Ferritin Nanocage Conjugated Hybrid Hydrogel for Tissue Engineering and Drug Delivery Applications

Strategies of functionalized GelMA-based bioinks for bone regeneration: Recent advances and future perspectives

Gelatin methacryloyl (GelMA) hydrogels is a widely used bioink because of its good biological properties and tunable physicochemical properties, which has been widely used in a variety of tissue engineering and tissue regeneration. However, pure GelMA is limited by the weak mechanical strength and the lack of continuous osteogenic induction environment, which is difficult to meet the needs of bone repair. Moreover, GelMA hydrogels are unable to respond to complex stimuli and therefore are unable to adapt to physiological and pathological microenvironments. This review focused on the functionalization strategies of GelMA hydrogel based bioinks for bone regeneration. The synthesis process of GelMA hydrogel was described in details, and various functional methods to meet the requirements of bone regeneration, including mechanical strength, porosity, vascularization, osteogenic differentiation, and immunoregulation for patient specific repair, etc. In addition, the response strategies of smart GelMA-based bioinks to external physical stimulation and internal pathological microenvironment stimulation, as well as the functionalization strategies of GelMA hydrogel to achieve both disease treatment and bone regeneration in the presence of various common diseases (such as inflammation, infection, tumor) are also briefly reviewed. Finally, we emphasized the current challenges and possible exploration directions of GelMA-based bioinks for bone regeneration.

Protein nanoparticles as drug delivery systems for cancer theranostics

Protein-based nanoparticles have garnered significant attention in theranostic applications due to their superior biocompatibility, exceptional biodegradability and ease of functionality. Compared to other nanocarriers, protein-based nanoparticles offer additional advantages, including biofunctionality and precise molecular recognition abilities, which make them highly effective in navigating complex biological environments. Moreover, proteins can serve as powerful tools with self-assembling structures and reagents that enhance cell penetration. And their derivation from abundant renewable sources and ability to degrade into harmless amino acids further enhance their suitability for biomedical applications. However, protein-based nanoparticles have so far not realized their full potential. In this review, we summarize recent advances in the use of protein nanoparticles in tumor diagnosis and treatment and outline typical methods for preparing protein nanoparticles. The review of protein nanoparticles may provide useful new insights into the development of biomaterial fabrication.

Thermally Reversible Gel-Sol Transition of Hydrogels via Dissociation and Association of an Artificial Protein Nanocage

Oligomeric protein nanocages often disassemble into their subunits and reassemble by external stimuli. Thus, using these nanocages as cross-linkers for hydrogel network structures is a promising approach to allow hydrogels to undergo stimuli-responsive gel-sol transitions or self-healing. Here, we report hydrogels that show a reversible gel-sol transition resulting from the heat-induced dissociation and reassociation of protein nanocages. The hydrogel contained the 60-mer artificial protein nanocage, TIP60, as a supramolecular cross-linker for polyethylene glycol network structures. The hydrogel showed a gel-to-sol transition upon heating at a temperature above the melting point of TIP60 and immediately returned to a gel state upon cooling to room temperature. During the heating and cooling treatment of the hydrogel, small-angle X-ray scattering analysis suggested the dissociation and reassociation of TIP60. Furthermore, we demonstrated redox-responsive cargo release from TIP60 in the hydrogel. These results showed the potential of TIP60 as a component of multi-stimuli-responsive hydrogels.

Nanoarchitecture-Integrated Hydrogel Systems toward Therapeutic Applications

Hydrogels, as one of the most feasible soft biomaterials, have gained considerable attention in therapeutic applications by virtue of their tunable properties including superior patient compliance, good biocompatibility and biodegradation, and high cargo-loading efficiency. However, hydrogel application is still limited by some challenges like inefficient encapsulation, easy leakage of loaded cargoes, and the lack of controllability. Recently, nanoarchitecture-integrated hydrogel systems were found to be therapeutics with optimized properties, extending their bioapplication. In this review, we briefly presented the category of hydrogels according to their synthetic materials and further discussed the advantages in bioapplication. Additionally, various applications of nanoarchitecture hybrid hydrogels in biomedical engineering are systematically summarized, including cancer therapy, wound healing, cardiac repair, bone regeneration, diabetes therapy, and obesity therapy. Last, the current challenges, limitations, and future perspectives in the future development of nanoarchitecture-integrated flexible hydrogels are addressed.

