Administration strategies for proteins and peptides

Unlocking nature's arsenal: Nanotechnology for targeted delivery of venom toxins in cancer therapy

AIM

The aim of the present review is to shed light on the nanotechnological approaches adopted to overcome the shortcomings associated with the delivery of venom peptides which possess inherent anti-cancer properties.

BACKGROUND

Venom peptides although have been reported to demonstrate anti-cancer effects, they suffer from several disadvantages such as in vivo instability, off-target adverse effects, limited drug loading and low bioavailability. This review presents a comprehensive compilation of different classes of nanocarriers while underscoring their advantages, disadvantages and potential to carry such peptide molecules for in vivo delivery. It also discusses various nanotechnological aspects such as methods of fabrication, analytical tools to assess these nanoparticulate formulations, modulation of nanocarrier polymer properties to enhance loading capacity, stability and improve their suitability to carry toxic peptide drugs.

CONCLUSION

Nanotechnological approaches bear great potential in delivering venom peptide-based molecules as anticancer agents by enhancing their bioavailability, stability, efficacy as well as offering a spatiotemporal delivery approach. However, the challenges associated with toxicity and biocompatibility of nanocarriers must be duly addressed.

PERSPECTIVES

The everlasting quest for new breakthroughs for safer delivery of venom peptides in human subjects is fuelled by unmet clinical needs in the current landscape of chemotherapy. In addition, exhaustive efforts are required in obtaining and purifying the venom peptides followed by designing and optimizing scale up technologies.

The Role of the Unbinding Cycle on the Coordination Abilities of the Bi-Cyclopeptides toward Cu(II) Ions

Bicyclic peptides have attracted the interest of pharmaceutical companies because of their remarkable properties, putting them on a new path in medicine. Their conformational rigidity improves proteolytic stability and leads to rapid penetration into tissues via any possible route of administration. Moreover, elimination of renal metabolism is of great importance, for example, for people with a history of liver diseases. In addition, each ring can function independently, making bicyclic peptides extremely versatile molecules for further optimization. In this paper, we compared the potentiometric and spectroscopic properties studied by UV-vis, MCD, and EPR of four synthetic analogues of the bi-cyclic peptide c(PKKHP-c(CFWKTC)-PKKH) (BCL). In particular, we correlated the structural and spectral properties of complexes with coordinating abilities toward Cu(II) ions of MCL1 (Ac-PKKHPc(CFWKTC)PKKH-NH2) that contains the unbinding cycle and N- and C-terminal linear parts with two histidine residues, one per part; two monocyclic ligands containing one histidine residue, both in the N-terminal position, i.e., MCL2 (Ac-PKKHPc(CFWKTC)PKKS-NH2) and in the C-terminal position, i.e., MCL3 (Ac-PKKSPc(CFWKTC)PKKH-NH2), respectively; and the linear structure LNL (Ac-PKKHPSFWKTSPKKH-NH2). Potentiometric results have shown that the bicyclic structure promotes the involvement of the side chain imidazole donors in Cu(II) binding. On the other hand, the results obtained for the mono-cyclic analogues lead to the conclusion that the coordination of the histidine moiety as an anchoring group is promoted by its location in the peptide sequence further from the nonbinding cycle, strongly influencing the involvement of the amide donors in Cu(II) coordination.

Investigating the Impact of Network Functionalization on Protein Adsorption to Polymer Nanogels

This study explores the impact of network functionalization and chemical composition on the pH-responsive behavior of polymer nanogels and their adsorption of proteins. Using a thermodynamic theory informed by a molecular model, this work evaluates the interactions of three proteins with varying isoelectric points (insulin, myoglobin, and cytochrome c) and pH-responsive nanogels based on methacrylic acid or allylamine motifs. Three different functionalization strategies are considered, with pH-responsive segments distributed randomly, at the center, or on the surface of the polymer network. Our results show that the spatial distribution of functional units affects both the nanogels' mechanical response to pH changes and the level and localization of adsorbed proteins. The dependence of protein adsorption on the salt concentration is also investigated, with the conclusion that it is best to encapsulate proteins at low salt concentrations and aim for release at high salt concentrations. These results provide valuable information for the design of pH-responsive nanogels as vehicles for protein encapsulation, transport, and administration.

Development and Evaluation of PEG-gelatin-based Microparticles to Enhance the Oral Delivery of Insulin

BACKGROUND

Diabetes mellitus is a global disease identified by hyperglycemia due to defects in insulin secretion, insulin action, or both.

OBJECTIVE

The main objective of this research was to evaluate the ability of gelatinized Poly(ethylene glycol) (PEG) microparticles to be used as carriers for oral insulin delivery via double emulsion preparation.

METHODS

Five different batches of the formulation consisting of gelatin:PEG were prepared as follows: 0:1 (W1), 1:0 (W2), 1:1 (W3), 1:3 (W4), and 3:1 (W5). The prepared microparticles (from insulin-loaded batches) had particle sizes ranging from 19.5 ± 0.32-23.9 ± 0.22 μm and encapsulation and loading capacities ranging from 78.8 ± 0.24-88.9 ± 0.95 and 22.2 ± 0.96-29.7 ± 0.86%, respectively. The minimum and maximum in vitro release rates were 8.0 and 66.0%, respectively, for batches W1 and W2 at 8 h.

