Advances in PEGylation of important biotech molecules: delivery aspects

Injectable long-acting formulations (ILAFs) and manufacturing techniques

INTRODUCTION

Most therapeutics delivered using short-acting formulations need repeated administration, which can harm patient compliance and raise failure risks related to inconsistent treatment. Injectable long-acting formulations (ILAFs) are controlled/sustained-release formulations fabricated to deliver active pharmaceutical ingredients (APIs) and extend their half-life over days to months. Longer half-lives of ILAFs minimize the necessity for frequent doses, increase patient compliance, and reduce the risk of side effects from intravenous (IV) infusions. Using ILAF technologies, the immediate drug release can also be controlled, thereby minimizing potential adverse effects due to high initial drug blood concentrations.

AREA COVERED

In this review, we have discussed various ILAFs, their physiochemical properties, fabrication technologies, advantages, and practical issues, as well as address some major challenges in their application. Especially, the approved ILAFs are highlighted.

EXPERT OPINION

ILAFs are sustained-release formulations with extended activity, which can improve patient compliance. ILAFs are designed to deliver APIs like proteins and peptides and extend their half-life over days to months. The specific properties of each ILAF preparation, such as extended-release and improved drug targeting capabilities, make them an effective approach for precise and focused therapy. Furthermore, this is especially helpful for biopharmaceuticals with short biological half-lives and low stability since most environmental conditions can protect them from sustained-release delivery methods.

Microencapsulation for Pharmaceutical Applications: A Review

In order to improve bioavailability, stability, control release, and target delivery of active pharmaceutical ingredients (APIs), as well as to mask their bitter taste, to increase their efficacy, and to minimize their side effects, a variety of microencapsulation (including nanoencapsulation, particle size <100 nm) technologies have been widely used in the pharmaceutical industry. Commonly used microencapsulation technologies are emulsion, coacervation, extrusion, spray drying, freeze-drying, molecular inclusion, microbubbles and microsponge, fluidized bed coating, supercritical fluid encapsulation, electro spinning/spray, and polymerization. In this review, APIs are categorized by their molecular complexity: small APIs (compounds with low molecular weight, like Aspirin, Ibuprofen, and Cannabidiol), medium APIs (compounds with medium molecular weight like insulin, peptides, and nucleic acids), and living microorganisms (such as probiotics, bacteria, and bacteriophages). This article provides an overview of these microencapsulation technologies including their processes, matrix, and their recent applications in microencapsulation of APIs. Furthermore, the advantages and disadvantages of these common microencapsulation technologies in terms of improving the efficacy of APIs for pharmaceutical treatments are comprehensively analyzed. The objective is to summarize the most recent progresses on microencapsulation of APIs for enhancing their bioavailability, control release, target delivery, masking their bitter taste and stability, and thus increasing their efficacy and minimizing their side effects. At the end, future perspectives on microencapsulation for pharmaceutical applications are highlighted.

Increasing the versatility of the biphenyl-fused-dioxacyclodecyne class of strained alkynes

Biphenyl-fused-dioxacyclodecynes are a promising class of strained alkyne for use in Cu-free 'click' reactions. In this paper, a series of functionalised derivatives of this class of reagent, containing fluorescent groups, are described. Studies aimed at understanding and increasing the reactivity of the alkynes are also presented, together with an investigation of the bioconjugation of the reagents with an azide-labelled protein.

Polyethylene Glycol 20k. Does It Fluoresce?

Polyethylene glycol (PEG) is a polyether compound commonly used in biological research and medicine because it is biologically inert. This simple polymer exists in variable chain lengths (and molecular weights). As they are devoid of any contiguous π-system, PEGs are expected to lack fluorescence properties. However, recent studies suggested the occurrence of fluorescence properties in non-traditional fluorophores like PEGs. Herein, a thorough investigation has been conducted to explore if PEG 20k fluoresces. Results of this combined experimental and computational study suggested that although PEG 20k could exhibit "through-space" delocalization of lone pairs of electrons in aggregates/clusters, formed via intermolecular and intramolecular interactions, the actual contributor of fluorescence between 300 and 400 nm is the stabilizer molecule, i.e., 3-tert-butyl-4-hydroxyanisole present in the commercially available PEG 20k. Therefore, the reported fluorescence properties of PEG should be taken with a grain of salt, warranting further investigation.

Anti-Cancer Peptides: Status and Future Prospects

The dramatic rise in cancer incidence, alongside treatment deficiencies, has elevated cancer to the second-leading cause of death globally. The increasing morbidity and mortality of this disease can be traced back to a number of causes, including treatment-related side effects, drug resistance, inadequate curative treatment and tumor relapse. Recently, anti-cancer bioactive peptides (ACPs) have emerged as a potential therapeutic choice within the pharmaceutical arsenal due to their high penetration, specificity and fewer side effects. In this contribution, we present a general overview of the literature concerning the conformational structures, modes of action and membrane interaction mechanisms of ACPs, as well as provide recent examples of their successful employment as targeting ligands in cancer treatment. The use of ACPs as a diagnostic tool is summarized, and their advantages in these applications are highlighted. This review expounds on the main approaches for peptide synthesis along with their reconstruction and modification needed to enhance their therapeutic effect. Computational approaches that could predict therapeutic efficacy and suggest ACP candidates for experimental studies are discussed. Future research prospects in this rapidly expanding area are also offered.

PEGylation Strategy for Improving the Pharmacokinetic and Antitumoral Activity of the IL-2 No-alpha Mutein

BACKGROUND

In a previous work, an IL-2Rβγ biased mutant derived from human IL-2 and called IL-2noα, was designed and developed. Greater antitumor effects and lower toxicity were observed compared to native IL-2. Nevertheless, mutein has some disadvantages, such as a very short half-life of about 9-12 min, propensity for aggregation, and solubility problems.

OBJECTIVE

In this study, PEGylation was employed to improve the pharmacokinetic and antitumoral properties of the novel protein.

METHODS

Pegylated IL-2noα was characterized by polyacrylamide gel electrophoresis, size exclusion chromatography, in vitro cell proliferation and in vivo cell expansion bioassays, and pharmacokinetic and antitumor studies.