Column-free purification of an artificial protein nanocage, TIP60

Protein nanocages, which have inner cavities and surface pores, are attractive materials for various applications, such as in catalysts and medicine. Recently, we produced an artificial protein nanocage, TIP60, and demonstrated its potential as a stimuli-responsive nanocarrier. In the present study, we report a simple purification method for TIP60 that can replace time-consuming and costly affinity chromatography purification. TIP60, which has an anionic surface charge, aggregated at mildly acidic pH and redissolved at neutral pH, maintaining its cage structure. This pH-responsive reversible precipitation allowed us to purify TIP60 from soluble fractions of the E. coli cell lysate by controlling the pH. Compared with conventional Ni-NTA column purification, the pH-responsive precipitation method provided purified TIP60 with similar purity (∼80%) and higher yield. This precipitation purification method should facilitate the large-scale investigation and practical use of TIP60 nanocages.

Graphene Hydrogel as a Porous Scaffold for Cartilage Regeneration

Porous scaffolds have widely been exploited in cartilage tissue regeneration. However, it is often difficult to understand how the delicate hierarchical structure of the scaffold material affects the regeneration process. Graphene materials are versatile building blocks for robust and biocompatible porous structures, enabling investigation of structural cues on tissue regeneration otherwise challenging to ascertain. Here, we utilize a graphene hydrogel with stable and tunable structure as a model scaffold to examine the effect of porous structure on matrix remodeling associated with ingrowth of chondrocytes on scaffolds. We observe much-accelerated yet balanced cartilage remodeling correlating the ingrowth of chondrocytes into the graphene scaffold with an open pore structure on the surface. Importantly, such an enhanced remodeling selectively promotes the expression of collagen type II fibrils over proteoglycan aggrecan, hence clearly illustrating that chondrocytes maintain a stable phenotype when they migrate into the scaffold while offering new insights into scaffold design for cartilage repair.

Flexible polymeric patch based nanotherapeutics against non-cancer therapy

Flexible polymeric patches find widespread applications in biomedicine because of their biological and tunable features including excellent patient compliance, superior biocompatibility and biodegradation, as well as high loading capability and permeability of drug. Such polymeric patches are classified into microneedles (MNs), hydrogel, microcapsule, microsphere and fiber depending on the formed morphology. The combination of nanomaterials with polymeric patches allows for improved advantages of increased curative efficacy and lowered systemic toxicity, promoting on-demand and regulated drug administration, thus providing the great potential to their clinic translation. In this review, the category of flexible polymeric patches that are utilized to integrate with nanomaterials is briefly presented and their advantages in bioapplications are further discussed. The applications of nanomaterials embedded polymeric patches in non-cancerous diseases were also systematically reviewed, including diabetes therapy, wound healing, dermatological disease therapy, bone regeneration, cardiac repair, hair repair, obesity therapy and some immune disease therapy. Alternatively, the limitations, latest challenges and future perspectives of such biomedical therapeutic devices are addressed.

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The most explored polymeric patches, such as microneedle, hydrogel, microsphere, microcapsule, and fiber are summarized.

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Polymeric patches integrated with a diversity of nanomaterials are systematically overviewed in non-cancer therapy.

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The future prospective for the development of polymeric patch based nanotherapeutics is discussed.

