Development of novel polymer haemoglobin based particles as an antioxidant, antibacterial and an oxygen carrier agents

This innovative work aims to develop highly biocompatible and degradable nanoparticles by encapsulating haemoglobin (Hb) within poly-ε-caprolactone for novel biomedical applications. We used a modified double emulsion solvent evaporation method to fabricate the particles. A Scanning electron microscope (SEM) characterized them for surface morphology. Fourier Transform Infrared Spectroscopy (FTIR) and Ultraviolet-visible spectroscopies (UV-visible) elucidated preserved chemical and biological structure of encapsulated haemoglobin. The airproof equilibrium apparatus obtained the oxygen-carrying capacity and P50 values. The DPPH assay assessed free radical scavenging potential. The antibacterial properties were observed using four different bacterial strains by disk diffusion method. The MTT assay investigates the cytotoxic effects on mouse fibroblast cultured cell lines (L-929). The MTT assay showed that nanoparticles have no toxicity over large concentrations. The well-preserved structure of Hb within particles, no toxicity, high oxygen affinity, P50 value, and IC50 values open the area of new research, which may be used as artificial oxygen carriers, antioxidant, and antibacterial agents, potential therapeutic agents as well as drug carrier particles to treat the cancerous cells. The novelty of this work is the antioxidant and antibacterial properties of developed nanoparticles are not been reported yet. Results showed that the prepared particles have strong antioxidant and antibacterial potential.

Synthesis of bioactive hemoglobin-based oxygen carrier nanoparticles via metal-phenolic complexation

The transfusion of donor red blood cells (RBCs) is seriously hampered by important drawbacks that include limited availability and portability, the requirement of being stored in refrigerated conditions, a short shelf life or the need for RBC group typing and crossmatching. Thus, hemoglobin (Hb)-based oxygen (O2) carriers (HBOCs) which make use of the main component of RBCs and the responsible protein for O2 transport, hold a lot of promise in modern transfusion and emergency medicine. Despite the great progress achieved, it is still difficult to create HBOCs with a high Hb content to attain the high O2 demands of our body. Herein a metal-phenolic self-assembly approach that can be conducted in water and in one step to prepare nanoparticles (NPs) fully made of Hb (Hb-NPs) is presented. In particular, by combining Hb with polyethylene glycol, tannic acid (TA) and manganese ions, spherical Hb-NPs with a uniform size around 350-525 nm are obtained. The functionality of the Hb-NPs is preserved as shown by their ability to bind and release O2 over multiple rounds. The binding mechanism of TA and Hb is thoroughly investigated by UV-vis absorption and fluorescence spectroscopy. The binding site number, apparent binding constant at two different temperatures and the corresponding thermodynamic parameters are identified. The results demonstrate that the TA-Hb interaction takes place through a static mechanism in a spontaneous process as shown by the decrease in Gibbs free energy. The associated increase in entropy suggests that the TA-Hb binding is dominated by hydrophobic interactions.

Structural and functional alterations of polydopamine-coated hemoglobin: New insights for the development of successful oxygen carriers

One of the major factors that is currently hindering the development of hemoglobin (Hb)-based oxygen carriers (HBOCs) is the autoxidation of Hb into nonfunctional methemoglobin. Modification with polydopamine (PDA), which is a biocompatible free radical scavenger has shown the ability to protect Hb against oxidation. Due to its tremendous potential in the development of successful HBOCs, herein, we conduct a thorough evaluation of the effect of PDA on the stability, aggregation, structure and function of the underlying Hb. By UV-vis spectrometry we show that PDA can prevent Hb's aggregation while thermal denaturation studies indicate that, although PDA coating resulted in a lower midpoint transition temperature, it was also able to protect the protein from full denaturation. These results are further corroborated by differential scanning calorimetry. Circular dichroism reveals that PDA can promote changes in Hb's secondary structure while, by UV-vis spectroscopy, we show that PDA also interacts with the porphyrin complex located in Hb's hydrophobic pocket. Last but not least, affinity studies show that PDA-coated Hb has a higher capability for oxygen release. Such an effect is further enhanced at lower pH. Importantly, through molecular docking simulations we provide a plausible explanation for the observed experimental results.