RESULTS

Insulin-loaded MPs induced a significant decrease in glucose levels, with a reduction from 100 to 33.35% in batch W5 at 9 h compared to that of subcutaneous insulin (100 to 22.63%). A liver function study showed that the formulation caused no obvious toxicity to the experimental rats.

CONCLUSION

Gelatinized PEG-based microparticles as insulin delivery systems may open a new window into the development of oral insulin for diabetic treatment.

Unveiling the Pain Relief Potential: Harnessing Analgesic Peptides from Animal Venoms

The concept of pain encompasses a complex interplay of sensory and emotional experiences associated with actual or potential tissue damage. Accurately describing and localizing pain, whether acute or chronic, mild or severe, poses a challenge due to its diverse manifestations. Understanding the underlying origins and mechanisms of these pain variations is crucial for effective management and pharmacological interventions. Derived from a wide spectrum of species, including snakes, arthropods, mollusks, and vertebrates, animal venoms have emerged as abundant repositories of potential biomolecules exhibiting analgesic properties across a broad spectrum of pain models. This review focuses on highlighting the most promising venom-derived toxins investigated as potential prototypes for analgesic drugs. The discussion further encompasses research prospects, challenges in advancing analgesics, and the practical application of venom-derived toxins. As the field continues its evolution, tapping into the latent potential of these natural bioactive compounds holds the key to pioneering approaches in pain management and treatment. Therefore, animal toxins present countless possibilities for treating pain caused by different diseases. The development of new analgesic drugs from toxins is one of the directions that therapy must follow, and it seems to be moving forward by recommending the composition of multimodal therapy to combat pain.

Generation of a thermostable, oral Zika vaccine that protects against virus challenge in non-human primates

Here we report the development of a thermally stable, orally administered, candidate Zika vaccine using human serotype 5 adenovirus (AdHu5). We engineered AdHu5 to express the genes for the envelope and NS1 proteins of Zika virus. AdHu5 was formulated using a proprietary platform, OraPro, comprising a mix of sugars and modified amino acids that can overcome elevated temperatures (37 C), and an enteric coated capsule that protects the integrity of the AdHu5 from the acid in the stomach. This enables the delivery AdHu5 to the immune system of the small intestine. We show that oral delivery of AdHu5 elicited antigen-specific serum IgG immune responses in a mouse model and in a non-human primate model. Importantly, these immune responses were able reduce viral counts in mice and to prevent detectable viraemia in the non-human primates on challenge with live Zika virus. This candidate vaccine has significant advantages over many current vaccines that are maintained in a cold or ultra-cold chain and require parenteral administration.

Microneedle-Mediated Transdermal Delivery of Biopharmaceuticals

Transdermal delivery provides numerous benefits over conventional routes of administration. However, this strategy is generally limited to a few molecules with specific physicochemical properties (low molecular weight, high potency, and moderate lipophilicity) due to the barrier function of the stratum corneum layer. Researchers have developed several physical enhancement techniques to expand the applications of the transdermal field; among these, microneedle technology has recently emerged as a promising platform to deliver therapeutic agents of any size into and across the skin. Typically, hydrophilic biomolecules cannot penetrate the skin by passive diffusion. Microneedle insertion disrupts skin integrity and compromises its protective function, thus creating pathways (microchannels) for enhanced permeation of macromolecules. Microneedles not only improve stability but also enhance skin delivery of various biomolecules. Academic institutions and industrial companies have invested substantial resources in the development of microneedle systems for biopharmaceutical delivery. This review article summarizes the most recent research to provide a comprehensive discussion about microneedle-mediated delivery of macromolecules, covering various topics from the introduction of the skin, transdermal delivery, microneedles, and biopharmaceuticals (current status, conventional administration, and stability issues), to different microneedle types, clinical trials, safety and acceptability of microneedles, manufacturing and regulatory issues, and the future of microneedle technology.

Preclinical In-Vivo Safety of a Novel Thyrotropin-Releasing Hormone-Loaded Biodegradable Nanoparticles After Intranasal Administration in Rats and Primates

Thyrotropin-releasing hormone (TRH) and TRH-like peptides carry a therapeutic potential for neurological conditions. Nanoparticles (NP) made of the biodegradable polymer, Poly(Sebacic Anhydride) (PSA), have been developed to carry TRH, intended for intranasal administration to patients. There is limited information on the safety of biodegradable polymers when given intranasally, and therefore, we have performed two preclinical safety and toxicity studies in cynomolgus monkeys and rats using TRH-PSA nanoparticles. The rats and monkeys were dosed intranasally for 42 days or 28 days, respectively, and several animals were followed for additional 14 days. Animals received either placebo, vehicle (PSA), or different concentrations of TRH-PSA. No systemic adverse effects were seen. Changes in T3 or T4 concentrations were observed in some TRH-PSA-treated animals, which did not have clinical or microscopic correlates. No effect was seen on TSH or prolactin concentrations. In the monkey study, microscopic changes in the nasal turbinates were observed, which were attributed to incidental mechanical trauma caused during administration. Taken together, the TRH-loaded PSA NPs have proven to be safe, with no local or systemic adverse effects attributed to the drug loaded nanoparticles. These findings provide additional support to the growing evidence of the safety of peptide-loaded NPs for intranasal delivery and pave the way for future clinical trials in humans.