Gelatin-methacryloyl hydrogels containing turnip mosaic virus for fabrication of nanostructured materials for tissue engineering

Current tissue engineering techniques frequently rely on hydrogels to support cell growth, as these materials strongly mimic the extracellular matrix. However, hydrogels often need ad hoc customization to generate specific tissue constructs. One popular strategy for hydrogel functionalization is to add nanoparticles to them. Here, we present a plant viral nanoparticle the turnip mosaic virus (TuMV), as a promising additive for gelatin methacryloyl (GelMA) hydrogels for the engineering of mammalian tissues. TuMV is a flexuous, elongated, tubular protein nanoparticle (700–750 nm long and 12–15 nm wide) and is incapable of infecting mammalian cells. These flexuous nanoparticles spontaneously form entangled nanomeshes in aqueous environments, and we hypothesized that this nanomesh structure could serve as a nanoscaffold for cells. Human fibroblasts loaded into GelMA-TuMV hydrogels exhibited similar metabolic activity to that of cells loaded in pristine GelMA hydrogels. However, cells cultured in GelMA-TuMV formed clusters and assumed an elongated morphology in contrast to the homogeneous and confluent cultures seen on GelMA surfaces, suggesting that the nanoscaffold material per se did not favor cell adhesion. We also covalently conjugated TuMV particles with epidermal growth factor (EGF) using a straightforward reaction scheme based on a Staudinger reaction. BJ cells cultured on the functionalized scaffolds increased their confluency by approximately 30% compared to growth with unconjugated EGF. We also provide examples of the use of GelMA-TuMV hydrogels in different biofabrication scenarios, include casting, flow-based-manufacture of filaments, and bioprinting. We envision TuMV as a versatile nanobiomaterial that can be useful for tissue engineering.

A lipidic mesophase with tunable release properties for the local delivery of macromolecules: the apoferritin nanocage, a case study

Lipid mesophases are able to incorporate and release a plethora of molecules, spanning from hydrophobic drugs to small hydrophilic proteins and therefore they have been widely used as drug delivery systems. However, their 3-5 nm water channels do not allow the release of large hydrophilic molecules such as monoclonal antibodies and therapeutic proteins. To overcome this major geometrical constraint, we designed a gel by mixing monoacylglycerol lipids, generally recognized as safe for human and/or animal use by FDA, and phospholipids, to obtain a material with swollen water channels suitable to host and further release macromolecules. Apoferritin, a 12 nm nanocage protein with intrinsic tumor-targeting properties able to incorporate several molecules, was selected here as the hydrophilic model protein to be embedded in the biocompatible gel. When immersed completely in the release media, mesophases with a swollen water channel of 22 nm, composed of monoolein and doped with 5 mole% of DOPS and 10 mole% of Chol allowed us to achieve a protein release of 60%, which is 120 times higher with respect to that obtained by employing non swollen-LMPs composed only of monoolein. Thus, the formulation can be administered locally to the rectal or vaginal mucosa, reducing the drawbacks often associated with the parenteral administration of bio-therapeutics. This approach would pave the way for the local application of other biomacromolecules (including human ferritin, monoclonal antibodies and antibody drug-conjugates) in those diseases easily reachable by a local application such as rectal or vaginal cancer.

Nanocage Ferritin Reinforced Polyacrylamide Hydrogel for Wearable Flexible Strain Sensors

Biocomposite hydrogels are promising for applications in wearable flexible strain sensors. Nevertheless, the existing biocomposite hydrogels are still hard to meet all requirements, which limits the practical application. Here, inspired by the structure and composition of natural ferritin, we design a PAAm-Ferritin hybrid hydrogel through a facile method. Ferritin is uniformly distributed in the cross-linking networks and acts as a nanocage spring model, leading to the enhanced tensile strength of the hydrogel. The fracture stress is 99 kPa at 1400% maximum elongation. As fabricated PAAm-Ferritin hybrid hydrogels exhibit high toughness and low elastic modulus (21 kPa). The PAAm-Ferritin hybrid hydrogels present excellent biocompatibility and increased conductivity compared with PAAm hydrogel. Impressively, as a wearable flexible strain sensor, the PAAm-Ferritin hybrid hydrogels have high sensitivity (gauge factor = 2.06), excellent reliability, and cycling stability. This study indicates the feasibility of utilizing ferritin to synthesize functional materials, which is conducive to expanding the use of protein synthesis of materials technology and application fields.