Structural optimization and prospect of constructing hemoglobin oxygen carriers based on hemoglobin

The current global shortage of organ resources, the imbalance in donor-recipient demand and the increasing number of high-risk donors make organ preservation a necessity to consider appropriate storage options. The current method of use often has risks such as blood group mismatch, short shelf life, and susceptibility. HBOCs have positive effects such as anti-apoptotic, anti-inflammatory, antioxidant and anti-proliferative, which have significant advantages in organ storage. Therefore, it is the common pursuit of researchers to design and synthesize HBOCs with safety, ideal oxygen-carrying capacity, easy storage, etc. that are widely applicable and optimal for different organs. There has been a recent advancement in understanding HBOCs mechanisms, which is discussed in this review.

Hemoglobin-stabilized gold nanoclusters displaying oxygen transport ability, self-antioxidation, auto-fluorescence properties and long-term storage potential

The development of hemoglobin (Hb)-based oxygen carriers (HBOCs) holds a lot of potential to overcome important drawbacks of donor blood such as a short shelf life or the potential risk of infection. However, a crucial limitation of current HBOCs is the autoxidation of Hb into methemoglobin (metHb), which lacks oxygen-carrying capacity. Herein, we address this challenge by fabricating a Hb and gold nanoclusters (AuNCs) composite (Hb@AuNCs) which preserves the exceptional features of both systems. Specifically, the Hb@AuNCs retain the oxygen-transporting properties of Hb, while the AuNCs provide antioxidant functionality as shown by their ability to catalytically deplete harmful reactive oxygen species (ROS). Importantly, these ROS-scavenging properties translate into antioxidant protection by minimizing the autoxidation of Hb into non-functional metHb. Furthermore, the AuNCs render Hb@AuNCs with auto-fluorescence properties which could potentially allow them to be monitored once administered into the body. Last but not least, these three features (i.e., oxygen transport, antioxidant and fluorescence properties) are well maintained following storage as a freeze-dried product. Thus, overall, the as-prepared Hb@AuNCs hold the potential to be used as a multifunctional blood surrogate in the near future.

Construction and Evaluation of Zeolitic Imidazolate Framework-Encapsulated Hemoglobin Microparticles as Oxygen Carriers

Artificial oxygen carriers, such as favorably hemoglobin-based oxygen carriers, have received considerable attention due to some drawbacks of human donor blood. Among all oxygen carriers, the metal organic framework (MOF) exhibits excellent oxygen-carrying capacity due to its good encapsulation efficiency and competitive biocompatibility. Recently, zeolitic imidazolate frameworks (ZIFs) with unique structure have attracted much attention due to their outstanding solvothermal stability. Notably, ZIF-8, the prototypical ZIF, has been utilized to load hemoglobin (Hb) as a potential blood substitute. In this work, another ZIF material, which possesses a high oxygen binding/release capability, suitable safety profile, high stability, and efficiency as a potential oxygen carrier, was used to encapsulate Hb in an environment-friendly condition.

Metal-organic framework-based oxygen carriers with antioxidant protection as a result of a polydopamine coating

