Biocompatible and Biodegradable Polymersome Encapsulated Hemoglobin: A Potential Oxygen Carrier

Polymersomes for Therapeutic Protein and Peptide Delivery: Towards Better Loading Properties

Therapeutics based on proteins and peptides have profoundly transformed the landscape of treatment for diseases, from diabetes mellitus to cancers, yet the short half-life and low bioavailability of therapeutic proteins and peptides hinder their wide applications. To break through this bottleneck, biomolecules-loaded polymersomes with strong adjustability and versatility have attracted more and more attentions recently. Loading proteins or peptides into polymersomes is the first but extremely important step towards developing high-quality formulation products. However, increasing protein and peptide loading content is quite challenging due to the inherent nature of self-assembled vesicle formation mechanism and physiochemical characteristics of biomacromolecules. This review highlights the potential of polymersomes as the next-generation therapeutic proteins and peptides carrier and emphatically introduces novel approaches and recent progress to achieve satisfactory encapsulation capability of polymersomes for proteins and peptides. On the one hand, with the help of intermolecular interactions, such as electrostatic, lipid-protein, and hydrophobic interactions, the drug loading could be significantly improved. On the other hand, loading improvement could be attained through innovation of preparation methods, ranging from modified traditional film hydration techniques to the novel phase-guided assembly method.

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.

Silk Fibroin Particles as Carriers in the Development of Hemoglobin-Based Oxygen Carriers

Oxygen therapeutics have a range of applications in transfusion medicine and disease treatment. Synthetic molecules and all-natural or semi-synthetic hemoglobin-based oxygen carriers (HBOCs) have seen success as potential circulating oxygen carriers. However, many early HBOC products stalled in development due to side effects from excess hemoglobin in the blood stream and hemoglobin entering the tissue. To overcome these issues, research has focused on increasing the molecular diameter of hemoglobin by polymerizing hemoglobin molecules or encapsulating hemoglobin in liposomal carriers. This work leverages the properties of silk fibroin, a cytocompatible and non-thrombogenic biopolymer, known to entrap protein-based cargo, to engineer a fully protein-based oxygen carrier. Herein, an all-aqueous solvent evaporation technique was used to form silk particles via phase separation from a bulk polyvinyl alcohol phase (PVA). Particles size was tuned, and particles were formed with and without hemoglobin. The encapsulation efficiency and ferrous state of hemoglobin were analyzed, resulting in 60% encapsulation efficiency and a maximum of 20% ferric hemoglobin, yielding 100 µg/mL active hemoglobin in certain sfHBOC formulations. The system did not elicit a strong inflammation response in vitro, demonstrating the potential for this particle system to serve as an injectable HBOC.

Silk Fibroin Particles as Carriers in the Development of All-Natural Hemoglobin-Based Oxygen Carriers (HBOCs)

Oxygen therapeutics have a range of applications in transfusion medicine and disease treatment. Synthetic molecules and all-natural or semi-synthetic hemoglobin-based oxygen carriers (HBOCs) have seen success as potential circulating oxygen carriers. However, many early HBOC products were removed from the market due to side effects from excess hemoglobin in the blood stream and hemoglobin entering the tissue. To overcome these issues, research has focused on increasing the molecular diameter of hemoglobin by polymerizing hemoglobin molecules or encapsulating hemoglobin in liposomal carriers, where immune responses and circulation times remain a challenge. This work looks to leverage the properties of silk fibroin, a cytocompatible and non-thrombogenic biopolymer, known to entrap protein-based cargo, to engineer a silk fibroin-hemoglobin-based oxygen carrier (sfHBOC). Herein, an all-aqueous solvent evaporation technique was used to form silk fibroin particles with and without hemoglobin to tailor the formulation for specific particle sizes. The encapsulation efficiency and ferrous state of hemoglobin were analyzed, resulting in 60% encapsulation efficiency and a maximum of 20% ferric hemoglobin, yielding 100 µg/mL active hemoglobin in certain sfHBOC formulations. The system did not elicit a strong inflammation response in vitro, demonstrating the potential for this particle system to serve as an injectable HBOC.

