Comparative efficacy of blood cell immunocamouflage by membrane grafting of methoxypoly(ethylene glycol) and polyethyloxazoline

iRGD mediated pH-responsive mesoporous silica enhances drug accumulation in tumors

The limited penetration of nanocarriers into tumors and the slow release of drugs from these carriers to tumor cells are significant challenges in cancer therapy. In this study, we developed a novel drug delivery carrier derived from mesoporous silica, dually modified with the tumor-homing cyclic peptide iRGD (CRGDKGPDC) and the pH-responsive polymer poly(2-ethyl-2-oxazoline) (PEOz) for treating triple-negative breast cancer. The carrier selectively bound to the αvβ3 integrin receptor, which is specifically expressed in MDA-MB-231 breast cancer cells and vessels. Subsequently, it penetrated deep into the tumor parenchyma through NRP-1 receptor-dependent internalization, with the drug-loaded particles releasing drugs rapidly in the acidic cytoplasmic environment. Results indicated that the drug release rate of PEOz-modified formulations was pH-dependent. Lysosomal escape experiments demonstrated that PEOz-modified particles efficiently escaped lysosomes to release drugs. In vitro cytotoxicity assays revealed that iRGD-functionalized particles were more cytotoxic to NRP-1-positive MDA-MB-231 cells compared to NRP-1-negative MCF-7 cells. Cellular uptake studies demonstrated that iRGD mediated enhanced endocytosis of nanoparticles into MDA-MB-231 cells. In vitro tumor cell spheroid penetration assays confirmed that the PEOz and iRGD dual-modified carrier facilitated deeper distribution of DOX in multicellular spheroids compared to free DOX. Moreover, in a nude mouse model of triple-negative breast cancer, the dual-modified drug-loaded carrier significantly inhibited tumor growth without inducing weight loss or liver and kidney damage. This dual-modified mesoporous silica presents a novel and promising delivery carrier for enhancing cancer treatment.

Pegylation, a Successful Strategy to Address the Storage and Instability Problems of Blood Products: Review 2011-2021

Conjugation of polyethylene glycol (PEGylation) to blood proteins and cells has emerged as a successful approach to address some of the issues attributed to the storage of blood products, including their short half-life and instability. In this regard, this review study aims to compare the influence of different PEGylation strategies on the quality of several blood products like red blood cells (RBCs), platelets, plasma proteins, i.e., albumin, coagulation factor VIII, and antibodies. The results indicated that conjugating succinimidyl carbonate methoxyPEG (SCmPEG) to platelets could improve blood transfusion safety by preventing these cells from being attached to low-load hidden bacteria in blood products. Moreover, coating of 20 kD succinimidyl valerate (SVA)-mPEG to RBCs was able to extend the half-life and stability of these cells during storage, as well as immune camouflage their surface antigens to prevent alloimmunisation. As regards albumin products, PEGylation improved the albumin stability, especially during sterilization, and there was a relationship between the molecular weight (MW) of PEG molecules and the biological half-life of the conjugate. Although coating antibodies with short-chain PEG molecules could enhance their stabilities, these modified proteins were cleared from the blood faster. Also, branched PEG molecules enhanced the retention and shielding of the fragmented and bispecific antibodies. Overall, the results of this literature review indicate that PEGylation can be considered a useful tool for enhancing the stability and storage of blood components.

