Silica-Coated Nanoparticles with a Core of Zinc, l-Arginine, and a Peptide Designed for Oral Delivery

Chitosan based surface modulation of core-shell nanoparticles for oral delivery of exenatide via balancing mucus penetration and cellular uptake

Oral delivery of peptide and protein drugs (PDs) is hindered by the impermeable intestinal mucosa, which consists of both the mucus layer and the epithelium. Therefore, double-layer (mucus layer and epithelium) overcoming nanocarriers need to be designed to enhance the transporting efficiency of PDs. However, the requirements for surface properties to penetrate these two barriers are quite distinct. In this study, nanoparticles (NPs) with balanced mucus permeation and cellular uptake were developed by modulating surface properties to improve the endocytosis efficiency of exenatide (EXT). The EXT-loaded ovolecithin (Lipoid E 80)/dextran/bovine serum albumin (EDB) NPs, solidified by sodium trimetaphosphate (STMP), were prepared through double emulsification combined with interfacial crosslinking solidification. The EDB NPs were then coated with cationic polyelectrolyte chitosan (CS) shell to form CS-EDB NPs, which exhibited 83.50 ± 0.44 % of encapsulation efficiency (EE), a particle size of approximately 277.0 ± 3.96 nm, and a Zeta potential of -16.2 ± 0.71 mV. Compared to uncoated EDB NPs, CS-EDB NPs showed a 1.1-fold reduction in mucus penetration (Papp), as measured using the Transwell mucus-penetrating model. However, CS-EDB NPs demonstrated a 2.15-fold and 1.77-fold increase in cellular uptake and transepithelial transport efficiency across a Caco-2/E-12 co-culture model, respectively, primarily driven by energy-dependent endocytosis and partially mediated by macropinocytosis. Furthermore, CS-EDB NPs achieved 13.29 % of pharmacological bioavailability and effectively regulated blood glucose, serum lipid levels, and improved islet function upon long-term administration. In conclusion, the core-shell structured CS-EDB NPs successfully protected against the harsh gastrointestinal tract (GIT) environment, providing improved endocytosis efficiency by slightly compromising mucus penetration while significantly enhancing cellular uptake, offering a promising approach for the oral delivery of PDs.

Bioinspired orthogonal-shaped protein-biometal nanocrystals enable oral protein absorption

With the growing number of marketed biological drugs, the development of technological strategies for their oral systemic absorption, becomes increasingly important. The harsh gastrointestinal environment and low permeability of the intestinal epithelium, represent a huge challenge for their systemic delivery. Herein, bioinspired in the physiological insulin-Zn interaction, the design of orthogonal-shaped protein-biometal hybrid nanocrystals, further enveloped by a bilayer of functional biomaterials, is reported. The nanocrystals exhibited a size of 80 nm, a neutral surface charge and a high insulin loading. In vitro studies showed the capacity of the nanocomplexes to control the release of the associated insulin, while preserving its stability. In vivo evaluation showed sustained blood glucose reductions in both healthy and diabetic rats (up to 40 % and 80 %, respectively), while chronic immunotoxicity studies in mice indicated no toxicity effect. Preliminary efficacy studies in healthy awake pigs following oral capsule administration showed over 20 % absolute bioavailability.

Cistanche deserticola polysaccharide-functionalized dendritic fibrous nano-silica as oral vaccine adjuvant delivery enhancing both the mucosal and systemic immunity

Oral vaccines are a safe and convenient alternative to injected vaccines and have great potential to prevent major infectious diseases. However, the harsh gastrointestinal (GI) environment, mucus barriers, low immunogenicity, and lack of effective and safe mucosal adjuvants are the major challenges for oral vaccine delivery. In recent years, nanoparticle-based strategies have become attractive for improving oral vaccine delivery. Here, the dendritic fibrous nano-silica (DFNS) grafted with Cistanche deserticola polysaccharide (CDP) nanoparticles (CDP-DFNS) were prepared and investigated how to impact the immune responses. CDP-DFNS facilitated the antigen uptake in mouse bone marrow-derived dendritic cells (BMDCs), and induce the activation of DCs in vitro. Furthermore, in vivo experiments, the result showed that the uptake efficiency by Peyer's patches (PPs) of CDP-DFNS/BSA was the best. And CDP-DFNS/BSA then significantly activated the DCs in lamina propria (LP), and T/B cells in PPs and mesenteric lymph nodes (MLNs). Moreover, the memory T cell responses in later period of vaccination was stronger than other groups. In addition, CDP-DFNS/BSA enhanced BSA-specific antibody IgG, IgA production, and SIgA secretion, was effective at inducing a strong mixed Th1/Th2 response and mucosal antibody responses. These results indicated that CDP-DFNS deserves further consideration as an oral vaccine adjuvant delivery system.