Current perspectives of artificial oxygen carriers as red blood cell substitutes: a review of old to cutting-edge technologies using in vitro and in vivo assessments

Background

Several circumstances such as accidents, surgery, traumatic hemorrhagic shock, and other causalities cause major blood loss. Allogenic blood transfusion can be resuscitative for such conditions; however, it has numerous ambivalent effects, including supply shortage, needs for more time, cost for blood grouping, the possibility of spreading an infection, and short shelf-life. Hypoxia or ischemia causes heart failure, neurological problems, and organ damage in many patients. To address this emergent medical need for resuscitation and to treat hypoxic conditions as well as to enhance oxygen transportation, researchers aspire to achieve a robust technology aimed to develop safe and feasible red blood cell substitutes for effective oxygen transport.

Area covered

This review article provides an overview of the formulation, storage, shelf-life, clinical application, side effects, and current perspectives of artificial oxygen carriers (AOCs) as red blood cell substitutes. Moreover, the pre-clinical (in vitro and in vivo) assessments for the evaluation of the efficacy and safety of oxygen transport through AOCs are key considerations in this study. With the most significant technologies, hemoglobin- and perfluorocarbon-based oxygen carriers as well as other modern technologies, such as synthetically produced porphyrin-based AOCs and oxygen-carrying micro/nanobubbles, have also been elucidated.

Expert opinion

Both hemoglobin- and perfluorocarbon-based oxygen carriers are significant, despite having the latter acting as safeguards; they are cost-effective, facile formulations which penetrate small blood vessels and remove arterial blockages due to their nano-size. They also show better biocompatibility and longer half-life circulation than other similar technologies.

Microfluidic dual picoinjection based encapsulation of hemoglobin in alginate microcapsules reinforced by a poly(L-lysine)-g-poly(ethylene glycol)

Hemoglobin (Hb) encapsulation inside polysaccharide hydrogels has been considered a possible red blood cell (RBC) surrogate in transfusiology. Here we report on the microfluidic dual picoinjection assisted synthesis of Hb encapsulated alginate-poly(L-lysine)-g-poly(ethylene glycol) beads. This process is realized by the on-chip injections of blended Hb alginate solutions in emulsified aqueous calcium chloride (CaCl₂) droplets followed by a subsequent injection of an aqueous PLL-g-PEG into each emulsified aqueous droplet. The proposed fabrication approach was realized using a flow-focusing and two picoinjection sites in a single PDMS device. Aqueous CaCl₂ solution was emulsified and infused with Hb-alginate solution as the squeezed droplet passed through the first picoinjection site. The injection of PLL-g-PEG to reinforce the microgel and minimize the protein leaching was realized in the second picoinjection site located downstream from the first in the same microfluidic channel. In this process, monodisperse Hb-alginate-PLL-g-PEG particles with a diameter around the size of RBCs (9 μm) were obtained with around 80% of the 7.5 mg ml^-1 Hb included in the injected aqueous alginate retaining in the obtained microparticles. Microparticles with Hb loading (32.8 pg per bead) and retention (28.8 pg per bead) over a week of storage at 4 °C are in accordance with the average amount of Hb per RBC. The Hb-alginate-PLL-g-PEG microbeads fabricated in the size range of RBCs are significant for further exploration.

Scalable production and complete biophysical characterization of poly(ethylene glycol) surface conjugated liposome encapsulated hemoglobin (PEG-LEH)

Particle encapsulated hemoglobin (Hb)-based oxygen (O2) carriers (HBOCs) have clear advantages over their acellular counterparts because of their larger molecular diameter and lack of vasoactivity upon transfusion. Poly(ethylene glycol) surface conjugated liposome encapsulated Hb (PEG-LEH) nanoparticles are considered a promising class of HBOC for use as a red blood cell (RBC) substitute. However, their widespread usage is limited by manufacturing processes which prevent material scale up. In this study, PEG-LEH nanoparticles were produced via a scalable and robust process using a high-pressure cell disruptor, and their biophysical properties were thoroughly characterized. Hb encapsulation, methemoglobin (metHb) level, O2-PEG-LEH equilibria, PEG-LEH gaseous (oxygen, carbon monoxide, nitric oxide) ligand binding/release kinetics, lipocrit, and long-term storage stability allowed us to examine their potential suitability and efficacy as an RBC replacement. Our results demonstrate that PEG-LEH nanoparticle suspensions manufactured via a high-pressure cell disruptor have Hb concentrations comparable to whole blood (~12 g/dL) and possess other desirable characteristics, which may permit their use as potential lifesaving O2 therapeutics.

