrin (βCD) could be successfully introduced into the drug carrier systems by exploiting its unique affinity toward dexamethasone (DXM) as well as its role as topical penetration enhancer. The properties of βCD could be combined with those of thermoresponsive nanogels (tNGs) based on dendritic polyglycerol (dPG) as a crosslinker and linear thermoresponsive polyglycerol (tPG) inducing responsiveness to temperature changes. Electron paramagnetic resonance (EPR) studies localized the drug within the hydrophobic cavity of βCD by differences in its mobility and environmental polarity. In fact, the fabricated carriers combining a particulate delivery system with a conventional penetration enhancer, resulted in an efficient delivery of DXM to the epidermis and the dermis of human skin ex vivo (enhancement compared to commercial DXM cream: ∼2.5 fold in epidermis, ∼30 fold in dermis). Furthermore, DXM encapsulated in βCD tNGs applied to skin equivalents downregulated the expression of proinflammatory thymic stromal lymphopoietin (TSLP) and outperformed a commercially available DXM cream.

Doxorubicin Intracellular Remote Release from Biocompatible Oligo(ethylene glycol) Methyl Ether Methacrylate-Based Magnetic Nanogels Triggered by Magnetic Hyperthermia

Hybrid nanogels, composed of thermoresponsive polymers and superparamagnetic nanoparticles, are attractive nanocarriers for biomedical applications, being able-as a polymer matrix-to uptake and release high quantities of chemotherapeutic agents and-as magnetic nanoparticles-to be heated when exposed to an alternative magnetic field (AMF), better known as magnetic hyperthermia. Herein, biocompatible, pH-responsive, magnetoresponsive, and thermoresponsive nanogels, based on oligo(ethylene glycol) methyl ether methacrylate monomers and a methacrylic acid comonomer were prepared by conventional precipitation radical copolymerization in water, post-assembled by complexation with iron oxide magnetic nanoparticles (MNPs) of maghemite (γ-Fe₂O₃), and loaded with an anticancer drug (doxorubicin, DOX), for remotely controlled drug release by a "hot spot", as an athermal magnetic hyperthermia strategy against cancer. These nanogels, denoted MagNanoGels, with a hydrodynamic diameter from 328 to 460 nm, as a function of the MNP content, have a swelling-deswelling behavior at their volume phase temperature transition around 47 °C in a physiological medium (pH 7.5), which is above the human body temperature (37 °C). Applying an alternative magnetic field increases the release of DOX by 2-fold, while no macroscopic heating was recorded. This enhanced drug release is due to a shrinking of the polymer network by local heating, as illustrated by the MagNanoGel size decrease under an AMF. In cancer cells, not only do the DOX-MagNanoGels internalize DOX more efficiently than free DOX, but also DOX intracellular release can be remotely triggered under an AMF, in athermal conditions, thus enhancing DOX cytotoxicity.

Evolution of macromolecular complexity in drug delivery systems

Designing therapeutics is a process with many challenges. Even if the first hurdle - designing a drug that modulates the action of a particular biological target in vitro - is overcome, selective delivery to that target in vivo presents a major barrier. Side-effects can, in many cases, result from the need to use higher doses without targeted delivery. However, the established use of macromolecules to encapsulate or conjugate drugs can provide improved delivery, and stands to enable better therapeutic outcomes. In this Review, we discuss how drug delivery approaches have evolved alongside our ability to prepare increasingly complex macromolecular architectures. We examine how this increased complexity has overcome the challenges of drug delivery and discuss its potential for fulfilling unmet needs in nanomedicine.

Biocompatibility and characterization of polyglycerol-based thermoresponsive nanogels designed as novel drug-delivery systems and their intracellular localization in keratinocytes

Novel nanogels that possess the capacity to change their physico-chemical properties in response to external stimuli are promising drug-delivery candidates for the treatment of severe skin diseases. As thermoresponsive nanogels (tNGs) are capable of enhancing penetration through biological barriers such as the stratum corneum and are taken up by keratinocytes of human skin, potential adverse consequences of their exposure must be elucidated. In this study, tNGs were synthesized from dendritic polyglycerol (dPG) and two thermoresponsive polymers. tNG_dPG_tPG are the combination of dPG with poly(glycidyl methyl ether-co-ethyl glycidyl ether) (p(GME-co-EGE)) and tNG_dPG_pNIPAM the one with poly(N-isopropylacrylamide) (pNIPAM). Both thermoresponsive nanogels are able to incorporate high amounts of dexamethasone and tacrolimus, drugs used in the treatment of severe skin diseases. Cellular uptake, intracellular localization and the toxicological properties of the tNGs were comprehensively characterized in primary normal human keratinocytes (NHK) and in spontaneously transformed aneuploid immortal keratinocyte cell line from adult human skin (HaCaT). Laser scanning confocal microscopy revealed fluorescently labeled tNGs entered into the cells and localized predominantly within lysosomal compartments. MTT assay, comet assay and carboxy-H2DCFDA assay, demonstrated neither cytotoxic or genotoxic effects, nor any induction of reactive oxygen species of the tNGs in keratinocytes. In addition, both tNGs were devoid of eye irritation potential as shown by bovine corneal opacity and permeability (BCOP) test and red blood cell (RBC) hemolysis assay. Therefore, our study provides evidence that tNGs are locally well tolerated and underlines their potential for cutaneous drug delivery.