Trends in Drug Delivery Systems for Natural Bioactive Molecules to Treat Health Disorders: The Importance of Nano-Liposomes

Drug delivery systems are believed to increase pharmaceutical efficacy and the therapeutic index by protecting and stabilizing bioactive molecules, such as protein and peptides, against body fluids' enzymes and/or unsuitable physicochemical conditions while preserving the surrounding healthy tissues from toxicity. Liposomes are biocompatible and biodegradable and do not cause immunogenicity following intravenous or topical administration. Still, their most important characteristic is the ability to load any drug or complex molecule uncommitted to its hydrophobic or hydrophilic character. Selecting lipid components, ratios and thermo-sensitivity is critical to achieve a suitable nano-liposomal formulation. Nano-liposomal surfaces can be tailored to interact successfully with target cells, avoiding undesirable associations with plasma proteins and enhancing their half-life in the bloodstream. Macropinocytosis-dynamin-independent, cell-membrane-cholesterol-dependent processes, clathrin, and caveolae-independent mechanisms are involved in liposome internalization and trafficking within target cells to deliver the loaded drugs to modulate cell function. A successful translation from animal studies to clinical trials is still an important challenge surrounding the approval of new nano-liposomal drugs that have been the focus of investigations. Precision medicine based on the design of functionalized nano-delivery systems bearing highly specific molecules to drive therapies is a promising strategy to treat degenerative diseases.

Direct contact-mediated non-viral gene therapy using thermo-sensitive hydrogel-coated dressings

Nanotechnologies are being increasingly applied as systems for peptide and nucleic acid macromolecule drug delivery. However systemic targeting of these, or efficient topical and localized delivery remains an issue. A controlled release system that can be patterned and locally administered such as topically to accessible tissue (skin, eye, intestine) would therefore be transformative in realizing the potential of such strategies. We previously developed a technology termed GAG-binding enhanced transduction (GET) to efficiently deliver a variety of cargoes intracellularly, using GAG-binding peptides to mediate cell targeting, and cell penetrating peptides (CPPs) to promote uptake. Herein we demonstrate that the GET transfection system can be used with the moisturizing thermo-reversible hydrogel Pluronic-F127 (PF127) and methyl cellulose (MC) to mediate site specific and effective intracellular transduction and gene delivery through GET nanoparticles (NPs). We investigated hydrogel formulation and the temperature dependence of delivery, optimizing the delivery system. GET-NPs retain their activity to enhance gene transfer within our formulations, with uptake transferred to cells in direct contact with the therapy-laden hydrogel. By using Azowipe™ material in a bandage approach, we were able to show for the first-time localized gene transfer in vitro on cell monolayers. The ability to simply control localization of gene delivery on millimetre scales using contact-mediated transfer from moisture-providing thermo-reversible hydrogels will facilitate new drug delivery methods. Importantly our technology to site-specifically deliver the activity of novel nanotechnologies and gene therapeutics could be transformative for future regenerative medicine.

Subcutaneous Catabolism of Peptide Therapeutics: Bioanalytical Approaches and ADME Considerations

Many peptide drugs such as insulin and glucagon-like peptide (GLP-1) analogues are successfully administered subcutaneously (SC). Following SC injection, peptides may undergo catabolism in the SC compartment before entering systemic circulation, which could compromise their bioavailability and in turn affect their efficacy.This review will discuss how both technology and strategy have evolved over the past years to further elucidate peptide SC catabolism.Modern bioanalytical technologies (particularly liquid chromatography-high-resolution mass spectrometry) and bioinformatics platforms for data mining has prompted the development of in silico, in vitro and in vivo tools for characterizing peptide SC catabolism to rapidly address proteolytic liabilities and, ultimately, guide the design of peptides with improved SC bioavailability.More predictive models able to recapitulate the interplay between SC catabolism and other factors driving SC absorption are highly desirable to improve in vitro/in vivo correlations.We envision the routine incorporation of in vitro and in vivo SC catabolism studies in ADME screening funnels to develop more effective peptide drugs for SC delivery.

Investigating the stabilisation of IFN-α2a by replica exchange molecular dynamics simulation

Current biopharmaceutical drugs are mainly a class of peptides or proteins that play an essential role in the treatment of many diseases. Such peptides/proteins are usually thermally unstable and may lose their bioactivity when exposed to ambient conditions. Therefore, they are not suitable for long-term storage. Lyophilisation is the most common method to prolong shelf life of solid peptide/protein drugs; however, the freeze-drying process can lead to irreversible damage. In the present study, human interferon-alpha 2a (IFN-α2a) was selected as a model protein drug; four disaccharides (β-lactose, β-maltose, sucrose, and trehalose) were selected as bioactive protectants. We investigated the effects of different protectants on IFN-α2a under various ambient conditions (vacuum, dry state, and aqueous solution) using replica exchange molecular dynamics simulation. The protective effect of β-maltose on IFN-α2a was the highest in aqueous solution and dry state, β-lactose showed a poor protective effect in all three conditions, the performance of sucrose was good in all conditions, and trehalose showed a better protective effect under vacuum conditions and in aqueous solution. Disaccharides form H-bonds with water, thereby preventing water from the tertiary structure of proteins. Trehalose forms strong H-bonds with water which explains its extraordinary stability.

