Nanogel Tectonics for Tissue Engineering: Protein Delivery Systems with Nanogel Chaperones

Boron Agent Delivery Platforms Based on Natural Products for Boron Neutron Capture Therapy

Boron neutron capture therapy (BNCT) is one of the most promising modalities for cancer treatment due to its minimal invasiveness. Although two types of boron agents are clinically used, several issues persist in their delivery, including poor water solubility, instability in aqueous media, selectivity toward cancer cells, accumulation in cancer cells, retention time in tumor tissue, and efficiency in achieving the boron neutron capture reaction. Addressing these challenges, numerous groups have explored various boron agents to enhance the therapeutic benefits of BNCT. This review summarizes delivery platforms based on natural products for BNCT.

Poly(vinyl alcohol)-Incorporated Core-Shell Polymer Nanogels Functionalized by Block Copolymer Installation for Cisplatin Delivery

The functionalization approach for nanomaterials is of great importance for their application in drug delivery systems. Herein, an approach based on block copolymer installation into polymer nanogels was newly developed. Poly(vinyl alcohol)-incorporated polymer nanogels were prepared by a two-step dispersion/precipitation polymerization. Poly(methacrylic acid)-block-poly(3-fluorophenylboronic acid methacrylamide) (PMAA-b-PFPBMA) prepared by two-step reversible addition-fragmentation chain transfer polymerization was installed into the polymer nanogels via boronate ester formation. Furthermore, cisplatin as a cancer therapeutic drug was successfully loaded on the block copolymer-installed polymer nanogels, and cell death was achieved by using the resulting cisplatin-loaded nanogels. We believe that the functionality of the nanogels can be changed by varying the installed block copolymer, leading to the functionalization approach of polymer nanogels based on block copolymer installation, which will be of great utility in many fields.

Biomaterials for Protein Delivery: Opportunities and Challenges to Clinical Translation

The development of biomaterials for protein delivery is an emerging field that spans materials science, bioengineering, and medicine. In this review, we highlight the immense potential of protein-delivering biomaterials as therapeutic options and discuss the multifaceted challenges inherent to the field. We address current advancements and approaches in protein delivery that leverage stimuli-responsive materials, harness advanced fabrication techniques like 3D printing, and integrate nanotechnologies for greater targeting and improved stability, efficacy, and tolerability profiles. We also discuss the demand for highly complex delivery systems to maintain structural integrity and functionality of the protein payload. Finally, we discuss barriers to clinical translation, such as biocompatibility, immunogenicity, achieving reliable controlled release, efficient and targeted delivery, stability issues, scalability of production, and navigating the regulatory landscape for such materials. Overall, this review summarizes insights from a survey of the current literature and sheds light on the interplay between innovation and the practical implementation of biomaterials for protein delivery.

Cholesterol-Bearing Polysaccharide-Based Nanogels for Development of Novel Immunotherapy and Regenerative Medicine

Novel functional biomaterials are expected to bring about breakthroughs in developing immunotherapy and regenerative medicine through their application as drug delivery systems and scaffolds. Nanogels are defined as nanoparticles with a particle size of 100 nm or less and as having a gel structure. Nanogels have a three-dimensional network structure of cross-linked polymer chains, which have a high water content, a volume phase transition much faster than that of a macrogel, and a quick response to external stimuli. As it is possible to transmit substances according to the three-dimensional mesh size of the gel, a major feature is that relatively large substances, such as proteins and nucleic acids, can be taken into the gel. Furthermore, by organizing nanogels as a building block, they can be applied as a scaffold material for tissue regeneration. This review provides a brief overview of the current developments in nanogels in general, especially drug delivery, therapeutic applications, and tissue engineering. In particular, polysaccharide-based nanogels are interesting because they have excellent complexation properties and are highly biocompatible.

Multifunctional nanogel based on carboxymethyl cellulose interfering with cellular redox homeostasis enhances phycocyanobilin photodynamic therapy

The redox homeostasis defense mechanism of tumor cells is one of the prime reasons for the unsatisfactory effect of photodynamic therapy (PDT). So far, little attention has been paid to this obstacle. In this work, we reported a synthesizing simple yet versatile nanogel (BCPS), synthesized by cystamine dihydrochloride functionalized sodium carboxymethylcellulose (CMC-SS), bovine serum albumin, and Phycocyanobilin self-assembly. The BCPS reduced the levels of glutathione molecules by reacting with glutathione, thereby interfering with intracellular redox homeostasis and enhancing the sensitivity of tumor cells to PDT. The BCPS was shown to possess excellent serum stability, high blood compatibility, low toxic side effects, and higher reactive oxygen species (ROS) utilization. After irradiation, the BCPS could significantly increase intracellular ROS level by approximately 1.6-fold and decrease the IC50 to HeLa cells by approximately 1.5-fold, compared to the pre-functional drugs BCP. This proposed strategy, based on increasing the utilization rate of ROS in tumor cells is promising for application potentials in tumor therapy.