Production of Feline Universal Erythrocytes with Methoxy Polyethylene Glycol

Blood group mismatch in veterinary medicine is a significant problem in blood transfusion, sometimes leading to severe transfusion reactions and even patient death. Blood groups vary from species to species and there are three known blood groups in cats: A, B and AB. While A-type cats are most common, there is a shortage of feline B-type blood groups in cats. By using methoxy polyethylene glycol (mPEG) to protect antigenic epitopes on red blood cells (RBCs), we aimed to find the optimal conditions for the production of feline universal RBCs. The surfaces of feline A-type RBCs were treated with mPEG at various molecular weights and concentrations. Agglutination tests showed that the coating of feline A-type RBCs with mPEG of 20 kDa and 2 mM blocked hemagglutination to feline anti-A alloantibodies over 8 h. While no differences in RBC size and shape between intact and mPEG-treated RBCs were seen, coating RBCs with mPEG inhibited the binding of feline anti-A alloantibodies. Furthermore, the mPEG-treated RBCs did not cause spontaneous hemolysis or osmotic fragility, compared to control RBCs. According to a monocyte monolayer assay, mPEG treatment significantly reduced feline anti-A antibody-mediated phagocystosis of RBCs. These results confirm the potential of using activated mPEG on feline A-type RBC to create universal erythrocytes for transfusion to B-type cats.

Plasma Membrane-Derived Liposomes Exhibit Robust Antiviral Activity against HSV-1

Plasma membranes host a plethora of proteins and glycans on their outer surface that are exploited by viruses to enter the cells. In this study, we have utilized this property to limit a viral infection using plasma membrane-derived vesicles. We show that plasma membrane-derived liposomes are prophylactically and therapeutically competent at preventing herpes simplex virus type-1 (HSV-1) infection. Plasma membrane liposomes derived from human corneal epithelial (HCE) cells, which are natural targets of HSV-1 infection, as well as Vero and Chinese hamster ovary (CHO) cells were used in this study. Our study clearly demonstrates that HCE and Vero-derived cellular liposomes, which express the viral entry-specific cell surface protein receptors, exhibit robust antiviral activity especially when compared to CHO-derived liposomes, which lack the relevant HSV-1 entry receptors. Further experimentation of the plasma membrane-derived liposomes with HSV type-2 (HSV-2) and pseudorabies virus yielded similar results, indicating strong potential for the employment of these liposomes to study viral entry mechanisms in a cell free-environment.

Differential Leukocyte MicroRNA Responses Following Pan T Cell, Allorecognition and Allosecretome-Based Therapeutic Activation

Effective immunomodulation of T-cell responses is critical in treating both autoimmune diseases and cancer. Our previous studies have demonstrated that secretomes derived from control or methoxypolyethylene glycol mixed lymphocyte alloactivation assays exerted potent immunomodulatory activity that was mediated by microRNAs (miRNA). The immunomodulatory effects of biomanufactured miRNA-based allo-secretome therapeutics (SYN, TA1, IA1 and IA2) were compared to Pan T-cell activators (PHA and anti-CD3/CD28) and lymphocyte alloactivation. The differential effects of these activation strategies on resting peripheral blood mononuclear cells (PBMC) were assessed via T-cell proliferation, subset analysis and miRNA expression profiles. Mitogen-induced PBMC proliferation (> 85%) significantly exceeded that arising from either allostimulation (~ 30%) or the pro-inflammatory IA1 secretome product (~ 12%). Consequent to stimulation, the ratio of CD4 to CD8 cells of the resting PBMC (CD4:CD8; 1.7 ± 0.1) decreased in the Pan T cell, allrecognition and IA1 activated cells (averages of 1.1 ± 0.2; 1.2 ± 0.1 and 1.0 ± 0.1). These changes arose consequent to the expansion of both CD4⁺CD8⁺ and CD4^–CD8^– populations as well as the shrinkage of the CD4 subset and the expansion of the CD8 T cells. Importantly, these activation strategies induced vastly different miRNA expression profiles which were associated with significant differences in cellular differentiation and biological function. These findings support the concept that the “differential patterns of miRNA expression” regulate the biologic immune response in a “lock and key” manner. The biomanufacturing of miRNA-enriched secretome biotherapeutics may be a successful therapeutic approach for the systemic treatment of autoimmune diseases (TA1) and cancer (IA1).