Recent Advancement of Polymersomes as Drug Delivery Carrier

BACKGROUND

Biomedical applications of polymersomes have been explored, including drug and gene delivery, insulin delivery, hemoglobin delivery, the delivery of anticancer agents, and various diagnostic purposes.

OBJECTIVES

Polymersomes, which are self-assembled amphiphilic block copolymers, have received a lot of attention in drug delivery approaches. This review represents the methods of preparation of polymersomes including thin-film rehydration, electroformation, double emulsion, gel-assisted rehydration, PAPYRUS method, and solvent injection methods including various therapeutic applications of polymersomes.

METHODS

Data we searched from PubMed, Google Scholar, and Science Direct through searching of keywords: Polymersomes, methods of preparation, amphiphilic block copolymers, anticancer drug delivery Results: Polymersomes provide both hydrophilic and hydrophobic drug delivery to a targeted site with an increase in the stability of the formulation and reduce the cytotoxic side effects of drugs.

CONCLUSION

A wide range of biological applications, including drug and gene delivery, insulin delivery, hemoglobin delivery, delivery of anticancer agents as well as in various diagnostic purposes. Recently, polymersomes have been used more frequently because of their stability, reducing the encapsulated drug's leakage, site-specific drug delivery, and increasing the bioavailability of the drugs and different diagnostic purposes. The liposomes encapsulate only hydrophilic drugs, but polymersomes encapsulate both hydrophilic and hydrophobic drugs in their cores.

Polymer-Lipid Hybrid Materials

Hierarchic self-assembly underpins much of the form and function seen in synthetic or biological soft materials. Lipids are paramount examples, building themselves in nature or synthetically in a variety of meso/nanostructures. Synthetic block copolymers capture many of lipid's structural and functional properties. Lipids are typically biocompatible and high molecular weight polymers are mechanically robust and chemically versatile. The development of new materials for applications like controlled drug/gene/protein delivery, biosensors, and artificial cells often requires the combination of lipids and polymers. The emergent composite material, a "polymer-lipid hybrid membrane", displays synergistic properties not seen in pure components. Specific examples include the observation that hybrid membranes undergo lateral phase separation that can correlate in registry across multiple layers into a three-dimensional phase-separated system with enhanced permeability of encapsulated drugs. It is timely to underpin these emergent properties in several categories of hybrid systems ranging from colloidal suspensions to supported hybrid films. In this review, we discuss the form and function of a vast number of polymer-lipid hybrid systems published to date. We rationalize the results to raise new fundamental understanding of hybrid self-assembling soft materials as well as to enable the design of new supramolecular systems and applications.

Optimization of Hemoglobin Encapsulation within PLGA Nanoparticles and Their Investigation as Potential Oxygen Carriers

Hemoglobin (Hb)-based oxygen carriers (HBOCs) display the excellent oxygen-carrying properties of red blood cells, while overcoming some of the limitations of donor blood. Various encapsulation platforms have been explored to prepare HBOCs which aim to avoid or minimize the adverse effects caused by the administration of free Hb. Herein, we entrapped Hb within a poly(lactide-co-glycolide) (PLGA) core, prepared by the double emulsion solvent evaporation method. We study the effect of the concentrations of Hb, PLGA, and emulsifier on the size, polydispersity (PDI), loading capacity (LC), and entrapment efficiency (EE) of the resulting Hb-loaded PLGA nanoparticles (HbNPs). Next, the ability of the HbNPs to reversibly bind and release oxygen was thoroughly evaluated. When needed, trehalose, a well-known protein stabilizer that has never been explored for the fabrication of HBOCs, was incorporated to preserve Hb's functionality. The optimized formulation had a size of 344 nm, a PDI of 0.172, a LC of 26.9%, and an EE of 40.7%. The HbNPs were imaged by microscopy and were further characterized by FTIR and CD spectroscopy to assess their chemical composition and structure. Finally, the ability of the encapsulated Hb to bind and release oxygen over several rounds was demonstrated, showing the preservation of its functionality.