Rapid haemorrhage control to restore tissue oxygenation is essential in order to improve survival following traumatic injury. To this end, the current clinical standard relies on the timely administration of donor blood. However, limited availability and portability, special storage requirements, the need for blood type matching and risks of disease transmission result in severe logistical challenges, impeding the use of donor blood in pre-hospital scenarios. Therefore, great effort has been devoted to the development of haemoglobin (Hb)-based oxygen carriers (HBOCs), which could be used as a "bridge" to maintain tissue oxygenation until hospital admission. HBOCs hold the potential to diminish the deleterious effects of acute bleeding and associated mortality rates. We recently presented a novel HBOC, consisting of Hb-loaded metal organic framework (MOF)-based nanoparticles (NPs) (MOF^Hb-NPs), and demonstrated its ability to reversibly bind and release oxygen. However, a long standing challenge when developing HBOCs is that, over time, Hb oxidizes to non-functional methaemoglobin (metHb). Herein, we address this challenge by modifying the surface of the as-prepared MOF^Hb-NPs with an antioxidant polydopamine (PDA) coating. The conditions promoting the greatest PDA deposition are first optimized. Next, the ability of the resulting PDA-coated MOF^Hb-NPs to scavenge important reactive oxygen species is demonstrated both in a test tube and in the presence of two relevant cell lines (i.e., macrophages and endothelial cells). Importantly, this antioxidant protection translates into minimal metHb conversion.

Molecular Design of Monochromophore-Based Bifunctional Photosensitizers for Simultaneous Ratiometric Oxygen Reporting and Photodynamic Cancer Therapy

Monitoring the tumor oxygen level when implementing photodynamic therapy (PDT) on malignant cancer has vital significance but remains challenging yet. Herein, by structurally manipulating a 2,4-dimethylpyrrole-engineered asymmetric BODIPY scaffold with different kinds, numbers, and positions of halogen atoms, we rationally designed several monochromophore-based bifunctional photosensitizers, named BDPs (BDP-I, BDP-II, and BDP-III), with self-sensitized photooxidation characteristics for accurate oxygen reporting and photodynamic tumor ablation. We show that different ways of halogen regulation allow available tuning of BDPs' oxygen-dependent ratiometric fluorescence turn-ons upon light irradiation as well as type-II PDT efficiencies before and after self-sensitized photooxidation. Encouragingly, measuring the specific ratiometric signals of the most promising BDP-II enabled the direct observation of initial oxygen concentration in both living 4T1 cells and a tumor-bearing mice model, affording an alternative way for evaluating oxygen supplementation strategies. Meanwhile, the "always on" PDT effect of BDP-II ensured efficient tumor ablation via apoptosis. Our research was thus believed to be of instructive significance for future application of oxygen-related auxiliary strategies and the design of unimolecular multifunctional PDT agents for cancer precision therapy.

Synthesis of Nanoparticles Fully Made of Hemoglobin with Antioxidant Properties: A Step toward the Creation of Successful Oxygen Carriers

Transfusion of donor red blood cells (RBCs) is a crucial and widely employed clinical procedure. However, important constraints of blood transfusions include the limited availability of blood, the need for typing and cross-matching due to the RBC membrane antigens, the limited storage lifetime, or the risk for disease transmission. Hence, a lot of effort has been devoted to develop RBC substitutes, which are free from the limitations of donor blood. Despite the potential, the creation of hemoglobin (Hb)-based oxygen carriers is still facing important challenges. To allow for proper tissue oxygenation, it is essential to develop carriers with high Hb loading since Hb comprises about 96% of the RBCs' dry weight. In this work, nanoparticles (NPs) fully made of Hb are prepared by the desolvation precipitation method. Several parameters are screened (i.e., Hb concentration, desolvation ratio, time, and sonication intensity) to finally obtain Hb-NPs with a diameter of ∼568 nm and a polydispersity index (PDI) of 0.2. A polydopamine (PDA) coating is adsorbed to prevent the disintegration of the resulting Hb/PDA-NPs. Due to the antioxidant character of PDA, the Hb/PDA-NPs are able to deplete two harmful reactive oxygen species, namely, the superoxide radical anion and hydrogen peroxide. Such antioxidant protection also translates into minimizing the oxidation of the entrapped Hb to nonfunctional methemoglobin (metHb). This is a crucial aspect since metHb conversion also results in inflammatory reactions and dysregulated vascular tone. Finally, yet importantly, the reported Hb/PDA-NPs are also both hemo- and biocompatible and preserve the reversible oxygen-binding and releasing properties of Hb.

