Polymer/hemoglobin assemblies: biodegradable oxygen carriers for artificial red blood cells

Nanomaterial-related hemoglobin-based oxygen carriers, with emphasis on liposome and nano-capsules, for biomedical applications: current status and future perspectives

Oxygen is necessary for life and plays a key pivotal in maintaining normal physiological functions and treat of diseases. Hemoglobin-based oxygen carriers (HBOCs) have been studied and developed as a replacement for red blood cells (RBCs) in oxygen transport due to their similar oxygen-carrying capacities. However, applications of HBOCs are hindered by vasoactivity, oxidative toxicity, and a relatively short circulatory half-life. With advancements in nanotechnology, Hb encapsulation, absorption, bioconjugation, entrapment, and attachment to nanomaterials have been used to prepare nanomaterial-related HBOCs to address these challenges and pend their application in several biomedical and therapeutic contexts. This review focuses on the progress of this class of nanomaterial-related HBOCs in the fields of hemorrhagic shock, ischemic stroke, cancer, and wound healing, and speculates on future research directions. The advancements in nanomaterial-related HBOCs are expected to lead significant breakthroughs in blood substitutes, enabling their widespread use in the treatment of clinical diseases.

Effects of Nanobubbles on Photochemical Processes of Levofloxacin Photosensitizer

Photodynamic therapy (PDT) stands as an efficacious modality for the treatment of cancer and various diseases, in which optimization of the electron transfer and augmentation of the production of lethal reactive oxygen species (ROS) represent pivotal challenges to enhance its therapeutic efficacy. Empirical investigations have established that the spontaneous initiation of redox reactions associated with electron transfer is feasible and is located in the gas-liquid interfaces. Meanwhile, nanobubbles (NBs) are emerging as entities capable of furnishing a plethora of such interfaces, attributed to their stability and large surface/volume ratio in bulk water. Thus, NBs provide a chance to expedite the electron-transfer kinetics within the context of PDT in an ambient environment. In this paper, we present a pioneering exploration into the impact of nitrogen nanobubbles (N2-NBs) on the electron transfer of the photosensitizer levofloxacin (LEV). Transient absorption spectra and time-resolved decay spectra, as determined through laser flash photolysis, unequivocally reveal that N2-NBs exhibit a mitigating effect on the decay of the LEV excitation triplet state, thereby facilitating subsequent processes. Of paramount significance is the observation that the presence of N2-NBs markedly accelerates the electron transfer of LEV, albeit with a marginal inhibitory influence on its energy-transfer reaction. This observation is corroborated through absorbance measurements and offers compelling evidence substantiating the role of NBs in expediting electron transfer within the ambit of PDT. The mechanism elucidated herein sheds light on how N2-NBs intricately influence both electron-transfer and energy-transfer reactions in the photosensitizer LEV. These findings not only contribute to a nuanced understanding of the underlying processes but also furnish novel insights that may inform the application of NBs in the realm of photodynamic therapy.

Erythrocyte Membrane Camouflaged Nanotheranostics for Optical Molecular Imaging-Escorted Self-Oxygenation Photodynamic Therapy

Hypoxic tumor microenvironment (TME) hampers the application of oxygen (O2 )-dependent photodynamic therapy (PDT) in solid tumors. To address this problem, a biomimetic nanotheranostics (named MMCC@EM) is developed for optical molecular imaging-escorted self-oxygenation PDT. MMCC@EM is synthesized by encapsulating chlorin e6 (Ce6) and catalase (CAT) in metal-organic framework (MOF) nanoparticles with erythrocyte membrane (EM) camouflage. Based on the biomimetic properties of EM, MMCC@EM efficiently accumulates in tumor tissues. The enriched MMCC@EM achieves TME-activatable drug release, thereby releasing CAT and Ce6, and this process can be monitored through fluorescence (FL) imaging. In addition, endogenous hydrogen peroxide (H2 O2 ) will be decomposed by CAT to produce O2 , which can be reflected by the measurement of intratumoral oxygen concentration using photoacoustic (PA) imaging. Such self-oxygenation nanotheranostics effectively mitigate tumor hypoxia and improve the generation of singlet oxygen (1 O2 ). The 1 O2 disrupts mitochondrial function and triggers caspase-3-mediated cellular apoptosis. Furthermore, MMCC@EM triggers immunogenic cell death (ICD) effect, leading to an increased infiltration of cytotoxic T lymphocytes (CTLs) into tumor tissues. As a result, MMCC@EM exhibits good therapeutic effects in 4T1-tumor bearing mice under the navigation of FL/PA duplex imaging.

