Thermoresponsive Gelatin Nanogels

Hybrid colloidal gels with tunable elasticity formed by charge-driven assembly between spherical soft nanoparticles and discotic nanosilicates

Colloidal gels based on electrostatic interparticle attractions hold unexploited potential for tailoring their microstructure and properties. Here, we demonstrate that hetero-aggregation between oppositely charged particles with different geometries is a viable strategy for controlling their properties. Specifically, we studied hybrid colloidal gels prepared by the charge-driven assembly of oppositely charged spherical gelatin nanoparticles and two-dimensional (2D) nanosilicates. We show that the asymmetry between the building blocks and the resulting anisotropic interparticle interactions produces a variety of nanostructures and hybrid colloidal gels that exhibit high elasticity at low colloidal volume fractions. Tuning the competition between different attractive interactions in the system by varying the spatial charge heterogeneity on the 2D nanosheets, composition, and ionic strength was found to alter the mechanism of gel formation and their rheological properties. Remarkably, increasing the mass ratio of 2D nanosheets to spherical nanoparticles at a constant total mass fraction affords hybrid gels that exhibit an inverse relationship between elasticity and volume fraction. However, these hybrid gels are easily fluidized and exhibit rapid structural recovery once the stress is removed. These features allow for the engineering of versatile 3D-printable hybrid colloidal gels, whose structure and viscoelastic response are governed by parameters that have not been explored before.

Cisplatin encapsulated nanoparticles from polymer blends for anti-cancer drug delivery

Synthesis of cubic nanostructure for cisplatin encapsulation.

Photo/thermal response of polypyrrole-modified calcium alginate/gelatin microspheres based on helix-coil structural transition and the controlled release of agrochemicals

Responsive controlled-release systems can not only improve the efficiency of agrochemical utilization but also increase crop yield and reduce environmental pollution caused by excessive use of agrochemicals. In this paper, the helix-coil structural transition of gelatin was adopted to construct a novel stimuli-responsive controlled-release system called polypyrrole/Ca-alginate/gelatin (PPy/Ca-alginate/Gel). In PPy/Ca-alginate/Gel, Ca-alginate and gelatin form a semi-interpenetrating network in which uncross-linked gelatin can undergo a free helix-coil structural transition due to the photothermal effect of PPy. The structural transition of gelatin will lead to changes in the functional groups and microstructure of semi-interpenetrating hydrogels and furthermore achieve the release of template agrochemical molecules embedded in hydrogels. By using carbendazim as a template molecule, the photothermal conversion and controlled release of PPy/Ca-alginate/Gel were systematically studied. After 600 s of light irradiation, its temperature could be increased by 17 ℃. The release of carbendazim in microspheres reached 91.8 % after 8 h of light irradiation, while it was only 13.3 % in the dark. The results indicated that PPy/Ca-alginate/Gel have excellent controlled-release and sustained-release properties and broad application potential in agriculture.

Thermoresponsive Nanogels Based on Different Polymeric Moieties for Biomedical Applications

Nanogels, or nanostructured hydrogels, are one of the most interesting materials in biomedical engineering. Nanogels are widely used in medical applications, such as in cancer therapy, targeted delivery of proteins, genes and DNAs, and scaffolds in tissue regeneration. One salient feature of nanogels is their tunable responsiveness to external stimuli. In this review, thermosensitive nanogels are discussed, with a focus on moieties in their chemical structure which are responsible for thermosensitivity. These thermosensitive moieties can be classified into four groups, namely, polymers bearing amide groups, ether groups, vinyl ether groups and hydrophilic polymers bearing hydrophobic groups. These novel thermoresponsive nanogels provide effective drug delivery systems and tissue regeneration constructs for treating patients in many clinical applications, such as targeted, sustained and controlled release.

Bioprintable tough hydrogels for tissue engineering applications

Bioprinting is an advanced fabrication approach to engineer complex living structures as the conventional fabrication methods are incapable of integrating structural and biological complexities. It offers the versatility of printing different cell incorporated hydrogels (bioink) layer by layer; offering control over spatial resolution and cell distribution to mimic native tissue architectures. However, the bioprinting of tough hydrogels involve additional complexities, such as employing complex crosslinking or reinforcing mechanisms during printing and pre/post printing cellular activities. Solving this complexity requires attention from engineering, material science and cell biology perspectives. In this review, we discuss different types of bioprinting techniques with focus on current state-of-the-art in bioink formulations and pivotal characteristics of bioinks for tough hydrogel printing. We discuss the scope of transition from 3D to 4D bioprinting and some of the advanced characterization techniques for in-depth understanding of the 3D printing process from the microstructural perspective, along with few specific applications and conclude with the future perspectives in biofabrication of hydrogels for tissue engineering applications.