Protein-based bioactive coatings: from nanoarchitectonics to applications

Protein-based bioactive coatings have emerged as a versatile and promising strategy for enhancing the performance and biocompatibility of diverse biomedical materials and devices. Through surface modification, these coatings confer novel biofunctional attributes, rendering the material highly bioactive. Their widespread adoption across various domains in recent years underscores their importance. This review systematically elucidates the behavior of protein-based bioactive coatings in organisms and expounds on their underlying mechanisms. Furthermore, it highlights notable advancements in artificial synthesis methodologies and their functional applications in vitro. A focal point is the delineation of assembly strategies employed in crafting protein-based bioactive coatings, which provides a guide for their expansion and sustained implementation. Finally, the current trends, challenges, and future directions of protein-based bioactive coatings are discussed.

Challenges in Permeability Assessment for Oral Drug Product Development

Drug permeation across the intestinal epithelium is a prerequisite for successful oral drug delivery. The increased interest in oral administration of peptides, as well as poorly soluble and poorly permeable compounds such as drugs for targeted protein degradation, have made permeability a key parameter in oral drug product development. This review describes the various in vitro, in silico and in vivo methodologies that are applied to determine drug permeability in the human gastrointestinal tract and identifies how they are applied in the different stages of drug development. The various methods used to predict, estimate or measure permeability values, ranging from in silico and in vitro methods all the way to studies in animals and humans, are discussed with regard to their advantages, limitations and applications. A special focus is put on novel techniques such as computational approaches, gut-on-chip models and human tissue-based models, where significant progress has been made in the last few years. In addition, the impact of permeability estimations on PK predictions in PBPK modeling, the degree to which excipients can affect drug permeability in clinical studies and the requirements for colonic drug absorption are addressed.

Structural basis of insulin fibrillation

Insulin is a hormone responsible for maintaining normal glucose levels by activating insulin receptor (IR) and is the primary treatment for diabetes. However, insulin is prone to unfolding and forming cross-β fibers. Fibrillation complicates insulin storage and therapeutic application. Molecular details of insulin fibrillation remain unclear, hindering efforts to prevent fibrillation process. Here, we characterized insulin fibrils using cryo-electron microscopy (cryo-EM), showing multiple forms that contain one or more of the protofilaments containing both the A and B chains of insulin linked by disulfide bonds. We solved the cryo-EM structure of one of the fibril forms composed of two protofilaments at 3.2-Å resolution, which reveals both the β sheet conformation of the protofilament and the packing interaction between them that underlie the fibrillation. On the basis of this structure, we designed several insulin mutants that display reduced fibrillation while maintaining native IR signaling activity. These designed insulin analogs may be developed into more effective therapeutics for type 1 diabetes.

An Investigation into the Acidity-Induced Insulin Agglomeration: Implications for Drug Delivery and Translation