Exploring the Potential of Nanogels: From Drug Carriers to Radiopharmaceutical Agents

Nanogels open up access to a wide range of applications and offer among others hopeful approaches for use in the field of biomedicine. This review provides a brief overview of current developments of nanogels in general, particularly in the fields of drug delivery, therapeutic applications, tissue engineering, and sensor systems. Specifically, cyclodextrin (CD)-based nanogels are important because they have exceptional complexation properties and are highly biocompatible. Nanogels as a whole and CD-based nanogels in particular can be customized in a wide range of sizes and equipped with a desired surface charge as well as containing additional molecules inside and outside, such as dyes, solubility-mediating groups or even biological vector molecules for pharmaceutical targeting. Currently, biological investigations are mainly carried out in vitro, but more and more in vivo applications are gaining importance. Modern molecular imaging methods are increasingly being used for the latter. Due to an extremely high sensitivity and the possibility of obtaining quantitative data on pharmacokinetic and pharmacodynamic properties, nuclear methods such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) using radiolabeled compounds are particularly suitable here. The use of radiolabeled nanogels for imaging, but also for therapy, is being discussed.

Nano-injectable pH/NIR-responsive hydrogel for chemo-photothermal synergistic drug delivery

Conventional cancer treatments are highly toxic and ineffective; therefore, it is essential to develop less toxic and minimally invasive treatment methods. A pH/Near Infra-red (NIR) dual-responsive, nano-injectable smart hydrogel was fabricated by incorporating CuS nanoparticles into the hydrogel networks formed by a random copolymer of N-isopropylacrylamide (NIPAM) and double-bond functionalized uracil. Microstructural characterizations of synthesized polymer and hydrogels were carried out using transmission electron microscope (TEM), scanning electron microscope (SEM), nuclear magnetic resonance (NMR) and fourier transform infrared spectroscopy (FT-IR). Multiple hydrogen bonding interactions between uracils function as physical cross-linking points to construct the network structure of the polymeric nanogel without the addition of additional cross-linking agents, ensuring the material's safety. The amino group on the structure of uracil gives the uracil-modified polymeric hydrogel excellent pH responsiveness. Notably, as a temperature-responsive material, poly (N-isopropylacrylamide) (PNIPAM) nanogel solution can achieve in situ gel formation (within 100 s at 37°C) above its lower critical solution temperature (LCST), granting injectability to polymeric solutions. Moreover, using a hierarchical construction strategy, the variable loading of DOX and CuS was achieved. First, a heterogeneous system was created by encapsulating doxorubicin (DOX) inside the nanogel via hydrophobic and π-π stacking interactions, followed by the introduction of CuS nanoparticles as photosensitizers outside of the nanogels. Due to the presence of CuS nanoparticles, the gel is able to convert NIR light into local heat to enhance the destruction of tumor cells while simultaneously achieving rapid in situ gel formation. The in situ-forming hydrogel showed promising tissue biocompatibility. The in vitro antitumor test demonstrated the capacity of the nanocomposite hydrogel for chemo-photothermal synergistic therapy. Therefore, this prepared platform has the potential to become a safe and effective, smart-responsive drug carrier for chemotherapy and PTT synergy, a minimally invasive material for tumor treatment.

Preparation of Cholesterol-Modified Hyaluronic Acid Nanogel-Based Hydrogel and the Inflammatory Evaluation Using Macrophage-like Cells

Nanogels are candidate biomaterials for tissue engineering and drug delivery. In the present study, a cholesterol-hyaluronic acid hydrogel was developed, and the pro-inflammatory response of macrophages to the hydrogel was investigated to determine its use in biomedical applications. Hyaluronic acid modified with cholesterol (modification rate: 0-15%) and maleimide (Chol-HA) was synthesized. The Chol-HA nanogel was formed through self-assembly via hydrophobic cholesterol interactions in aqueous solution. The Chol-HA hydrogel was formed through chemical crosslinking of the Chol-HA nanogel via a Michael addition reaction between the maleimide and thiol groups of 4arm-PEGSH. We found that the Chol-HA hydrogels with 5, 10, and 15% cholesterol inhibited the pro-inflammatory response of HiBiT-THP-1 cells, suggesting that the cholesterol contributed to the macrophage response. Furthermore, Interleukin 4 (IL-4) encapsulated in the hydrogel of the Chol-HA nanogel enhanced the inhibition of the inflammatory response in HiBiT-THP-1 cells. These results provide useful insights into the biomedical applications of hydrogels.