Dendritic polyglycerol and N-isopropylacrylamide based thermoresponsive nanogels as smart carriers for controlled delivery of drugs through the hair follicle

Nanoparticles with a size of several hundred nanometers can effectively penetrate into the hair follicles and may serve as depots for controlled drug delivery. However, they can neither overcome the hair follicle barrier to reach the viable cells nor release the loaded drug adequately. On the other hand, small drug molecules cannot penetrate deep into the hair follicles. Thus, the most efficient way for drug delivery through the follicular route is to employ nanoparticles that can release the drug close to the target structure upon exposure to some external or internal stimuli. Accordingly, 100-700 nm sized thermoresponsive nanogels with a phase transition temperature of 32-37 °C were synthesized by the precipitation polymerization technique using N-isopropylacrylamide as a monomer, acrylated dendritic polyglycerol as a crosslinker, VA-044 as an initiator, and sodium dodecyl sulphate as a stabilizer. The follicular penetration of the indodicarbocyanine (IDCC) labeled nanogels into the hair follicles and the release of coumarin 6, which was loaded as a model drug, in the hair follicles were assessed ex vivo using porcine ear skin. Confocal laser scanning microscopy (CLSM) enabled independent tracking of the nanogels and the loaded dye, although it is not as precise and accurate as standard analytical methods. The results showed that, unlike smaller nanogels (<100 nm), medium and larger sized nanogels (300-500 nm) penetrated effectively into the hair follicles with penetration depths proportional to the nanogel size. The release of the loaded dye in the hair follicles increased significantly when the investigation on penetration was carried out above the cloud point temperature of the nanogels. The follicular penetration of the nanogels from the colloidal dispersion and a 2.5% hydroxyethyl cellulose gel was not significantly different.

Thermoresponsive Polymers with Lower Critical Solution Temperature- or Upper Critical Solution Temperature-Type Phase Behaviour Do Not Induce Toxicity to Human Endothelial Cells

Thermoresponsive polymers have gained extensive attention as biomedical materials especially for targeted drug delivery systems. We have recently developed water-soluble polypeptide-based thermoresponsive polymers that exhibit lower critical solution temperature (LCST)- or upper critical solution temperature (UCST)-type phase behaviours. In this study, the toxicity of these polymers to human umbilical vein endothelial cells (HUVECs) was investigated to assess the safety and biocompatibility. Up to 100 μg/ml, thermoresponsive polymers did not induce cytotoxicity to HUVECs, showing as unaltered mitochondrial viability assessed as cell counting kit-8 (CCK-8) assay and membrane integrity assessed as lactate dehydrogenase (LDH) assay. Inflammatory response, assessed as the release of chemokine-soluble monocyte chemotactic protein 1 (sMCP-1) and interleukin-8 (IL-8) as well as cytokine IL-6, was not significantly affected by the polymers. In addition, 1 μM thapsigargin (TG), an endoplasmic reticulum (ER) stress inducer, significantly decreased mitochondrial viability, but did not affect membrane integrity or inflammatory response. The presence of thermoresponsive polymers with LCST-type phase behaviour did not further affect the effects of TG. In conclusion, the thermoresponsive polymers used in this study are not toxic to endothelial cells and therefore could be further considered as safe materials for biomedical applications.

Specific uptake mechanisms of well-tolerated thermoresponsive polyglycerol-based nanogels in antigen-presenting cells of the skin