Insulin undergoes agglomeration with (subtle) changes in its biochemical environment, including acidity, application of heat, ionic imbalance, and exposure to hydrophobic surfaces. The therapeutic impact of such unwarranted insulin agglomeration is unclear and needs further evaluation. A systematic investigation was conducted on recombinant human insulin-with or without labeling with fluorescein isothiocyanate-while preparing insulin suspensions (0.125, 0.25, and 0.5 mg/mL) at pH 3. The suspensions were incubated (37 °C) and analyzed at different time points (t = 2, 4, 24, 48, and 72 h). Transmission electron microscopy and nanoparticle tracking analysis identified colloidally stable (zeta potential 15 ± 5 mV) spherical agglomerates of unlabeled insulin (100-500 nm). Circular dichroism established the preservation of insulin's secondary structure rich in α-helices despite exposure to an acidic environment (pH 3) for 72 h. Furthermore, fluorescence lifetime imaging microscopy illustrated an acidic core inside these spherical agglomerates, while the acidity gradually lessened toward the periphery. Some of these smaller agglomerates fused to form larger chunks with discrete zones of acidity. The data indicated a primary nucleation-driven mechanism of acid-induced insulin agglomeration under physiologically relevant conditions.

Material design for oral insulin delivery

Frequent insulin injections remain the primary method for controlling the blood glucose level of individuals with diabetes mellitus but are associated with low compliance. Accordingly, oral administration has been identified as a highly desirable alternative due to its non-invasive nature. However, the harsh gastrointestinal environment and physical intestinal barriers pose significant challenges to achieving optimal pharmacological bioavailability of insulin. As a result, researchers have developed a range of materials to improve the efficiency of oral insulin delivery over the past few decades. In this review, we summarize the latest advances in material design that aim to enhance insulin protection, permeability, and glucose-responsive release. We also explore the opportunities and challenges of using these materials for oral insulin delivery.

Oral delivery of biomacromolecules by overcoming biological barriers in the gastrointestinal tract: an update

INTRODUCTION

Biomacromolecules have proven to be an attractive choice for treating diseases due to their properties of strong specificity, high efficiency, and low toxicity. Besides greatly improving the patient's complaint, oral delivery of macromolecules also complies with hormone physiological secretion, which has become one of the most innovative fields of research in recent years.

AREAS COVERED

Oral delivery biological barriers for biomacromolecule, transport mechanisms, and various administration strategies were discussed in this review, including absorption enhancers, targeting nanoparticles, mucoadhesion nanoparticles, mucus penetration nanoparticles, and intelligent bionic drug delivery systems.

EXPERT OPINION

The oral delivery of biomacromolecules has important clinical implications; however, these are still facing the challenges of low bioavailability due to certain barriers. Various promising technologies have been developed to overcome the barriers and improve the therapeutic effect of oral biomacromolecules. By considering safety and efficacy comprehensively, the development of intelligent nanoparticles based on the GIT environment has demonstrated some promise in overcoming these barriers; however, a more comprehensive understanding of the oral fate of oral biomacromolecules is still required.

Covalently-Bonded Coating of L-Arginine Modified Magnetic Nanoparticles with Dextran Using Co-Precipitation Method

In this study, L-arginine (Arg) modified magnetite (Fe₃O₄) nanoparticles (RMNPs) were firstly synthesized through a one-step co-precipitation method, and then these aminated nanoparticles (NPs) were, again, coated by pre-oxidized dextran (Dext), in which aldehyde groups (DextCHO) have been introduced on the polymer chain successfully via a strong chemical linkage. Arg, an amino acid, acts as a mediator to link the Dext to a magnetic core. The as-synthesized Arg-modified and Dext-coated arginine modified Fe₃O₄ NPs were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM). Both synthesized samples, XRD pattern and FT-IR spectra proved that the core is magnetite. FT-IR confirmed that the chemical bonds of Arg and Dext both exist in the samples. SEM images showed that the NPs are spherical and have an acceptable distribution size, and the VSM analysis indicated the superparamagnetic behavior of samples. The saturation magnetization was decreased after Dext coating, which confirms successive coating RMNPs with Text. In addition, the TGA analysis demonstrated that the prepared magnetic nanocomposites underwent various weight loss levels, which admitted the modification of magnetic cores with Arg and further coating with Dext.

