Enzymatic- and light-degradable hybrid nanogels: Crosslinking of polyacrylamide with acrylate-functionalized Dextrans containing photocleavable linkers

The development of microfluidic-based western blotting: Technical advances and future perspectives

Over the past two decades significant technical advancement in the field of western blotting has been made possible through the utilization of microfluidic technologies. In this review we provide a critical overview of these advancements, highlighting the advantages and disadvantages of each approach. Particular attention is paid to the development of now commercially available systems, including those for single cell analysis. This review also discusses more recent developments, including algorithms for automation and/or improved quantitation, the utilization of different materials/chemistries, use of projection electrophoresis, and the development of triBlots. Finally, the review includes commentary on future advances in the field based on current developments, and the potential of these systems for use as point-of-care devices in healthcare.

Stimuli-responsive destructible polymeric hydrogels based on irreversible covalent bond dissociation

Covalently crosslinked stimuli-destructible hydrogels with the ability of irreversible bond dissociation have attracted great attentions due to their biodegradability, stability against hydrolysis, and controlled solubility upon insertion of desired triggers.

Soft synthetic microgels as mimics of mycoplasma

Artificial model colloids are of special interest in the development of advanced sterile filters, as they are able to efficiently separate pleomorphic, highly deformable and infectious bacteria such as mycoplasma, which, until now, has been considered rather challenging and laborious. This study presents a full range of different soft to super soft synthetic polymeric microgels, including two types with similar hydrodynamic mean diameter, i.e., 180 nm, and zeta potential, i.e., -25 ± 10 mV, but different deformability, synthesized by inverse miniemulsion terpolymerization of acrylamide, sodium acrylate and N,N'-methylenebisacrylamide. These microgels were characterized by means of dynamic, electrophoretic and static light scattering techniques. In addition, the deformability of the colloids was investigated by filter cake compressibility studies during ultrafiltration in dead-end mode, analogously to a study of real mycoplasma, i.e., Acholeplasma laidlawii, to allow for a direct comparison. The results indicate that the variation of the synthesis parameters, i.e., crosslinker content, polymeric solid content and content of sodium acrylate, has a significant impact on the swelling behavior of the microgels in aqueous solution as well as on their deformability under filtration conditions. A higher density of chemical crosslinking points results in less swollen and more rigid microgels. Furthermore, these parameters determine electrokinetic properties of the more or less permeable colloids. Overall, it is shown that these soft synthetic microgels can be obtained with tailor-made properties, covering the size of smallest species of and otherwise similar to real mycoplasma. This is a relevant first step towards the future use of synthetic microgels as mimics for mycoplasma.

Dual Photo- and pH-Responsive Spirooxazine-Functionalized Dextran Nanoparticles

A dual photo- and pH-responsive spirooxazine-functionalized polymer was synthesized by functionalization of dextran with a spirooxazine derivative (SO-COOH). The functionalized dextran derivatives can form nanoparticles in aqueous medium. Under UV light irradiation, the spirooxazine-functionalized dextran (Dex-SO) nanoparticles isomerize to zwitterionic merocyanine-functionalized dextran (Dex-MC), which leads to aggregation. However, the process is reversible upon irradiation with visible light. Under acidic conditions, the hydrophobic spirooxazine is protonated, and the nanoparticles aggregate or swell at pH values of 5 or 3, respectively. The encapsulation of the hydrophobic fluorescent dye Nile Red as model drug allowed us to gain more information about the structural changes under stimulation of UV light and acid treatment.

Synthesis of pH-degradable polyglycerol-based nanogels by iEDDA-mediated crosslinking for encapsulation of asparaginase using inverse nanoprecipitation

Biocompatible, environmentally responsive, and scalable nanocarriers are needed for targeted and triggered delivery of therapeutic proteins. Suitable polymers, preparation methods, and crosslinking chemistries must be considered for nanogel formation. Biocompatible dendritic polyglycerol (dPG) is used in the mild, surfactant-free inverse nanoprecipitation method for nanogel preparation. The biocompatible, fast, and bioorthogonal inverse electron demand Diels-Alder (iEDDA) crosslinking chemistry is used. In this work, the synthesis of pH-degradable nanogels, based on tetrazine, norbonene, and bicyclo[6.1.0]nonyne (BCN) functionalized macromonomers, is reported. The macromonomers are non-toxic up to 2.5 mg mL−1 in three different cell lines. Nanogels are obtained in the size range of 47 to 200 nm and can be degraded within 48 h at pH 4.5 (BA-gels), and pH 3 (THP-gels), respectively. Encapsulation of asparaginase (32 kDa) yield encapsulation efficiencies of up to 93% at 5 wt.% feed. Overall, iEDDA-crosslinked pH-degradable dPG-nanogels from inverse nanoprecipitation are promising candidates for biomedical applications.