Self-Assembled Peptide Hydrogels in Regenerative Medicine

Regenerative medicine is a complex discipline that is becoming a hot research topic. Skin, bone, and nerve regeneration dominate current treatments in regenerative medicine. A new type of drug is urgently needed for their treatment due to their high vulnerability to damage and weak self-repairing ability. A self-assembled peptide hydrogel is a good scaffolding material in regenerative medicine because it is similar to the cytoplasmic matrix environment; it promotes cell adhesion, migration, proliferation, and division; and its degradation products are natural and harmless proteins. However, fewer studies have examined the specific mechanisms of self-assembled peptide hydrogels in promoting tissue regeneration. This review summarizes the applications and mechanisms of self-assembled short peptide and peptide hydrogels in skin, bone, and neural healing to improve their applications in tissue healing and regeneration.

Nanosilver-functionalized polysaccharides as a platform for wound dressing

Polysaccharides that are naturally sourced have enormous promise as wound dressings, due to their wider availability and reasonable cost and good biocompatibility. Furthermore, nanosilver extensively applied in wound treatment is attributed to its broad spectrum of antimicrobial effects and lesser drug resistance. Consequently, wound dressings in corporating nanosilver have attracted wide-scale interest in wound healing, and nanosilver-functionalized polysaccharide-based wound dressings present an affordable option for healing of chronic wounds. This review encompasses preparation methods, classification, and antibacterial performances of nanosilver wound dressings. The prospective research arenas of nanosilver-based wound polysaccharide dressings are also elaborated. The review attempts to include a summary of the most recent advancements in silver nanotechnology as well as guidance for the investigation of nanosilver-functionalized polysaccharide-based wound dressings.

Polymeric nanoparticle-based nanovaccines for cancer immunotherapy

Therapeutic cancer vaccines, which are designed to amplify tumor-specific T cell responses, have been envisioned as one of the most powerful tools for effective cancer immunotherapy. However, increasing the potency, quality and durability of the vaccine response remains a big challenge. In recent years, materials-based delivery systems focusing on the co-delivery of antigens and adjuvants to enhance cancer vaccination therapy have attracted increasing interest. Among various materials, polymeric nanoparticles (NPs) with different physicochemical properties which can incorporate multiple immunological cues are of great interest. In this review, the recent progress in the design and construction of both ex vivo subunit and in situ cancer vaccines using polymeric NPs is summarized. Especially, we will focus on how these NPs improve the adjuvanticity of vaccines. The design principles of polymeric NPs for ex vivo subunit cancer vaccines and in situ cancer vaccination are also discussed. Finally, we want to briefly discuss molecular chaperones in cancer immunity and the applications of our unique self-assembly mixed shell polymeric micelle-based nanochaperones for cancer vaccines.

Promising Nanomedicines of Shikonin for Cancer Therapy

Malignant tumor, the leading cause of death worldwide, poses a serious threat to human health. For decades, natural product has been proven to be an essential source for novel anticancer drug discovery. Shikonin (SHK), a natural molecule separated from the root of Lithospermum erythrorhizon, shows great potential in anticancer therapy. However, its further clinical application is significantly restricted by poor bioavailability, adverse effects, and non-selective toxicity. With the development of nanotechnology, nano drug delivery systems have emerged as promising strategies to improve bioavailability and enhance the therapeutic efficacy of drugs. To overcome the shortcoming of SHK, various nano drug delivery systems such as liposomes, polymeric micelles, nanoparticles, nanogels, and nanoemulsions, were developed to achieve efficient delivery for enhanced antitumor effects. Herein, this review summarizes the anticancer pharmacological activities and pharmacokinetics of SHK. Additionally, the latest progress of SHK nanomedicines in cancer therapy is outlined, focusing on long circulation, tumor targeting ability, tumor microenvironment responsive drug release, and nanosystem-mediated combination therapy. Finally, the challenges and prospects of SHK nanomedicines in the future clinical application are spotlighted.

Fabry disease: Mechanism and therapeutics strategies

Fabry disease is a monogenic disease characterized by a deficiency or loss of the α-galactosidase A (GLA). The resulting impairment in lysosomal GLA enzymatic activity leads to the pathogenic accumulation of enzymatic substrate and, consequently, the progressive appearance of clinical symptoms in target organs, including the heart, kidney, and brain. However, the mechanisms involved in Fabry disease-mediated organ damage are largely ambiguous and poorly understood, which hinders the development of therapeutic strategies for the treatment of this disorder. Although currently available clinical approaches have shown some efficiency in the treatment of Fabry disease, they all exhibit limitations that need to be overcome. In this review, we first introduce current mechanistic knowledge of Fabry disease and discuss potential therapeutic strategies for its treatment. We then systemically summarize and discuss advances in research on therapeutic approaches, including enzyme replacement therapy (ERT), gene therapy, and chaperone therapy, as well as strategies targeting subcellular compartments, such as lysosomes, the endoplasmic reticulum, and the nucleus. Finally, the future development of potential therapeutic strategies is discussed based on the results of mechanistic studies and the limitations associated with these therapeutic approaches.