Amyloid Fibrillation of Insulin: Amelioration Strategies and Implications for Translation

Insulin is a therapeutically relevant molecule with use in treating diabetes patients. Unfortunately, it undergoes a range of untoward and often unpredictable physical transformations due to alterations in its biochemical environment, including pH, ionic strength, temperature, agitation, and exposure to hydrophobic surfaces. The transformations are prevalent in its physiologically active monomeric form, while the zinc cation-coordinated hexamer, although physiologically inactive, is stable and less susceptible to fibrillation. The resultant molecular reconfiguration, including unfolding, misfolding, and hydrophobic interactions, often results in agglomeration, amyloid fibrillogenesis, and precipitation. As a result, a part of the dose is lost, causing a compromised therapeutic efficacy. Besides, the amyloid fibrils form insoluble deposits, trigger immunologic reactions, and harbor cytotoxic potential. The physical transformations also hold back a successful translation of non-parenteral insulin formulations, in addition to challenges related to encapsulation, chemical modification, purification, storage, and dosing. This review revisits the mechanisms and challenges that drive such physical transformations in insulin, with an emphasis on the observed amyloid fibrillation, and presents a critique of the current amelioration strategies before prioritizing some future research objectives.

Barriers to the Intestinal Absorption of Four Insulin-Loaded Arginine-Rich Nanoparticles in Human and Rat

Peptide drugs and biologics provide opportunities for treatments of many diseases. However, due to their poor stability and permeability in the gastrointestinal tract, the oral bioavailability of peptide drugs is negligible. Nanoparticle formulations have been proposed to circumvent these hurdles, but systemic exposure of orally administered peptide drugs has remained elusive. In this study, we investigated the absorption mechanisms of four insulin-loaded arginine-rich nanoparticles displaying differing composition and surface characteristics, developed within the pan-European consortium TRANS-INT. The transport mechanisms and major barriers to nanoparticle permeability were investigated in freshly isolated human jejunal tissue. Cytokine release profiles and standard toxicity markers indicated that the nanoparticles were nontoxic. Three out of four nanoparticles displayed pronounced binding to the mucus layer and did not reach the epithelium. One nanoparticle composed of a mucus inert shell and cell-penetrating octarginine (ENCP), showed significant uptake by the intestinal epithelium corresponding to 28 ± 9% of the administered nanoparticle dose, as determined by super-resolution microscopy. Only a small fraction of nanoparticles taken up by epithelia went on to be transcytosed via a dynamin-dependent process. In situ studies in intact rat jejunal loops confirmed the results from human tissue regarding mucus binding, epithelial uptake, and negligible insulin bioavailability. In conclusion, while none of the four arginine-rich nanoparticles supported systemic insulin delivery, ENCP displayed a consistently high uptake along the intestinal villi. It is proposed that ENCP should be further investigated for local delivery of therapeutics to the intestinal mucosa.

Add Sugar to Chitosan: Mucoadhesion and In Vitro Intestinal Permeability of Mannosylated Chitosan Nanocarriers

Crosslinked chitosan nanocarriers (140–160 nm) entrapping coumarin-6 (λ_ex/em = 455/508 nm) with or without surface mannosylation were synthesized and assessed for cytotoxicity, adherence and cellular uptake in Caco-2 cells, flux across Caco-2 monolayers, and mucoadhesion to porcine mucin. Mannosylated and non-mannosylated nanocarriers demonstrated biocompatibility with slow release of coumarin-6 at pH 6.8 and 7.4 over 24 h. Adherence of the non-mannosylated nanocarriers (50 and 150 µg/mL) to Caco-2 cells was ~10% over 24 h, whereas cellular uptake of 25–30% was noted at 4 h. The mannosylated nanocarriers showed a similar adherence to non-mannosylated nanocarriers after 24 h, but a lower cellular uptake (~20%) at 1 h, comparable uptake at 4 h, and a higher uptake (~25–30%) at 24 h. Overall, the nanocarriers did not affect the integrity of Caco-2 monolayers. Mannosylated nanocarriers elicited higher P_app of 1.6 × 10⁻⁶ cm/s (50 µg/mL) and 1.2 × 10⁻⁶ (150 µg/mL) than the non-mannosylated ones: 9.8 × 10⁻⁷ cm/s (50 µg/mL) and 1.0 × 10⁻⁶ (150 µg/mL) after 2 h. Non-mannosylated chitosan nanocarriers elicited enhanced adhesion to porcine gut mucin via mucin-filled microchannels due to higher cationic charge density. These results underpin the importance of surface chemistry in the biological interactions of nanocarriers, while highlighting the role of surface hydrophilicity in mucopermeation due to mannosylation.