Blood Group Antigen Shielding Facilitated by Selective Cell Surface Engineering

Production of red blood cells (RBCs) without immunogenicity of blood group antigens is of special interest in blood transfusion therapy in clinical chemistry. In this study, a selective cell surface engineering method was developed for the preparation of antigen-shielded RBCs based on molecular imprinting. Using an epitope imprinting method, biocompatible molecularly imprinted nanogels (MIgels) were prepared with a high affinity to the blood group antigens of RBCs. The antigen-shielded RBCs could avoid the agglutination caused by blood group mismatch, resulting in the antigen-shielded RBCs in efficiently substituting RBCs in case of a shortage of blood supply. Moreover, the antigen-shielded RBCs could maintain the normal physiological structure and functions of the original RBCs. We believe that the selective cell surface engineering presented in this work may offer significant benefits in specific cell protection for biomedical application.

Thermosensitive Hydrogel Based on Poly(2-Ethyl-2-Oxazoline)-Poly(D,L-Lactide)-Poly(2-Ethyl-2-Oxazoline) for Sustained Salmon Calcitonin Delivery

This study developed a thermosensitive hydrogel based on poly(2-ethyl-2-oxazoline)-poly(D,L-lactide)-poly(2-ethyl-2-oxazoline) (PPP) for the delivery of salmon calcitonin to improve the hypocalcemic effect. The tube inversion and rheological tests revealed that the copolymer solution underwent temperature-dependent sol-gel-sol transitions. Observation by scanning electron microscopy (SEM) showed that the hydrogel exhibited a porous three-dimensional network. The swelling test demonstrated that there was a maximum swelling ratio at low temperature (25°C) as compared with the high temperature (37°C). In vitro release revealed that the PPP hydrogel were capable of sustained release of salmon calcitonin (sCT). The in vivo biodegradability study indicated the good degradability of PPP hydrogel. More importantly, the in vivo retention time of the hydrogel in situ was significantly prolonged after subcutaneous injection of the PPP hydrogel compared to the F127 hydrogel. In vivo pharmacodynamics analysis showed that the hypocalcemic effect of both PPP and F127 hydrogel was significantly greater than that of sCT solution, and the mean serum Ca reduction effect could be maintained for 24 h of PPP hydrogel, indicating that PPP hydrogel could achieve a significant enhanced hypocalcemic effect. In conclusion, the PPP hydrogel has been shown to be prospective as a controlled release carrier for injection delivery of protein drugs.

Cancer cell membrane-coated mesoporous silica loaded with superparamagnetic ferroferric oxide and Paclitaxel for the combination of Chemo/Magnetocaloric therapy on MDA-MB-231 cells

To effectively inhibit the growth of breast cancer cells (MDA-MB-231 cells) by the combination method of chemotherapy and magnetic hyperthermia, we fabricated a biomimetic drug delivery (CSiFePNs) system composed of mesoporous silica nanoparticles (MSNs) containing superparamagnetic ferroferric oxide and Paclitaxel (PTX) coated with MDA-MB-231 cell membranes (CMs). In the in vitro cytotoxicity tests, the MDA-MB-231 cells incubated with CSiFePNs obtained IC50 value of 0.8 μgL-1, 3.5-fold higher than that of SiFePNs. The combination method of chemotherapy and magnetic hyperthermia can effectively inhibit the growth of MDA-MB-231 cells.

Polyoxazolines based mixed micelles as PEG free formulations for an effective quercetin antioxidant topical delivery

This study aims to prove the value of the polyoxazolines polymer family as surfactant in formulations for topical application and as an alternative to PEG overuse. The amphiphilic polyoxazolines (POx) were demonstrated to have less impact on cell viability of mice fibroblasts (NIH3T3) than their PEG counterparts. Mixed micelles, made of POx and phosphatidylcholine, were manufactured using thin film and high pressure homogenizer process. The mixed micelles were optimized to produce nanosized vesicles of about 20 nm with a spherical shape and stable over 28 days. The natural lipophilic antioxidant, quercetin, was successfully encapsulated (encapsulation efficiency 94 ± 4% and drug loading 3.6 ± 0.2%) in the mixed micelles with no morphological variation. Once loaded in the formulation, the quercetin impact on cell viability of NIH3T3 was decreased while its antioxidant activity remained unchanged. This work highlights the capacity of amphiphilic POx to create, in association with phospholipids, stable nanoformulations which show promise for topical delivery of antioxidant and ensure skin protection against oxidative stress.