Stimuli-Responsive Polymeric Nanocarriers for Drug Delivery, Imaging, and Theragnosis

In the past few decades, polymeric nanocarriers have been recognized as promising tools and have gained attention from researchers for their potential to efficiently deliver bioactive compounds, including drugs, proteins, genes, nucleic acids, etc., in pharmaceutical and biomedical applications. Remarkably, these polymeric nanocarriers could be further modified as stimuli-responsive systems based on the mechanism of triggered release, i.e., response to a specific stimulus, either endogenous (pH, enzymes, temperature, redox values, hypoxia, glucose levels) or exogenous (light, magnetism, ultrasound, electrical pulses) for the effective biodistribution and controlled release of drugs or genes at specific sites. Various nanoparticles (NPs) have been functionalized and used as templates for imaging systems in the form of metallic NPs, dendrimers, polymeric NPs, quantum dots, and liposomes. The use of polymeric nanocarriers for imaging and to deliver active compounds has attracted considerable interest in various cancer therapy fields. So-called smart nanopolymer systems are built to respond to certain stimuli such as temperature, pH, light intensity and wavelength, and electrical, magnetic and ultrasonic fields. Many imaging techniques have been explored including optical imaging, magnetic resonance imaging (MRI), nuclear imaging, ultrasound, photoacoustic imaging (PAI), single photon emission computed tomography (SPECT), and positron emission tomography (PET). This review reports on the most recent developments in imaging methods by analyzing examples of smart nanopolymers that can be imaged using one or more imaging techniques. Unique features, including nontoxicity, water solubility, biocompatibility, and the presence of multiple functional groups, designate polymeric nanocues as attractive nanomedicine candidates. In this context, we summarize various classes of multifunctional, polymeric, nano-sized formulations such as liposomes, micelles, nanogels, and dendrimers.

Review of Stimuli-Responsive Polymers in Drug Delivery and Textile Application

This review describes some commercially available stimuli-responsive polymers of natural and synthetic origin, and their applications in drug delivery and textiles. The polymers of natural origin such as chitosan, cellulose, albumin, and gelatin are found to show both thermo-responsive and pH-responsive properties and these features of the biopolymers impart sensitivity to act differently under different temperatures and pH conditions. The stimuli-responsive characters of these natural polymers have been discussed in the review, and their respective applications in drug delivery and textile especially for textile-based transdermal therapy have been emphasized. Some practically important thermo-responsive polymers such as pluronic F127 (PF127) and poly(N-isopropylacrylamide) (pNIPAAm) of synthetic origin have been discussed in the review and they are of great importance commercially because of their in situ gel formation capacity. Some pH-responsive synthetic polymers have been discussed depending on their surface charge, and their drug delivery and textile applications have been discussed in this review. The selected stimuli-responsive polymers of synthetic origin are commercially available. Above all, the applications of bio-based or synthetic stimuli-responsive polymers in textile-based transdermal therapy are given special regard apart from their general drug delivery applications. A special insight has been given for stimuli-responsive hydrogel drug delivery systems for textile-based transdermal therapy, which is critical for the treatment of skin disease atopic dermatitis.

Thermo-responsive polymers and their application as smart biomaterials

This review summarises smart thermo-responsive polymeric materials with reversible and ‘on–off’ remotely switchable properties for a wide range of biomedical and biomaterials applications.

Electro-optical Memory of a Nanoengineered Amorphous Blue-Phase-III Polymer Scaffold

An electro-optical (EO) memory device is presented, which is based on a 3D nanostructured polymer scaffold of the amorphous blue phase III (BPIII) of cholesteric liquid crystals (LCs), which can impart optical isotropy, optical activity, and sub-millisecond EO response of BPIII to conventional nematic LCs. This functional scaffold also enables the first experimental observation of the long debated structure of BPIII.

Radiation Engineering of Multifunctional Nanogels

Nanogels combine the favourable properties of hydrogels with those of colloids. They can be soft and conformable, stimuli-responsive and highly permeable, and can expose a large surface with functional groups for conjugation to small and large molecules, and even macromolecules. They are among the very few systems that can be generated and used as aqueous dispersions. Nanogels are emerging materials for targeted drug delivery and bio-imaging, but they have also shown potential for water purification and in catalysis. The possibility of manufacturing nanogels with a simple process and at relatively low cost is a key criterion for their continued development and successful application. This paper highlights the most important structural features of nanogels related to their distinctive properties, and briefly presents the most common manufacturing strategies. It then focuses on synthetic approaches that are based on the irradiation of dilute aqueous polymer solutions using high-energy photons or electron beams. The reactions constituting the basis for nanogel formation and the approaches for controlling particle size and functionality are discussed in the context of a qualitative analysis of the kinetics of the various reactions.

Thermoresponsive and Mechanical Properties of Poly(L-proline) Gels

Gelation of the left helical N-substituted homopolypeptide poly(L-proline) (PLP) in water was explored, employing rheological and small-angle scattering studies at different temperatures and concentrations in order to investigate the network structure and its mechanical properties. Stiff gels were obtained at 10 wt % or higher at 5 °C, the first time gelation has been observed for homopolypeptides. The secondary structure and helical rigidity of PLP has large structural similarities to gelatin but as gels the two materials show contrasting trends with temperature. With increasing temperature in D2O, the network stiffens, with broad scattering features of similar correlation length for all concentrations and molar masses of PLP. A thermoresponsive transition was also achieved between 5 and 35 °C, with moduli at 35 °C higher than gelatin at 5 °C. The brittle gels could tolerate strains of 1% before yielding with a frequency-independent modulus over the observed range, similar to natural proline-rich proteins, suggesting the potential for thermoresponsive or biomaterial-based applications.

Templateless synthesis of polyacrylamide-based Nanogels via RAFT dispersion polymerization

This paper reports on the synthesis of well-defined polyacrylamide-based nanogels via reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization, highlighting a templateless route for the efficient synthesis of nanogels based on water-soluble polymers. RAFT dispersion polymerization of acrylamide in co-nonsolvents of water-tert-butanol mixtures by chain extension from poly(dimethylacrylamide) shows well-controlled polymerization process, uniform nanogel size, and excellent colloidal stability. The versatility of this approach is further demonstrated by introducing a hydrophobic co-monomer (butyl acrylate) without disturbing the dispersion polymerization process.