Advances in oral peptide drug nanoparticles for diabetes mellitus treatment

Peptide drugs play an important role in diabetes mellitus treatment. Oral administration of peptide drugs is a promising strategy for diabetes mellitus because of its convenience and high patient compliance compared to parenteral administration routes. However, there are a series of formidable unfavorable conditions present in the gastrointestinal (GI) tract after oral administration, which result in the low oral bioavailability of these peptide drugs. To overcome these challenges, various nanoparticles (NPs) have been developed to improve the oral absorption of peptide drugs due to their unique in vivo properties and high design flexibility. This review discusses the unfavorable conditions present in the GI tract and provides the corresponding strategies to overcome these challenges. The review provides a comprehensive overview on the NPs that have been constructed for oral peptide drug delivery in diabetes mellitus treatment. Finally, we will discuss the rational application and give some suggestions that can be utilized for the development of oral peptide drug NPs. Our aim is to provide a systemic and comprehensive review of oral peptide drug NPs that can overcome the challenges in GI tract for efficient treatment of diabetes mellitus.

•Oral administration of peptide drugs is a promising strategy for diabetes mellitus treatment

•A series of formidable unfavorable conditions in gastrointestinal tract result in the low oral bioavailability of peptide drugs

•Nanoparticles can improve the oral bioavailability of peptide drugs

Chiral mesoporous silica nano-screws as an efficient biomimetic oral drug delivery platform through multiple topological mechanisms

In the microscale, bacteria with helical body shapes have been reported to yield advantages in many bio-processes. In the human society, there are also wisdoms in knowing how to recognize and make use of helical shapes with multi-functionality. Herein, we designed atypical chiral mesoporous silica nano-screws (CMSWs) with ideal topological structures (e.g., small section area, relative rough surface, screw-like body with three-dimension chirality) and demonstrated that CMSWs displayed enhanced bio-adhesion, mucus-penetration and cellular uptake (contributed by the macropinocytosis and caveolae-mediated endocytosis pathways) abilities compared to the chiral mesoporous silica nanospheres (CMSSs) and chiral mesoporous silica nanorods (CMSRs), achieving extended retention duration in the gastrointestinal (GI) tract and superior adsorption in the blood circulation (up to 2.61- and 5.65-times in AUC). After doxorubicin (DOX) loading into CMSs, DOX@CMSWs exhibited controlled drug release manners with pH responsiveness in vitro. Orally administered DOX@CMSWs could efficiently overcome the intestinal epithelium barrier (IEB), and resulted in satisfactory oral bioavailability of DOX (up to 348%). CMSWs were also proved to exhibit good biocompatibility and unique biodegradability. These findings displayed superior ability of CMSWs in crossing IEB through multiple topological mechanisms and would provide useful information on the rational design of nano-drug delivery systems.

Hyaluronic Acid Coated Chitosan Nanoparticles for Insulin Oral Delivery: Fabrication, Characterization and Hypoglycemic Ability

Oral administration of insulin faces multiple biological challenges, such as varied digestive environments, mucin exclusion and low epithelial cells absorption. In the present study, a hyaluronic acid coated chitosan nanoparticle delivery system was fabricated for insulin oral delivery. It is hypothesized that the developed nanoparticles will protect insulin from digestive degradation, promote intestinal epithelial cell absorption and exert strong in vivo hyperglycemic ability. Nanoparticles formulated by chitosan (CS) and sodium tripolyphosphate (TPP) was optimized to form the core nanoparticles (CNP). Hyaluronic acid (HA) was further applied to coat CNP (HCP) to improve stability, reduce enzymatic degradation and promote absorption of insulin. HCP promoted insulin uptake by Caco-2 cells, absorbed less mucin and improved intestinal absorption. Moreover, in vivo test demonstrated that oral administration of insulin-loaded HCP exerts strong and continuous hyperthermia effect (with PA of 13.8%). In summary, HCP is a promising delivery platform for insulin oral administration in terms of protecting insulin during digestion, facilitating its absorption and ultimately promoting its oral bioavailability. This article is protected by copyright. All rights reserved.