Human-Body-Temperature Triggerable Phase Transition of W-VO2@PEG Nanoprobes with Strong and Switchable NIR-II Absorption for Deep and Contrast-Enhanced Photoacoustic Imaging

The immense potential of temperature-responsive nanomaterials for use as contrast agents has propelled much recent research and development in the field of photoacoustic (PA) imaging, while the exorbitant transition temperature exceeding the human-tolerable range and the low reversibility of the reported temperature-sensitive nanosystems are still two severe issues that hinder effective imaging and long-term monitoring in practical applications. Herein, we propose a high-performing thermoresponsive polyethylene glycol-coated tungsten-doped vanadium dioxide (W-VO₂@PEG) nanoprobe (NP) with strong and switchable optical absorption in the near-infrared-II (NIR-II) biowindow (1000-1700 nm) near human-body temperature, to achieve deep and contrast-enhanced PA imaging. Our study shows that the PA signal amplitude of W-VO₂@PEG NPs at 1064 nm increases up to 260% when the temperature increases from 35 °C to 45 °C, with a signal fluctuation of less than 10% after 10 temperature cycles, therefore enabling great potential of "off-to-on" dynamic contrast-enhanced imaging capability in deep-seated tissues. Experiments on tissue-mimicking phantoms and in vitro chicken breast showed that, by levering the prepared W-VO₂@PEG NPs and dynamically modulating the temperature field with an external NIR optical stimulus, contrast-enhanced PA images of the target can be obtained with an imaging depth up to 1.5 cm. Furthermore, in vivo potential of the prepared thermoresponsive NPs for the detection and identification of deep-seated tumors by directly comparing to conventional "always on" NPs has been demonstrated. Our work will offer feasible guidance for the development of smart temperature-activatable PA NPs with improved imaging depth and imaging contrast.

Multifunctional GelMA platforms with nanomaterials for advanced tissue therapeutics

Polymeric hydrogels are fascinating platforms as 3D scaffolds for tissue repair and delivery systems of therapeutic molecules and cells. Among others, methacrylated gelatin (GelMA) has become a representative hydrogel formulation, finding various biomedical applications. Recent efforts on GelMA-based hydrogels have been devoted to combining them with bioactive and functional nanomaterials, aiming to provide enhanced physicochemical and biological properties to GelMA. The benefits of this approach are multiple: i) reinforcing mechanical properties, ii) modulating viscoelastic property to allow 3D printability of bio-inks, iii) rendering electrical/magnetic property to produce electro-/magneto-active hydrogels for the repair of specific tissues (e.g., muscle, nerve), iv) providing stimuli-responsiveness to actively deliver therapeutic molecules, and v) endowing therapeutic capacity in tissue repair process (e.g., antioxidant effects). The nanomaterial-combined GelMA systems have shown significantly enhanced and extraordinary behaviors in various tissues (bone, skin, cardiac, and nerve) that are rarely observable with GelMA. Here we systematically review these recent efforts in nanomaterials-combined GelMA hydrogels that are considered as next-generation multifunctional platforms for tissue therapeutics. The approaches used in GelMA can also apply to other existing polymeric hydrogel systems.

Advances in Ultrasound-Responsive Hydrogels for Biomedical Applications

Various intelligent hydrogels have been developed for biomedical applications because they can achieve multiple, variable, controllable and reversible changes in their shape and properties in a spatial and temporal manner,...