RESULTS

IL-2noα-conjugates with polyethylene glycol (PEG) of 1.2 kDa, 20 kDa, and 40 kDa were obtained by classical acylation. No significant changes in the secondary and tertiary structures of the modified protein were detected. A decrease in biological activity in vitro and a significant improvement in half-life were observed, especially for IL-2noα-PEG20K. PEGylation of IL-2noα with PEG20K did not affect the capacity of the mutant to induce preferential expansion of T effector cells over Treg cells. This pegylated IL-2noα exhibited a higher antimetastatic effect compared to unmodified IL-2noα in the B16F0 experimental metastases model, even when administered at lower doses and less frequently.

CONCLUSION

PEG20K was selected as the best modification strategy, to improve the blood circulation time of the IL-2noα with a superior antimetastatic effect achieved with lower doses.

Anticancer peptides mechanisms, simple and complex

Peptide therapy has started since 1920s with the advent of insulin application, and now it has emerged as a new approach in treatment of diseases including cancer. Using anti-cancer peptides (ACPs) is a promising way of cancer therapy as ACPs are continuing to be approved and arrived at major pharmaceutical markets. Traditional cancer treatments face different problems like intensive adverse effects to patient's body, cell resistance to conventional chemical drugs and in some worse cases the occurrence of cell multidrug resistance (MDR) of cancerous tissues against chemotherapy. On the other hand, there are some benefits conceived for peptides usage in treatment of diseases specifically cancer, as these compounds present favorable characteristics such as smaller size, high activity, low immunogenicity, good biocompatibility in vivo, convenient and rapid way of synthesis, amenable to sequence modification and revision and there is no limitation for the type of cargo they carry. It is possible to achieve an optimum molecular and functional structure of peptides based on previous experience and bank of peptide motif data which may result in novel peptide design. Bioactive peptides are able to form pores in cell membrane and induce necrosis or apoptosis of abnormal cells. Moreover, recent researches have focused on the tumor recognizing peptide motifs with the ability to permeate to cancerous cells with the aim of cancer treatment at earlier stages. In this strategy the most important factors for addressing cancer are choosing peptides with easy accessibility to tumor cell without cytotoxicity effect towards normal cells. The peptides must also meet acceptable pharmacokinetic requirements. In this review, the characteristics of peptides and cancer cells are discussed. The various mechanisms of peptides' action proposed against cancer cells make the next part of discussion. It will be followed by giving information on peptides application, various methods of peptide designing along with introducing various databases. Future aspects of peptides for employing in area of cancer treatment come as conclusion at the end.

Mono-PEGylated lysozyme purification with increased productivity and isomer differentiation through heparin monolith chromatography

PEGylated protein purification with the required quality attributes has represented a bioengineering challenge and Affinity Monolith Chromatography (AMC) has never been exploited for this goal. This work reports the generation of a heparin-modified affinity monolith disk by reductive alkylation with raised ligand density for its use as chromatographic support in the separation of lysozyme PEGylation reactions (LPRs) with three different PEG sizes (1, 20 and 40 kDa). For immobilized heparin determination a modified toluidine colorimetric assay adapted to microplate format was proposed. The heparin modified-disk was able to differentiate positional isomers of 20 kDa mono-PEGylated lysozyme at neutral pH using a salt linear gradient. Identity of PEG-conjugates was verified by SDS-PAGE and positional isomers were partially characterized by peptide mapping mass spectrometry. 20 kDa mono-PEGylated lysozyme conjugate purity (99.69 ± 0.05%) was comparable with traditional chromatographic methods while productivity (0.0964 ± 0.0001 mg/mL*min) was increased up to 6.1 times compared to that obtained in heparin packed-bed affinity chromatography procedures. The proposed AMC method represents a reliable, efficient, easy-handling, fast and single-step operation for the analysis or preparative isolation of PEGylated proteins containing a heparin binding domain.

Folate Conjugated Polyethylene Glycol Probe for Tumor-Targeted Drug Delivery of 5-Fluorouracil

A targeted delivery system is primarily intended to carry a potent anticancer drug to specific tumor sites within the bodily tissues. In the present study, a carrier system has been designed using folic acid (FA), bis-amine polyethylene glycol (PEG), and an anticancer drug, 5-fluorouracil (5-FU). FA and PEG were joined via an amide bond, and the resulting FA-PEG-NH₂ was coupled to 5-FU producing folate-polyethylene glycol conjugated 5-fluorouracil (FA-PEG-5-FU). Spectroscopic techniques (UV-Vis, ¹HNMR, FTIR, and HPLC) were used for the characterization of products. Prodrug (FA-PEG-5-FU) was analyzed for drug release profile (in vitro) up to 10 days and compared to a standard anticancer drug (5-FU). Folate conjugate was also analyzed to study its folate receptors (FR) mediated transport and in vitro cytotoxicity assays using HeLa cancer cells/Vero cells, respectively, and antitumor activity in tumor-bearing mice models. Folate conjugate showed steady drug release patterns and improved uptake in the HeLa cancer cells than Vero cells. Folate conjugate treated mice group showed smaller tumor volumes; specifically after the 15th day post-treatment, tumor sizes were decreased significantly compared to the standard drug group (5-FU). Molecular docking findings demonstrated importance of Trp138, Trp140, and Lys136 in the stabilization of flexible loop flanking the active site. The folic acid conjugated probe has shown the potential of targeted drug delivery and sustained release of anticancer drug to tumor lesions with intact antitumor efficacy.

Evaluation of Liposome-Loaded Microbubbles as a Theranostic Tool in a Murine Collagen-Induced Arthritis Model

Rheumatoid arthritis (RA) is an autoimmune disease characterized by severe inflammation of the synovial tissue. Here, we assess the feasibility of liposome-loaded microbubbles as theranostic agents in a murine arthritis model. First, contrast-enhanced ultrasound (CEUS) was used to quantify neovascularization in this model since CEUS is well-established for RA diagnosis in humans. Next, the potential of liposome-loaded microbubbles and ultrasound (US) to selectively enhance liposome delivery to the synovium was evaluated with in vivo fluorescence imaging. This procedure is made very challenging by the presence of hard joints and by the limited lifetime of the microbubbles. The inflamed knee joints were exposed to therapeutic US after intravenous injection of liposome-loaded microbubbles. Loaded microbubbles were found to be quickly captured by the liver. This resulted in fast clearance of attached liposomes while free and long-circulating liposomes were able to accumulate over time in the inflamed joints. Our observations show that murine arthritis models are not well-suited for evaluating the potential of microbubble-mediated drug delivery in joints given: (i) restricted microbubble passage in murine synovial vasculature and (ii) limited control over the exact ultrasound conditions in situ given the much shorter length scale of the murine joints as compared to the therapeutic wavelength.