Nanotechnologies for the delivery of biologicals: Historical perspective and current landscape

Biological macromolecule-based therapeutics irrupted in the pharmaceutical scene generating a great hope due to their outstanding specificity and potency. However, given their susceptibility to degradation and limited capacity to overcome biological barriers new delivery technologies had to be developed for them to reach their targets. This review aims at analyzing the historical seminal advances that shaped the development of the protein/peptide delivery field, along with the emerging technologies on the lead of the current landscape. Particularly, focus is made on technologies with a potential for transmucosal systemic delivery of protein/peptide drugs, followed by approaches for the delivery of antigens as new vaccination strategies, and formulations of biological drugs in oncology, with special emphasis on mAbs. Finally, a discussion of the key challenges the field is facing, along with an overview of prospective advances are provided.

Synthesis and In Vivo Evaluation of Insulin-Loaded Whey Beads as an Oral Peptide Delivery System

For many diabetics, daily, lifelong insulin injections are required to effectively manage blood glucose levels and the complications associated with the disease. This can be a burden and reduces patient quality of life. Our goal was to develop a more convenient oral delivery system that may be suitable for insulin and other peptides. Insulin was entrapped in 1.5-mm beads made from denatured whey protein isolate (dWPI) using gelation. Beads were then air-dried with fumed silica, Aerosil^®. The encapsulation efficiency was ~61% and the insulin loading was ~25 µg/mg. Dissolution in simulated gastric-, and simulated intestinal fluids (SGF, SIF) showed that ~50% of the insulin was released from beads in SGF, followed by an additional ~10% release in SIF. The omission of Aerosil^® allowed greater insulin release, suggesting that it formed a barrier on the bead surface. Circular dichroism analysis of bead-released insulin revealed an unaltered secondary structure, and insulin bioactivity was retained in HepG2 cells transfected to assess activation of the endogenous insulin receptors. Insulin-entrapped beads were found to provide partial protection against pancreatin for at least 60 min. A prototype bead construct was then synthesised using an encapsulator system and tested in vivo using a rat intestinal instillation bioassay. It was found that 50 IU/kg of entrapped insulin reduced plasma glucose levels by 55% in 60 min, similar to that induced by subcutaneously (s.c.)-administered insulin (1 IU/kg). The instilled insulin-entrapped beads produced a relative bioavailability of 2.2%. In conclusion, when optimised, dWPI-based beads may have potential as an oral peptide delivery system.

Oral Coadministration of Zn-Insulin with d-Form Small Intestine-Permeable Cyclic Peptide Enhances Its Blood Glucose-Lowering Effect in Mice

Oral delivery of insulin remains a challenge owing to its poor permeability across the small intestine and enzymatic digestion in the gastrointestinal tract. In a previous study, we identified a small intestine-permeable cyclic peptide, C-DNPGNET-C (C-C disulfide bond, cyclic DNP peptide), which facilitated the permeation of macromolecules. Here, we showed that intraintestinal and oral coadministration of insulin with the cyclic DNP derivative significantly reduced blood glucose levels by increasing the portal plasma insulin concentration following permeation across the small intestine of mice. We also found that protecting the cyclic DNP derivative from enzymatic digestion in the small intestine of mice using d-amino acids and by the cyclization of DNP peptide was essential to enhance cyclic DNP derivative-induced insulin absorption across the small intestine. Furthermore, intraintestinal and oral coadministration of insulin hexamer stabilized by zinc ions (Zn-insulin) with cyclic D-DNP derivative was more effective in facilitating insulin absorption and inducing hypoglycemic effects in mice than the coadministration of insulin with the cyclic D-DNP derivative. Moreover, Zn-insulin was more resistant to degradation in the small intestine of mice compared to insulin. Intraintestinal and oral coadministration of Zn-insulin with cyclic DNP derivative also reduced blood glucose levels in a streptozotocin-induced diabetes mellitus mouse model. A single intraintestinal administration of the cyclic D-DNP derivative did not induce any cytotoxicity, either locally in the small intestine or systemically. In summary, we demonstrated that coadministration of Zn-insulin with cyclic D-DNP derivative could enhance oral insulin absorption across the small intestine in mice.