Polymer nano-systems for the encapsulation and delivery of active biomacromolecular therapeutic agents

Biomacromolecular therapeutic agents, particularly proteins, antigens, enzymes, and nucleic acids are emerging as powerful candidates for the treatment of various diseases and the development of the recent vaccine based on mRNA highlights the enormous potential of this class of drugs for future medical applications. However, biomacromolecular therapeutic agents present an enormous delivery challenge compared to traditional small molecules due to both a high molecular weight and a sensitive structure. Hence, the translation of their inherent pharmaceutical capacity into functional therapies is often hindered by the limited performance of conventional delivery vehicles. Polymer drug delivery systems are a modular solution able to address those issues. In this review, we discuss recent developments in the design of polymer delivery systems specifically tailored to the delivery challenges of biomacromolecular therapeutic agents. In the future, only in combination with a multifaceted and highly tunable delivery system, biomacromolecular therapeutic agents will realize their promising potential for the treatment of diseases and for the future of human health.

Biomaterials for human space exploration: A review of their untapped potential

As biomaterial advances make headway into lightweight radiation protection, wound healing dressings, and microbe resistant surfaces, a relevance to human space exploration manifests itself. To address the needs of the human in space, a knowledge of the space environment becomes necessary. Both an understanding of the environment itself and an understanding of the physiological adaptations to that environment must inform design parameters. The space environment permits the fabrication of novel biomaterials that cannot be produced on Earth, but benefit Earth. Similarly, designing a biomaterial to address a space-based challenge may lead to novel biomaterials that will ultimately benefit Earth. This review describes several persistent challenges to human space exploration, a variety of biomaterials that might mitigate those challenges, and considers a special category of space biomaterial. STATEMENT OF SIGNIFICANCE: This work is a review of the major human and environmental challenges facing human spaceflight, and where biomaterials may mitigate some of those challenges. The work is significant because a broad range of biomaterials are applicable to the human space program, but the overlap is not widely known amongst biomaterials researchers who are unfamiliar with the challenges to human spaceflight. Additionaly, there are adaptations to microgravity that mimic the pathology of certain disease states ("terrestrial analogs") where treatments that help the overwhelmingly healthy astronauts can be applied to help those with the desease. Advances in space technology have furthered the technology in that field on Earth. By outlining ways that biomaterials can promote human space exploration, space-driven advances in biomaterials will further biomaterials technology.

Stepping stones to the future of haemoglobin-based blood products: clinical, preclinical and innovative examples

Critical overview of the different oxygen therapeutics developed so far to be used when donor blood is not available.

Hemoglobin-based Oxygen Carriers: Current State-of-the-art and Novel Molecules

In blood, the primary role of red blood cells (RBCs) is to transport oxygen via highly regulated mechanisms involving hemoglobin (Hb). Hb is a tetrameric porphyrin protein comprising of two α- and two β-polypeptide chains, each containing an iron-containing heme group capable of binding one oxygen molecule. In military as well as civilian traumatic exsanguinating hemorrhage, rapid loss of RBCs can lead to suboptimal tissue oxygenation and subsequent morbidity and mortality. In such cases, transfusion of whole blood or RBCs can significantly improve survival. However, blood products including RBCs present issues of limited availability and portability, need for type matching, pathogenic contamination risks, and short shelf-life, causing substantial logistical barriers to their prehospital use in austere battlefield and remote civilian conditions. While robust research is being directed to resolve these issues, parallel research efforts have emerged toward bioengineering of semisynthetic and synthetic surrogates of RBCs, using various cross-linked, polymeric, and encapsulated forms of Hb. These Hb-based oxygen carriers (HBOCs) can potentially provide therapeutic oxygenation when blood or RBCs are not available. Several of these HBOCs have undergone rigorous preclinical and clinical evaluation, but have not yet received clinical approval in the USA for human use. While these designs are being optimized for clinical translations, several new HBOC designs and molecules have been reported in recent years, with unique properties. The current article will provide a comprehensive review of such HBOC designs, including current state-of-the-art and novel molecules in development, along with a critical discussion of successes and challenges in this field.