The Antibacterial Effect of PEGylated Carbosilane Dendrimers on P. aeruginosa Alone and in Combination with Phage-Derived Endolysin

The search for new microbicide compounds is of an urgent need, especially against difficult-to-eradicate biofilm-forming bacteria. One attractive option is the application of cationic multivalent dendrimers as antibacterials and also as carriers of active molecules. These compounds require an adequate hydrophilic/hydrophobic structural balance to maximize the effect. Herein, we evaluated the antimicrobial activity of cationic carbosilane (CBS) dendrimers unmodified or modified with polyethylene glycol (PEG) units, against planktonic and biofilm-forming P. aeruginosa culture. Our study revealed that the presence of PEG destabilized the hydrophilic/hydrophobic balance but reduced the antibacterial activity measured by microbiological cultivation methods, laser interferometry and fluorescence microscopy. On the other hand, the activity can be improved by the combination of the CBS dendrimers with endolysin, a bacteriophage-encoded peptidoglycan hydrolase. This enzyme applied in the absence of the cationic CBS dendrimers is ineffective against Gram-negative bacteria because of the protective outer membrane shield. However, the endolysin-CBS dendrimer mixture enables the penetration through the membrane and then deterioration of the peptidoglycan layer, providing a synergic antimicrobial effect.

Toxicity And Surface Modification Of Dendrimers: A Critical Review

As compared to other nano polymers, dendrimers have novel three dimensional, synthetic hyperbranched, nano-polymeric structures. The characteristic of these supramolecular dendritic structures has a high degree of significant surface as well as core functionality in the transportation of drugs for targeted therapy, specifically in host-guest response, gene transfer therapy and imaging of biological systems. However, there are conflicting shreds of evidence regarding biological safety and dendrimers toxicity due to their positive charge at the surface. It includes cytotoxicity, hemolytic toxicity, haematological toxicity, immunogenicity and in vivo toxicity. Therefore to resolve these problems surface modification of the dendrimer group is one of the methods. From that point, this review involves different strategies which reduce the toxicity and improve the biocompatibility of different types of dendrimers. From that viewpoint, we broaden the structural and safe characteristics of the dendrimers in the biomedical and pharmaceutical fields.

Sphingomyelin nanosystems loaded with uroguanylin and etoposide for treating metastatic colorectal cancer

Colorectal cancer is the third most frequently diagnosed cancer malignancy and the second leading cause of cancer-related deaths worldwide. Therefore, it is of utmost importance to provide new therapeutic options that can improve survival. Sphingomyelin nanosystems (SNs) are a promising type of nanocarriers with potential for association of different types of drugs and, thus, for the development of combination treatments. In this work we propose the chemical modification of uroguanylin, a natural ligand for the Guanylyl Cyclase (GCC) receptor, expressed in metastatic colorectal cancer tumors, to favour its anchoring to SNs (UroGm-SNs). The anti-cancer drug etoposide (Etp) was additionally encapsulated for the development of a combination strategy (UroGm-Etp-SNs). Results from in vitro studies showed that UroGm-Etp-SNs can interact with colorectal cancer cells that express the GCC receptor and mediate an antiproliferative response, which is more remarkable for the drugs in combination. The potential of UroGm-Etp-SNs to treat metastatic colorectal cancer cells was complemented with an in vivo experiment in a xenograft mice model.

Tuning the Surface Chemistry of Second-Harmonic-Active Lithium Niobate Nanoprobes Using a Silanol-Alcohol Condensation Reaction

The surface functionalization of nanoparticles (NPs) is of great interest for improving the use of NPs in, for example, therapeutic and diagnostic applications. The conjugation of specific molecules with NPs through the formation of covalent linkages is often sought to provide a high degree of colloidal stability and biocompatibility, as well as to provide functional groups for further surface modification. NPs of lithium niobate (LiNbO₃) have been explored for use in second-harmonic-generation (SHG)-based bioimaging, expanding the applications of SHG-based microscopy techniques. The efficient use of SHG-active LiNbO₃ NPs as probes will, however, require the functionalization of their surfaces with molecular reagents such as polyethylene glycol and fluorescent molecules to enhance their colloidal and chemical stability and to enable a correlative imaging platform. Herein, we demonstrate the surface functionalization of LiNbO₃ NPs through the covalent attachment of alcohol-based reagents through a silanol-alcohol condensation reaction. Alcohol-based reagents are widely available and can have a range of terminal functional groups such as carboxylic acids, amines, and aldehydes. Attaching these molecules to NPs through the silanol-alcohol condensation reaction could diversify the reagents available to modify NPs, but this reaction pathway must first be established as a viable route to modifying NPs. This study focuses on the attachment of a linear alcohol functionalized with carboxylic acid and its use as a reactive group to further tune the surface chemistry of LiNbO₃ NPs. These carboxylic acid groups were reacted to covalently attach other molecules to the NPs using copper-free click chemistry. This derivatization of the NPs provided a means to covalently attach polyethylene glycols and fluorescent probes to the NPs, reducing NP aggregation and enabling multimodal tracking of SHG nanoprobes, respectively. This extension of the silanol-alcohol condensation reaction to functionalize the surfaces of LiNbO₃ NPs can be extended to other types of nanoprobes for use in bioimaging, biosensing, and photodynamic therapies.