Nanogel-mediated delivery of oncomodulin secreted from regeneration-associated macrophages promotes sensory axon regeneration in the spinal cord

Preconditioning nerve injury enhances axonal regeneration of dorsal root ganglia (DRG) neurons in part by driving pro-regenerative perineuronal macrophage activation. How these macrophages influence the neuronal capacity of axon regeneration remains elusive. We report that oncomodulin (ONCM) is produced from the regeneration-associated macrophages and strongly influences regeneration of DRG sensory axons. We also attempted to promote sensory axon regeneration by nanogel-mediated delivery of ONCM to DRGs.

Methods:In vitro neuron-macrophage interaction model and preconditioning sciatic nerve injury were used to verify the necessity of ONCM in preconditioning injury-induced neurite outgrowth. We developed a nanogel-mediated delivery system in which electrostatic encapsulation of ONCM by a reducible epsilon-poly(_L-lysine)-nanogel (REPL-NG) enabled a controlled release of ONCM.

Results: Sciatic nerve injury upregulated ONCM in DRG macrophages. ONCM in macrophages was necessary to produce pro-regenerative macrophages in the in vitro model of neuron-macrophage interaction and played an essential role in preconditioning-induced neurite outgrowth. ONCM increased neurite outgrowth in cultured DRG neurons by activating a distinct gene set, particularly neuropeptide-related genes. Increasing extracellularly secreted ONCM in DRGs sufficiently enhanced the capacity of neurite outgrowth. Intraganglionic injection of REPL-NG/ONCM complex allowed sustained ONCM activity in DRG tissue and achieved a remarkable long-range regeneration of dorsal column sensory axons beyond spinal cord lesion.

Conclusion: NG-mediated ONCM delivery could be exploited as a therapeutic strategy for promoting sensory axon regeneration following spinal cord injury.

Three-Dimensional Culture of Cartilage Tissue on Nanogel-Cross-Linked Porous Freeze-Dried Gel Scaffold for Regenerative Cartilage Therapy: A Vibrational Spectroscopy Evaluation

This study presents a set of vibrational characterizations on a nanogel-cross-linked porous freeze-dried gel (NanoCliP-FD gel) scaffold for tissue engineering and regenerative therapy. This scaffold is designed for the in vitro culture of high-quality cartilage tissue to be then transplanted in vivo to enable recovery from congenital malformations in the maxillofacial area or crippling jaw disease. The three-dimensional scaffold for in-plate culture is designed with interface chemistry capable of stimulating cartilage formation and maintaining its structure through counteracting the dedifferentiation of mesenchymal stem cells (MSCs) during the formation of cartilage tissue. The developed interface chemistry enabled high efficiency in both growth rate and tissue quality, thus satisfying the requirements of large volumes, high matrix quality, and superior mechanical properties needed in cartilage transplants. We characterized the cartilage tissue in vitro grown on a NanoCliP-FD gel scaffold by human periodontal ligament-derived stem cells (a type of MSC) with cartilage grown by the same cells and under the same conditions on a conventional (porous) atelocollagen scaffold. The cartilage tissues produced by the MSCs on different scaffolds were comparatively evaluated by immunohistochemical and spectroscopic analyses. Cartilage differentiation occurred at a higher rate when MSCs were cultured on the NanoCliP-FD gel scaffold compared to the atelocollagen scaffold, and produced a tissue richer in cartilage matrix. In situ spectroscopic analyses revealed the cell/scaffold interactive mechanisms by which the NanoCliP-FD gel scaffold stimulated such increased efficiency in cartilage matrix formation. In addition to demonstrating the high potential of human periodontal ligament-derived stem cell cultures on NanoCliP-FD gel scaffolds in regenerative cartilage therapy, the present study also highlights the novelty of Raman spectroscopy as a non-destructive method for the concurrent evaluation of matrix quality and cell metabolic response. In situ Raman analyses on living cells unveiled for the first time the underlying physiological mechanisms behind such improved chondrocyte performance.

Stimuli-responsive polypeptide nanogels for trypsin inhibition

A new type of hydrophilic, biocompatible, and biodegradable polypeptide nanogel depots loaded with the natural serine protease inhibitor α1-antitrypsin (AAT) was applied for the inhibition of the inflammatory mediator trypsin. Two types of nanogels were prepared from linear synthetic polypeptides based on biocompatible and biodegradable poly[N ⁵-(2-hydroxyethyl)-ʟ-glutamine-ran-N ⁵-propargyl-ʟ-glutamine-ran-N ⁵-(6-aminohexyl)-ʟ-glutamine]-ran-N ⁵-[2-(4-hydroxyphenyl)ethyl)-ʟ-glutamine] (PHEG-Tyr) or biocompatible N ^α-ʟ-lysine-grafted α,β-poly[(2-propyne)-ᴅ,ʟ-aspartamide-ran-(2-hydroxyethyl)-ᴅʟ-aspartamide-ran-(2-(4-hydroxyphenyl)ethyl)-ᴅʟ-aspartamide] (N ^α-Lys-NG). Both nanogels were prepared by HRP/H₂O₂-mediated crosslinking in inverse miniemulsions with pH and temperature-stimuli responsive behavior confirmed by dynamic light scattering and zeta potential measurements. The loading capacity of PHEG-Tyr and N ^α-Lys-NG nanogels and their release profiles were first optimized with bovine serum albumin. The nanogels were then used for loading and release of AAT. PHEG-Tyr and N ^α-Lys-NG nanogels showed different loading capacities for AAT with the maximum (20%) achieved with N ^α-Lys-NG nanogel. In both cases, the nanogel depots demonstrated a burst release of AAT during the first 6 h, which could be favorable for quick inhibition of trypsin. A consequent pilot in vitro inhibition study revealed that both PHEG-Tyr and N ^α-Lys-NG nanogels loaded with AAT successfully inhibited the enzymatic activity of trypsin. Furthermore, the inhibitory efficiency of the AAT-loaded nanogels was higher than that of only AAT. Interestingly, also non-loaded PHEG-Tyr and N ^α-Lys-NG nanogels were shown to effectively inhibit trypsin because they contain suitable amino acids in their structures that effectively block the active site of trypsin.