Recent advances in dopamine-based materials constructed via one-pot co-assembly strategy

Dopamine-based materials have attracted widespread interest due to the outstanding physicochemical and biological properties. Since the first report on polydopamine (PDA) films, great efforts have been devoted to develop new fabrication strategies for obtaining novel nanostructures and desirable properties. Among them, one-pot co-assembly strategy offers a unique pathway for integrating multiple properties and functions into dopamine-based platform in a single simultaneous co-deposition step. This review focuses on the state of the art development of one-pot multicomponent self-assembly of dopamine-based materials and summarizes various single-step co-deposition approaches, including PDA-assisted adaptive encapsulation, co-assembly of dopamine with other molecules through non-covalent interactions or covalent interactions. Moreover, emerging applications of dopamine-based materials in the fields ranging from sensing, cancer therapy, catalysis, oil/water separation to antifouling are outlined. In addition, some critical remaining challenges and opportunities are discussed to pave the way towards the rational design and applications of dopamine-based materials.

In situ synthesis of fluorescent polydopamine on biogenic MnO2 nanoparticles as stimuli responsive multifunctional theranostics

Multifunctional nanocomposites have drawn great attention in clinical applications because of their ability to integrate diagnostic and therapeutic functions. Manganese dioxide (MnO₂), owing to its biocompatibility and magnetic resonance imaging (MRI) properties, has been widely applied in biomedical research. Our previous work on biogenic MnO₂ nanoparticles (Bio-MnO₂ NPs) revealed that intrinsic photothermal properties and stimuli-responsive MRI imaging are particularly promising for the development of theranostic systems. However, further improvement in the photothermal therapy (PTT) performance of Bio-MnO₂ NPs is still required. Herein, we have improved the PTT efficiency of Bio-MnO₂ NPs by in situ synthesis of fluorescent polydopamine (PDA) while generating additional stimuli responsive fluorescence properties in this system, thus further broadening the scope of their theranostic functions. These synthesis conditions are mild and green. The fluorescence of PDA was quenched by capping Bio-MnO₂ NPs and could be recovered upon degradation of Bio-MnO₂ NPs inside tumour cells. Additionally, Mn²⁺ released from the nanoparticles can support T₁-weighted MR imaging. Compared to the Bio-MnO₂ NPs alone, the integration of Bio-MnO₂ NPs and PDA significantly enhances the photothermal performance in vitro and in vivo. With their high biocompatibility, these multifunctional composite nanodevices hold great potential for fluorescence imaging and MRI-guided photothermal therapy.

Enzyme/GSH dual-responsive biodegradable nanohybrid for spatiotemporally specific photodynamic and hypoxia-augmented therapy against tumors

Photodynamic therapy (PDT) efficacy has been severely limited by the hypoxia in tumor microenvironment. A multitherapy modality was developed, integrating the advantages of each therapy and a nanocarrier: PDT and PDT-induced hypoxia-activated chemotherapy. Following PDT-induced hypoxia augmented in the periphery of the tumors, chemotherapy was locally activated. To this end, new indocyanine green (IR820) and a hypoxia-activated prodrug tirapazamine (TPZ) were loaded in glutathione (GSH) decomposable mesoporous organic silica nanoparticles (GMONs), tethered by hyaluronic acid (HA). This nanohybrid showed a tendency to accumulate and be retained in tumors, due to passive and active targeting. The IR820 produced singlet oxygen (¹O₂) under near-infrared (NIR) laser irradiation and concomitantly tumorous abnormality exacerbated hypoxia. TPZ-mediated hypoxia-activated chemotherapy acted to kill more tumor cells. In vivo results indicated that the tumor inhibition rate of dual-loaded nanohybrids was up to 76% under NIR laser irradiation. The immunofluorescence staining of tumor slices demonstrated that the superficial part of tumors experienced exacerbated hypoxia with laser irradiation, resulting in TPZ exerting powerful chemotherapy effects. This nanohybrid is expected to be valuable as spatiotemporally specific therapy for cancer.