A Nano-Emulsion Platform Functionalized with a Fully Human scFv-Fc Antibody for Atheroma Targeting: Towards a Theranostic Approach to Atherosclerosis

Atherosclerosis is at the onset of the cardiovascular diseases that are among the leading causes of death worldwide. Currently, high-risk plaques, also called vulnerable atheromatous plaques, remain often undiagnosed until the occurrence of severe complications, such as stroke or myocardial infarction. Molecular imaging agents that target high-risk atheromatous lesions could greatly improve the diagnosis of atherosclerosis by identifying sites of high disease activity. Moreover, a "theranostic approach" that combines molecular imaging agents (for diagnosis) and therapeutic molecules would be of great value for the local management of atheromatous plaques. The aim of this study was to develop and characterize an innovative theranostic tool for atherosclerosis. We engineered oil-in-water nano-emulsions (NEs) loaded with superparamagnetic iron oxide (SPIO) nanoparticles for magnetic resonance imaging (MRI) purposes. Dynamic MRI showed that NE-SPIO nanoparticles decorated with a polyethylene glycol (PEG) layer reduced their liver uptake and extended their half-life. Next, the NE-SPIO-PEG formulation was functionalized with a fully human scFv-Fc antibody (P3) recognizing galectin 3, an atherosclerosis biomarker. The P3-functionalized formulation targeted atheromatous plaques, as demonstrated in an immunohistochemistry analyses of mouse aorta and human artery sections and in an Apoe^-/- mouse model of atherosclerosis. Moreover, the formulation was loaded with SPIO nanoparticles and/or alpha-tocopherol to be used as a theranostic tool for atherosclerosis imaging (SPIO) and for delivery of drugs that reduce oxidation (here, alpha-tocopherol) in atheromatous plaques. This study paves the way to non-invasive targeted imaging of atherosclerosis and synergistic therapeutic applications.

Biomimetic hydrogels designed for cartilage tissue engineering

Cartilage-like hydrogels based on materials like gelatin, chondroitin sulfate, hyaluronic acid and polyethylene glycol are reviewed and contrasted, revealing existing limitations and challenges on biomimetic hydrogels for cartilage regeneration.

PEGylating poly(p-phenylene vinylene)-based bioimaging nanoprobes

HYPOTHESIS

Conjugated polymer nanoparticles (CNPs) have attracted considerable attention within bioimaging due to their excellent optical properties and biocompatibility. However, unspecific adsorption of proteins hampers their effective use as advanced bioimaging probes. Controlled methodologies made possible tailor-made functional poly(p-phenylene vinylene), enabling one-pot synthesis of CNPs containing functional surface groups. Hence, it should be feasible to PEGylate these CNPs to tune the uptake by cell lines representative for the brain without imparting their optical properties.

EXPERIMENTS

CNPs consisting of the statistical copolymer 2-(5'-methoxycarbonylpentyloxy)-5-methoxy-1,4-phenylenevinylene and poly(2-methoxy-5-(3',7'-dimethoxyoctyloxy)-1,4-phenylenevinylene) were fabricated by miniemulsion solvent evaporation technique. Surface carboxylic acid groups were used to covalently attach amine-terminated polyethylene glycol (PEG) of different molecular weights. We investigated the effect of grafting CNPs with PEG chains on their intrinsic optical properties, protein adsorption behavior and uptake by representative brain cell lines.

FINDINGS

PEGylation did not affect the optical properties and biocompatibility of our CNPs. Moreover, a significant decrease in protein corona formation and unspecific uptake in central nervous system cell lines, depending on PEG chain length, was observed. This is the first report indicating that PEGylation does not affect the CNPs role as excellent bioimaging tools and can be adapted to tune biological interactions with brain cells.

PEGylation and Cell-Penetrating Peptides: Glimpse into the Past and Prospects in the Future

Several drug molecules have shown low bioavailability and pharmacokinetic profile due to metabolism by enzymes, excretion by the renal system, or due to other physiochemical properties of drug molecules. These problems have resulted in the loss of efficacy and the gain of side effects associated with drug molecules. PEGylation is one of the strategies to overcome these pharmacokinetic issues and has been successful in the clinic. Cell-penetrating Peptides (CPPs) help to deliver molecules across biological membranes and could be used to deliver cargo selectively to the intracellular site or to the drug target. Hence CPPs could be used to improve the efficacy and selectivity of the drug. However, due to the peptidic nature of CPPs, they have a low pharmacokinetic profile. Using PEGylation and CPPs together as a component of a drug delivery system, the and efficacy of drug molecules could be improved. The other important pharmacokinetic properties such as short half-life, solubility, stability, absorption, metabolism, and elimination could be also improved. Here in this review, we summarized PEGylated CPPs or PEGylation based formulations for CPPs used in a drug delivery system for several biomedical applications until August 2019.

Lymph-directed immunotherapy - Harnessing endogenous lymphatic distribution pathways for enhanced therapeutic outcomes in cancer

The advent of immunotherapy has revolutionised the treatment of some cancers. Harnessing the immune system to improve tumour cell killing is now standard clinical practice and immunotherapy is the first line of defence for many cancers that historically, were difficult to treat. A unifying concept in cancer immunotherapy is the activation of the immune system to mount an attack on malignant cells, allowing the body to recognise, and in some cases, eliminate cancer. However, in spite of a significant proportion of patients that respond well to treatment, there remains a subset who are non-responders and a number of cancers that cannot be treated with these therapies. These limitations highlight the need for targeted delivery of immunomodulators to both tumours and the effector cells of the immune system, the latter being highly concentrated in the lymphatic system. In this context, macromolecular therapies may provide a significant advantage. Macromolecules are too large to easily access blood capillaries and instead typically exhibit preferential uptake via the lymphatic system. In contexts where immune cells are the therapeutic target, particularly in cancer therapy, this may be advantageous. In this review, we examine in brief the current immunotherapy approaches in cancer and how macromolecular and nanomedicine strategies may improve the therapeutic profiles of these drugs. We subsequently discuss how therapeutics directed either by parenteral or mucosal administration, can be taken up by the lymphatics thereby accessing a larger proportion of the body's immune cells. Finally, we detail drug delivery strategies that have been successfully employed to target the lymphatics.

