Research Progress in Oxygen Carrier Design and Application

Organ preservation: current limitations and optimization approaches

Despite the annual rise in patients with end-stage diseases necessitating organ transplantation, the scarcity of high-quality grafts constrains the further development of transplantation. The primary causes of the graft shortage are the scarcity of standard criteria donors, unsatisfactory organ preservation strategies, and mismatching issues. Organ preservation strategies are intimately related to pre-transplant graft viability and the incidence of adverse clinical outcomes. Static cold storage (SCS) is the current standard practice of organ preservation, characterized by its cost-effectiveness, ease of transport, and excellent clinical outcomes. However, cold-induced injury during static cold preservation, toxicity of organ preservation solution components, and post-transplantation reperfusion injury could further exacerbate graft damage. Long-term ex vivo dynamic machine perfusion (MP) preserves grafts in a near-physiological condition, evaluates graft viability, and cures damage to grafts, hence enhancing the usage and survival rates of marginal organs. With the increased use of extended criteria donors (ECD) and advancements in machine perfusion technology, static cold storage is being gradually replaced by machine perfusion. This review encapsulates the latest developments in cryopreservation, subzero non-freezing storage, static cold storage, and machine perfusion. The emphasis is on the injury mechanisms linked to static cold storage and optimization strategies, which may serve as references for the optimization of machine perfusion techniques.

Copper-Based Metal-Organic Framework as a Potential Therapeutic Gas Carrier: Optimization, Synthesis, Characterization, and Computational Studies

The broad spectrum of health conditions and the global pandemic, leading to inadequate medical oxygen supply and management, has driven interest in developing porous nanocarriers for effective oxygenation strategies. We aim to develop an injectable oxygen carrier with regard to biocompatibility, safety, prehospital availability, and universal applicability. In this study, we have tried to identify important functional sites on metal-organic frameworks (MOFs) for gas binding with the help of Grand canonical Monte Carlo simulation. We have synthesized a copper-based MOF (Cu-BTC) with a 1,3,5-benzenetricarboxylic acid linker through a solvothermal approach as a competent porous adsorbent for oxygen storage and delivery. To optimize process variables, we performed statistical analysis using response surface methodology. A quadratic model was developed to study the interaction between independent variables and the response (i.e., maximizing surface area), whose adequacy is validated by the correlation between experimental and predicted values using the ANOVA method. The synthesized Cu-BTC, before and after oxygen loading, was characterized using X-ray diffraction, surface area, along with pore distribution measurement, particle size analysis, scanning electron microscopy, transmission electron microscopy, and gas adsorption studies. The Cu-BTC MOF exhibited an oxygen uptake of 4.6 mmol g-1, the highest among all the oxygen carriers reported in the literature under the same operating conditions. Overall, our findings suggest that this synthesized Cu-BTC with high surface area (1389 m2 g-1), high porosity, optimum oxygen uptake, and good biocompatibility would show potential toward efficient storage and delivery (direct to the targeted site) of medical oxygen to raise the blood oxygen saturation level.

Recent Advances in Glutathione Depletion-Enhanced Porphyrin-Based nMOFs for Photodynamic Therapy

Photodynamic therapy has established itself as a clinical treatment for certain superficial cancers by converting oxygen into cytotoxic singlet oxygen to eradicate cancer cells. Porphyrin-based nanoscale metal-organic frameworks have emerged as promising photosensitive platforms due to their ability to prevent the hydrophobic aggregation quenching of porphyrin molecules and enhance accumulation at the tumor site, thereby becoming a focal point in photodynamic materials research. However, the elevated levels of glutathione and other reductive substances within cancer cells can alleviate the oxidative stress induced by singlet oxygen from the photodynamic therapy process, thus protecting intracellular biomolecular structures from damage. Consequently, it is crucial to design functionalized nanoplatforms that integrate glutathione depletion with porphyrin-based metal-organic frameworks to significantly boost photodynamic therapy efficacy. Moreover, the excess glutathione within cells can disrupt the structure of porphyrin-based metal-organic frameworks, which not only increases the capacity of porphyrin molecules to generate singlet oxygen upon light exposure but also aids in the recovery of their fluorescence imaging capabilities. Additionally, this specificity minimizes the photosensitizing harm of porphyrin-based metal-organic frameworks to other normal tissues. This review compiles recent advancements in developing porphyrin-based metal-organic frameworks for enhanced phototherapy through glutathione depletion. It aims to promote the further application of porphyrin-based metal-organic frameworks in phototherapy and provide valuable insights for preclinical applications. By highlighting strategies that improve therapeutic outcomes while maintaining safety profiles, this summary seeks to advance the development of more effective and targeted cancer treatments.