Enhancing the pro-inflammatory anti-cancer T cell response via biomanufactured, secretome-based, immunotherapeutics

T lymphocytes play a critical role in the pro-inflammatory anti-cancer response; hence, significant pharmacologic efforts have been made to enhance the endogenous T cell response. Unfortunately, significant toxicity arises consequent to pan T cell activation. In contrast, the less robust T cell alloresponse has also demonstrated an anti-cancer effect, but poses an inherent risk of GvHD. To overcome the GvHD risk, an acellular pro-inflammatory agent (IA1) has been biomanufactured from the secretome of the allorecognition response. To assess IA1's immunomodulatory activity, T cell proliferation and differentiation were determined in vitro. The pro-inflammatory properties of the IA1 therapeutic were mediated by the miRNA-enriched fractions. Moreover, cross-species efficacy was observed consequent to the evolutionary conservation of miRNA. IA1 exerted no toxicity to resting PBMC but induced significant proliferation of resting CD3⁺ (CD4⁺ and CD8⁺) T cells and skewed the response towards a pro-inflammatory state (i.e., increased Teff:Treg ratio). Crucially, IA1-activated PBMC demonstrated a potent inhibition of cancer cell (HeLa and SH-4 melanoma) proliferation relative to the resting PBMC. The anti-proliferation effect of IA1-activated PBMC was noted within ˜12 h versus 4-5 days for resting cells. A second biomanufactured therapeutic (IA2; produced using HeLa cells) surprisingly demonstrated direct toxicity to cancer cells but was less effective than IA1 in inducing a cell-mediated response. This study demonstrates that miRNA-enriched therapeutics can be biomanufactured from the secretome and can induce a potent pro-inflammatory, anti-cancer, effect on resting lymphocytes.

Microfluidic analysis of red blood cell deformability as a means to assess hemin-induced oxidative stress resulting from Plasmodium falciparum intraerythrocytic parasitism

Hemolytic anemia is one of the hallmarks of malaria and leads to an increase in oxidized heme (hemin) within the plasma of infected individuals. While scavenger proteins sequester much of the circulating heme, it has been hypothesized that extracellular heme may play a central role in malaria pathogenesis. We have previously developed the multiplex fluidic plunger (MFP) device for the measurement of red blood cell (RBC) deformability. Here, we demonstrate that the measurement of changes in RBC deformability is a sensitive method for inferring heme-induced oxidative stress. We further show that extracellular hemin concentration correlates closely with changes in RBC deformability and we confirm that this biophysical change correlates with other indicators of cell stress. Finally, we show that reduced erythrocyte deformability corresponds with both erythrophagocytosis and RBC osmotic fragility. The MFP microfluidic device presents a simple and potentially inexpensive alternative to existing methods for measuring hemolytic cell stress that could ultimately be used to perform clinical assessment of disease progression in severe malaria.