Advanced polymeric nanotechnology to augment therapeutic delivery and disease diagnosis

Therapeutic and diagnostic payloads are usually associated with properties that compromise their efficacy, such as poor aqueous solubility, short half-life, low bioavailability, nonspecific accumulation and diverse side effects. Nanotechnological solutions have emerged to circumvent some of these drawbacks, augmenting therapeutic and/or diagnostic outcomes. Nanotechnology has benefited from the rise in polymer science research for the development of novel nanosystems for therapeutic and diagnostic purposes. Polymers are a widely used class of biomaterials, with a considerable number of regulatory approvals for application in clinics. In addition to their versatility in production and functionalization, several synthetic and natural polymers demonstrate biocompatible properties that dictate their successful biological performance. This article highlights the physicochemical characteristics of a variety of natural and synthetic biocompatible polymers, as well as their role in the manufacture of nanotechnology-based systems, state-of-art applications in disease treatment and diagnosis, and current challenges in finding a way to clinics.

Developing PEGylated Reversed D-Peptide as a Novel HER2-Targeted SPECT Imaging Probe for Breast Cancer Detection

Human epidermal growth factor receptor-2 (HER2)-enriched breast cancer is characterized by strong invasiveness, high recurrence rate, and poor prognosis. HER2-specific imaging can help screening right patients for appropriate HER2-targeted therapies. Previously, we have developed a ^99mTc-labeled HER2-targeted H6 peptide for SPECT imaging of breast cancer. However, the poor metabolic stability and high gallbladder uptake hamper its clinical application. In this study, a retro-inverso D-peptide of H6 (RDH6) was designed to increase the metabolic stability. PEGylation was used to improve its water solubility and in vivo pharmacokinetics. The results showed that the D-amino acids in ^99mTc-PEG₄-RDH6 brought better metabolic stability than ^99mTc-PEG₄-H6, thus achieving higher tumor uptake. As the length of the PEG chain increases, the hydrophilicity of the probes gradually increased, which may also be the main cause for the decreased liver uptake. Compared with radiotracers modified by PEG₄ and PEG₁₂, ^99mTc-PEG₂₄-RDH6 had a comparable tumor uptake and the lowest liver radioactivity. The SPECT imaging demonstrated that ^99mTc-PEG₂₄-RDH6 could specifically distinguish HER2-positive tumors from HER2-negative tumors with better imaging contrast, which thus has the potential for clinical screening of HER2-positive breast patients.

Site-Specific Lipidation of a Small-Sized Protein Binder Enhances the Antitumor Activity through Extended Blood Half-Life

Protein and peptide therapeutics tend to have a short blood circulation time mainly caused by rapid clearance in kidney, leading to a low therapeutic efficacy. Here, we demonstrate that the antitumor activity of a small-sized protein binder can be significantly enhanced by prolonged blood half-life through site-specific lipidation. An unnatural amino acid was genetically incorporated into a specific site with the highest accessibility in a human interleukin-6 (IL-6)-targeting protein binder with a size of 30.8 kDa, followed by conjugation with palmitic acid using cooper-free click chemistry. The resulting protein binder was shown to have a binding capacity for serum albumin, maintaining a comparable binding affinity for human IL-6 to the native protein binder. The terminal half-life of the lipidated protein binder was estimated to be 10.7 h, whereas the native one had a half-life of 20 min, resulting in a significantly enhanced tumor suppression effect. The present approach can be generally applied to small-sized therapeutic proteins for the elongation of circulation time and increase of bioavailability in blood, consequently enhancing their therapeutic efficacy.

Anti-cancer peptides: classification, mechanism of action, reconstruction and modification

Anti-cancer peptides (ACPs) are a series of short peptides composed of 10-60 amino acids that can inhibit tumour cell proliferation or migration, or suppress the formation of tumour blood vessels, and are less likely to cause drug resistance. The aforementioned merits make ACPs the most promising anti-cancer candidate. However, ACPs may be degraded by proteases, or result in cytotoxicity in many cases. To overcome these drawbacks, a plethora of research has focused on reconstruction or modification of ACPs to improve their anti-cancer activity, while reducing their cytotoxicity. The modification of ACPs mainly includes main chain reconstruction and side chain modification. After summarizing the classification and mechanism of action of ACPs, this paper focuses on recent development and progress about their reconstruction and modification. The information collected here may provide some ideas for further research on ACPs, in particular their modification.

Thio-Bromo "Click" Reaction Derived Polymer-Peptide Conjugates for Their Self-Assembled Fibrillar Nanostructures

The synthesis and self-assembly of peptide-polymer conjugates into fibrillar nanostructures are reported, based on the amyloidogenic peptide KLVFF. A strategy for rational synthesis of polymer-peptide conjugates is documented via tethering of the amyloidogenic peptide segment LVFF (Aβ_17-20 ) and its modified derivative FFFF to the hydrophilic poly(ethylene glycol) monomethyl ether (mPEG) polymer via thio-bromo based "click" chemistry. The resultant conjugates mPEG-LVFF-OMe and mPEG-FFFF-OMe are purified via preparative gel permeation chromatography technique (with a yield of 61% and 64%, respectively), and are successfully characterized via combination of spectroscopic and chromatographic methods, including electrospray ionization time-of-flight mass spectrometry. The peptide-guided self-assembling behavior of the as-constructed amphiphilic supramolecular materials is further investigated via transmission electron microscopic and circular dichroism spectroscopic analysis, exhibiting fibrillar nanostructure formation in binary aqueous solution mixture.

Insight into Protein-Polymer Conjugate Relaxation Dynamics: The Importance of Polymer Grafting

The bio and chemical physics of protein-polymer conjugates are related to parameters that characterize each component. With this work, it is intended to feature the dynamical properties of the protein-polymer conjugate myoglobin (Mb)-poly(ethyl ethylene phosphate), in the ps and ns time scales, in order to understand the respective roles of the protein and of the polymer size in the dynamics of the conjugate. Elastic and quasi-elastic neutron scattering is performed on completely hydrogenated samples with variable number of polymer chains covalently attached to the protein. The role of the polymer length in the protein solvation and internal dynamics is investigated using two conjugates formed by polymers of different molecular weight. It is confirmed that the flexibility of the complex increases with the number of grafted polymer chains and that a sharp dynamical transition appears when either grafting density or polymer molecular weight are high. It is shown that protein size is crucial for the polymer structural organization and interaction on the protein surface and it is established that the glass properties of the polymer change upon conjugation. The results give a better insight of the equivalence of the polymer coating and the role of water on the surface of proteins.