A pH-responsive polymer-coated CaO2as oxygen-generating nanoparticlein situfor enhanced chemo-photodynamic synergistic therapy against tumors

Photodynamic therapy (PDT) has emerged as an efficient strategy for tumor treatment. However, Insufficient amounts of inherent hypoxia and intrinsic hydrogen peroxide (H2O2) in the tumor microenvironment severely constrained PDT, as oxygen is the critical substrate for photosensitivity reaction. Here, a pH-responsive H2O2and O2self-supplying hybrid nanoparticle was designed. Through, the calcium peroxide (CaO2) as carriers loading a chemotherapeutic drug a photosensitizer 5,10,15,20-tetrakis(4-aminophenyl) porphyrin (TAPP) and doxorubicin (DOX), was covered with polyacrylic acid (PAA) to build up a feature material DOX-TAPP-CaO2@OA@PAA (denoted as DTCOP) through the reverse microemulsion method. In the acidic tumor microenvironment conditions exposing the water-sensitive CaO2nanocore to generate hydrogen peroxide (H2O2) and O2, the self-supplied O2alleviates hypoxia to enhance the PDT, and releasing DOX and TAPP. Synthetic characterization shows that the succeeded synthesized Nanocarriers could effectively carry DOX and TAPP to the tumor site and release O2at the low pH of TME. And the experimental results demonstrated that this interpose exogenous oxygen strategy is efficient at inhibition of tumor growth bothin vitroandin vivo. The nanocomposite exhibits excellent biocompatibility and the ability to inhibit tumor growth and has significant potential for the treatment of hypoxic tumors.

Oxygen-releasing biomaterials for regenerative medicine

Oxygen is critical to the survival, function and fate of mammalian cells. Oxygen tension controls cellular behavior through metabolic programming, which in turn controls tissue regeneration. A variety of biomaterials with oxygen-releasing capabilities have been developed to provide oxygen supply to ensure cell survival and differentiation for therapeutic efficacy, and to prevent hypoxia-induced tissue damage and cell death. However, controlling the oxygen release with spatial and temporal accuracy is still technically challenging. In this review, we provide a comprehensive overview of organic and inorganic materials available as oxygen sources, including hemoglobin-based oxygen carriers (HBOCs), perfluorocarbons (PFCs), photosynthetic organisms, solid and liquid peroxides, and some of the latest materials such as metal-organic frameworks (MOFs). Additionally, we introduce the corresponding carrier materials and the oxygen production methods and present state-of-the-art applications and breakthroughs of oxygen-releasing materials. Furthermore, we discuss the current challenges and the future perspectives in the field. After reviewing the recent progress and the future perspectives of oxygen-releasing materials, we predict that smart material systems that combine precise detection of oxygenation and adaptive control of oxygen delivery will be the future trend for oxygen-releasing materials in regenerative medicine.

Recent advances in micro-sized oxygen carriers inspired by red blood cells

Supplementing sufficient oxygen to cells is always challenging in biomedical engineering fields such as tissue engineering. Originating from the concept of a 'blood substitute', nano-sized artificial oxygen carriers (AOCs) have been studied for a long time for the optimization of the oxygen supplementation and improvement of hypoxia environments in vitro and in vivo. When circulating in our bodies, micro-sized human red blood cells (hRBCs) feature a high oxygen capacity, a unique biconcave shape, biomechanical and rheological properties, and low frictional surfaces, making them efficient natural oxygen carriers. Inspired by hRBCs, recent studies have focused on evolving different AOCs into microparticles more feasibly able to achieve desired architectures and morphologies and to obtain the corresponding advantages. Recent micro-sized AOCs have been developed into additional categories based on their principal oxygen-carrying or oxygen-releasing materials. Various biomaterials such as lipids, proteins, and polymers have also been used to prepare oxygen carriers owing to their rapid oxygen transfer, high oxygen capacity, excellent colloidal stability, biocompatibility, suitable biodegradability, and long storage. In this review, we concentrated on the fabrication techniques, applied biomaterials, and design considerations of micro-sized AOCs to illustrate the advances in their performances. We also compared certain recent micro-sized AOCs with hRBCs where applicable and appropriate. Furthermore, we discussed existing and potential applications of different types of micro-sized AOCs.