Engineered nanogels are of high value for a targeted and controlled transport of compounds due to the ability to change their chemical properties by external stimuli. As it has been indicated that nanogels possess a high ability to penetrate the stratum corneum, it cannot be excluded that nanogels interact with dermal dendritic cells, especially in diseased skin. In this study the potential crosstalk of the thermoresponsive nanogels (tNGs) with the dendritic cells of the skin was investigated with the aim to determine the immunotoxicological properties of the nanogels. The investigated tNGs were made of dendritic polyglycerol (dPG) and poly(glycidyl methyl ether-co-ethyl glycidyl ether) (p(GME-co-EGE)), as polymer conferring thermoresponsive properties. Although the tNGs were taken up, they displayed neither cytotoxic and genotoxic effects nor any induction of reactive oxygen species in the tested cells. Interestingly, specific uptake mechanisms of the tNGs by the dendritic cells were depending on the nanogels cloud point temperature (Tcp), which determines the phase transition of the nanoparticle. The study points to caveolae-mediated endocytosis as being the major tNGs uptake mechanism at 37°C, which is above the Tcp of the tNGs. Remarkably, an additional uptake mechanism, beside caveolae-mediated endocytosis, was observed at 29°C, which is the Tcp of the tNGs. At this temperature, which is characterized by two different states of the tNGs, macropinocytosis was involved as well. In summary, our study highlights the impact of thermoresponsivity on the cellular uptake mechanisms which has to be taken into account if the tNGs are used as a drug delivery system.

Programmable Quantitative DNA Nanothermometers

Developing molecules, switches, probes or nanomaterials that are able to respond to specific temperature changes should prove of utility for several applications in nanotechnology. Here, we describe bioinspired strategies to design DNA thermoswitches with programmable linear response ranges that can provide either a precise ultrasensitive response over a desired, small temperature interval (±0.05 °C) or an extended linear response over a wide temperature range (e.g., from 25 to 90 °C). Using structural modifications or inexpensive DNA stabilizers, we show that we can tune the transition midpoints of DNA thermometers from 30 to 85 °C. Using multimeric switch architectures, we are able to create ultrasensitive thermometers that display large quantitative fluorescence gains within small temperature variation (e.g., > 700% over 10 °C). Using a combination of thermoswitches of different stabilities or a mix of stabilizers of various strengths, we can create extended thermometers that respond linearly up to 50 °C in temperature range. Here, we demonstrate the reversibility, robustness, and efficiency of these programmable DNA thermometers by monitoring temperature change inside individual wells during polymerase chain reactions. We discuss the potential applications of these programmable DNA thermoswitches in various nanotechnology fields including cell imaging, nanofluidics, nanomedecine, nanoelectronics, nanomaterial, and synthetic biology.

Stimuli-responsive nanogel composites and their application in nanomedicine

Nanogels are nanosized crosslinked polymer networks capable of absorbing large quantities of water. Specifically, smart nanogels are interesting because of their ability to respond to biomedically relevant changes like pH, temperature, etc. In the last few decades, hybrid nanogels or composites have been developed to overcome the ever increasing demand for new materials in this field. In this context, a hybrid refers to nanogels combined with different polymers and/or with nanoparticles such as plasmonic, magnetic, and carbonaceous nanoparticles, among others. Research activities are focused nowadays on using multifunctional hybrid nanogels in nanomedicine, not only as drug carriers but also as imaging and theranostic agents. In this review, we will describe nanogels, particularly in the form of composites or hybrids applied in nanomedicine.

Multifunctional hybrid nanogels for theranostic applications

This paper reviews a wide set of theranostic applications based on the special properties associated with composite nanogels. The nanogels presented here are mostly hybridized with quantum dots, magnetic nanoparticles, and plasmonic metal noble nanoparticles. These inorganic components confer nanogels multifunctional properties that extend their applications from drug delivery systems to diagnosis and therapy. Nanogels can also be surface functionalized with specific ligands to achieve targeted therapy and reduce toxicity. This versatility makes hybrid nanogels very promising agents for imaging, diagnosis and treatment of cancer and other diseases.

Shell Cross-Linked Polymeric Micelles as Camptothecin Nanocarriers for Anti-HCV Therapy

A suitable carrier for camptothecin to act as therapy against the hepatitis C virus is presented. The carrier relies on an amphiphilic hybrid dendritic-linear-dendritic block copolymer, derived from pluronic F127 and bis-MPA dendrons, that forms micelles in aqueous solution. The dendrons admit the incorporation of multiple photoreactive groups that allow the clean and effective preparation of covalently cross-linked polymeric micelles (CLPM), susceptible of loading hydrophilic and lipophilic molecules. Cell-uptake experiments using a newly designed fluorophore, derived from rhodamine B, demonstrate that the carrier favors the accumulation of its cargo within the cell. Furthermore, loaded with camptothecin, it is efficient in fighting against the hepatitis C virus while shows lower cytotoxicity than the free drug.

Facile ultrasonication approach for the efficient synthesis of ethylene glycol-based thermoresponsive nanogels

A facile synthesis of thermoresponsive nanogels (NGs) with potential applications as drug delivery systems is reported.

Engineering thermoresponsive polyether-based nanogels for temperature dependent skin penetration

Improved skin penetration of thermoresponsive nanogels into human skin at temperatures above the phase-transition temperature.