Application of N-Dodecyl l-Peptide to Enhance Serum Stability while Maintaining Inhibitory Effects on Myometrial Contractions Ex Vivo

N-Alkylation and N-acylation of the prostaglandin-F_2α allosteric modulator l-PDC31 were performed to install various alkyl, PEG and isoprenoid groups onto the l-enantiomer of the peptide. Among the different bio-conjugates studied, the N-dodecyl analog reduced prostaglandin-F_2α-induced mouse myometrium contractions ex vivo. Furthermore, N-dodecyl-l-PDC31 exhibited improved stability in a mouse serum assay, likely due to protection from protease degradation by the lipid chain.

Poly(ethylene glycol) Grafting of Nanoparticles Prevents Uptake by Cells and Transport Through Cell Barrier Layers Regardless of Shear Flow and Particle Size

It has long been a central tenet of biomedical research that coating of nanoparticles with hydrated polymers can improve their performance in biomedical applications. However, the efficacy of the approach in vivo is still debated. In vitro model systems to test the performance of engineered nanoparticles for in vivo applications often use nonrepresentative cell lines and conditions for uptake and toxicity tests. We use our platform of monodisperse iron oxide nanoparticles densely grafted with nitrodopamide-poly(ethylene glycol) (PEG) to probe cell interactions with a set of cell types and culture conditions that are relevant for applications in which nanoparticles are injected into the bloodstream. In the past, these particles have proved to have excellent stability and negligible interaction with proteins and membranes under physiological conditions. We test the influence of flow on the uptake of nanoparticles. We also investigate the transport through endothelial barrier cell layers, as well as the effect that PEG-grafted iron oxide nanoparticles have on cell layers relevant for nanoparticles injected into the bloodstream. Our results show that the dense PEG brush and resulting lack of nonspecific protein and membrane interaction lead to negligible cell uptake, toxicity, and transport across barrier layers. These results contrast with far less well-defined polymer-coated nanoparticles that tend to aggregate and consequently strongly interact with cells, for example, by endocytosis.

Oxidative Amide Coupling from Functionally Diverse Alcohols and Amines Using Aerobic Copper/Nitroxyl Catalysis

The aerobic Cu/ABNO catalyzed oxidative coupling of alcohols and amines is highlighted in the synthesis of amide bonds in diverse drug-like molecules (ABNO=9-azabicyclo[3.3.1]nonane N-oxyl). The robust method leverages the privileged reactivity of alcohols bearing electronegative hetero- atoms (O, F, N, Cl) in the β-position. The reaction tolerates over 20 unique functional groups and is demonstrated on a 15 mmol scale under air. Steric constraints of the catalyst allow for chemoselective amidation of primary amines in the presence of secondary amines. All catalyst components are commercially available, and the reaction proceeds under mild conditions with retention of stereocenters in both reaction partners, while producing only water as a by-product.

Design and anti-tumor activity of self-loaded nanocarriers of siRNA

Polypeptide carriers have a good cell compatibility, rich functionality, and facile synthesis and modification, make them promising materials as siRNA vectors. Phenylalanine dipeptide (FF) has been previously assessed as an siRNA vector and showed to have two major drawbacks, namely poor water solubility and poor serum stability. Herein, the FF backbone was modified by ligating a PEG-Arg-Ala (PEG-RA) sequence at the N-terminus to increase its hydrophilicity and serum stability. Arg is a typical amino acid in the cell penetrating peptide, which can increase the efficiency of cell internalization. Ala acts as a spacer to avoid steric hindrance. The target sequence PEG-RAFF was synthesized by a solid phase peptide synthesis. The morphology, particle size, and siRNA ratio were assessed by SEM, TEM, DLS, and gel electrophoresis. Further, MCF-7 cells were used as a model and survivin-siRNA as a passenger to assess cell internalization, inhibition of gene expression rate, and apoptosis rate using confocal microscopy, real-time PCR, and flow cytometry. At a concentration of 1 mg/mL, PEG-RAFF took the form of nanovesicles with a diameter of 154.74 ± 14.36 nm. The optimal PEG-RAFF to siRNA ratio was N/P = 100:1. Compared with the control group, the red fluorescence of TAMRA(Carboxytetramethylrhodamine, Red fluorescence)-siRNA transfected into cells was clearly visible in the confocal microscope image. The inhibition rate of survivin was 67.99 ± 10.31%, and the apoptotic rate was 16.07%. Therefore, PEG-RAFF has potential as an siRNA carrier in cancer treatment.

Glucagon-Like Peptide-1 Receptor Agonists and Strategies To Improve Their Efficiency

Type 2 diabetes mellitus (T2DM) is increasing in global prevalence and is associated with serious health problems (e.g., cardiovascular disease). Various treatment options are available for T2DM, including the incretin hormone glucagon-like peptide-1 (GLP-1). GLP-1 is a therapeutic peptide secreted from the intestines following food intake, which stimulates the secretion of insulin from the pancreas. The native GLP-1 has a very short plasma half-life, owning to renal clearance and degradation by the enzyme dipeptidyl peptidase-4. To overcome this issue, various GLP-1 agonists with increased resistance to proteolytic degradation and reduced renal clearance have been developed, with several currently marketed. Strategies, such as controlled release delivery systems, methods to reduce renal clearance (e.g., PEGylation and conjugation to antibodies), and methods to improve proteolytic stability (e.g., stapling, cyclization, and glycosylation) provide means to further improve the ability of GLP-1 analogs. These will be discussed in this literature review.

Track analysis of the passage of rhodamine-labeled liposomes across porcine jejunal mucus in a microchannel device

AIM

To investigate how surface charge and hydrophilicity affect the mucopermeation of liposomes across intestinal mucus.

METHODOLOGY

Rhodamine-labeled liposomes (∼120-130 nm) with different surface charges were investigated for their capacity to flux across fresh porcine jejunal mucus in a microchannel device. Fluorescent microscopy and tracking analysis were used to measure liposome movement, while fluorescence lifetime imaging microscopy was utilized to determine mucus pH.