Protein antigen conjugated with cholesteryl amino-pullulan nanogel shows delayed degradation in dendritic cells and augmented immunogenicity

Carriers that augment delivery, immunogenicity or both are crucial in the development of vaccines especially component vaccines as components of pathogens are often poorly immunogenic. Cholesteryl pullulan (CHP) that forms nano-sized hydrogel (nanogel) and encapsulates proteins was shown to be useful in the delivery of vaccines. Here we demonstrate that subcutaneous immunization of mice with bovine serum albumin (BSA) chemically conjugated to NH₂-CHP nanogel induces strong antibody production. This augmented antibody production requires covalent conjugation between BSA and CHP, but does not require nanogel formation. Conjugation of NH₂-CHP nanogel induces persistence of BSA in dendritic cells (DCs) in vivo. As resistance to lysosomal degradation was previously shown to augment antigen presentation by DCs, conjugation of antigens with CHP nanogel may enhance antibody production to antigens by delaying lysosomal degradation. Therefore, delayed degradation of antigens by covalent conjugation with nanoparticles may be a good strategy for the development of effective vaccines.

Construction of Hybrid Cell Spheroids Using Cell-Sized Cross-Linked Nanogel Microspheres as an Artificial Extracellular Matrix

The introduction of functional material supports or spacers into cell spheroids increases the free volume, allowing oxygen, nutrients, and waste products to diffuse in and out more freely. Here, a biocompatible polysaccharide spacer material was investigated. Microspheres were prepared by cross-linking cholesterol-modified pullulan (CHP) nanogels with poly(ethylene glycol) (PEG). The ratio of modified CHP nanogel to PEG cross-linker was optimized to give uniform microspheres with an average diameter of approximately 14 μm. Rhodamine B-labeled microspheres showed a homogeneous assembly with bone marrow-derived mesenchymal stem cells (1:1 ratio) to create hybrid cell spheroids. The addition of the cross-linked nanogel spacers did not affect the cell viability, indicating that the microspheres provided a biocompatible scaffold that supported cell proliferation. In addition, the microspheres were stable under culture conditions over 14 days. The hybrid cell spheroids were scaled up to millimeter size to demonstrate their potential as a transplantable treatment, and the cells were found to maintain their high viability. The hybrid cell spheroids are expected to support the production of organoids.

Advances in Hyaluronic-Acid-Based (Nano)Devices for Cancer Therapy

Cancer is the main cause of fatality all over the world with a considerable growth rate. Many biologically active nanoplatforms are exploited for tumor treatment. Of nanodevices, hyaluronic acid (HA)-based systems have shown to be promising candidates for cancer therapy due to their high biocompatibility and cell internalization. Herein, surface functionalization of different nanoparticles (NPs), e.g., organic- and inorganic-based NPs, is highlighted. Subsequently, HA-based nanostructures and their applications in cancer therapy are presented.

Temperature/Reduction Dual Response Nanogel Is Formed by In Situ Stereocomplexation of Poly (Lactic Acid)

A novel type of dual responsive nanogels was synthesized by physical crosslinking of polylactic acid stereocomplexation: temperature and reduction dual stimulation responsive gels were formed in situ by mixing equal amounts of PLA (Poly (Lactic Acid)) enantiomeric graft copolymer micellar solution; the properties of double stimulation response make it more targeted in the field of drug release. The structural composition of the gels was studied by proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy (FT-IR). Using transmission electron microscope (TEM) and dynamic light scattering (DLS) instruments, the differences in morphology and particle size were analyzed (indicating that nanogels have dual stimulus responses of temperature sensitivity and reduction). The Wide-Angle X-ray diffractionr (WAXD) was used to prove the stereocomplexation of PLA in the gels, the mechanical properties and gelation process of the gels were studied by rheology test. The physically cross-linked gel network generated by the self-recombination of micelles and then stereo-complexation has a more stable structure. The results show that the micelle properties, swelling properties and rheological properties of nanogels can be changed by adjusting the degree of polymerization of polylactic acid. In addition, it provides a safe and practical new method for preparing stable temperature/reduction response physical cross-linked gel.

