Photoactivatable CO release from engineered protein crystals to modulate NF-κB activation

Near-infrared light triggered upconversion nanocomposites with multifunction of enhanced antimicrobial photodynamic therapy and gas therapy for inflammation regulation

Antibacterial photodynamic therapy (aPDT) is highly effective in killing bacteria, while the problem of hypoxia and limited light penetration in deep tissue has not been properly solved. In addition, few aPDT works take into account the regulation of inflammation, which is an important regulatory process after antimicrobial therapy and the final purpose of treatment. In this work, to address the above isssues, we have designed a multi-functional composite UCNPs-Ce6-Mn(CO)5Br@Silane (referred to as UCM@Si), which consists of several key components: Up-conversion nanoparticles (UCNPs: NaErF4:Tm3+@NaYF4:Yb3+), Chlorin e6 (Ce6) and Manganese pentacarbonyl bromide (Mn(CO)5Br). When exposed to near-infrared (NIR) light (980 nm), the UCNPs can emit strong red light at 655 nm which further trigger the aPDT of Ce6. The generated reactive oxygen (ROS) subsequently break the metal carbonyl bond of Mn(CO)5Br, leading to the production of carbon monoxide (CO) molecules as well as manganese ions (Mn2+), which further decomposes hydrogen peroxide (H2O2) in the microenvironment to oxygen (O2). Therefore, this simple nanocomposite not only provides substantial self-oxygen replenishment for enhanced aPDT, but also facilitates effective inflammation regulation via CO across a wide range of deep infections. This approach leverages the unique properties of these materials to combat bacterial infections by simultaneously killing bacteria, regulating inflammation, and enhancing the oxygen levels in the affected microenvironment. This O2 and CO gas based aPDT treatment system offers a promising approach to comprehensively address microbial-induced infectious diseases, particularly deep infections, holding the potential clinical applications.

Engineering of an in-cell protein crystal for fastening a metastable conformation of a target miniprotein

Protein crystals can be utilized as porous scaffolds to capture exogenous molecules. Immobilization of target proteins using protein crystals is expected to facilitate X-ray structure analysis of proteins that are difficult to be crystallized. One of the advantages of scaffold-assisted structure determination is the analysis of metastable structures that are not observed in solution. However, efforts to fix target proteins within the pores of scaffold protein crystals have been limited due to the lack of strategies to control protein-protein interactions formed in the crystals. In this study, we analyze the metastable structure of the miniprotein, CLN025, which forms a β-hairpin structure in solution, using a polyhedra crystal (PhC), an in-cell protein crystal. CLN025 is successfully fixed within the PhC scaffold by replacing the original loop region. X-ray crystal structure analysis and molecular dynamics (MD) simulation reveal that CLN025 is fixed as a helical structure in a metastable state by non-covalent interactions in the scaffold crystal. These results indicate that modulation of intermolecular interactions can trap various protein conformations in the engineered PhC and provides a new strategy for scaffold-assisted structure determination.

Pharmacological Targeting of Heme Oxygenase-1 in Osteoarthritis

Osteoarthritis (OA) is a common aging-associated disease that clinically manifests as joint pain, mobility limitations, and compromised quality of life. Today, OA treatment is limited to pain management and joint arthroplasty at the later stages of disease progression. OA pathogenesis is predominantly mediated by oxidative damage to joint cartilage extracellular matrix and local cells such as chondrocytes, osteoclasts, osteoblasts, and synovial fibroblasts. Under normal conditions, cells prevent the accumulation of reactive oxygen species (ROS) under oxidatively stressful conditions through their adaptive cytoprotective mechanisms. Heme oxygenase-1 (HO-1) is an iron-dependent cytoprotective enzyme that functions as the inducible form of HO. HO-1 and its metabolites carbon monoxide and biliverdin contribute towards the maintenance of redox homeostasis. HO-1 expression is primarily regulated at the transcriptional level through transcriptional factor nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2), specificity protein 1 (Sp1), transcriptional repressor BTB-and-CNC homology 1 (Bach1), and epigenetic regulation. Several studies report that HO-1 expression can be regulated using various antioxidative factors and chemical compounds, suggesting therapeutic implications in OA pathogenesis as well as in the wider context of joint disease. Here, we review the protective role of HO-1 in OA with a focus on the regulatory mechanisms that mediate HO-1 activity.