Artificial oxygen carriers and red blood cell substitutes: A historic overview and recent developments toward military and clinical relevance

Packed red blood cells are a critical component in the resuscitation of hemorrhagic shock. The availability of donor-derived blood products, however, suffers from issues of supply, immunogenicity, and pathogenic contamination. Deployment in remote or austere environments, such as the battlefield, is further hindered by the inherent perishability of blood products. To address the significant limitations of allogenic packed red blood cells and the urgent medical need for better resuscitative therapies for both combat casualties and civilians, there has been significant research invested in developing safe, effective, and field deployable artificial oxygen carriers. This article provides a comprehensive review of the most important technologies in the field of artificial oxygen carriers including cell-free and encapsulated hemoglobin-based oxygen carriers, perfluorocarbon emulsions, natural hemoglobin alternatives, as well as other novel technologies. Their development status, clinical, and military relevance are discussed. LEVEL OF EVIDENCE: Systematic review.

Polymeric nano-vesicles via intermolecular action to load and orally deliver insulin with enhanced hypoglycemic effect

To date few polymeric vesicles have been investigated to improve oral insulin (INS) absorption due to their limited loading capacity. Therefore, an amphiphilic polyphosphazene (PEOP) containing lipid-like octadecylphosphoethanolamine (OPA) groups and amino-modified poly(ethylene glycol) at the proper ratio was designed and synthesized in this study. It was found that PEOP can self-assemble into nano-vesicles, which displayed considerable loading capability for INS by taking advantage of the synergetic effect of the interaction between OPA and INS and the physical encapsulation by the aqueous lumen of the vesicles. Furthermore, PEOP vesicles can promote INS absorption across the subsequent lymphatic transport of PEOP vesicles after their uptake by the enterocytes in the gastrointestinal tract, and consequently achieve better hypoglycemic effects in vivo. These results suggested that PEOP vesicles have great potential as oral INS carriers for diabetes therapy.

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.   

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.

Gas Therapy: An Emerging “Green” Strategy for Anticancer Therapeutics

As an emerging area, gas therapy has attracted more and more attention in treating many diseases including cancer. The fabrication of stimuli‐responsive delivery systems with on‐demand release behavior is very promising for precision gas therapy, which can obtain optimal therapeutic performance without gas poisoning risks. In this review, the authors introduce the recent progress in the preparation of different kinds of gas carriers for efficient delivery of gaseous molecules (NO, H2S, CO, O2). Particularly, in order to achieve targeted accumulation of gaseous molecules in tumor tissues, gaseous molecules–integrated nanoparticles were constructed. Most importantly, by combination of gas therapy with other therapeutic modalities such as chemotherapy, photodynamic therapy (PDT), and radiotherapy, various multifunctional nanocarriers have been designed for synergistic cancer therapy. Especially, the recent developments of multifunctional gas‐carrying nanocarriers for synergistic cancer therapy are discussed in detail.

Polymersome nanoparticles for delivery of Wnt-activating small molecules

Spatiotemporal control of drug delivery is important for a number of medical applications and may be achieved using polymersome nanoparticles (PMs). Wnt signalling is a molecular pathway activated in various physiological processes, including bone repair, that requires precise control of activation. Here, we hypothesise that PMs can be stably loaded with a small molecule Wnt agonist, 6-bromoindirubin-3'-oxime (BIO), and activate Wnt signalling promoting the osteogenic differentiation in human primary bone marrow stromal cells (BMSCs). We showed that BIO-PMs induced a 40% increase in Wnt signaling activation in reporter cell lines without cytotoxicity induced by free BIO. BMSCs incubated with BIO-PMs showed a significant up-regulation of the Wnt target gene AXIN2 (14 ± 4 fold increase, P < 0.001) and a prolonged activation of the osteogenic gene RUNX2. We conclude that BIO-PMs could represent an innovative approach for the controlled activation of Wnt signaling for promoting bone regeneration after fracture.