Traditional Chinese medicine promotes bone regeneration in bone tissue engineering

Bone tissue engineering (BTE) is a promising method for the repair of difficult-to-heal bone tissue damage by providing three-dimensional structures for cell attachment, proliferation, and differentiation. Traditional Chinese medicine (TCM) has been introduced as an effective global medical program by the World Health Organization, comprising intricate components, and promoting bone regeneration by regulating multiple mechanisms and targets. This study outlines the potential therapeutic capabilities of TCM combined with BTE in bone regeneration. The effective active components promoting bone regeneration can be generally divided into flavonoids, alkaloids, glycosides, terpenoids, and polyphenols, among others. The chemical structures of the monomers, their sources, efficacy, and mechanisms are described. We summarize the use of compounds and medicinal parts of TCM to stimulate bone regeneration. Finally, the limitations and prospects of applying TCM in BTE are introduced, providing a direction for further development of novel and potential TCM.

Toxicity Profiling of Bacterial Inclusion Bodies in Human Caco-2 Cells

Bacterial inclusion bodies (IBs) are discrete macromolecular complexes that appear in recombinant prokaryotic cells under stress conditions. These structures are often discarded for biotechnological uses given the difficulty in recovering proteins of interest from them in a soluble form. However, recent approaches have revealed the potential of these protein clusters as biomaterials to promote cell growth and as protein depots for the release of recombinant proteins for biotechnological and biomedical applications. Although these kinds of natural supramolecular complexes have attracted great interest, no comprehensive study of their toxicity in cell cultures has been carried out. In this study, caco-2 cells were exposed to natural IBs, soluble protein-only nanoparticles (NPs), and non-assembled versions of the same protein for comparative purposes. Cytotoxicity, oxidative stress, and genotoxicity were analyzed for all these protein formats. Natural IBs and soluble protein formats demonstrated their safety in eukaryotic cells. No cytotoxicity, genotoxicity, or oxidative stress was detected in caco-2 cells exposed to the protein samples in any of the experimental conditions evaluated, which covered protein concentrations used in previous biological activity assays. These conditions evaluated the activity of protein samples obtained from three prokaryotic hosts [Escherichia coli and the endotoxin-free expression systems Lactococcus lactis and ClearColi® BL21 (DE3)]. Our results demonstrate that natural IBs and soluble protein nanoparticles are non-toxic materials for eukaryotic cells and that this may represent an interesting alternative to the classical unassembled format of recombinant proteins for certain applications in biotechnology and biomedicine.

Oral nanomedicine for modulating immunity, intestinal barrier functions, and gut microbiome

The gastrointestinal tract (GIT) affects not only local diseases in the GIT but also various systemic diseases. Factors that can affect the health and disease of both GIT and the human body include 1) the mucosal immune system composed of the gut-associated lymphoid tissues and the lamina propria, 2) the intestinal barrier composed of mucus and intestinal epithelium, and 3) the gut microbiota. Selective delivery of drugs, including antigens, immune-modulators, intestinal barrier enhancers, and gut-microbiome manipulators, has shown promising results for oral vaccines, immune tolerance, treatment of inflammatory bowel diseases, and other systemic diseases, including cancer. However, physicochemical and biological barriers of the GIT present significant challenges for successful translation. With the advances of novel nanomaterials, oral nanomedicine has emerged as an attractive option to not only overcome these barriers but also to selectively deliver drugs to the target sites in GIT. In this review, we discuss the GIT factors and physicochemical and biological barriers in the GIT. Furthermore, we present the recent progress of oral nanomedicine for oral vaccines, immune tolerance, and anti-inflammation therapies. We also discuss recent advances in oral nanomedicine designed to fortify the intestinal barrier functions and modulate the gut microbiota and microbial metabolites. Finally, we opine about the future directions of oral nano-immunotherapy.

Designing Short Peptides to Block the Interaction of SARS-CoV-2 and Human ACE2 for COVID-19 Therapeutics

To date, the current COVID-19 pandemic caused by SARS-CoV-2 has infected 99.2 million while killed 2.2 million people throughout the world and is still spreading widely. The unavailability of potential therapeutics against this virus urges to search and develop new drugs. SARS-CoV-2 enters human cells by interacting with human angiotensin-converting enzyme 2 (ACE2) receptor expressed on human cell surface through utilizing receptor-binding domain (RBD) of its spike glycoprotein. The RBD is highly conserved and is also a potential target for blocking its interaction with human cell surface receptor. We designed short peptides on the basis of our previously reported truncated ACE2 (tACE2) for increasing the binding affinity as well as the binding interaction network with RBD. These peptides can selectively bind to RBD with much higher affinities than the cell surface receptor. Thus, these can block all the binding residues required for binding to cell surface receptor. We used selected amino acid regions (21–40 and 65–75) of ACE2 as scaffold for the de novo peptide design. Our designed peptide Pep1 showed interactions with RBD covering almost all of its binding residues with significantly higher binding affinity (−13.2 kcal mol⁻¹) than the cell surface receptor. The molecular dynamics (MD) simulation results showed that designed peptides form a stabilized complex with RBD. We suggest that blocking the RBD through de novo designed peptides can serve as a potential candidate for COVID-19 treatment after further clinical investigations.