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

Photoactivatable (alternatively, photoremovable, photoreleasable, or photocleavable) protecting groups (PPGs), also known as caged or photocaged compounds, are used to enable non-invasive spatiotemporal photochemical control over the release of species of interest. Recent years have seen the development of PPGs activatable by biologically and chemically benign visible and near-infrared (NIR) light. These long-wavelength-absorbing moieties expand the applicability of this powerful method and its accessibility to non-specialist users. This review comprehensively covers organic and transition metal-containing photoactivatable compounds (complexes) that absorb in the visible- and NIR-range to release various leaving groups and gasotransmitters (carbon monoxide, nitric oxide, and hydrogen sulfide). The text also covers visible- and NIR-light-induced photosensitized release using molecular sensitizers, quantum dots, and upconversion and second-harmonic nanoparticles, as well as release via photodynamic (photooxygenation by singlet oxygen) and photothermal effects. Release from photoactivatable polymers, micelles, vesicles, and photoswitches, along with the related emerging field of photopharmacology, is discussed at the end of the review.

A multifunctional anti-inflammatory drug that can specifically target activated macrophages, massively deplete intracellular H2O2, and produce large amounts CO for a highly efficient treatment of osteoarthritis

Specifically inhibiting the proliferation of activated macrophages and clearing the high levels of reactive oxygen species (ROS) secreted by macrophages is crucial for osteoarthritis (OA) treatment. Moreover, if the clearance of these high levels of ROS can be simultaneously used to induce oxidation-responsive release of anti-inflammatory drugs, the therapeutic effect of OA may be further improved. Here, a multifunctional anti-inflammatory drug (CPHs) based on a peptide dendrimer nanogel was constructed by physically encapsulating CORM-401 and wrapping its surface with folic acid (FA)-modified hyaluronic acid (HA). CPHs is capable of efficiently entering activated macrophages via FA- and HA-mediated specific targeting effects and then rapidly release large amounts of CO by massive consumption of H₂O₂. The generated CO effectively suppresses the secretion of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α by inhibiting cell proliferation; inducing the activation of heme oxygenase (HO-1), and downregulating the expression of p38 MAPK, NF-kB (p50/p65) and TLR-2. In vivo experiments further confirmed that CPHs can massively deplete ROS in OA joints and effectively suppress the degradation of articular cartilage and their extracellular matrix. More importantly, CPHs is non-toxic to normal macrophages, and the high levels of CO generated in the joints do not result in notable changes in the HbCO levels in blood. Together, these results show that CPHs is an effective and safe anti-inflammatory drug and has essential application prospects in OA treatment.

Strategies for engineering advanced nanomedicines for gas therapy of cancer

As an emerging and promising treatment method, gas therapy has attracted more and more attention for treatment of inflammation-related diseases, especially cancer. However, therapeutic/therapy-assisted gases (NO, CO, H₂S, H₂, O₂, SO₂ and CO₂) and most of their prodrugs lack the abilities of active intratumoral accumulation and controlled gas release, resulting in limited cancer therapy efficacy and potential side effects. Therefore, development of nanomedicines to realize tumor-targeted and controlled release of therapeutic/therapy-assisted gases is greatly desired, and also the combination of other therapeutic modes with gas therapy by multifunctional nanocarrier platforms can augment cancer therapy efficacy and also reduce their side effects. The design of nanomedicines with these functions is vitally important, but challenging. In this review, we summarize a series of engineering strategies for construction of advanced gas-releasing nanomedicines from four aspects: (1) stimuli-responsive strategies for controlled gas release; (2) catalytic strategies for controlled gas release; (3) tumor-targeted gas delivery strategies; (4) multi-model combination strategies based on gas therapy. Moreover, we highlight current issues and gaps in knowledge, and envisage current trends and future prospects of advanced nanomedicines for gas therapy of cancer. This review aims to inspire and guide the engineering of advanced gas-releasing nanomedicines.

Polyhedra, spindles, phage nucleus and pyramids: Structural biology of viral superstructures

Viral infection causes comprehensive rearrangements of the cell that reflect as much host defense mechanisms as virus-induced structures assembled to facilitate infection. Regardless of their pro- or antiviral role, large intracellular structures are readily detectable by microscopy and often provide a signature characteristic of a specific viral infection. The structural features and localization of these assemblies have thus been commonly used for the diagnostic and classification of viruses since the early days of virology. More recently, characterization of viral superstructures using molecular and structural approaches have revealed very diverse organizations and roles, ranging from dynamic viral factories behaving like liquid organelles to ultra-stable crystals embedding and protecting virions. This chapter reviews the structures, functions and biotechnological applications of virus-induced superstructures with a focus on assemblies that have a regular organization, for which detailed structural descriptions are available. Examples span viruses infecting all domains of life including the assembly of virions into crystalline arrays in eukaryotic and bacterial viruses, nucleus-like compartments involved in the replication of large bacteriophages, and pyramid-like structures mediating the egress of archaeal viruses. Among these superstructures, high-resolution structures are available for crystalline objects produced by insect viruses: viral polyhedra which function as the infectious form of occluded viruses, and spindles which are potent virulence factors of entomopoxviruses. In turn, some of these highly symmetrical objects have been used to develop and validate advanced structural approaches, pushing the boundary of structural biology.