Bioengineered Protein-based Adhesives for Biomedical Applications

Protein-based adhesives with their robust adhesion performance and excellent biocompatibility have been extensively explored over years. In particular, the unique adhesion behaviours of mussel and sandcastle worm inspired the development of synthetic adhesives. However, the chemical synthesized adhesives often demonstrate weak underwater adhesion performance and poor biocompatibility/biodegradability, limiting their further biomedical applications. In sharp contrast, genetically engineering endows the protein-based adhesives the ability to maintain underwater adhesion property as well as biocompatibility/biodegradability. Herein, we outline recent advances in the design and development of protein-based adhesives by genetic engineering. We summarize the fabrication and adhesion performance of elastin-like polypeptide-based adhesives, followed by mussel foot protein (mfp) based adhesives and other sources protein-based adhesives, such as, spider silk spidroin and suckerin. In addition, the biomedical applications of these bioengineered protein-based adhesives are presented. Finally, we give a brief summary and perspective on the future development of bioengineered protein-based adhesives.

Osteogenic Response to Polysaccharide Nanogel Sheets of Human Fibroblasts After Conversion Into Functional Osteoblasts by Direct Phenotypic Cell Reprogramming

Human dermal fibroblasts (HDFs) were converted into osteoblasts using a ALK inhibitor II (inhibitor of transforming growth factor-β signal) on freeze-dried nanogel-cross-linked porous (FD-NanoClip) polysaccharide sheets or fibers. Then, the ability of these directly converted osteoblasts (dOBs) to produce calcified substrates and the expression of osteoblast genes were analyzed in comparison with osteoblasts converted by exactly the same procedure but seeded onto a conventional atelocollagen scaffold. dOBs exposed to FD-NanoClip in both sheet and fiber morphologies produced a significantly higher concentration of calcium deposits as compared to a control cell sample (i.e., unconverted fibroblasts), while there was no statistically significant difference in calcification level between dOBs exposed to atelocollagen sheets and the control group. The observed differences in osteogenic behaviors were interpreted according to Raman spectroscopic analyses comparing different polysaccharide scaffolds and Fourier transform infrared spectroscopy analyses of dOB cultures. This study substantiates a possible new path to repair large bone defects through a simplified transplantation procedure using FD-NanoClip sheets with better osteogenic outputs as compared to the existing atelocollagen scaffolding material.

CD44-Targeted and Enzyme-Responsive Photo-Cross-Linked Nanogels with Enhanced Stability for In Vivo Protein Delivery

One of the biggest challenges of the protein delivery system is to realize stable and high protein encapsulation efficiency in blood circulation and rapid release of protein in the targeted tumor cells. To overcome these hurdles, we fabricated enzyme-responsive photo-cross-linked nanogels (EPNGs) through UV-triggered chemical cross-linking of cinnamyloxy groups in the side chain of PEGylation hyaluronic acid (HA) for CD44-targeted transport of cytochrome c (CC). The EPNGs showed high loading efficiency and excellent stability in different biological media. Notably, CC leakage effectively suppressed under physiological conditions but accelerated release in the presence of hyaluronidase, an overexpressed enzyme in tumor cells. Moreover, thiazolylblue tetrazolium bromide (MTT) results indicated that the vacant EPNGs showed excellent nontoxicity, while CC-loaded EPNGs exhibited higher killing efficiency to CD44-positive A549 cells than to CD44-negative HepG2 cells and free CC. Confocal images confirmed that CC-loaded EPNGs could effectively be internalized by CD44-mediated endocytosis pathway and rapidly escape from the endo/lysosomal compartment. Human lung tumor-bearing mice imaging assays further revealed that CC-loaded EPNGs actively target tumor locations. Remarkably, CC-loaded EPNGs also exhibited enhanced antitumor activity with negligible systemic toxicity. These results implied that these EPNGs have appeared as stable and promising nanocarriers for tumor-targeting protein delivery.

Photodynamic therapy using self-assembled nanogels comprising chlorin e6-bearing pullulan

With minimal invasiveness and spatiotemporal therapeutic effects, photodynamic therapy is one of the most promising candidates for cancer treatment. Here, we developed a facile self-assembled nanogel using photosensitizer-grafted polysaccharides called chlorin e6-bearing pullulan. Chlorin e6 is used as a photosensitizer in cancer therapy. The anti-cancer effect of photodynamic therapy with our nanogel system was 780 times higher than that of the commercially available photosensitizer Photofrin. Finally, we demonstrated that actively growing cancer cell spheroids can be completely suppressed after treatment. Our system could efficiently induce tumor regression in tumor xenograft mice.