An effective intracellular delivery system of monoclonal antibody for treatment of tumors: erythrocyte membrane-coated self-associated antibody nanoparticles

Antibody-based drugs have attracted much attention for their targeting ability, high efficacy and low toxicity. But it is difficult for those intrabodies, a kind of antibody whose targets are intracellular biomarkers, to become effective drugs due to the lack of intracellular delivery strategy and their short circulation time in blood. Human telomerase reverse transcriptase (hTERT), an important biomarker for tumors, is expressed only in cytoplasm instead of on cell membrane. In this study, the anti-hTERT blocking monoclonal antibody (mAb), as the model intrabody, was used to prepare nanoparticles (NPs), followed by the encapsulation of erythrocyte membrane (EM), to obtain the EM-coated anti-hTERT mAb NPs delivery system. The final NPs showed a z-average hydrodynamic diameter of about 197.3 nm. The in vitro cellular uptake by HeLa cells confirmed that compared with free anti-hTERT mAb, the EM-coated anti-hTERT mAb NPs exhibited a significantly increased uptake by tumor cells. Besides, the pharmacokinetic study confirmed that the EM encapsulation can remarkably prolong the circulation time and increase the area under curve (AUC) of NPs in blood. The EM-coated anti-hTERT mAb NPs exhibited a remarkably decreased uptake by macrophages than uncoated NPs, which may be responsible for the prolonged circulation time and increased AUC. Furthermore, the frozen section of tumor tissue was performed and proved that the EM-coated anti-hTERT mAb NPs can be more effectively accumulated in tumor tissues than the free mAb and uncoated NPs. In summary, this study indicated that EM-coated anti-hTERT mAb NPs are an effective delivery system for the long circulation and intracellular delivery of an intrabody, and make it possible for the intracellular biomarkers to become the potential targets of drugs.

Inhibition of allogeneic cytotoxic T cell (CD8+) proliferation via polymer-induced Treg (CD4+) cells

T cell-mediated immune rejection remains a barrier to successful transplantation. Polymer-based bioengineering of cells may provide an effective means of preventing allorecognition and the proliferation of cytotoxic (CD8⁺) T lymphocytes (CTL). Using MHC-disparate murine splenocytes modified with succinimidyl valerate activated methoxypoly(ethylene glycol) [SVA-mPEG] polymers, the effects of leukocyte immunocamouflage on CD8⁺ and CD4⁺ alloproliferation and T regulatory (Treg) cell induction were assessed in a mixed lymphocyte reaction (MLR) model. Polymer-grafting effectively camouflaged multiple leukocyte markers (MHC class I and II, TCR and CD3) essential for effective allorecognition. Consequent to the polymer-induced immunocamouflage of the cell membrane, both CD8⁺ and CD4⁺ T cell alloproliferation were significantly inhibited in a polymer dose-dependent manner. The loss of alloproliferation correlated with the induction of Treg cells (CD4⁺CD25⁺Foxp3⁺). The Tregs, surprisingly, arose primarily via differentiation of naive, non-proliferating, CD4⁺ cells. Of biologic importance, the polymer-induced Treg were functional and exhibited potent immunosuppressive activity on allogeneic CTL proliferation. These results suggest that immunocamouflage-mediated attenuation of alloantigen-TCR recognition can prevent the tissue destructive allogeneic CD8⁺ T cell response, both directly and indirectly, through the generation/differentiation of functional Tregs. Immunocamouflage induced tolerance could be clinically valuable in attenuating T cell-mediated transplant rejection and in the treatment of autoimmune diseases.

STATEMENT OF SIGNIFICANCE

While our previous studies have demonstrated that polymer-grafting to MHC disparate leukocytes inhibits CD4⁺ cell proliferation, the effects of PEGylation on the alloproliferation of CD8⁺ cytotoxic T cells (CTL) was not examined. As shown here, PEGylation of allogeneic leukocytes prevents the generation of the CTL response responsible for acute rejection. The loss of CTL proliferation is consequent to the polymer-based attenuation of allorecognition and the induction of T regulatory cells (Tregs). Interestingly, the Tregs are primarily generated via the differentiation of non-proliferating naive T cells. Importantly, the Tregs are functional and effectively induce a tolerogenic environment when transferred to an alloresponsive environment. The use of polymer-modified leukocytes provides a unique approach to effectively maximize the biologic production of functional Tregs both in vitro and in vivo. By using this approach it may be possible to attenuate unwanted alloresponses (e.g., graft rejection) or to treat autoimmune diseases.