Systematic Screening of Different Polyglycerin-Based Dienophile Macromonomers for Efficient Nanogel Formation through IEDDA Inverse Nanoprecipitation

Alternatives for strain-promoted azide-alkyne cycloaddition (SPAAC) chemistries are needed because of the employment of expensive and not easily scalable precursors such as bicyclo[6.1.0]non-4-yne (BCN). Inverse electron demand Diels Alder (iEDDA)-based click chemistries, using dienophiles and tetrazines, offer a more bioorthogonal and faster toolbox, especially in the biomedical field. Here, the straightforward synthesis of dendritic polyglycerin dienophiles (dPG-dienophiles) and dPG-methyl-tetrazine (dPG-metTet) as macromonomers for a fast, stable, and scalable nanogel formation by inverse nanoprecipitation is reported. Nanogel size-influencing parameters are screened such as macromonomer concentration and water-to-acetone ratio are screened. dPG-norbonene and dPG-cyclopropene show fast and stable nanogel formation in the size range of 40-200 nm and are thus used for the coprecipitation of the model protein myoglobin. High encapsulation efficiencies of more than 70% at a 5 wt% feed ratio are obtained in both cases, showing the suitability of the mild gelation chemistry for the encapsulation of small proteins.

The Potential of Stimuli-Responsive Nanogels in Drug and Active Molecule Delivery for Targeted Therapy

Nanogels (NGs) are currently under extensive investigation due to their unique properties, such as small particle size, high encapsulation efficiency and protection of active agents from degradation, which make them ideal candidates as drug delivery systems (DDS). Stimuli-responsive NGs are cross-linked nanoparticles (NPs), composed of polymers, natural, synthetic, or a combination thereof that can swell by absorption (uptake) of large amounts of solvent, but not dissolve due to the constituent structure of the polymeric network. NGs can undergo change from a polymeric solution (swell form) to a hard particle (collapsed form) in response to (i) physical stimuli such as temperature, ionic strength, magnetic or electric fields; (ii) chemical stimuli such as pH, ions, specific molecules or (iii) biochemical stimuli such as enzymatic substrates or affinity ligands. The interest in NGs comes from their multi-stimuli nature involving reversible phase transitions in response to changes in the external media in a faster way than macroscopic gels or hydrogels due to their nanometric size. NGs have a porous structure able to encapsulate small molecules such as drugs and genes, then releasing them by changing their volume when external stimuli are applied.

Biodegradable hydrophilic carriers for the oral delivery of hematological factor IX for hemophilia B treatment

Current protein replacement therapies for hemophilia B, a genetic bleeding disorder caused by a deficiency in coagulation factor IX, rely on IV injections and infusions. Oral delivery of factor IX is a desirable needle-free option, especially for prophylaxis. We have developed a biodegradable, pH-responsive hydrogel microcarrier system based on the poly(methacrylic acid)-grafted-poly(ethylene glycol) [P(MAA-g-EG)]. Incorporation of an enzymatically degradable peptide crosslinking agent allows for site-specific degradation by trypsin in the small intestine. P(MAA-g-EG) polymer was synthesized by UV polymerization, and then subsequently crosslinked with peptide crosslinking agent using EDC-NHS chemistry. Physical characterization included FTIR for determining the composition of the peptide crosslinked polymer and SEM for microparticle morphology. The pH-responsive swelling and enzyme-specific degradation were confirmed by bright-field microscopy and the corresponding kinetics were determined by turbidimetric measurements. Evaluating the drug delivery application of this degradable system, factor IX release studies showed site-specific release, and in vitro transport studies resulted in improved factor IX absorption. Incorporation of the degradable crosslinking agent significantly improved the delivery potential as compared to previously reported non-degradable drug delivery systems. Using this degradable P(MAA-g-EG) system as a delivery vehicle for factor IX can possibly lead to an orally administered prophylactic treatment for hemophilia B patients.