PEGylation Improved Electrochemiluminescence Supramolecular Assembly of Iridium(III) Complexes in Apoferritin for Immunoassays Using 2D/2D MXene/TiO2 Hybrids as Signal Amplifiers

Dynamic self-assembly of iridium complexes in water-soluble nanocontainers is an important bottom-up process for fabricating electrochemiluminescence (ECL) bioprobes. PEGylated apoferritin (PEG-apoHSF) as the host offers a confined space to alter and modify the self-assembly of trans-bis(2-phenylpyridine)(acetylacetonate)iridium(III) [Ir(ppy)₂(acac)] based on a pH-dependent depolymerization/reassembly pathway, allowing the formation of ECL-active iridium cores in PEG-apoHSF cavities (Ir@PEG-apoHSF). With an improved encapsulation ratio in PEG-apoHSF, the coreactant ECL behavior of the fabricated Ir@PEG-apoHSF nanodots with tri-n-propylamine (TPrA) was further demonstrated, exhibiting maximum ECL emission at 530 nm that was theoretically dominated by the band gap transition. The application of Ir@PEG-apoHSF as a bioprobe in a "signal-on" ECL immunosensing system was developed based on electroactive Ti₃C₂T_x MXenes/TiO₂ nanosheet (Ti₃C₂T_x/TiO₂) hybrids. Combining with the efficiently catalyzed electro-oxidation of TPrA and Ir(ppy)₂(acac) by Ti₃C₂T_x/TiO₂ hybrids, the developed immunosensor showed dramatically amplified ECL responses toward the target analyte of neuron-specific enolase (NSE). Under experimental conditions, linear quantification of NSE from 100 fg/mL to 50 ng/mL was well established by this assay, achieving a limit of detection (LOD) of 35 fg/mL. The results showcased the capability of PEGylated apoHSF to host and stabilize water-insoluble iridium complexes as ECL emitters for aqueous biosensing and immunoassays.

Facile Encapsulation of Iridium(III) Complexes in Apoferritin Nanocages as Promising Electrochemiluminescence Nanodots for Immunoassays

A class of water-soluble electrochemiluminescence (ECL) nanodots were prepared by encapsulating ECL-active iridium complexes into biocompatible horse spleen apoferritin (apoHSF) nanocages for immunoassays. The preparation feasibility was achieved based on the pH-induced disassembly/reassembly nature originated from apoHSF. Two iridium nanodots (1 and 2) with high ECL efficiency were separately prepared by directing the self-assembly of two water-insoluble luminescent complexes, Ir(ppy)₃ (ppy = 2-phenylpyridine) and Ir(ppy)₂(acac) (ppy = 2-phenylpyridine and acac = acetylacetonate), in the apoHSF cavity. Using tri-n-propylamine (TPrA) as a coreactant, the electrochemistry and "oxidative-reductive" ECL mechanisms for nanodots 1 and 2 were investigated, respectively. After demonstrating the spectroscopic property and relative ECL efficiency, the ECL emission of nanodots 1 and 2 quenched by TPrA^• radicals at high potential was further studied and circumvented by optimizing the potential range and TPrA concentration for generating strong and stable ECL emission in aqueous media. The well-inherited biological functions of apoHSF in nanodots allow the convenient external modification of an antibody to act as a signal probe, thus a versatile ECL immunoassay paradigm was established. Acceptable results from this assay enabled the rapid and accurate detection of biomarkers in real samples. The unprecedented use of apoHSF is feasible and applicable for water-insoluble iridium complexes to fabricate a wide variety of biocompatible ECL nanodots for potential bioanalysis.

Design and Development of Hybrid Hydrogels for Biomedical Applications: Recent Trends in Anticancer Drug Delivery and Tissue Engineering

The applications of hydrogels in biomedical field has been since multiple decades. Discoveries in biology and chemistry render this platform endowed with much engineering potentials and growing continuously. Novel approaches in constructing these materials have led to the production of complex hybrid hydrogels systems that can incorporate both natural and synthetic polymers and other functional moieties for mediated cell response, tunable release kinetic profiles, thus they are used and research for diverse biomedical applications. Recent advancement in this field has established promising techniques for the development of biorelevant materials for construction of hybrid hydrogels with potential applications in the delivery of cancer therapeutics, drug discovery, and re-generative medicines. In this review, recent trends in advanced hybrid hydrogels systems incorporating nano/microstructures, their synthesis, and their potential applications in tissue engineering and anticancer drug delivery has been discussed. Examples of some new approaches including click reactions implementation, 3D printing, and photopatterning for the development of these materials has been briefly discussed. In addition, the application of biomolecules and motifs for desired outcomes, and tailoring of their transport and kinetic behavior for achieving desired outcomes in hybrid nanogels has also been reviewed.