Therapeutic delivery of oxygen using artificial oxygen carriers demonstrates the possibility of treating a wide range of diseases

Artificial oxygen carriers have emerged as potential substitutes for red blood cells in situations of major blood loss, including accidents, surgical procedures, trauma, childbirth, stomach ulcers, hemorrhagic shock, and blood vessel ruptures which can lead to sudden reduction in blood volume. The therapeutic delivery of oxygen utilizing artificial oxygen carriers as red blood cell substitutes presents a promising avenue for treating a spectrum of disease models. Apart from that, the recent advancement of artificial oxygen carriers intended to supplant conventional blood transfusions draws significant attention due to the exigencies of warfare and the ongoing challenges posed by the COVID-19 pandemic. However, there is a pressing need to formulate stable, non-toxic, and immunologically inert oxygen carriers. Even though numerous challenges are encountered in the development of artificial oxygen carriers, their applicability extends to various medical treatments, encompassing elective and cardiovascular surgeries, hemorrhagic shock, decompression illness, acute stroke, myocardial infarction, sickle cell crisis, and proficient addressing conditions such as cerebral hypoxia. Therefore, this paper provides an overview of therapeutic oxygen delivery using assorted types of artificial oxygen carriers, including hemoglobin-based, perfluorocarbon-based, stem cell-derived, and oxygen micro/nanobubbles, in the treatment of diverse disease models. Additionally, it discusses the potential side effects and limitations associated with these interventions, while incorporating completed and ongoing research and recent clinical developments. Finally, the prospective solutions and general demands of the perfect artificial oxygen carriers were anticipated to be a reference for subsequent research endeavors.

Efficient conversion of hemoglobin to a non-vasoactive oxygen carrier by site-specific cross-linking with azido acyl methyl phosphates followed by bio-orthogonal CuAAC with a bis-alkyne

While cross-linked hemoglobin tetramers are functional acellular oxygen carriers, their ability to scavenge endogenous nitric oxide (NO) by endothelial pore penetration results in adverse cardiovascular effects. Animal studies established that cross-linked human hemoglobins, chemically joined into a double protein, avoid NO scavenging, presumably due to their larger size preventing penetration into endothelial regions that produce NO. In the present report, we utilize azide-containing acyl phosphate reagents to form cross-linked hemoglobins then bio-orthogonally click-couple them with a bis-alkyne (CuAAC). The production of these larger oxygen-carrying hemoglobin conjugates is obtained in high yields through subunit-specific cross-linking between each βLys82 ε-amino group. The methyl phosphate leaving groups provide electrostatically induced β-subunit site-selectivity, producing azido-cross-linked hemoglobin that undergoes highly efficient CuAAC compared with previous cross-linkers. The acyl phosphates also efficiently cross-link both T-state and R-state hemoglobin. The resulting bis- and tris-tetrameric hemoglobin conjugates exhibit oxygen affinity and cooperativity that are comparable to those of the native protein. The hemoglobin derivatives from the process we describe can function as sources of oxygen in biomedical applications, such as in ex-vivo donor organ perfusion.

A mesoporous theranostic platform for ultrasound and photoacoustic dual imaging-guided photothermal and enhanced starvation therapy for cancer

Tumor starvation therapy utilizing glucose oxidase (GOx), has gained traction due to its non-invasive and bio-safe attributes. However, its effectiveness is often hampered by severe hypoxia in the tumor microenvironment (TME), limiting GOx's catalytic activity. To address this issue, a multifunctional nanosystem based on mesoporous polydopamine nanoparticles (MPDA NPs) was developled to alleviate TME hypoxia. This nanosystem integrated GOx modification and oxygenated perfluoropentane (PFP) encapsulation to address hypoxia-related challenges in the TME. Under NIR laser irradiation, the MPDA NPs exhibit significant photothermal conversion efficacy, activating targeted tumor photothermal therapy (PTT), while also serving as proficient photoacoustic (PA) imaging agents. The ensuing temperature rise facilitates oxygen (O2) release and induces liquid-gas conversion of PFP, generating microbubbles for enhanced ultrasound (US) imaging signals. The supplied oxygen alleviates local hypoxia, thereby enhancing GOx-mediated endogenous glucose consumption for tumor starvation. Overall, the integration of ultrasound/photoacoustic dual imaging-guided PTT and starvation therapy within MPDA-GOx@PFP@O2 nanoparticles (MGPO NPs) presents a promising platform for enhancing the efficacay of tumor treatment by overcoming the complexities of the TME. STATEMENT OF SIGNIFICANCE: A multifunctional MPDA-based theranostic nanoagent was developed for US/PAI imaging-guided PTT and starvation therapy against tumor hypoxia by direct O2 delivery. The incorporation of oxygenated perfluoropentane (PFP) within the mesoporous structure of MGPO not only enables efficient US imaging but also helps in alleviating tumor hypoxia. Moreover, the strong near-infrared (NIR) absorption of MGPO NPs promote the generation of PFP microbubbles and release of oxygen, thereby enhancing US imaging and GOx-mediated starvation therapy. Such a multifunctional nanosystem leverages synergistic effects to enhance therapeutic efficacy while incorporating US/PA imaging for precise visualization of the tumor.