PLGA-based biodegradable microspheres in drug delivery: recent advances in research and application

Biodegradable microspheres have been widely used in the field of medicine due to their ability to deliver drug molecules of various properties through multiple pathways and their advantages of low dose and low side effects. Poly (lactic-co-glycolic acid) copolymer (PLGA) is one of the most widely used biodegradable material currently and has good biocompatibility. In application, PLGA with a specific monomer ratio (lactic acid and glycolic acid) can be selected according to the properties of drug molecules and the requirements of the drug release rate. PLGA-based biodegradable microspheres have been studied in the field of drug delivery, including the delivery of various anticancer drugs, protein or peptide drugs, bacterial or viral DNA, etc. This review describes the basic knowledge and current situation of PLGA biodegradable microspheres and discusses the selection of PLGA polymer materials. Then, the preparation methods of PLGA microspheres are introduced, including emulsification, microfluidic technology, electrospray, and spray drying. Finally, this review summarizes the application of PLGA microspheres in drug delivery and the treatment of pulmonary and ocular-related diseases.

Quality by Design Approach for the Development of Liposome Carrying Ghrelin for Intranasal Administration

The therapeutic use of peptides has increasingly recognized in the development of new therapies. However, the susceptible enzymatic cleavage is a barrier that needs to overcome. Nose-to-brain delivery associated with liposomes can protect peptides against biodegradation and improve the accessibility to brain targets. The aim was to develop a liposomal formulation as ghrelin carrier. The quality by design (QbD) approach was used as a strategy for method development. The initial risk assessments were carried out using a fishbone diagram. A screening design study was performed for the critical material attributes/critical process parameters (CMAs/CPPs) on critical quality attributes (CQAs). Liposomes were obtained by hydrating phospholipid films, followed by extrusion or homogenization, and coated with chitosan. The optimized liposome formulation was produced by high-pressure homogenization coated with chitosan, and the resulted were liposomes size 72.25 ± 1.46 nm, PDI of 0.300 ± 0.027, the zeta potential of 50.3 ± 1.46 mV, and encapsulation efficiency of 53.2%. Moreover, chitosan coating improved performance in ex vivo permeation and mucoadhesion analyzes when compared to the uncoated liposome. In this context, chitosan coating is essential for the performance of the formulations in the ex vivo permeation and mucoadhesion analyzes. The intranasal administration of ghrelin liposomes coated with chitosan offers an innovative opportunity to treat cachexia.

Impact of Chemical Composition on the Nanostructure and Biological Activity of α-Galactosidase-Loaded Nanovesicles for Fabry Disease Treatment

Fabry disease is a rare lysosomal storage disorder characterized by a deficiency of α-galactosidase A (GLA), a lysosomal hydrolase. The enzyme replacement therapy administering naked GLA shows several drawbacks including poor biodistribution, limited efficacy, and relatively high immunogenicity in Fabry patients. An attractive strategy to overcome these problems is the use of nanocarriers for encapsulating the enzyme. Nanoliposomes functionalized with RGD peptide have already emerged as a good platform to protect and deliver GLA to endothelial cells. However, low colloidal stability and limited enzyme entrapment efficiency could hinder the further pharmaceutical development and the clinical translation of these nanoformulations. Herein, the incorporation of the cationic miristalkonium chloride (MKC) surfactant to RGD nanovesicles is explored, comparing two different nanosystems-quatsomes and hybrid liposomes. In both systems, the positive surface charge introduced by MKC promotes electrostatic interactions between the enzyme and the nanovesicles, improving the loading capacity and colloidal stability. The presence of high MKC content in quatsomes practically abolishes GLA enzymatic activity, while low concentrations of the surfactant in hybrid liposomes stabilize the enzyme without compromising its activity. Moreover, hybrid liposomes show improved efficacy in cell cultures and a good in vitro/in vivo safety profile, ensuring their future preclinical and clinical development.

Doping control analysis of small peptides: A decade of progress

Small peptides are handled in the field of sports drug testing analysis as a separate group doping substances. It is a diverse group, which includes but is not limited to growth hormone releasing-factors and gonadotropin-releasing hormone analogues. Significant progress has been achieved during the past decade in the doping control analysis of these peptides. In this article, achievements in the application of liquid chromatography-mass spectrometry-based methodologies are reviewed. To meet the augmenting demands for analyzing an increasing number of samples for the presence of an increasing number of prohibited small peptides, testing methods have been drastically simplified, whilst their performance level remained constant. High-resolution mass spectrometers have been installed in routine laboratories and became the preferred detection technique. The discovery and implementation of metabolites/catabolites in testing methods led to extended detection windows of some peptides, thus, contributed to more efficient testing in the anti-doping community.