Nanomaterials for Tumor Hypoxia Relief to Improve the Efficacy of ROS-Generated Cancer Therapy

Given the fact that excessive levels of reactive oxygen species (ROS) induce damage to proteins, lipids, and DNA, various ROS-generating agents and strategies have been explored to induce cell death and tumor destruction by generating ROS above toxic threshold. Unfortunately, hypoxia in tumor microenvironment (TME) not only promotes tumor metastasis but also enhances tumor resistance to the ROS-generated cancer therapies, thus leading to ineffective therapeutic outcomes. A variety of nanotechnology-based approaches that generate or release O2 continuously to overcome hypoxia in TME have showed promising results to improve the efficacy of ROS-generated cancer therapy. In this minireview, we present an overview of current nanomaterial-based strategies for advanced cancer therapy by modulating the hypoxia in the TME and promoting ROS generation. Particular emphasis is put on the O2 supply capability and mechanism of these nanoplatforms. Future challenges and opportunities of design consideration are also discussed. We believe that this review may provide some useful inspiration for the design and construction of other advanced nanomaterials with O2 supply ability for overcoming the tumor hypoxia-associated resistance of ROS-mediated cancer therapy and thus promoting ROS-generated cancer therapeutics.

Impact of chemistry on the preparation and post-modification of multilayered hollow microcapsules

In the last few years, various chemical bondings and interactions were rationally adopted to develop different multilayered microcapsules, where the empty interior accommodated various important cargoes, including bioactive molecules, nanoparticles, antibodies, enzymes, etc., and the thin membrane protected/controlled the release of the loaded cargo. Eventually, such materials are with immense potential for a wide range of prospective applications related to targeted drug delivery, sensing, bio-imaging, developing biomimetic microreactors, and so on. The emphasis on the use of various chemistries for the development of functional and useful microcapsules is rarely illustrated in the literature in the past. In this feature article, the rational uses of different chemistries for (a) preparing and (b) post-modifying various functional microcapsules are accounted. The appropriate selection of chemical bondings/interactions, including electrostatic interaction, host-guest interaction, hydrogen bonding, and covalent bonding, allowed the integration of essential constituents during the layer-by-layer deposition process for 'in situ' tailoring of the relevant and diverse properties of the hollow microcapsules. Recently, different chemically reactive hollow microcapsules were also introduced through the strategic association of 'click chemistry', ring-opening azlactone reaction, thiol-ene reaction, and 1,4-conjugate addition reaction for facile and desired post covalent modifications of the multilayer membrane. The strategic selection of chemistry remained as the key basis to synthesize smart and useful microcapsules.

Expanding the Limits of Photodynamic Therapy: The Design of Organelles and Hypoxia-Targeting Nanomaterials for Enhanced Photokilling of Cancer

Photodynamic therapy (PDT) is a minimally invasive clinical protocol that combines a nontoxic photosensitizer (PS), appropriate visible light, and molecular oxygen for cancer treatment. This triad generates reactive oxygen species (ROS) in situ, leading to different cell death pathways and limiting the arrival of nutrients by irreversible destruction of the tumor vascular system. Despite the number of formulations and applications available, the advancement of therapy is hindered by some characteristics such as the hypoxic condition of solid tumors and the limited energy density (light fluence) that reaches the target. As a result, the use of PDT as a definitive monotherapy for cancer is generally restricted to pretumor lesions or neoplastic tissue of approximately 1 cm in size. To expand this limitation, researchers have synthesized functional nanoparticles (NPs) capable of carrying classical photosensitizers with self-supplying oxygen as well as targeting specific organelles such as mitochondria and lysosomes. This has improved outcomes in vitro and in vivo. This review highlights the basis of PDT, many of the most commonly used strategies of functionalization of smart NPs, and their potential to break the current limits of the classical protocol of PDT against cancer. The application and future perspectives of the multifunctional nanoparticles in PDT are also discussed in some detail.