Understanding the burst release phenomenon: toward designing effective nanoparticulate drug-delivery systems

Burst release of encapsulated drug with release of a significant fraction of payload into release medium within a short period, both in vitro and in vivo, remains a challenge for translation. Such unpredictable and uncontrolled release is often undesirable, especially from the perspective of developing sustained-release formulations. Moreover, a brisk release of the payload upsets optimal release kinetics. This account strives toward understanding burst release noticed in nanocarriers and investigates its causes. Various mathematical models to explain such untimely release were also examined, including their strengths and weaknesses. Finally, the account revisits current techniques of limiting burst release from nanocarriers and prioritizes future directions that harbor potential of fruitful translation by reducing such occurrences.

Cloaking Silica Nanoparticles with Functional Protein Coatings for Reduced Complement Activation and Cellular Uptake

Silica-coated nanoparticles are widely used in biomedical applications such as theranostics, imaging, and drug delivery. While silica-coated nanoparticles are biocompatible, experimental evidence shows that they can trigger innate immune reactions, and a broader understanding of what types of reactions are caused and how to mitigate them is needed. Herein, we investigated how the noncovalent surface functionalization of silica nanoparticles with purified proteins can inhibit nanoparticle-induced complement activation and macrophage uptake, two of the most clinically relevant innate immune reactions related to nanomedicines. Silica nanoparticles were tested alone and after coating with bovine serum albumin, human serum albumin, fibrinogen, complement factor H (FH), or immunoglobulin G (IgG) proteins. Enzyme-linked immunosorbent assays measuring the generation of various complement activation products indicated that silica nanoparticles induce complement activation via the alternative pathway. All protein coatings other than IgG protected against complement activation to varying extents. Most proteins acted as steric blockers to inhibit complement protein deposition on the nanoparticle surface, while FH coatings were biologically active and inhibited a key step in the amplification loop of complement activation, as confirmed by Western blot analysis. Flow cytometry and fluorescence microscopy experiments further revealed that complement activation-inhibiting protein coatings blunted macrophage uptake as well. Taken together, our findings demonstrate a simple and effective way to coat silica nanoparticles with purified protein coatings in order to mitigate innate immune reactions. Such methods are readily scalable and might constitute a useful strategy for improving the immunological safety profile of silica and silica-coated nanoparticles as well as other types of inorganic nanoparticles.

Systemic delivery of peptides by the oral route: Formulation and medicinal chemistry approaches

In its 33 years, ADDR has published regularly on the po5tential of oral delivery of biologics especially peptides and proteins. In the intervening period, analysis of the preclinical and clinical trial failures of many purported platform technologies has led to reflection on the true status of the field and reigning in of expectations. Oral formulations of semaglutide, octreotide, and salmon calcitonin have completed Phase III trials, with oral semaglutide being approved by the FDA in 2019. The progress made with oral peptide formulations based on traditional permeation enhancers is against a background of low and variable oral bioavailability values of ~1%, leading to a current perception that only potent peptides with a viable cost of synthesis can be realistically considered. Desirable features of candidates should include a large therapeutic index, some stability in the GI tract, a long elimination half-life, and a relatively low clearance rate. Administration in nanoparticle formats have largely disappointed, with few prototypes reaching clinical trials: insufficient particle loading, lack of controlled release, low epithelial particle uptake, and lack of scalable synthesis being the main reasons for discontinuation. Disruptive technologies based on engineered devices promise improvements, but scale-up and toxicology aspects are issues to address. In parallel, medicinal chemists are synthesizing stable hydrophobic macrocyclic candidate peptides of lower molecular weight and with potential for greater oral bioavailability than linear peptides, but perhaps without the same requirement for elaborate drug delivery systems. In summary, while there have been advances in understanding the limitations of peptides for oral delivery, low membrane permeability, metabolism, and high clearance rates continue to hamper progress.