RESULTS

Mucopermeation was dependent on hydrophilicity and surface charge - anionic liposomes permeated more than cationic. The most cationic liposomal prototype agglomerated mucus. Presence of Na⁺, K⁺ and Mg²⁺ increased both speed and straightness of the pathways for all prototypes. Cationic but not anionic liposomes caused acidification (pH 2.5).

CONCLUSION

Acidification caused by cationic liposomes explains their ability to interfere with mucus stability. Surface charge of liposomes strongly influences mucopermeation capability.

Protein-Polymer Dynamics as Affected by Polymer Coating and Interactions

We investigate the relaxation dynamics of protein-polymer conjugates by neutron scattering spectroscopy to understand to which extent the coating of a protein by a polymer can replace water in promoting thermal structural fluctuations. For this purpose, we compare the dynamics of protein-polymer mixtures to that of conjugates with a variable number of polymers covalently attached to the protein. Results show that the flexibility of the protein is larger in protein-polymer mixtures than in native protein or in conjugates, even in the dry state. Upon hydration, both the native protein and the conjugate show equivalent dynamics, suggesting that the polymer grafted on the protein surface adsorbs all water molecules.

Pentagalloyl Glucose and Its Functional Role in Vascular Health: Biomechanics and Drug-Delivery Characteristics

Pentagalloyl glucose (PGG) is an elastin-stabilizing polyphenolic compound that has significant biomedical benefits, such as being a free radical sink, an anti-inflammatory agent, anti-diabetic agent, enzymatic resistant properties, etc. This review article focuses on the important benefits of PGG on vascular health, including its role in tissue mechanics, the different modes of pharmacological administration (e.g., oral, intravenous and endovascular route, intraperitoneal route, subcutaneous route, and nanoparticle based delivery and microbubble-based delivery), and its potential therapeutic role in vascular diseases such as abdominal aortic aneurysms (AAA). In particular, the use of PGG for AAA suppression and prevention has been demonstrated to be effective only in the calcium chloride rat AAA model. Therefore, in this critical review we address the challenges that lie ahead for the clinical translation of PGG as an AAA growth suppressor.

Novel Intravaginal Drug Delivery System Based on Molecularly PEGylated Lipid Matrices for Improved Antifungal Activity of Miconazole Nitrate

The aim of this study was to investigate the potential of microparticles based on biocompatible phytolipids [Softisan® 154 (SF) (hydrogenated palm oil) and super-refined sunseed oil (SO)] and polyethylene glycol- (PEG-) 4000 to improve intravaginal delivery of miconazole nitrate (MN) for effective treatment of vulvovaginal candidiasis (VVC). Lipid matrices (LMs) consisting of rational blends of SF and SO with or without PEG-4000 were prepared by fusion and characterized and employed to formulate MN-loaded solid lipid microparticles (SLMs) by melt-homogenization. The SLMs were characterized for physicochemical properties, anticandidal activity, and stability. Spherical discrete microparticles with good physicochemical properties and mean diameters suitable for vaginal drug delivery were obtained. Formulations based on SO:SF (1:9) and containing highest concentrations of PEG-4000 (4 %w/w) and MN (3.0 %w/w) were stable and gave highest encapsulation efficiency (83.05–87.75%) and inhibition zone diameter (25.87±0.94–26.33±0.94 mm) and significantly (p<0.05) faster and more powerful fungicidal activity regarding killing rate constant values (7.10 x 10⁻³–1.09 x 10⁻² min⁻¹) than commercial topical solution of MN (Fungusol®) (8.00 x 10⁻³ min⁻¹) and pure MN sample (5.160 x 10⁻³ min⁻¹). This study has shown that MN-loaded SLMs based on molecularly PEGylated lipid matrices could provide a better option to deal with VVC.

Polymer tube nanoreactors via DNA-origami templated synthesis

We describe the stepwise synthesis of precise polymeric objects programmed by a 3D DNA tube transformed from a common 2D DNA tile as a precise biotemplate for atom transfer radical polymerization. The catalytic interior space of the DNA tube was utilized for synthesizing a bio-inspired polymer, polydopamine.

Surface Modification of Cisplatin-Complexed Gold Nanoparticles and Its Influence on Colloidal Stability, Drug Loading, and Drug Release

Cisplatin-complexed gold nanoparticles (Pt^II-AuNP) provide a promising strategy for chemo-radiation-based anticancer drugs. Effective design of such platforms necessitates reliable assessment of surface engineering on a quantitative basis and its influence on drug payload, stability, and release. In this paper, poly(ethylene glycol) (PEG)-stabilized Pt^II-AuNP was synthesized as a model antitumor drug platform, where Pt^II is attached via a carboxyl-terminated dendron ligand. Surface modification by PEG and its influence on drug loading, colloidal stability, and drug release were assessed. Complexation with Pt^II significantly degrades colloidal stability of the conjugate; however, PEGylation provides substantial improvement of stability in conjunction with an insignificant trade-off in drug loading capacity compared with the non-PEGylated control (<20% decrease in loading capacity). In this context, the effect of varying PEG concentration and molar mass was investigated. On a quantitative basis, the extent of PEGylation was characterized and its influence on dispersion stability and drug load was examined using electrospray differential mobility analysis (ES-DMA) hyphenated with inductively coupled plasma mass spectrometry (ICP-MS) and compared with attenuated total reflectance-FTIR. Using ES-DMA-ICP-MS, AuNP conjugates were size-classified based on their electrical mobility, while Pt^II loading was simultaneously quantified by determination of Pt mass. Colloidal stability was quantitatively evaluated in biologically relevant media. Finally, the pH-dependent Pt^II release performance was evaluated. We observed 9% and 16% Pt^II release at drug loadings of 0.5 and 1.9 Pt^II/nm², respectively. The relative molar mass of PEG had no significant influence on Pt^II uptake or release performance, while PEGylation substantially improved the colloidal stability of the conjugate. Notably, the Pt^II release over 10 days (examined at 0.5 Pt^II/nm² drug loading) remained constant for non-PEGylated, 1K-PEGylated, and 5K-PEGylated conjugates.