Strategies to load therapeutics into polysaccharide-based nanogels with a focus on microfluidics: A review

Nowadays nanoparticles are increasingly investigated for the targeted and controlled delivery of therapeutics, as suggested by the high number of research articles (2400 in 2000 vs 8500 in 2020). Among them, almost 2% investigated nanogels in 2020. Nanogels or nanohydrogels (NGs) are nanoparticles formed by a swollen three-dimensional network of synthetic polymers or natural macromolecules such as polysaccharides. NGs represent a highly versatile nanocarrier, able to deliver a number of therapeutics. Currently, NGs are undergoing clinical trials for the delivery of anti-cancer vaccines. Herein, the strategies to load low molecular weight drugs, (poly)peptides and genetic material into polysaccharide NGs as well as to formulate NGs-based vaccines are summarized, with a focus on the microfluidics approach.

Characterization and Specification of a Trivalent Protein-Based Pneumococcal Vaccine Formulation Using an Adjuvant-Free Nanogel Nasal Delivery System

We previously developed a safe and effective nasal vaccine delivery system using a self-assembled nanosized hydrogel (nanogel) made from a cationic cholesteryl pullulan. Here, we generated three pneumococcal surface protein A (PspA) fusion antigens as a universal pneumococcal nasal vaccine and then encapsulated each PspA into a nanogel and mixed the three resulting monovalent formulations into a trivalent nanogel-PspA formulation. First, to characterize the nanogel-PspA formulations, we used native polyacrylamide gel electrophoresis (PAGE) to determine the average number of PspA molecules encapsulated per nanogel molecule. Second, we adopted two methods-a densitometric method based on lithium dodecyl sulfate (LDS)-PAGE and a biologic method involving sandwich enzyme-linked immunosorbent assay (ELISA)-to determine the PspA content in the nanogel formulations. Third, treatment of nanogel-PspA formulations by adding methyl-β-cyclodextrin released each PspA in its native form, as confirmed through circular dichroism (CD) spectroscopy. However, when nanogel-PspA formulations were heat-treated at 80 °C for 16 h, CD spectroscopy showed that each PspA was released in a denatured form. Fourth, we confirmed that the nanogel-PspA formulations were internalized into nasal mucosa effectively and that each PspA was gradually released from the nanogel in epithelial cells in mice. Fifth, LDS-PAGE densitometry and ELISA both indicated that the amount of trivalent PspA was dramatically decreased in the heat-treated nanogel compared with that before heating. When mice were immunized nasally using the heat-treated formulation, the immunologic activity of each PspA was dramatically reduced compared with that of the untreated formulation; in both cases, the immunologic activity correlated well with the content of each PspA as determined by LDS-PAGE densitometry and ELISA. Finally, we confirmed that the trivalent nanogel-PspA formulation induced equivalent titers of PspA-specific serum IgG and mucosal IgA Abs in immunized mice. These results show that the specification methods we developed effectively characterized our nanogel-based trivalent PspA nasal vaccine formulation.

Cholesteryl-Conjugated Ribonuclease A Exhibits Enzyme Activity in Aqueous Solution and Resistance to Dimethyl Sulfoxide

Using bovine pancreatic ribonuclease A (RNase A) and cholesterol, we synthesized cholesteryl-conjugated ribonuclease A (CHRNase A) to evaluate the influence of a conjugated hydrophobic moiety on protein function. Nuclear magnetic resonance and matrix-assisted laser desorption/ionization time-of-flight spectrometry suggested that one cholesteryl group was conjugated to RNase A. Differential scanning calorimetry indicated that CHRNase A was denatured in the solid state but was folded in phosphate buffer (0.05 mol/L, pH 6.5). CHRNase A resembled RNase A in its secondary structure, but circular dichroism (CD) spectra revealed that the helical content of CHRNase A was decreased and the tertiary structure of CHRNase A differed from that of RNase A. Furthermore, fluorescence measurements, CD spectra, an 8-anilino-1-naphthalenesulfonic acid ammonium salt-based assay, and surface tension measurements suggested that cholesterol was conjugated to a tyrosine residue on the protein surface. The relative activity of CHRNase A to RNase A was 79 ± 7%, and the enzyme activity of CHRNase A by adding β-cyclodextrin (β-CyD) increased to 129 ± 7%. Therefore, we considered that the cholesteryl group interacted with substrate (cytidine 2'3'-cyclic monophosphate monosodium salt) to inhibit the enzyme reaction. Finally, the environment around tyrosine residues in CHRNase A in dimethyl sulfoxide was similar to that of native RNase A in phosphate buffer (0.05 mol/L, pH 6.5). These results suggest that cholesterol conjugation to RNase A altered RNase A functionality, including improvement of RNase A resistance to dimethyl sulfoxide and modulation of the ability of β-CyD to control RNase A enzymatic activity.

Hierarchical and heterogeneous hydrogel system as a promising strategy for diversified interfacial tissue regeneration

A state-of-the-art review on the design and preparation of hierarchical and heterogeneous hydrogel systems for interfacial tissue regeneration.