Erythrocyte-Inspired Functional Materials for Biomedical Applications

Erythrocytes are the most abundant cells in the blood. As the results of long-term natural selection, their specific biconcave discoid morphology and cellular composition are responsible for gaining excellent biological performance. Inspired by the intrinsic features of erythrocytes, various artificial biomaterials emerge and find broad prospects in biomedical applications such as therapeutic delivery, bioimaging, and tissue engineering. Here, a comprehensive review from the fabrication to the applications of erythrocyte-inspired functional materials is given. After summarizing the biomaterials mimicking the biological functions of erythrocytes, the synthesis strategies of particles with erythrocyte-inspired morphologies are presented. The emphasis is on practical biomedical applications of these bioinspired functional materials. The perspectives for the future possibilities of the advanced erythrocyte-inspired biomaterials are also discussed. It is hoped that the summary of existing studies can inspire researchers to develop novel biomaterials; thus, accelerating the progress of these biomaterials toward clinical biomedical applications.

Innovative strategies for photodynamic therapy against hypoxic tumor

Photodynamic therapy (PDT) is applied as a robust therapeutic option for tumor, which exhibits some advantages of unique selectivity and irreversible damage to tumor cells. Among which, photosensitizer (PS), appropriate laser irradiation and oxygen (O₂) are three essential components for PDT, but the hypoxic tumor microenvironment (TME) restricts the O₂ supply in tumor tissues. Even worse, tumor metastasis and drug resistance frequently happen under hypoxic condition, which further deteriorate the antitumor effect of PDT. To enhance the PDT efficiency, critical attention has been received by relieving tumor hypoxia, and innovative strategies on this topic continue to emerge. Traditionally, the O₂ supplement strategy is considered as a direct and effective strategy to relieve TME, whereas it is confronted with great challenges for continuous O₂ supply. Recently, O₂-independent PDT provides a brand new strategy to enhance the antitumor efficiency, which can avoid the influence of TME. In addition, PDT can synergize with other antitumor strategies, such as chemotherapy, immunotherapy, photothermal therapy (PTT) and starvation therapy, to remedy the inadequate PDT effect under hypoxia conditions. In this paper, we summarized the latest progresses in the development of innovative strategies to improve PDT efficacy against hypoxic tumor, which were classified into O₂-dependent PDT, O₂-independent PDT and synergistic therapy. Furthermore, the advantages and deficiencies of various strategies were also discussed to envisage the prospects and challenges in future study.

Oxygen-evolving hollow polydopamine alleviates tumour hypoxia for enhancing photodynamic therapy in cancer treatment

Hypoxia, a characteristic hallmark of solid tumours, restricts the therapeutic effect of photodynamic therapy (PDT) for cancer treatment. To address this issue, a facile and nanosized oxygen (O₂) bubble template is established by mixing oxygenated water and water-soluble solvents for guiding hollow polydopamine (HPDA) synthesis, and O₂ is encapsulated in the cavity of HPDA. HPDA with abundant catechol is designed as a carrier for zinc phthalocyanine (ZnPc, a boronic acid modified photosensitizer) via borate ester bonds to fabricate nanomedicine (denoted as HZNPs). The in vitro and in vivo results indicate that O₂-evolving HZNPs could alleviate tumour hypoxia and enhance PDT-anticancer efficiency. Melanin-like HPDA with a photothermal conversion rate (η) of 38.2% shows excellent synergistic photothermal therapy (PTT) efficiency in cancer treatment.

Hypoxia-alleviated sonodynamic therapy based on a hybrid protein oxygen carrier to enhance tumor inhibition

Sonodynamic therapy (SDT) is a highly attractive therapy due to its advantages of being non-invasive and having good penetration depth, but tumor hypoxia extremely restricts its therapeutic effect. Here, a novel oxygen-enhanced hybrid protein nanosonosensitizer system (MnPcS@HPO) is designed using human serum albumin (HSA) and hemoglobin (Hb) through disulfide reconfiguration, followed by encapsulating Mn-phthalocyanine (MnPcS), aiming to develop O₂ self-supplementing nanoparticles (NPs) for enhanced SDT. Benefitting from the O₂-carrying ability of Hb and the tumor-targeting property of HSA, the MnPcS@HPO NPs are able to target tumor sites and alleviate hypoxia. Meanwhile, as a sonosensitizer, MnPcS is excited under US irradiation and activates dioxygen to generate abundant singlet oxygen (¹O₂), resulting in oxidative damage of tumor cells. Guided by photoacoustic and magnetic resonance dual-modal imaging, the MnPcS@HPO NPs alleviate tumor hypoxia and achieve good SDT efficiency for suppressing tumor growth. This work presents a novel insight into enhanced SDT antitumor activity through natural protein-mediated tumor microenvironment improvement.