Design and intestinal mucus penetration mechanism of core-shell nanocomplex

The objective of this study was to design intestinal mucus-penetrating core-shell nanocomplex by functionally mimicking the surface of virus, which can be used as the carrier for peroral delivery of macromolecules, and further understand the influence of nanocomplex surface properties on the mucosal permeation capacity. Taking insulin as a model drug, the core was formed by the self-assembly among positively charged chitosan, insulin and negatively charged sodium tripolyphosphate, different types of alginates were used as the shell forming material. The nanocomplex was characterized by dynamic light scattering (DLS), atomic force microscopy (AFM) and FTIR. Nanocomplex movement in mucus was recorded using multiple particle tracking (MPT) method. Permeation and uptake of different nanocomplex were studied in rat intestine. It was demonstrated that alginate coating layer was successfully formed on the core and the core-shell nanocomplex showed a good physical stability and improved enzymatic degradation protection. The mucus penetration and MPT study showed that the mucus penetration capacity of the nanocomplex was surface charge and coating polymer structure dependent, nanocomplex with negative alginate coating had 1.6-2.5 times higher mucus penetration ability than that of positively charged chitosan-insulin nanocomplex. Moreover, the mucus penetration ability of the core-shell nanocomplex was alginate structure dependent, whereas alginate with lower G content and lower molecular weight showed the best permeation enhancing ability. The improvement of intestine permeation and intestinal villi uptake of the core-shell nanocomplex were further confirmed in rat intestine and multiple uptake mechanisms were involved in the transport process. In conclusion, core-shell nanocomplex composed of oppositely charged materials could provide a strategy to overcome the mucus barrier and enhance the mucosal permeability.

Pre-clinical study of a TNFR1-targeted 18F probe for PET imaging of breast cancer

Tumor necrosis factor receptor 1 (TNFR1) is overexpressed in several varieties of carcinoma, including breast cancer. WH701 (Ala-Thr-Ala-Gln-Ser-Ala-Tyr-Gly), which was identified by phage display, can specifically bind to TNFR1. In this study, we labeled WH701 with ¹⁸F and investigated its tumor diagnostic value. WH701 was synthesized by standard Fmoc-solid phase synthetic protocols and conjugated by NOTA-NHS. NOTA-WH701 was radiolabeled with ¹⁸F using NOTA-AlF chelation reaction. The tumor target properties were evaluated in vitro and in vivo using MCF-7 xenografts and inflammation models. [¹⁸F]AlF-NOTA-WH701 was labeled in 25 min with a decay-corrected yield of 38.1 ± 4.8% (n = 5) and a specific activity of 10.4-13.0 GBq/μmol. WH701 had relatively high affinity for MCF-7 cells in vitro and [¹⁸F]AlF-NOTA-WH701 displayed relatively high tumor uptake in vivo. The tumor to muscle ratio was 4.25 ± 0.56 at 30 min post-injection (p.i.); further, there was a significant difference between the tumor/muscle and inflammation/muscle (3.22 ± 0.56) ratio, which could differentiate the tumor and inflammation. The tumor uptake of [¹⁸F]AlF-NOTA-WH701 could be inhibited by 71.1% by unlabeled WH701 at 30 min p.i. We have developed a promising PET tracer [¹⁸F]AlF-NOTA-WH701 for the noninvasive detection of breast cancer in vivo.

Scratching the Surface: Resurfacing Proteins to Endow New Properties and Function

Protein engineering is an emerging discipline that dovetails modern molecular biology techniques with high-throughput screening, laboratory evolution technologies, and computational approaches to modify sequence, structure, and, in some cases, function and properties of proteins. The ultimate goal is to develop new proteins with improved or designer functions for use in biotechnology, medicine, and basic research. One way to engineer proteins is to change their solvent-exposed regions through focused or random "protein resurfacing." In this review we explain what protein resurfacing is, and discuss recent examples of how this strategy is used to generate proteins with altered or broadened recognition profiles, improved stability, solubility, and expression, cell-penetrating ability, and reduced immunogenicity. Additionally we comment on how these properties can be further improved using chemical resurfacing approaches. Protein resurfacing will likely play an increasingly important role as more biologics enter clinical use, and we present some arguments to support this view.

Surface-modified mucoadhesive microgels as a controlled release system for miconazole nitrate to improve localized treatment of vulvovaginal candidiasis

The use of conventional vaginal formulations of miconazole nitrate (MN) in the treatment of deep-seated VVC (vulvovaginal candidiasis) is limited by poor penetration capacity and low solubility of MN, short residence time and irritation at the application site. Surface-modified mucoadhesive microgels were developed to minimize local irritation, enhance penetration capacity and solubility and prolong localized vaginal delivery of MN for effective treatment of deep-seated VVC. Solid lipid microparticles (SLMs) were prepared from matrices consisting of hydrogenated palm oil (Softisan® 154, SF) and super-refined sunseed oil (SO) with or without polyethylene glycol (PEG)-4000, characterized for physicochemical performance and used to prepare mucoadhesive microgels (MMs) encapsulating MN, employing Polycarbophil as bioadhesive polymer. The MMs were evaluated for physicochemical performance and in vitro drug release in simulated vaginal fluid (pH=4.2), whereas mucoadhesive, rheological and stability tests, anticandidal efficacy in immunosuppressed estrogen-dependent female rats and vaginal tolerance test in rabbits were performed with optimized formulation. The amorphicity of 1:9 phytolipid blend (SO:SF) was increased in the presence of PEG-4000. The physicochemical properties of the SLMs and MMs indicated their suitability for vaginal drug delivery. Overall, MN-loaded PEGylated MMs exhibited significantly (p<0.05) more prolonged drug release than non-PEGylated MMs. Additionally, optimized PEGylated MMs was stable at 40±2°C over a period of 6months, viscoelastic, mucoadhesive, non-sensitizing, histopathologically safe and gave remarkably (p<0.05) higher reduction in Candida albicans load (86.06%) than Daktarin® (75.0%) and MN-loaded polymeric-hydrogel (47.74%) in treated rats in 12days. Thus, PEGylated MMs is promising for effective and convenient treatment of VVC.