Metal-Assisted Assembly of Protein Containers Loaded with Inorganic Nanoparticles

Protein containers are suitable building blocks for bioinorganic materials. Here, we show that high concentrations of magnesium ions induce the formation of a unitary protein scaffold, whereas low magnesium concentration leads to a binary protein scaffold. The molecular interactions in the protein scaffold were characterized with X-ray crystallography to high resolution. We show that the unitary framework can be applied for the assembly of inorganic nanoparticles such as metal oxides into highly ordered bioinorganic structures. Our work emphasizes the structural tunability of protein-container-based materials, important for adjusting emerging properties of such materials.

Flexible Modulation of CO-Release Using Various Nuclearity of Metal Carbonyl Clusters on Graphene Oxide for Stroke Remediation

Utilizing the size-dependent adsorption properties of ruthenium carbonyl clusters (Ru-carbon monoxide (CO)) onto graphene oxide (GO), a facile CO-release platform for in situ vasodilation as a treatment for stroke-related vascular diseases is developed. The rate and amount of formation of the CO-release-active Ru^II (CO)₂ species can be modulated by a simple mixing procedure at room temperature. The subsequent thermally induced oxidation of Ru^II (CO)₂ to RuO₂ on the GO surface results in the release of CO. Further modulation of thermal and CO-release properties can be achieved via a hybridization of medium- and high-nuclearity of Ru-CO clusters that produces a RuO₂ /Ru^II (CO)₂ /⁶ Ru-CO-GO composite, where ⁶ Ru-CO-GO provides a photothermally activated reservoir of Ru^II (CO)₂ species and the combined infrared absorption properties of GO and RuO₂ provides photothermal response for in situ CO-release. The RuO₂ /Ru^II (CO)₂ /⁶ Ru-CO-GO composite does not produce any cytotoxicity and the efficacy of the composite is further demonstrated in a cortical photothrombotic ischemia rat model.

Structure of in cell protein crystals containing organometallic complexes

The molecular structures of in cell protein crystals containing organometallic Pd(allyl) complexes were determined by performing microfocus X-ray diffraction experiments. The coordination sites in a polyhedrin mutant with deletion of selected amino acid residues located at the interface of the polyhedrin trimer are dramatically altered compared to those of the wild-type composite.

Crystalline protein scaffolds as a defined environment for the synthesis of bioinorganic materials

We discuss synthetic strategies and applications of highly ordered bioinorganic materials based on crystalline protein scaffolds.

Functionalization of protein crystals with metal ions, complexes and nanoparticles

Self-assembled proteins have specific functions in biology. With inspiration provided by natural protein systems, several artificial protein assemblies have been constructed via site-specific mutations or metal coordination, which have important applications in catalysis, material and bio-supramolecular chemistry. Similar to natural protein assemblies, protein crystals have been recognized as protein assemblies formed of densely-packed monomeric proteins. Protein crystals can be functionalized with metal ions, metal complexes or nanoparticles via soaking, co-crystallization, creating new metal binding sites by site-specific mutations. The field of protein crystal engineering with metal coordination is relatively new and has gained considerable attention for developing solid biomaterials as well as structural investigations of enzymatic reactions, growth of nanoparticles and catalysis. This review highlights recent and significant research on functionalization of protein crystals with metal coordination and future prospects.

Crystal Engineering of Self-Assembled Porous Protein Materials in Living Cells

Crystalline porous materials have been investigated for development of important applications in molecular storage, separations, and catalysis. The potential of protein crystals is increasing as they become better understood. Protein crystals have been regarded as porous materials because they present highly ordered 3D arrangements of protein molecules with high porosity and wide range of pore sizes. However, it remains difficult to functionalize protein crystals in living cells. Here, we report that polyhedra, a natural crystalline protein assembly of polyhedrin monomer (PhM) produced in insect cells infected by cypovirus, can be engineered to extend porous networks by deleting selected amino acid residues located on the intermolecular contact region of PhM. The adsorption rates and quantities of fluorescent dyes stored within the mutant crystals are increased relative to those of the wild-type polyhedra crystal (WTPhC) under both in vitro and in vivo conditions. These results provide a strategy for designing self-assembled protein materials with applications in molecular recognition and storage of exogenous substances in living cell as well as an entry point for development of bioorthogonal chemistry and in vivo crystal structure analysis.

Near infrared light-mediated photoactivation of cytotoxic Re(i) complexes by using lanthanide-doped upconversion nanoparticles

Photoactivation of cytotoxic Re(i) complexes by using lanthanide doped upconversion nanoparticles upon near infrared illumination was demonstrated to selectively activate Re(i) complexes in tumor cells for enhanced anti-cancer effect.