Conquering the Hypoxia Limitation for Photodynamic Therapy

Photodynamic therapy (PDT) has aroused great research interest in recent years owing to its high spatiotemporal selectivity, minimal invasiveness, and low systemic toxicity. However, due to the hypoxic nature characteristic of many solid tumors, PDT is frequently limited in therapeutic effect. Moreover, the consumption of O₂ during PDT may further aggravate the tumor hypoxic condition, which promotes tumor proliferation, metastasis, and invasion resulting in poor prognosis of treatment. Therefore, numerous efforts have been made to increase the O₂ content in tumor with the goal of enhancing PDT efficacy. Herein, these strategies developed in past decade are comprehensively reviewed to alleviate tumor hypoxia, including 1) delivering exogenous O₂ to tumor directly, 2) generating O₂ in situ, 3) reducing tumor cellular O₂ consumption by inhibiting respiration, 4) regulating the TME, (e.g., normalizing tumor vasculature or disrupting tumor extracellular matrix), and 5) inhibiting the hypoxia-inducible factor 1 (HIF-1) signaling pathway to relieve tumor hypoxia. Additionally, the O₂ -independent Type-I PDT is also discussed as an alternative strategy. By reviewing recent progress, it is hoped that this review will provide innovative perspectives in new nanomaterials designed to combat hypoxia and avoid the associated limitation of PDT.

Nanoparticles-mediated emerging approaches for effective treatment of ischemic stroke

Ischemic stroke leads to high disability and mortality. The limited delivery efficiency of most therapeutic substances is a major challenge for effective treatment of ischemic stroke. Inspired by the prominent merit of nanoscale particles in brain targeting and blood-brain barrier (BBB) penetration, various functional nanoparticles have been designed as promising drug delivery platforms that are expected to improve the therapeutic effect of ischemic stroke. Based on the complex pathological mechanisms of ischemic stroke, this review outline and summarize the rationally designed nanoparticles-mediated emerging approaches for effective treatment of ischemic stroke, including recanalization therapy, neuroprotection therapy, and combination therapy. On this bases, the potentials and challenges of nanoparticles in the treatment of ischemic stroke are revealed, and new thoughts and perspectives are proposed for the design of feasible nanoparticles for effective treatment of ischemic stroke.

Novel amphiphilic fluorine-containing nanocarriers for oxygen self-sufficiency "AND" GSH depletion sequentially to enhance photodynamic therapy

In order to maximize the retention of the photodynamic therapy (PDT) efficacy, while avoiding the dilemma of hypoxia and high reducing substances in tumor tissue, fluoropolymers were synthesized in a simple and effective methods. Fluorous effect with good oxygen carrying capacity was endowed by the fluorine-containing section in fluoropolymers and the perfluorodecalin (PFD) together, the reaction site with GSH was provided by the disulfide bond, which enhanced PDT efficiency through the sequential "AND" logic gate design. Two kind of fluorine-containing nanocarriers (M-Ce6 and E-Ce6) were obtained by solvent evaporation or ultrasound emulsification with PFD, respectively. In vitro, both of them showed promising high ROS generation under photoirradiation. Benefiting by cavitation effects, E-Ce6 had a more significant statistical difference in cellular uptake. Furthermore, the cells incubating with E-Ce6 hardly were noticed that the hypoxia signal appeared under hypoxia, while reducing the intracellular GSH content by more than 15%. Through the sequential "AND" logic gate design, ROS production even under hypoxia and GSH conditions of E-Ce6 was also almost 1.5 times that of Ce6 under normoxia. Enhancing effect of E-Ce6 was 13.47 times and 6.85 times, while selectivity ratio reached 5.13 times and 4.81 times compared with Ce6 and M-Ce6. The two-pronged strategy showed a high potential for delivering the Ce6 to deep inside of cancer cells and killing it in the simulated tumor by PDT. These above results demonstrated the potential of E-Ce6, as oxygen self-sufficiency and GSH depletion nanocarriers for combined enhancement of photodynamic therapy.