Highly Penetrable and On-Demand Oxygen Release with Tumor Activity Composite Nanosystem for Photothermal/Photodynamic Synergetic Therapy

A deep penetrating and pH-responsive composite nanosystem was strategically developed to improve the efficacy of synergetic photothermal/photodynamic therapy (PTT/PDT) against hypoxic tumor. The designed nanosystem ([PHC]PP@HA NPs) was constructed by coloading hemoglobin (Hb) and chlorin e6 on polydopamine to build small-sized PHC NPs, which were encapsulated inside the polymer micelles (poly(ethylene glycol)-poly(ethylenimine)) and then capped with functionalized hyaluronic acid. The pH-responsive feature made [PHC]PP@HA NPs retain an initial size of ∼140 nm in blood circulation but rapidly release small PHC NPs (∼10 nm) with a high tumor-penetrating ability in the tumor microenvironment. The in vitro penetration experiment showed that the penetration depth of PHC NPs in the multicellular tumor spheroids exceeded 110 μm. The [PHC]PP@HA NPs exhibited excellent biocompatibility, deep tumor permeability, high photothermal conversion efficiency (47.09%), and low combination index (0.59) under hypoxic conditions. Notably, the nanosystem can freely adjust the release of oxygen and damaging PHC NPs in an on-demand manner on the basis of the feedback of tumor activity. This feedback tumor therapy significantly improved the synergistic effect of PTT/PDT and reduced its toxic side effects. The in vivo antitumor results showed that the tumor inhibition rate of [PHC]PP@HA NPs with an on-demand oxygen supply of Hb was ∼100%, which was much better than those of PTT alone and Hb-free nanoparticles ([PC]PP@HA NPs). Consequently, the [PHC]PP@HA NP-mediated PTT/PDT guided by feedback tumor therapy achieved an efficient tumor ablation with an extremely low tumor recurrence rate (8.3%) 60 d later, indicating the versatile potential of PTT/PDT.

Lymph node-targeted immune-activation mediated by imiquimod-loaded mesoporous polydopamine based-nanocarriers

Toll-like receptor (TLR) agonists are the potent stimulants of innate immune system and hold promises as an adjuvant for anticancer immunotherapy. Unfortunately, most of them are limited by a prompt dissemination, and thus caused "wasted inflammation". Hence, how to restrict their action radius into lymphoid tissues is of great relevance to enhance their efficacy and concomitantly alleviates the side effects. Here, imiquimod (R837), a TLR 7 agonist, was loaded into mesoporous polydopamine (MPDA) nanocarriers with high efficiency. Moreover, its surface was modified by polyvinyl pyrrolidone (PVP) to enhance their lymphatic drainage ability. These nano-adjuvants have obvious advantages in promoting dendritic cell (DC) maturation in comparison to free R837. Moreover, their transportation and retention ability in proximal lymph nodes (LNs) were also confirmed, by which lymphatic drug exposure can be maximized to a great extent. Consequently, effective DC activation and CD8⁺ T cell responses were observed as expected by R837 released in draining LNs. This effect was further enhanced by the presence of endogenous tumor antigens from apoptosis debris induced by MPDA-based photothermal effect, and thus led to the growth inhibition of subcutaneous B16 melanomas. The results demonstrated the great potency against melanoma of the designed PVP-MPDA@R837 nano-adjuvants by combining photothermal conversion property of MPDA with lymphatic-focused immune-activation.