Liposomes and polymersomes: a comparative review towards cell mimicking

Minimal cells: we compare and contrast liposomes and polymersomes for a bettera priorichoice and design of vesicles and try to understand the advantages and shortcomings associated with using one or the other in many different aspects (properties, synthesis, self-assembly, applications).

Bio-inspired nanomedicine strategies for artificial blood components

Blood is a fluid connective tissue where living cells are suspended in noncellular liquid matrix. The cellular components of blood render gas exchange (RBCs), immune surveillance (WBCs) and hemostatic responses (platelets), and the noncellular components (salts, proteins, etc.) provide nutrition to various tissues in the body. Dysfunction and deficiencies in these blood components can lead to significant tissue morbidity and mortality. Consequently, transfusion of whole blood or its components is a clinical mainstay in the management of trauma, surgery, myelosuppression, and congenital blood disorders. However, donor-derived blood products suffer from issues of shortage in supply, need for type matching, high risks of pathogenic contamination, limited portability and shelf-life, and a variety of side-effects. While robust research is being directed to resolve these issues, a parallel clinical interest has developed toward bioengineering of synthetic blood substitutes that can provide blood's functions while circumventing the above problems. Nanotechnology has provided exciting approaches to achieve this, using materials engineering strategies to create synthetic and semi-synthetic RBC substitutes for enabling oxygen transport, platelet substitutes for enabling hemostasis, and WBC substitutes for enabling cell-specific immune response. Some of these approaches have further extended the application of blood cell-inspired synthetic and semi-synthetic constructs for targeted drug delivery and nanomedicine. The current study provides a comprehensive review of the various nanotechnology approaches to design synthetic blood cells, along with a critical discussion of successes and challenges of the current state-of-art in this field. WIREs Nanomed Nanobiotechnol 2017, 9:e1464. doi: 10.1002/wnan.1464 For further resources related to this article, please visit the WIREs website.

Traceable PEO-poly(ester) micelles for breast cancer targeting: The effect of core structure and targeting peptide on micellar tumor accumulation

Traceable poly(ethylene oxide)-poly(ester) micelles were developed through chemical conjugation of a near-infrared (NIR) dye to the poly(ester) end by click chemistry. This strategy was tried for micelles with poly(ε-caprolactone) (PCL) or poly(α-benzyl carboxylate-ε-caprolactone) (PBCL) cores. The surface of both micelles was also modified with the breast cancer targeting peptide, P18-4. The results showed the positive contribution of PBCL over PCL core on micellar thermodynamic and kinetic stability as well as accumulation in primary orthotopic MDA-MB-231 tumors within 4-96 h following intravenous administration in mice. This was in contrast to in vitro studies where better uptake of PEO-PCL versus PEO-PBCL micelles by MDA-MB-231 cells was observed. The presence of P18-4 enhanced the in vitro cell uptake and homing of both polymeric micelles in breast tumors, but only at early time points. In conclusion, the use of developed NIR labeling technique provided means for following the fate of PEO-poly(ester) based nano-carriers in live animals. Our results showed micellar stabilization through the use of PBCL over PCL cores, to have a more significant effect in enhancing the level and duration of nano-carrier accumulation in primary breast tumors than the modification of polymeric micellar surface with breast tumor targeting peptide, P18-4.