Nanomedicine-Based Strategies Assisting Photodynamic Therapy for Hypoxic Tumors: State-of-the-Art Approaches and Emerging Trends

Since the first clinical cancer treatment in 1978, photodynamic therapy (PDT) technologies have been largely improved and approved for clinical usage in various cancers. Due to the oxygen-dependent nature, the application of PDT is still limited by hypoxia in tumor tissues. Thus, the development of effective strategies for manipulating hypoxia and improving the effectiveness of PDT is one of the most important area in PDT field. Recently, emerging nanotechnology has benefitted progress in many areas, including PDT. In this review, after briefly introducing the mechanisms of PDT and hypoxia, as well as basic knowledge about nanomedicines, we will discuss the state of the art of nanomedicine-based approaches for assisting PDT for treating hypoxic tumors, mainly based on oxygen replenishing strategies and the oxygen dependency diminishing strategies. Among these strategies, we will emphasize emerging trends about the use of nanoscale metal-organic framework (nMOF) materials and the combination of PDT with immunotherapy. We further discuss future perspectives and challenges associated with these trends in both the aspects of mechanism and clinical translation.

Recent progress of hypoxia-modulated multifunctional nanomedicines to enhance photodynamic therapy: opportunities, challenges, and future development

Hypoxia, a salient feature of most solid tumors, confers invasiveness and resistance to the tumor cells. Oxygen-consumption photodynamic therapy (PDT) suffers from the undesirable impediment of local hypoxia in tumors. Moreover, PDT could further worsen hypoxia. Therefore, developing effective strategies for manipulating hypoxia and improving the effectiveness of PDT has been a focus on antitumor treatment. In this review, the mechanism and relationship of tumor hypoxia and PDT are discussed. Moreover, we highlight recent trends in the field of nanomedicines to modulate hypoxia for enhancing PDT, such as oxygen supply systems, down-regulation of oxygen consumption and hypoxia utilization. Finally, the opportunities and challenges are put forward to facilitate the development and clinical transformation of PDT.

Nanomedicine-Enabled Modulation of Tumor Hypoxic Microenvironment for Enhanced Cancer Therapy

Hypoxia is a common condition of solid tumors that is mainly caused by enhanced tumor proliferative activity and dysfunctional vasculature. In the treatment of hypoxic human solid tumors, many conventional therapeutic approaches (e.g., oxygen-dependent photodynamic therapy, anticancer drug-based chemotherapy or X-ray induced radiotherapy) become considerably less effective or ineffective. In recent years, various strategies have been explored to deliver or generate oxygen inside solid tumors to overcome tumorous hypoxia and show promising evidence to improve the antitumor efficiency. In this review, the extrinsic regulation of tumor hypoxia via nanomaterial delivery is discussed followed by a summary of the mechanisms through which the modulated tumor hypoxic microenvironment improves therapeutic efficacy. The review concludes with future perspectives, to specifically address the translation of nanomaterial-based therapeutic strategies for clinical applications.

Insight into the efficiency of oxygen introduced photodynamic therapy (PDT) and deep PDT against cancers with various assembled nanocarriers

Photodynamic therapy (PDT) has been used in the treatment of cancers and other benign diseases for several years in clinic. However, the hypoxia of tumors and the penetration limitation of excitation light to tissues can dramatically reduce the efficacy of PDT to cancers. To overcome these drawbacks, various assembled nanocarriers such as nanoparticles, nanocapsules, nanocrystals, and so on were introduced. The assembled nanocarriers have the ability of loading photosensitizers, delivering O₂ into tumors, generating O₂ in situ in tumors, as well as turning near-infrared (NIR) light, X-rays, and chemical energy into ultraviolet or visible light. Therefore, it is easy for the nanocarriers to improve the hypoxia microenvironment or increase the treatment depth of cancers, which will improve the efficiency of PDT to some degree. In recent years, a number of investigations were focused on these subjects. We will summarize the advances of nanocarriers in PDT, especially in O₂ introduction PDT and deep PDT. The perspectives, challenges, and potential in translation of PDT will also be discussed. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Lipid-Based Structures Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Molecular Assemblies of Biomimetic Microcapsules

Layer-by-layer (LbL) assembly is a most commonly used method to prepare various microcapsules based on the electrostatic interactions, hydrogen bonding, covalent bonding, and so on. Among these interactions, Schiff base bond formed in covalent assembly not only has an advantage in stability, but also enables the assembled microcapsules with autofluorescence and pH sensitivity. In this Article, we will mainly describe the construction of biomimetic microcapsules through Schiff base mediated LbL assembly. The structures and properties of the assembled microcapsules are introduced and their applications as drug carriers are highlighted.

Towards feedback-controlled nanomedicines for smart, adaptive delivery

IMPACT STATEMENT

The timing and rate of release of pharmaceuticals from advanced drug delivery systems is an important property that has received considerable attention in the scientific literature. Broadly, these mostly fall into two classes: controlled release with a prolonged release rate or triggered release where the drug is rapidly released in response to an environmental stimulus. This review aims to highlight the potential for developing adaptive release systems that more subtlety modulate the drug release profile through continuous communication with its environment facilitated through feedback control. By reviewing the key elements of this approach in one place (fundamental principles of nanomedicine, enzymatic nanoreactors for medical therapies and feedback-controlled chemical systems) and providing additional motivating case studies in the context of chronobiology, we hope to inspire innovative development of novel "chrononanomedicines."