Advanced nanotechnology for hypoxia-associated antitumor therapy

Hypoxia is a hallmark of the tumor microenvironment, which promotes the proliferation, metastasis and invasion of tumors and stimulates the resistance of cancer treatments, leading to the serious consequence of tumor recurrence. Many nanotechnology-based studies have been conducted to improve the efficacy of cancer treatments using a hypoxia strategy. This is usually achieved by (i) activating bioreductive prodrugs in the tumor hypoxic/exacerbated hypoxic microenvironment, or (ii) delivering therapeutic agents to hypoxic tumor tissue using targeting molecules. Normally, a good therapeutic effect can be expected upon modulating the hypoxic microenvironment for tumor treatments. To achieve this, various nanotechnology strategies based on overcoming hypoxia have been exploited to alleviate tumor hypoxia and enhance the therapeutic efficacy of tumor therapy, including (i) reducing oxygen consumption by inhibiting cell respiration, (ii) normalizing tumor vessels to promote blood flow in the tumor, (iii) carrying exogenous oxygen into the tumor, and (iv) generating oxygen in situ. The strategy of in situ oxygen production is refined, and the scope of this strategy is further expanded. Finally, the inspiration of using advanced nanotechnology in hypoxia-associated antitumor therapy guides the study of tumor hypoxia for clinical use.

Haemoglobin-loaded metal organic framework-based nanoparticles camouflaged with a red blood cell membrane as potential oxygen delivery systems

Metal organic frameworks are used to protect hemoglobin from denaturation thus preserving its excellent oxygen-binding and releasing properties. Decorating with cell membranes minimizes protein adsorption holding potential for long circulation.   

Metal-Organic Framework Encapsulating Hemoglobin as a High-Stable and Long-Circulating Oxygen Carriers to Treat Hemorrhagic Shock

As an oxygen-transporting protein, free hemoglobin (Hb) often suffers from the disadvantage of undesirable stability and short blood circulation, which severely impairs the potential clinical applications as the blood substitute. In this work, Hb was facilely encapsulated into a kind of metal-organic frameworks (MOFs) (ZIF-8) inspired by the natural biomineralization process. The obtained ZIF-8 encapsulating Hb (ZIF-8@Hb) showed the small hydrodynamic size of 180.8 nm and neutral zeta potential of -2.1 mV by adjusting the ratio of Hb in ZIF-8 frameworks. Intriguingly, Hb encapsulated by ZIF-8 exhibited significantly enhanced stability in alkaline, oxidation, high temperature, or enzymatic environment compared with free Hb because of the excellent protective MOF coatings. More importantly, the negative charge of Hb neutralized the original positive charge of ZIF-8, which led to the better biocompatibility, lower protein adsorption, and macrophage uptake of ZIF-8@Hb than bare ZIF-8 nanoparticles. Furthermore, ZIF-8@Hb displayed extended blood circulation with the elimination half-life of 13.9 h as well as reduced nonspecific distribution in normal organs compared with free Hb or ZIF-8 nanoparticles. With the above advantages, ZIF-8@Hb showed significantly extended survival time of mice in a disease model of hemorrhagic shock compared with free Hb or bare ZIF-8 nanoparticles. Overall, this work offers a high-stable and long-circulating oxygen carrier platform, which may find wide applications as a blood substitute to treat various oxygen-relevant diseases.

The Chemistry of Lyophilized Blood Products

With the development of new biologics and bioconjugates, storage and preservation have become more critical than ever before. Lyophilization is a method of cell and protein preservation by removing a solvent such as water from a substance followed by freezing. This technique has been used in the past and still holds promise for overcoming logistic challenges in safety net hospitals with limited blood banking resources, austere environments such as combat, and mass casualty situations where existing resources may be outstripped. This method allows for long-term storage and transport but requires the bioconjugation of preservatives to prevent cell destabilization. Trehalose is utilized as a bioconjugate in platelet and red blood cell preservation to maintain protein thermodynamics and stabilizing protein formulations in liquid and freeze-dried states. Biomimetic approaches have been explored as alternatives to cryo- and lyopreservation of blood components. Intravascular hemostats such as PLGA nanoparticles functionalized with PEG motifs, topical hemostats utilizing fibrinogen or chitosan, and liposomal encapsulated hemoglobin with surface modifications are effectively stored long-term through bioconjugation. In thinking about the best methods for storage and transport, we are focusing this topical review on blood products that have the longest track record of preservation and looking at how these methods can be applied to synthetic systems.