Transdermal Delivery Systems for Biomolecules

Purpose

The present review article focuses on highlighting the main technologies used as tools that improve the delivery of transdermal biomolecules, addressing them from the point of view of research in the development of transdermal systems that use physical and chemical permeation enhancers and nanocarrier systems or a combination of them.

Results

Transdermal drug delivery systems have increased in importance since the late 1970s when their use was approved by the Food and Drug Administration (FDA). They appeared to be an alternative resource for the administration of many potent drugs. The first transdermal drug delivery system used for biomolecules was for the treatment of hormonal disorders. Biomolecules have been used primarily in many treatments for cancer and diabetes, vaccines, hormonal disorders, and contraception.

Conclusions

The latest technologies that have used such transdermal biomolecule transporters include electrical methods (physical penetration enhancers), some chemical penetration enhancers and nanocarriers. All of them allow the maintenance of the physical and chemical properties of the main proteins and peptides through these clinical treatments, allowing their efficient storage, transport, and release and ensuring the achievement of their target and better results in the treatment of many diseases.

Graphical abstract

Tailor-Made Fluorinated Ionic Liquids for Protein Delivery

Nowadays, pharmaceutical companies are facing several challenges with the development and approval of new biological products. The unique properties of several fluorinated ionic liquids (FILs), such as their high surfactant power in aqueous solutions, their chemical and biological stability, and low toxicity, favor their application in the pharmaceutical industry. Furthermore, the numerous combinations between cations and anions, in the FILs design, enlarge the possibilities to construct a successful delivery system. Several FILs also proved to not affect the activity, stability, and secondary structure of the therapeutic protein lysozyme. This work aims to study the aggregation behavior of distinct FILs in the protein suitable medium, in the presence or absence of lysozyme. Besides, different incubation conditions were tested to guarantee the optimal enzymatic activity of the protein at more stable delivery systems. Following the optimization of the incubation conditions, the quantification of the encapsulated lysozyme was performed to evaluate the encapsulation efficiency of each FIL-based system. The release of the protein was tested applying variables such as time, temperature, and ultrasound frequency. The experimental results suggest that the aggregation behavior of FILs is not significantly influenced by the protein and/or protein buffer and supports their application for the design of delivery systems with high encapsulation efficiencies, maintaining the biological activity of either encapsulated and released protein.

From Animal Poisons and Venoms to Medicines: Achievements, Challenges and Perspectives in Drug Discovery

Animal poisons and venoms are comprised of different classes of molecules displaying wide-ranging pharmacological activities. This review aims to provide an in-depth view of toxin-based compounds from terrestrial and marine organisms used as diagnostic tools, experimental molecules to validate postulated therapeutic targets, drug libraries, prototypes for the design of drugs, cosmeceuticals, and therapeutic agents. However, making these molecules applicable requires extensive preclinical trials, with some applications also demanding clinical trials, in order to validate their molecular target, mechanism of action, effective dose, potential adverse effects, as well as other fundamental parameters. Here we go through the pitfalls for a toxin-based potential therapeutic drug to become eligible for clinical trials and marketing. The manuscript also presents an overview of the current picture for several molecules from different animal venoms and poisons (such as those from amphibians, cone snails, hymenopterans, scorpions, sea anemones, snakes, spiders, tetraodontiformes, bats, and shrews) that have been used in clinical trials. Advances and perspectives on the therapeutic potential of molecules from other underexploited animals, such as caterpillars and ticks, are also reported. The challenges faced during the lengthy and costly preclinical and clinical studies and how to overcome these hindrances are also discussed for that drug candidates going to the bedside. It covers most of the drugs developed using toxins, the molecules that have failed and those that are currently in clinical trials. The article presents a detailed overview of toxins that have been used as therapeutic agents, including their discovery, formulation, dosage, indications, main adverse effects, and pregnancy and breastfeeding prescription warnings. Toxins in diagnosis, as well as cosmeceuticals and atypical therapies (bee venom and leech therapies) are also reported. The level of cumulative and detailed information provided in this review may help pharmacists, physicians, biotechnologists, pharmacologists, and scientists interested in toxinology, drug discovery, and development of toxin-based products.

Microneedle Mediated Transdermal Delivery of Protein, Peptide and Antibody Based Therapeutics: Current Status and Future Considerations

The success of protein, peptide and antibody based therapies is evident - the biopharmaceuticals market is predicted to reach $388 billion by 2024 [1], and more than half of the current top 20 blockbuster drugs are biopharmaceuticals. However, the intrinsic properties of biopharmaceuticals has restricted the routes available for successful drug delivery. While providing 100% bioavailability, the intravenous route is often associated with pain and needle phobia from a patient perspective, which may translate as a reluctance to receive necessary treatment. Several non-invasive strategies have since emerged to overcome these limitations. One such strategy involves the use of microneedles (MNs), which are able to painlessly penetrate the stratum corneum barrier to dramatically increase transdermal drug delivery of numerous drugs. This review reports the wealth of studies that aim to enhance transdermal delivery of biopharmaceutics using MNs. The true potential of MNs as a drug delivery device for biopharmaceuticals will not only rely on acceptance from prescribers, patients and the regulatory authorities, but the ability to upscale MN manufacture in a cost-effective manner and the long term safety of MN application. Thus, the current barriers to clinical translation of MNs, and how these barriers may be overcome are also discussed.