Recent and prominent examples of nano- and microarchitectures as hemoglobin-based oxygen carriers

Blood transfusions, which usually consist in the administration of isolated red blood cells (RBCs), are crucial in traumatic injuries, pre-surgical conditions and anemias. Although RBCs transfusion from donors is a safe procedure, donor RBCs can only be stored for a maximum of 42 days under refrigerated conditions and, therefore, stockpiles of RBCs for use in acute disasters do not exist. With a worldwide shortage of donor blood that is expected to increase over time, the creation of oxygen-carriers with long storage life and compatibility without typing and cross-matching, persists as one of the foremost important challenges in biomedicine. However, research has so far failed to produce FDA approved RBCs substitutes (RBCSs) for human usage. As such, due to unacceptable toxicities, the first generation of oxygen-carriers has been withdrawn from the market. Being hemoglobin (Hb) the main component of RBCs, a lot of effort is being devoted in assembling semi-synthetic RBCS utilizing Hb as the oxygen-carrier component, the so-called Hb-based oxygen carriers (HBOCs). However, a native RBC also contains a multi-enzyme system to prevent the conversion of Hb into non-functional methemoglobin (metHb). Thus, the challenge for the fabrication of next-generation HBOCs relies in creating a system that takes advantage of the excellent oxygen-carrying capabilities of Hb, while preserving the redox environment of native RBCs that prevents or reverts the conversion of Hb into metHb. In this review, we feature the most recent advances in the assembly of the new generation of HBOCs with emphasis in two main approaches: the chemical modification of Hb either by cross-linking strategies or by conjugation to other polymers, and the Hb encapsulation strategies, usually in the form of lipidic or polymeric capsules. The applications of the aforementioned HBOCs as blood substitutes or for oxygen-delivery in tissue engineering are highlighted, followed by a discussion of successes, challenges and future trends in this field.

Oxygenating the way for enhanced chemophototherapy

Hypoxia is behind tumor resistance in both chemotherapy and photodynamic therapy. This editorial highlights a study by Cai et al. [12] that a hemoglobin and human serum albumin hybrid protein nanoparticle can simultaneously deliver O₂, chemotherapeutics, and photosensitizers to tumors for enhanced chemophototherapy.

Tumor-targeted hybrid protein oxygen carrier to simultaneously enhance hypoxia-dampened chemotherapy and photodynamic therapy at a single dose

Hypoxia is a characteristic feature of solid tumors and an important causation of resistance to chemotherapy and photodynamic therapy (PDT). It is challenging to develop efficient functional nanomaterials for tumor oxygenation and therapeutic applications.

Methods: Through disulfide reconfiguration to hybridize hemoglobin and albumin, tumor-targeted hybrid protein oxygen carriers (HPOCs) were fabricated, serving as nanomedicines for precise tumor oxygenation and simultaneous enhancement of hypoxia-dampened chemotherapy and photodynamic therapy. Based on encapsulation of doxorubicin (DOX) and chlorin e6 (Ce6) into HPOCs to form ODC-HPOCs, the mechanism and therapeutic efficacy of oxygen-enhanced chemo-PDT was investigated in vitro and in vivo.

Results: The precise oxygen preservation and release of the HPOC guaranteed sufficient tumor oxygenation, which is able to break hypoxia-induced chemoresistance by downregulating the expressions of hypoxia-inducible factor-1α (HIF-1α), multidrug resistance 1 (MDR1) and P-glycoprotein (P-gp), resulting in minimized cellular efflux of chemodrug. Moreover, the oxygen supply is fully exploited for upgrading the generation of reactive oxygen species (ROS) during the photodynamic process. As a result, only a single-dose treatment of the HPOCs-based chemo-PDT exhibited superior tumor suppression. The combination therapy was guided by in vivo fluorescence/photoacoustic imaging with nanoparticle tracking and oxygen monitoring.

Conclusion: This well-defined HPOC as a versatile nanosystem is expected to pave a new way for breaking multiple hypoxia-induced therapeutic resistances to achieve highly effective treatment of solid tumors.