Design of pH-Responsive Biomaterials to Enable the Oral Route of Hematological Factor IX

The oral administration of hematological factor IX (FIX) can offer a convenient prophylactic treatment for hemophilia B patients. pH-Responsive hydrogels based on poly(methacrylic acid)-grafted-poly(ethylene glycol) (P(MAA-g-EG)) have been engineered as delivery vehicles for FIX. In oral delivery, such hydrogel carriers protected FIX from the gastric environment and released it under intestinal conditions as demonstrated by evaluation of the loading and release of FIX. Tailoring of the hydrogel networks improved the loading of FIX within the microcarriers, which is critical for minimizing protein degradation. Optimizing the loading conditions by increasing the incubation time and using a reduced ionic strength buffer further improved the delivery potential of the microcarriers. The presence of the microcarriers significantly enhanced the oral absorption of FIX in vitro. As shown in this work, P(MAA-g-EG) microcarriers are promising candidates for the oral delivery of FIX.

Enzyme- and pH-Responsive Microencapsulated Nanogels for Oral Delivery of siRNA to Induce TNF-α Knockdown in the Intestine

Inflammatory bowel diseases (IBD) manifest from excessive intestinal inflammation. Local delivery of siRNA that targets these inflammatory cytokines would provide a novel treatment approach. Microencapsulated nanogels are designed and validated as platforms for oral delivery of siRNA targeting TNF-α, a common clinical target of IBD treatments. The preferred platform was designed to (i) protect siRNA-loaded nanogels from the harsh acidic environment of the upper GI tract and (ii) enzymatically degrade and release the nanogels once the carrier has reached the intestinal region. This platform consists of microgels composed of poly(methacrylic acid-co-N-vinyl-2-pyrrolidone) (P[MAA-co-NVP]) cross-linked with a trypsin-degradable peptide linker. The P(MAA-co-NVP) backbone is designed to collapse around and protect encapsulated nanogel from degradation at the low pH levels seen in the stomach (pH 2-4). At pH levels of 6-7.5, as typically observed in the intestine, the P(MAA-co-NVP) matrix swells, potentially facilitating diffusion of intestinal fluid and degradation of the matrix by intestinal enzymes such as trypsin, thus "freeing" the therapeutic nanogels for delivery and cellular uptake within the intestine. TNF-α siRNA-loaded nanogels released from this platform were capable of inducing potent knockdown of secreted TNF-α levels in murine macrophages, further validating the potential for this approach to be used for the treatment of IBD.

Preparation of photodegradable polyacrylamide hydrogels via micellar copolymerization and determination of their phototunable elasticity and swelling behaviors

A photo-decomposable hydrophobic crosslinker was synthesized and utilized to obtain photo-tunable hydrogelsviafree radical micellar copolymerization.

Intracellular delivery cellulose-based bionanogels with dual temperature/pH-response for cancer therapy

Polysaccharide-based crosslinked nanogles (bionanogels) exhibiting multiple stimuli-responsive release of encapsulated therapeutics hold a great potential as tumor-targeting intracelluar durg delivery nanocarriers. Herein, we report the synthesis of monodisperse dual temperature/acidic pH-responsive bionanogels (DuR-BNGs) by aqueous crosslinking polymerization through temperature-induced self-association method. The DuR-BNGs have prolonged colloidal stability and negligible non-specific interactions with proteins. In response to acidic pH at higher temperature (above lower critical solution temperature), they exhibit synergistic release of anticancer drugs as a consequence of both acidic pH-sensitivity of carboxymethyl cellulose and temperature-induced volume change of grafted thermoresponsive copolymers. In vitro cell culture results suggest that new colloidally-stable DuR-BNG is a promising candidate promoting dual stimuli-responsive drug release for cancer therapy.

Enzymatic biodegradation of hydrogels for protein delivery targeted to the small intestine

Multiresponsive poly(methacrylic acid-co-N-vinylpyrrolidone) hydrogels were synthesized with biodegradable oligopeptide crosslinks. The oligopeptide crosslinks were incorporated using EDC-NHS zero-length links between the carboxylic acid groups of the polymer and free primary amines on the peptide. The reaction of the peptide was confirmed by primary amine assay and IR spectroscopy. The microgels exhibited pH-responsive swelling as well as enzyme-catalyzed degradation targeted by trypsin present in the small intestine, as demonstrated upon incubation with gastrointestinal fluids from rats. Relative turbidity was used to evaluate enzyme-catalyzed degradation as a function of time, and initial trypsin concentration controlled both the degradation mechanism as well as the extent of degradation. Trypsin activity was effectively extinguished by incubation at 70 °C, and both the microgels and degradation products posed no cytotoxic effect toward two different cell lines. The microgels demonstrated pH-dependent loading of the protein insulin for oral delivery to the small intestine.