Modified Thymosin Alpha 1 Distributes and Inhibits the Growth of Lung Cancer in Vivo

Targeted therapy of tumors is an effective method for treating cancer. Thymosin alpha 1 (Tα1), a hormone that contains 28 amino acids, is already approved for cancer treatment. However, its clinical application is limited because of the lack of tumor targeting. Considering that RGD can specifically bind to integrin, the anticancer drug can have a targeted therapeutic effect on tumors when it combines with a peptide containing an RGD sequence. We produced a polypeptide, Tα1-RGDR, by binding Tα1 to RGDR. The RGDR can combine with the αvβ3 and NRP-1 domains, which are highly expressed on the surface of the tumor, to achieve the effect of tumor targeting. This work aimed to investigate the difference of antitumor activity and tumor targeting between Tα1 modified by RGDR and Tα1 by using H460 and LLC tumor models. Results showed that Tα1-RGDR had remarkable antitumor effects, and its tumor targeting was better than that of Tα1. Hence, Tα1-RGDR is a promising antitumor drug.

Recent Advances in Encapsulation, Protection, and Oral Delivery of Bioactive Proteins and Peptides using Colloidal Systems

There are many areas in medicine and industry where it would be advantageous to orally deliver bioactive proteins and peptides (BPPs), including ACE inhibitors, antimicrobials, antioxidants, hormones, enzymes, and vaccines. A major challenge in this area is that many BPPs degrade during storage of the product or during passage through the human gut, thereby losing their activity. Moreover, many BPPs have undesirable taste profiles (such as bitterness or astringency), which makes them unpleasant to consume. These challenges can often be overcome by encapsulating them within colloidal particles that protect them from any adverse conditions in their environment, but then release them at the desired site-of-action, which may be inside the gut or body. This article begins with a discussion of BPP characteristics and the hurdles involved in their delivery. It then highlights the characteristics of colloidal particles that can be manipulated to create effective BPP-delivery systems, including particle composition, size, and interfacial properties. The factors impacting the functional performance of colloidal delivery systems are then highlighted, including their loading capacity, encapsulation efficiency, protective properties, retention/release properties, and stability. Different kinds of colloidal delivery systems suitable for encapsulation of BPPs are then reviewed, such as microemulsions, emulsions, solid lipid particles, liposomes, and microgels. Finally, some examples of the use of colloidal delivery systems for delivery of specific BPPs are given, including hormones, enzymes, vaccines, antimicrobials, and ACE inhibitors. An emphasis is on the development of food-grade colloidal delivery systems, which could be used in functional or medical food applications. The knowledge presented should facilitate the design of more effective vehicles for the oral delivery of bioactive proteins and peptides.

Peptide-protein based nanofibers in pharmaceutical and biomedical applications

In recent years, electrospun fibers have found wide use, especially in pharmaceutical area and biomedical applications, related to the various advantages such as high surface-volume ratio, high solubility and having wide usage areas they have provided. Biocompatible and biodegradable fibers can be obtained by using peptide-protein structures of plant and animal derived along with synthetic polymers. Plant-derived proteins used in nanofiber production can be listed as, zein, soy protein, and gluten and animal derived proteins can be listed as casein, silk fibroin, hemoglobine, bovine serum albumin, elastin, collagen, gelatin, and keratin. Plant and animal proteins and synthetic peptides used in electrospun fiber production were reviewed in detail. In addition, the important physical properties of these materials for the electrospinning process and their use in pharmaceutical and biomedical areas were discussed.

Generation of a lentiviral vector system to efficiently express bioactive recombinant human prolactin hormones

The contribution of the pleiotropic hormone Prolactin (PRL) to several physiological and pathological processes is still unknown. To clarify the role of PRL in these processes during the last decade, different human PRL antagonists have been produced to either partially or fully block the wild type hormone activity. In this work, we have cloned these wild type and antagonist sequences in lentivectors (LV) to express them as recombinant self-processing polypeptides by employing a P2A sequence (hPRL-P2A-GFP). We show that these LVs can efficiently transduce and express the hPRL proteins in different cell types and that the P2A sequence does not affect their activities. Additionally, we have tested their activities in paracrine and autocrine cell culture experiments. Our results demonstrate that these recombinant hPRL-P2A proteins are bioactive in both paracrine and autocrine modes, highlighting the potential usefulness of these hPRL-containing LVs for determining the contribution of hPRL to different biological processes.