Facile assembly and loading of theranostic polymersomes via multi-impingement flash nanoprecipitation

Flash nanoprecipitation (FNP) has proven to be a powerful tool for the rapid and scalable assembly of solid-core nanoparticles from block copolymers. The process can be performed using a simple confined impingement jets mixer and provides an efficient and reproducible method of loading micelles with hydrophobic drugs. To date, FNP has not been applied for the fabrication of complex or vesicular nanoarchitectures capable of encapsulating hydrophilic molecules or bioactive protein therapeutics. Here, we present FNP as a single customizable method for the assembly of bicontinuous nanospheres, filomicelles and vesicular, multilamellar and tubular polymersomes from poly(ethylene glycol)-bl-poly(propylene sulfide) block copolymers. Multiple impingements of polymersomes assembled via FNP were shown to decrease vesicle diameter and polydispersity, allowing gram-scale fabrication of monodisperse polymersomes within minutes. Furthermore, we demonstrate that FNP supports the simultaneous loading of both hydrophobic and hydrophilic molecules respectively into the polymersome membrane and aqueous lumen, and encapsulated enzymes were found to be released and remain active following vesicle lysis. As an example application, theranostic polymersomes were generated via FNP that were dual loaded with the immunosuppressant rapamycin and a fluorescent dye to link targeted immune cells with the elicited immunomodulation of T cells. By expanding the capabilities of FNP, we present a rapid, scalable and reproducible method of nanofabrication for a wide range of nanoarchitectures that are typically challenging to assemble and load with therapeutics for controlled delivery and theranostic strategies.

Asymmetrical Polymer Vesicles for Drug delivery and Other Applications

Scientists have been attracted by polymersomes as versatile drug delivery systems since the last two decades. Polymersomes have the potential to be versatile drug delivery systems because of their tunable membrane formulations, stabilities in vivo, various physicochemical properties, controlled release mechanisms, targeting abilities, and capacities to encapsulate a wide range of drugs and other molecules. Asymmetrical polymersomes are nano- to micro-sized polymeric capsules with asymmetrical membranes, which means, they have different outer and inner coronas so that they can exhibit better endocytosis rate and endosomal escape ability than other polymeric systems with symmetrical membranes. Hence, asymmetrical polymersomes are highly promising as self-assembled nano-delivery systems in the future for in vivo therapeutics delivery and diagnostic imaging applications. In this review, we prepared a summary about recent research progresses of asymmetrical polymersomes in the following aspects: synthesis, preparation, applications in drug delivery and others.

Artificial Blood Substitutes: First Steps on the Long Route to Clinical Utility

The 21st century is challenging for human beings. Increased population growth, population aging, generation of new infectious agents, and natural disasters are some threatening factors for the current state of blood transfusion. However, it seems that science and technology not only could overcome these challenges but also would turn many human dreams to reality in this regard. Scientists believe that one of the future evolutionary innovations could be artificial blood substitutes that might pave the way to a new era in transfusion medicine. In this review, recent status and progresses in artificial blood substitutes, focusing on red blood cells substitutes, are summarized. In addition, steps taken toward the development of artificial blood technology and some of their promises and hurdles will be highlighted. However, it must be noted that artificial blood is still at the preliminary stages of development, and to fulfill this dream, ie, to routinely transfuse artificial blood into human vessels, we still have to strengthen our knowledge and be patient.

Humid Heat Autoclaving of Hybrid Nanoparticles Achieved by Decreased Nanoparticle Concentration and Improved Nanoparticle Stability Using Medium Chain Triglycerides as a Modifier

PURPOSE

Humid heat autoclaving is a facile technique widely used in the sterilization of injections, but the high temperature employed would destroy nanoparticles composed of biodegradable polymers. The aim of this study was to investigate whether incorporation of medium chain triglycerides (MCT) could stabilize nanoparticles composed of poly (ethylene glycol)-b-polycaprolactone (PEG-b-PCL) during autoclaving (121°C, 10 min).

METHODS

Polymeric nanoparticles with different MCT contents were prepared by dialysis. Block copolymer degradation was studied by GPC. The critical aggregation concentrations of nanoparticles at different temperatures were determined using pyrene fluorescence. The size, morphology and weight averaged molecular weight of pristine/autoclaved nanoparticles were studied using DLS, TEM and SLS, respectively. Drug loading content and release profile were determined using RP-HPLC.