Gold nanoparticle-guarded large-pore mesoporous silica nanocomposites for delivery and controlled release of cytochrome c

Efficient delivery of active proteins to specific cells and organs is one of the most important issues in medical applications. However, in most cases, proteins without appropriate carriers face numerous barriers when delivered to the target, due to their unsatisfied properties, such as poor stability, short half-life, and low membrane permeability. Herein, we have presented a large-pore mesoporous silica nanoparticle (LPMSN)-based protein delivery system. LPMSNs were obtained with ethyl acetate as a pore expander. A 2,3-dimethylmaleamic acid-containing silane coupling agent was modified on LPMSNs to provide pH-triggered charge reversal. After Cytochrome c (CC) was encapsulated in the large pores of LPMSNs, amino-terminated polyethylene glycol-modified gold nanoparticles (AuNPs) served as gateguards to cap the tunnels of LPMSNs and to avoid the leakage of CC. Above nanocomposites exhibited the capability to deliver active CC into cancer cells, charge reversal-induced protein release, as well as to initiate the apoptosis machinery of cancer cells in vitro. Importantly, the nanocomposites significantly inhibited tumor growth and extended survival rate without obvious side effects. This study provides a smart and efficient protein delivery platform with good safety profiles for efficacious tumor protein therapy in vivo.

In Vivo Regeneration of Large Bone Defects by Cross-Linked Porous Hydrogel: A Pilot Study in Mice Combining Micro Tomography, Histological Analyses, Raman Spectroscopy and Synchrotron Infrared Imaging

The transplantation of engineered three-dimensional (3D) bone graft substitutes is a viable approach to the regeneration of severe bone defects. For large bone defects, an appropriate 3D scaffold may be necessary to support and stimulate bone regeneration, even when a sufficient number of cells and cell cytokines are available. In this study, we evaluated the in vivo performance of a nanogel tectonic 3D scaffold specifically developed for bone tissue engineering, referred to as nanogel cross-linked porous-freeze-dry (NanoCliP-FD) gel. Samples were characterized by a combination of micro-computed tomography scanning, Raman spectroscopy, histological analyses, and synchrotron radiation-based Fourier transform infrared spectroscopy. NanoCliP-FD gel is a modified version of a previously developed nanogel cross-linked porous (NanoCliP) gel and was designed to achieve highly improved functionality in bone mineralization. Spectroscopic imaging of the bone tissue grown in vivo upon application of NanoCliP-FD gel enables an evaluation of bone quality and can be employed to judge the feasibility of NanoCliP-FD gel scaffolding as a therapeutic modality for bone diseases associated with large bone defects.

Synthesis and Characterization of Cholesteryl Conjugated Lysozyme (CHLysozyme)

Hydrophobic interaction is important for protein conformation. Conjugation of a hydrophobic group can introduce intermolecular hydrophobic contacts that can be contained within the molecule. It is possible that a strongly folded state can be formed in solution compared with the native state. In this study, we synthesized cholesteryl conjugated lysozyme (CHLysozyme) using lysozyme and cholesterol as the model protein and hydrophobic group, respectively. Cholesteryl conjugation to lysozyme was confirmed by nuclear-magnetic resonance. Differential-scanning calorimetry suggested that CHLysozyme was folded in solution. CHLysozyme secondary structure was similar to lysozyme, although circular dichroism spectra indicated differences to the tertiary structure. Fluorescence measurements revealed a significant increase in the hydrophobic surface of CHLysozyme compared with that of lysozyme; CHLysozyme self-associated by hydrophobic interaction of the conjugated cholesterol but the hydrophobic surface of CHLysozyme decreased with time. The results suggested that hydrophobic interaction changed from intramolecular interaction to an intermolecular interaction. Furthermore, the relative activity of CHLysozyme to lysozyme increased with time. Therefore, CHLysozyme likely forms a folded state with an extended durability of activity. Moreover, lysozyme was denatured in 100% DMSO but the local environment of tryptophan in CHLysozyme was similar to that of a native lysozyme. Thus, this study suggests that protein solution stability and resistance to organic solvents may be improved by conjugation of a hydrophobic group.

Hydrophobic Monomers Recognize Microenvironments in Hydrogel Microspheres during Free-Radical-Seeded Emulsion Polymerization

The three-dimensional structure of nanocomposite microgels was precisely determined by cryo-electron micrography. Several nanocomposite microgels that differ with respect to their nanocomposite structure, which were obtained from seeded emulsion polymerization in the presence of microgels, were used as model nanocomposite materials for cryo-electron micrography. The obtained three-dimensional segmentation images of these nanocomposite microgels provide important insights into the interactions between the hydrophobic monomers and the microgels, that is, hydrophobic styrene monomers recognize molecular-scale differences in polarity within the microgels during the emulsion polymerization. This result led to the formation of unprecedented multi-layered nanocomposite microgels, which promise substantial potential in colloidal applications.