Photolabile ROMP gels using ortho-nitrobenzyl functionalized crosslinkers

The photosensitivity of ROMP gels to UV light is broadly tunable based on the structure of o-nitrobenzyl-derived crosslinkers.

Synthesis of nanostructured materials in inverse miniemulsions and their applications

Polymeric nanogels, inorganic nanoparticles, and organic-inorganic hybrid nanoparticles can be prepared via the inverse miniemulsion technique. Hydrophilic functional cargos, such as proteins, DNA, and macromolecular fluoresceins, may be conveniently encapsulated in these nanostructured materials. In this review, the progress of inverse miniemulsions since 2000 is summarized on the basis of the types of reactions carried out in inverse miniemulsions, including conventional free radical polymerization, controlled/living radical polymerization, polycondensation, polyaddition, anionic polymerization, catalytic oxidation reaction, sol-gel process, and precipitation reaction of inorganic precursors. In addition, the applications of the nanostructured materials synthesized in inverse miniemulsions are also reviewed.

Facile preparation of photodegradable hydrogels by photopolymerization

Photodegradable hydrogels have emerged as a powerful material platform for studying and directing cell behaviors, as well as for delivering drugs. The premise of this technique is to use a cytocompatible light source to cleave linkers within a hydrogel, thus causing reduction of matrix stiffness or liberation of matrix-tethered biomolecules in a spatial-temporally controlled manner. The most commonly used photodegradable units are molecules containing nitrobenzyl moieties that absorb light in the ultraviolet (UV) to lower visible wavelengths (~280 to 450 nm). Because photodegradable linkers and hydrogels reported in the literature thus far are all sensitive to UV light, highly efficient UV-mediated photopolymerizations are less likely to be used as the method to prepare these hydrogels. As a result, currently available photodegradable hydrogels are formed by redox-mediated radical polymerizations, emulsion polymerizations, Michael-type addition reactions, or orthogonal click chemistries. Here, we report the first photodegradable poly(ethylene glycol)-based hydrogel system prepared by step-growth photopolymerization. The model photolabile peptide cross-linkers, synthesized by conventional solid phase peptide synthesis, contained terminal cysteines for step-growth thiol-ene photo-click reactions and a UV-sensitive 2-nitrophenylalanine residue in the peptide backbone for photo-cleavage. Photolysis of this peptide was achieved through adjusting UV light exposure time and intensity. Photopolymerization of photodegradable hydrogels containing photolabile peptide cross-linkers was made possible via a highly efficient visible light-mediated thiol-ene photo-click reaction using a non-cleavage type photoinitiator eosin-Y. Rapid gelation was confirmed by in situ photo-rheometry. Flood UV irradiation at controlled wavelength and intensity was used to demonstrate the photodegradability of these photopolymerized hydrogels.

Surfactant free preparation of biodegradable dendritic polyglycerol nanogels by inverse nanoprecipitation for encapsulation and release of pharmaceutical biomacromolecules

In this paper we report a novel approach to generate biodegradable polyglycerol nanogels on different length scales. We developed a mild, surfactant free inverse nanoprecipitation process to template hydrophilic polyglycerol nanoparticles. In situ crosslinking of the precipitated nanoparticles by bioorthogonal copper catalyzed click chemistry allows us to obtain size defined polyglycerol nanogels (100-1000nm). Biodegradability was achieved by the introduction of benzacetal bonds into the net points of the nanogel. Interestingly, the polyglycerol nanogels quickly degraded into low molecular weight fragments at acidic pH values, which are present in inflamed and tumor tissues as well as intracellular organelles, and they remained stable at physiological pH values for a long time. This mild approach to biodegradable polyglycerol nanogels allows us to encapsulate labile biomacromolecules such as proteins, including the therapeutic relevant enzyme asparaginase, into the protein resistant polyglycerol network. Enzymes were encapsulated with an efficacy of 100% and after drug release, full enzyme activity and structural integrity were retained. This new inverse nanoprecipitation procedure allows the efficient encapsulation and release of various biomacromolecules including proteins and could find many applications in polymer therapeutics and nanomedicine.