A photosensitizer loaded hemoglobin–polymer conjugate as a nanocarrier for enhanced photodynamic therapy

A hemoglobin–polymer conjugate (HbTcMs) with oxygen supply was applied to generate more singlet oxygen for enhanced photodynamic therapy.

Bioinspired Polydopamine-Coated Hemoglobin as Potential Oxygen Carrier with Antioxidant Properties

Oxidative side reaction is one of the major factors hindering the development of hemoglobin-based oxygen carriers (HBOCs). To avoid the oxidative toxicity, we designed and synthesized polydopamine-coated hemoglobin (Hb-PDA) nanoparticles via simple one-step assemblage without any toxic reagent. Hb-PDA nanoparticles showed oxidative protection of Hb by inhibiting the generation of methemoglobin (MetHb) and ferryl (Fe IV) Hb, as well as excellent antioxidant properties by scavenging free radicals and reactive oxygen species (ROS). Interestingly, the scavenging rate of Hb-PDA nanoparticles for ABTS⁺ radical is at most 89%, while for DPPH radical it reaches 49%. In addition, Hb-PDA efficiently reduced the intracellular H₂O₂-induced ROS generation. Moreover, Hb-PDA nanoparticles exhibited high oxygen affinity, low effect on blood constituents, and low cytotoxicity. The results indicate that polydopamine-coated hemoglobin might be a promising approach for constructing novel oxygen carriers with the capacity to reduce oxidative side reaction.

Reactive oxygen species generating systems meeting challenges of photodynamic cancer therapy

The reactive oxygen species (ROS)-mediated mechanism is the major cause underlying the efficacy of photodynamic therapy (PDT). The PDT procedure is based on the cascade of synergistic effects between light, a photosensitizer (PS) and oxygen, which greatly favors the spatiotemporal control of the treatment. This procedure has also evoked several unresolved challenges at different levels including (i) the limited penetration depth of light, which restricts traditional PDT to superficial tumours; (ii) oxygen reliance does not allow PDT treatment of hypoxic tumours; (iii) light can complicate the phototherapeutic outcomes because of the concurrent heat generation; (iv) specific delivery of PSs to sub-cellular organelles for exerting effective toxicity remains an issue; and (v) side effects from undesirable white-light activation and self-catalysation of traditional PSs. Recent advances in nanotechnology and nanomedicine have provided new opportunities to develop ROS-generating systems through photodynamic or non-photodynamic procedures while tackling the challenges of the current PDT approaches. In this review, we summarize the current status and discuss the possible opportunities for ROS generation for cancer therapy. We hope this review will spur pre-clinical research and clinical practice for ROS-mediated tumour treatments.

A biocompatible cobaltporphyrin-based complex micelle constructed via supramolecular assembly for oxygen transfer

Herein, a complex micelle as an oxygen nano-carrier is constructed through the hierarchical assembly of the diblock copolymer poly(ethylene glycol)-block-poly(l-lysine) (PEG-b-PLys), tetrakis(4-sulfonatophenyl)porphinato cobalt(ii) (Co(ii)TPPS), a heptapeptide (Cys-His-His-His-His-His-His) and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD). Co(ii)TPPS was encapsulated into the cavities of TM-β-CDs driven by the host-guest interaction so that the irreversible formation of a μ-oxo-dimer of Co(ii)TPPS can be effectively prevented. The imidazole groups of the heptapeptide were selected as good axial ligands coordinating to the centric cobalt of Co(ii)TPPS, which subtly constituted the five-coordinated precursor serving as an active functional centre for oxygen binding. The sixth position of Co(ii)TPPS can bind oxygen. Furthermore, the host-guest inclusion (TM-β-CD/Co(ii)TPPS) was loaded into the hydrophobic core of the complex micelle and tightly fixed with PLys chains. The hydrophilic PEG blocks stretched in the aqueous solution constitute the shells which stabilize the structure of the complex micelle as well as impart the complex micelle sufficient blood circulation time. Moreover, the complex micelle exhibited excellent biocompatibility and cellular uptake. Therefore, the rationally designed amphiphilic structure can work as promising artificial O2 carriers in vivo. Potentially, the complex micelle can be expected to change the anaerobic microenvironment and find applications in the repair of the cells damaged by cellular hypoxia.