Immunogenicity of murine mPEG-red blood cells and the risk of anti-PEG antibodies in human blood donors

The immunocamouflage of non-ABO blood group antigens by membrane-grafted methoxypoly(ethylene glycol) (mPEG) may attenuate the risk of red blood cell (RBC) alloimmunization. However, concerns have been raised over the immunogenic risk of PEG and PEG-RBCs. To assess this risk, murine and human studies were performed. Mice were exposed to soluble PEG prior to, or between, multiple transfusions (∼60-day intervals) of control or mPEG-RBCs, and cell survival was determined by flow cytometry. In some studies, the control and mPEG-RBC groups were reversed after one or more transfusions. Furthermore, human blood donors and commercial intravenous immunoglobulin products were examined to detect anti-PEG antibodies and to assess the risk for false positives. Naïve mice receiving chronic mPEG-RBC transfusions had normal RBC survival curves with no evidence of anti-PEG antibodies. Similarly, challenge with soluble PEG did not elicit anti-PEG antibodies in mice. Studies in humans revealed no evidence of a high prevalence of anti-PEG antibodies in either blood donors or commercial intravenous immunoglobulin. However, by use of the methods employed by studies identifying high levels of anti-PEG antibodies, a significant level (∼15%) of "false positives" were detected in commercial antibodies of known (non-PEG) specificities. These findings suggest that methodologic problems yielded a high rate of false positives in these earlier studies. These data continue to support the clinical utility of cellular PEGylation and the low immunogenic risk of grafted mPEG.

Effects of methoxypoly (Ethylene glycol) mediated immunocamouflage on leukocyte surface marker detection, cell conjugation, activation and alloproliferation

Tissue rejection occurs subsequent to the recognition of foreign antigens via receptor-ligand contacts between APC (antigen presenting cells) and T cells, resulting in initialization of signaling cascades and T cell proliferation. Bioengineering of donor cells by the covalent attachment of methoxypolyethylene glycol (mPEG) to membrane proteins (PEGylation) provides a novel means to attenuate these interactions consequent to mPEG-induced charge and steric camouflage. While previous studies demonstrated that polymer-mediated immunocamouflage decreased immune recognition both in vitro and in vivo, these studies monitored late events in immune recognition and activation such as T cell proliferation. Consequently little information has been provided concerning the early cellular events governing this response. Therefore, the effect of PEGylation was assessed by examining initial cell-cell interactions, changes to activation pathways, and apoptosis to understand the role that each may play in the decreased proliferative response observed in modified cells during the course of a mixed lymphocyte reaction (MLR). The mPEG-modified T cells resulted in significant immunocamouflage of lymphocyte surface proteins and decreased interactions with APC. Furthermore, mPEG-MLR exhibited decreased NFκB pathway activation, while exhibiting no significant differences in degree of cell death compared to the control MLR. These results suggest that PEGylation may prevent the direct recognition of foreign alloantigens by decreasing the stability and duration of initial cell-cell interactions.

A high capacity polymeric micelle of paclitaxel: Implication of high dose drug therapy to safety and in vivo anti-cancer activity

The poor solubility of paclitaxel (PTX), the commercially most successful anticancer drug, has long been hampering the development of suitable formulations. Here, we present translational evaluation of a nanoformulation of PTX, which is characterized by a facile preparation, extraordinary high drug loading of 50% wt. and PTX solubility of up to 45 g/L, excellent shelf stability and controllable, sub-100 nm size. We observe favorable in vitro and in vivo safety profiles and a higher maximum tolerated dose compared to clinically approved formulations. Pharmacokinetic analysis reveals that the higher dose administered leads to a higher exposure of the tumor to PTX. As a result, we observed improved therapeutic outcome in orthotopic tumor models including particularly faithful and aggressive "T11" mouse claudin-low breast cancer orthotopic, syngeneic transplants. The promising preclinical data on the presented PTX nanoformulation showcase the need to investigate new excipients and is a robust basis to translate into clinical trials.