An ex vivo method to evaluate vasoactivity induced by hemoglobin-based oxygen carriers in resistance vessels

Red blood cell substitutes offer a solution to the problem of blood shortage and side effects of blood transfusion. Hemoglobin-based oxygen carriers (HBOCs) are one of the promising substitutes for red blood cells. Vasoactivity, which refers to the side effect of HBOCs that causes vasoconstriction and subsequent hypertension, limits the clinical application of HBOCs. In this study, an ex vivo method for the evaluation of vasoactivity induced by HBOCs was established based on isolated rat mesenteric artery vessels and the DMT120CP system. The DMT120CP system, equipped with a flowmeter, permits the control of intravascular pressure, pressure gradient, and flow conditions with high accuracy, simulating the physiological conditions for isolated vessels. The concentration of noradrenaline was optimized to 1 × 10-6∼3 × 10-6 M. PEGylated bovine hemoglobin (PEG-bHb) was synthesized and perfused into the vessel for vasoactivity evaluation, with bHb as the positive control and PSS buffer solution as the negative control. PEG-bHb showed a hydration diameter of 15.5 ± 1.4 nm and a P50 value of 6.99 mmHg. PEG-bHb exhibited a colloid osmotic pressure of 64.1 mmHg and a viscosity of 1.73 cp at 40 mg/mL. The established vasoactivity evaluation method showed significant differences in samples (bHb or PEG-bHb) with different vasoactivity properties. The vasoconstriction percentage induced by PEG-bHb samples synthesized in different batches showed coefficients of variation less than 5%, indicating good applicability and repeatability. The established evaluation method can be applied to study the vasoactivity induction and elimination strategies, promoting the clinical application of HBOCs.

Novel perfluorocarbon-based oxygenation therapy alleviates Post-SAH hypoxic brain injury by inhibiting HIF-1α

In comparison to other stroke types, subarachnoid hemorrhage (SAH) is characterized by an early age of onset and often results in poor prognosis. The inadequate blood flow at the site of the lesion leads to localized oxygen deprivation, increased level of hypoxia-inducible factor-1α (HIF-1α), and triggers inflammatory responses and oxidative stress, ultimately causing hypoxic brain damage. Despite the potential benefits of oxygen (O2) administration, there is currently a lack of efficient focal site O2 delivery following SAH. Conventional clinical O2 supply methods, such as transnasal oxygenation and hyperbaric oxygen therapy, do not show the ideal therapeutic effect in severe SAH patients. The perfluorocarbon oxygen carrier (PFOC) demonstrates efficacy in transporting O2 and responding to elevated levels of CO2 at the lesion site. Through cellular experiments, we determined that PFOC oxygenation serves as an effective therapeutic approach in inhibiting hypoxia. Furthermore, our animal experiments showed that PFOC oxygenation outperforms O2 breathing, leading to microglia phenotypic switching and the suppression of inflammatory response via the inhibition of HIF-1α. Therefore, as a new type of O2 therapy after SAH, PFOC oxygenation can effectively reduce hypoxic brain injury and improve neurological function.

Mitochondrial Disruption Nanosystem Simultaneously Depressed Programmed Death Ligand-1 and Transforming Growth Factor-β to Overcome Photodynamic Immunotherapy Resistance

Currently, limited photosensitizers possess the capacity to reverse tumor hypoxia and reduce programmed death ligand-1 (PD-L1) and transforming growth factor-β (TGF-β) expression simultaneously, hindering the perfect photodynamic therapy (PDT) effect due to acquired immune resistance and the tumor hypoxic microenvironment. To tackle these challenges, in this research, we demonstrated that mitochondrial energy metabolism depression can be utilized as an innovative and efficient approach for reducing the expression of PD-L1 and TGF-β simultaneously, which may offer a design strategy for a more ideal PDT nanosystem. Through proteomic analysis of 5637 cells, we revealed that tamoxifen (TMX) can incredibly regulate PD-L1 expression in tumor cells. Then, to selectively deliver clinically used mitochondrial energy metabolism depressant TMX to solid tumors as well as design an ideal PDT nanosystem, we synthesized MHI-TMX@ALB by combining a mitochondria-targeted heptamethine cyanine PDT-dye MHI with TMX through self-assembly with albumin (ALB). Interestingly enough, the MHI-TMX@ALB nanoparticle demonstrated effective reversion of tumor hypoxia and inhibition of PD-L1 protein expression at a lower dosage (7.5 times to TMX), which then enhanced the efficacy of photodynamic immunotherapy via enhancing T-cell infiltration. Apart from this, by leveraging the heptamethine dye's targeting capacity toward tumors and TMX's role in suppressing TGF-β, MHI-TMX@ALB also more effectively mitigated 4T1 tumor lung metastasis development. All in all, the MHI-TMX@ALB nanoparticle could be used as a multifunctional economical PD-L1 and TGF-β codepression immune-regulating strategy, broadening the potential clinical applications for a more ideal PDT nanosystem.