Self-Monitoring Artificial Red Cells with Sufficient Oxygen Supply for Enhanced Photodynamic Therapy

Photodynamic therapy has been increasingly applied in clinical cancer treatments. However, native hypoxic tumoural microenvironment and lacking oxygen supply are the major barriers hindering photodynamic reactions. To solve this problem, we have developed biomimetic artificial red cells by loading complexes of oxygen-carrier (hemoglobin) and photosensitizer (indocyanine green) for boosted photodynamic strategy. Such nanosystem provides a coupling structure with stable self-oxygen supply and acting as an ideal fluorescent/photoacoustic imaging probe, dynamically monitoring the nanoparticle biodistribution and the treatment of PDT. Upon exposure to near-infrared laser, the remote-triggered photosensitizer generates massive cytotoxic reactive oxygen species (ROS) with sufficient oxygen supply. Importantly, hemoglobin is simultaneously oxidized into the more active and resident ferryl-hemoglobin leading to persistent cytotoxicity. ROS and ferryl-hemoglobin synergistically trigger the oxidative damage of xenograft tumour resulting in complete suppression. The artificial red cells with self-monitoring and boosted photodynamic efficacy could serve as a versatile theranostic platform.

Synthesis of the Hemoglobin-Conjugated Polymer Micelles by Thiol Michael Addition Reactions

Amphiphilic triblock copolymers mPEG-b-PMAC-b-PCL are synthesized using methoxyl poly(ethylene glycol), cyclic carbonic ester monomer including acryloyl group, and ε-caprolactone. Copolymers are self-assembled into core-shell micelles in aqueous solution. Thiolated hemoglobin (Hb) is conjugated with micelles sufficiently through thiol Michael addition reaction to form hemoglobin nanoparticles (HbNs) with 200 nm in diameter. The conjugation of Hb onto the micelle surface is further confirmed by X-ray photoelectron spectroscopy. Feeding ratio of copolymer micelles to Hb at 1:3 would lead to the highest hemoglobin loading efficiency 36.7 wt%. The UV results demonstrate that the gas transporting capacity of HbNs is well remained after Hb is conjugated with polymeric micelles. Furthermore, the obtained HbNs have no obvious detrimental effects on blood components in vitro. This system may thus have great potential as one of the candidates to be developed as oxygen carriers and provide a reference for the modification of protein drugs.

Hemoglobin-Based Nanoarchitectonic Assemblies as Oxygen Carriers

Safe and effective artificial oxygen carriers are the subject of great interest due to the problems of traditional blood transfusion and enormous demand in clinical use. In view of its unique oxygen-transport ability and normal metabolic pathways, hemoglobin is regarded as an ideal oxygen-carrying unit. With advances in nano-biotechnology, hemoglobin assemblies as artificial oxygen carriers achieve great development. Here, recent progress on hemoglobin-based oxygen carriers is highlighted in view of two aspects: acellular hemoglobin-based oxygen carriers and cellular hemoglobin-based oxygen carriers. These novel oxygen carriers exhibit advantages over traditional carriers and will greatly promote research on reliable and feasible oxygen carriers.

Cooperative self-assembly of porphyrins with polymers possessing bioactive functions

This review covers recent research on design strategies for the cooperative self-assembly of porphyrins with polymers and its implementation as bioactive assembly.

CaCO₃ templated micro-beads and -capsules for bioapplications

Porous CaCO₃ vaterite microparticles have been introduced a decade ago as sacrificial cores and becoming nowadays as one of the most popular templates to encapsulate bioactive molecules. This is due to the following beneficial features: i) mild decomposition conditions, ii) highly developed surface area, and iii) controlled size as well as easy and chip preparation. Such properties allow one to template and design particles with well tuned material properties in terms of composition, structure, functionality -- the parameters crucially important for bioapplications. This review presents a recent progress in utilizing the CaCO₃ cores for the assembly of micrometer-sized beads and capsules with encapsulated both small drugs and large biomacromolecules. Bioapplications of all the particles for drug delivery, biotechnology, and biosensing as well as future perspectives for templating are addressed.

PEGylated click polypeptides synthesized by copper-free microwave-assisted thermal click polymerization for selective endotoxin removal from protein solutions

PEGylated click polypeptides (PEG-CPs) containing α-amino side groups as well as PEG segments are designed for selective endotoxin removal from protein solutions. The PEG-CPs are synthesized via copper-free thermal click copolymerization from aspartic (or glutamic) acid-based dialkyne and diazide monomers (containing free amino side groups) and alkyne-terminated mPEGs or dialkyne-terminated PEGs. Microwave-assisting technology is introduced into thermal click chemistry to improve the reaction efficiency. The monomers and polymers are fully characterized using NMR, XPS, and MALDI-TOF MS. After immobilizing the PEGylated click polypeptides onto polystyrene microspheres, the adsorbents exhibit good endotoxin removal selectivity from BSA solutions.