Inhibition of Autoimmune Diabetes in NOD Mice by miRNA Therapy

Autoimmune destruction of the pancreatic islets in Type 1 diabetes is mediated by both increased proinflammatory (Teff) and decreased regulatory (Treg) T lymphocytes resulting in a significant decrease in the Treg:Teff ratio. The non-obese diabetic (NOD) mouse is an excellent in vivo model for testing potential therapeutics for attenuating the decrease in the Treg:Teff ratio and inhibiting disease pathogenesis. Here we show for the first time that a bioreactor manufactured therapeutic consisting of a complex of miRNA species (denoted as TA1) can effectively reset the NOD immune system from a proinflammatory to a tolerogenic state thus preventing or delaying autoimmune diabetes. Treatment of NOD mice with TA1 resulted in a systemic broad-spectrum upregulation of tolerogenic T cell subsets with a parallel downregulation of Teff subsets yielding a dramatic increase in the Treg:Teff ratio. Moreover, the murine-derived TA1 was highly effective in the inhibition of allorecognition of HLA-disparate human PBMC. TA1 demonstrated dose-responsiveness and exhibited equivalent or better inhibition of allorecognition driven proliferation than etanercept (a soluble TNF receptor). These findings demonstrate that miRNA-based therapeutics can effectively attenuate or arrest autoimmune disease processes and may be of significant utility in a broad range of autoimmune diseases including Type 1 diabetes.

Inhibition of phagocytic recognition of anti-D opsonized Rh D+ RBC by polymer-mediated immunocamouflage

The Rh D antigen posed both a significant clinical risk and inventory supply issue in transfusion medicine. The successful development of the immunocamouflaged RBC has the potential to address both the risk of acute anti‐D transfusion reactions and to improve D− blood inventory in geographic locations where D− blood is rare (e.g., China). The immunocamouflage of RBC was mediated by the covalent grafting of methoxy(polyethylene glycol) to the cell membrane thereby obscuring the D protein from the immune system. To determine the potential efficacy of mPEG‐D+ RBC in D− recipients, anti‐D alloantibodies from previously alloimmunized individuals were utilized. The effects of polymer chain size (2–30 kDa) and grafting concentration (0–4 mM) on antibody binding and erythrophagocytosis were determined using the clinically validated monocyte monolayer assay (MMA) and flow cytometry. The immunocamouflage of D was polymer size and grafting concentration dependent as determined using human anti‐D alloantibodies (both pooled [RhoGAM] and single donors). Importantly, the 20 kDa polymer provided excellent immunocamouflage of D and reached a clinically significant level of protection, as measured by the MMA, at grafting concentrations of ≥1.5 mM. These findings further support the potential use of immunocamouflaged RBC to reduce the risk of acute transfusion reactions following administration of D+ blood to D− recipients in situations where D− units are unavailable or supply is geographically constrained. Am. J. Hematol. 90:1165–1170, 2015. © 2015 Wiley Periodicals, Inc.

Delivery of drugs bound to erythrocytes: new avenues for an old intravascular carrier

For several decades, researchers have used erythrocytes for drug delivery of a wide variety of therapeutics in order to improve their pharmacokinetics, biodistribution, controlled release and pharmacodynamics. Approaches include encapsulation of drugs within erythrocytes, as well as coupling of drugs onto the red cell surface. This review focuses on the latter approach, and examines the delivery of red blood cell (RBC)-surface-bound anti-inflammatory, anti-thrombotic and anti-microbial agents, as well as RBC carriage of nanoparticles. Herein, we discuss the progress that has been made in surface loading approaches, and address in depth the issues relevant to surface loading of RBC, including intrinsic features of erythrocyte membranes, immune considerations, potential surface targets and techniques for the production of affinity ligands.