RESULTS

The protecting effect of MCT on nanoparticles was dependent on the amount of MCT incorporated. Nanoparticles with high MCT contents, which assumed an emulsion-like morphology, showed reduced block copolymer degradation and particle disassociation after incubation at 100°C for 24 h. Nanoparticles with high MCT content showed the lowest critical aggregation concentration (CAC) under either room temperature or 60°C and the lowest particle concentration among all samples. And the particle size, drug loading content, physical stability and release profile of nanoparticles with high MCT contents remained nearly unchanged after autoclaving.

CONCLUSION

Incorporation of high amount of MCT changed the morphology of PEG-b-PCL based nanoparticles to an emulsion-like structure and the nanoparticles prepared could withstand autoclaving due to improved particle stability and decreased particle concentration caused by MCT incorporation.

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.

Nanopolymersomes as potential carriers for rifampicin pulmonary delivery

Tuberculosis (TB) has been stated as "the greatest killer worldwide due to a single infectious agent" behind the human immunodeficiency virus. Standard short-term treatment includes the oral administration of a combination of "first-line" drugs. However, poor-patient compliance and adherence to the long-term treatments represent one of the mayor drawbacks of the TB therapy. An alternative to the oral route is the pulmonary delivery of anti-TB drugs for local or systemic administration. Nanotechnology offers an attractive platform to develop novel inhalable/respirable nanocarriers. The present investigation was focused on the encapsulation of rifampicin (RIF) (a "first-line" anti-TB drug) within nanopolymersomes (nanoPS) employing di- and tri-block poly(ethylene glycol) (PEG)-poly(ɛ-caprolactone) (PCL) based copolymers as biomaterials. The derivatives presented a number-average molecular weight between 12.2 KDa and 30.1 KDa and a hydrophobic/hydrophilic balance between 0.56 and 0.99. The nanoPS were able to enhance the apparent RIF aqueous solubility (up to 4.62 mg/mL) where the hydrodynamic diameters of the drug-loaded systems (1% w/v) were ranged between 65.8 nm and 94 nm at day 0 as determined by dynamic light scattering (DLS). Then, RIF-loaded systems demonstrated as excellent colloidal stability in aqueous media over 14 days with a spherical morphology as determined by transmission electron microscopy (TEM). Furthermore, RIF-loaded nano-sized PS promoted drug accumulation in macrophages (RAW 264.7) versus a drug solution representing promising results for a potential TB inhaled therapy.

Progressive Saturation Improves the Encapsulation of Functional Proteins in Nanoscale Polymer Vesicles

PURPOSE

To develop a technique that maximizes the encapsulation of functional proteins within neutrally charged, fully PEGylated and nanoscale polymer vesicles (i.e., polymersomes).

METHODS

Three conventional vesicle formation methods were utilized for encapsulation of myoglobin (Mb) in polymersomes of varying size, PEG length, and membrane thickness. Mb concentrations were monitored by UV-Vis spectroscopy, inductively coupled plasma optical emission spectroscopy (ICP-OES) and by the bicinchoninic acid (BCA) assay. Suspensions were subject to protease treatment to differentiate the amounts of surface-associated vs. encapsulated Mb. Polymersome sizes and morphologies were monitored by dynamic light scattering (DLS) and by cryogenic transmission electron microscopy (cryo-TEM), respectively. Binding and release of oxygen were measured using a Hemeox analyzer.

RESULTS

Using the established "thin-film rehydration" and "direct hydration" methods, Mb was found to be largely surface-associated with negligible aqueous encapsulation within polymersome suspensions. Through iterative optimization, a novel "progressive saturation" technique was developed that greatly increased the final concentrations of Mb (from < 0.5 to > 2.0 mg/mL in solution), the final weight ratio of Mb-to-polymer that could be reproducibly obtained (from < 1 to > 4 w/w% Mb/polymer), as well as the overall efficiency of Mb encapsulation (from < 5 to > 90%). Stable vesicle morphologies were verified by cryo-TEM; the suspensions also displayed no signs of aggregate formation for > 2 weeks as assessed by DLS. "Progressive saturation" was further utilized for the encapsulation of a variety of other proteins, ranging in size from 17 to 450 kDa.

CONCLUSIONS

Compared to established vesicle formation methods, "progressive saturation" increases the quantities of functional proteins that may be encapsulated in nanoscale polymersomes.

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