Biomedical application of photo-crosslinked gelatin hydrogels

Abstract

During the past decades, photo-crosslinked gelatin hydrogel (methacrylated gelatin, GelMA) has gained a lot of attention due to its remarkable application in the biomedical field. It has been widely used in cell transplantation, cell culture and drug delivery, based on its crosslinking to form hydrogels with tunable mechanical properties and excellent bio-compatibility when exposed to light irradiation to mimic the micro-environment of native extracellular matrix (ECM). Because of its unique biofunctionality and mechanical tenability, it has also been widely applied in the repair and regeneration of bone, heart, cornea, epidermal tissue, cartilage, vascular, peripheral nerve, oral mucosa, and skeletal muscle et al. The purpose of this review is to summarize the recent application of GelMA in drug delivery and tissue engineering field. Moreover, this review article will briefly introduce both the development of GelMA and the characterization of GelMA. Finally, we discuss the challenges and future development prospects of GelMA as a tissue engineering material and drug or gene delivery carrier, hoping to contribute to accelerating the development of GelMA in the biomedical field.

Graphical abstract

Protecting redesigned supercharged ferritin containers against protease by integration into acid-cleavable polyelectrolyte microgels

HYPOTHESIS

The application of ferritin containers as a promising drug delivery vehicle is limited by their low bioavailability in blood circulation due to unfavorable environments, such as degradation by protease. The integration of ferritin containers into the polymeric network of microgels through electrostatic interactions is expected to be able to protect ferritin against degradation by protease. Furthermore, a stimuli-responsive microgel system can be designed by employing an acid-degradable crosslinker during the microgel synthesis. This should enable ferritin release in an acidic environment, which will be useful for future drug delivery applications.

EXPERIMENTS

Nanoparticle/fluorophores-loaded ferritin was integrated into microgels during precipitation polymerization. The integration was monitored by transmission electron microscopy (TEM)² and fluorescence microscopy, respectively. After studying ferritin release in acidic solutions, we investigated the stability of ferritin inside microgels against degradation by chymotrypsin.

FINDINGS

About 80% of the applied ferritin containers were integrated into microgels and around 85% and 50% of them could be released in buffer pH 2.5 and 4.0, respectively. Total degradation of the microgels was not achieved due to the self-crosslinking of N-isopropylacrylamide (NIPAM). Finally, we prove that microgels could protect ferritin against degradation by chymotrypsin at 37 °C.

One-step construction of ferritin encapsulation drugs for cancer chemotherapy

Conventionally, a disassembly and reassembly method has been used for encapsulation of drug molecules in ferritin protein nano-cages. However, clinical applications of ferritin have been greatly restricted by its limited drug-loading capacity and process complexity. Here, we establish a simple high yield process for preparing high drug-loaded ferritin nanomedicine for industrial production. A complex of ferritin and a target drug was obtained by incubating the mixture at an appropriate pH. An electrostatic charge potential and small ferritin cavity facilitates the passage of drug molecules through the pores, traversing the ferritin shell and enabling deposition of the drug in the ferritin cavity. Compared to the disassembly/reassembly method, the loading capacity of a doxorubicin-loaded ferritin heavy chain (DOX-FTH), constructed by our novel method, was over 3-fold higher, while doxorubicin recovery was 10-fold higher. Results of transmission electron microscopy, size exclusion chromatography, dynamic light scattering, and zeta potential indicate that DOX-FTH exhibits the same physicochemical characteristics of natural apo-ferritin. Moreover, DOX-FTH can be taken up and induce apoptosis of cancer cells overexpressing TfR1. Here, we have demonstrated the successful introduction of more than ten drug molecule types into ferritin nano-cages using a novel method. These results demonstrate that this one-step method is a powerful production process to construct a drug-loading ferritin drug delivery system carrier.