Self-Assembled Human Adipose-Derived Stem Cell-Derived Extracellular Vesicle-Functionalized Biotin-Doped Polypyrrole Titanium with Long-Term Stability and Potential Osteoinductive Ability

Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs), containing proteins or microRNAs (miRNAs), possessing various biological activity and low immunogenicity, are considered promising for surface modification of bone grafts. However, the modification efficiency is not satisfied yet, resulting in compromised therapy effects. Here, we report a novel immobilized method by self-assembling biotinylated MSC-EVs onto the surface of biotin-doped polypyrrole titanium (Bio-Ppy-Ti) to improve its biofunctions in vitro and in vivo. Using this method, the amount of human adipose-derived stem cell-EVs (hASC-EVs) anchored onto the Bio-Ppy-Ti surface was 185-fold higher than that of pure Ti after ultrasonic concussion for 30 s and it remained stable on the Bio-Ppy-Ti surface for 14 days at 4 °C. Compared to pristine Ti, EV-Bio-Ppy-Ti exhibited enhanced cell compatibility and osteoinductivity for osteoblasts in vitro and anti-apoptosis ability in the ectopic bone formation mode. Gene chip analysis further demonstrated that several osteoinductive miRNAs were encapsulated in hASC-EVs, which may explain the high bone regeneration ability of EV-Bio-Ppy-Ti. Thus, this MSC-EV biotin-immobilized method appears to be highly efficient and long-term stable for bone graft bioactive modification, demonstrating its potential for clinical metal implants.

Nanoparticles: Oral Delivery for Protein and Peptide Drugs

Protein and peptide drugs have many advantages, such as high bioactivity and specificity, strong solubility, and low toxicity. Therefore, the strategies for improving the bioavailability of protein peptides are reviewed, including chemical modification of nanocarriers, absorption enhancers, and mucous adhesion systems. The status, advantages, and disadvantages of various strategies are systematically analyzed. The systematic and personalized design of various factors affecting the release and absorption of drugs based on nanoparticles is pointed out. It is expected to design a protein peptide oral delivery system that can be applied in the clinic.

Human cytotoxicity and octanol/water partition coefficients of fluorinated ionic liquids

The use of fluorinated ionic liquids (FILs) as novel materials in biological and pharmaceutical applications is an emerging research field. The knowledge of their cytotoxicity and that of 1-octanol/water partition coefficients are essential to assess their environmental risks, to estimate their toxicity and activity, or the hydrophilic/lipophilic balance, as well as to explore their properties as solvents in extraction processes or for successful drug design. The study of the cytotoxicity in four different human cell lines and the experimental measurement of the partition coefficient between 1-octanol and water (P_o/w), using the slow-stirring method, were carried out for several FILs. In both studies, the effect of the cation ([C₂C₁Im]⁺, [C₂C₁py]⁺, [C₄C₁pyr]⁺, [N_1112(OH)]⁺, or [N₄₄₄₄]⁺), the cationic alkyl side-chain length ([C_nC₁Im]⁺, with n = 2, 6, 8 or 12), and the anionic fluorinated chain length/anionic fluorinated domain size ([C₄F₉SO₃]¯, [C₈F₁₇SO₃]¯, or [N(C₄F₉SO₃)₂]¯) were analysed. The results reveal that both toxicity and partition properties are mainly influenced by the size of the cationic hydrogenated alkyl side-chain and that of the anionic fluorinated domain. The intrinsic tuneability of the FILs allows for their selection according to the lipophilic or hydrophilic character of the target biological system under consideration. The toxicity studies corroborate the biocompatible nature of some FILs tested in this work. Along, for all the FILs under study P_o/w < 1.00. Accordingly, a decadic logarithm of the bioconcentration factor in fish of 0.5 would be estimated, which is below the regulatory endpoint used by regulatory agencies.

Optimized Synthesis of Poly(deoxyribose) Isobutyrate, a Viscous Biomaterial for Bone Morphogenetic Protein-2 Delivery

Injectable and phase-transitioning carriers from natural polysaccharides have great potential for the minimally invasive delivery of therapeutic proteins in the field of bone tissue engineering. In this study, a novel and highly viscous drug carrier was synthesized by a sequential process of deoxyribose polycondensation and esterification. The effect of synthesis parameters on the molecular weight, viscosity, and adhesion of the material was studied and correlated to temperature and time of polycondensation ( T_p and t_p), time and temperature of esterification ( T_e and t_e), and the molar ratio of the monomer ( R). The formulations were evaluated for molecular weight and distribution properties using GPC, chemical structures by FTIR and NMR spectra, and rheological properties using a rheometer. Formulations illustrated a wide range of viscosities (0.736 to 2225 Pa s), adhesion (0.896 to 58.45 N), and molecular weights (637 to 4216 Da), where viscosity was significantly reduced in the presence of low amounts of solvents (10-20%). The sustained release of BSA was observed over 42 days in vitro. The biocompatibility of poly(deoxyribose) isobutyrate (PDIB) as well as its potential as a bone morphogenetic protein delivery system was assessed in vivo using a rat ectopic bone model, where bone nodules were observed at 2 weeks. In summary, PDIB is a promising molecule with multiple applications for protein delivery, including for bone tissue engineering.

Dispersible hydrolytically sensitive nanoparticles for nasal delivery of thyrotropin releasing hormone (TRH)

Nose-to-brain delivery of drugs is affected by nanoparticles (NPs) deposited on the olfactory surface and absorbed directly into the brain. Thyrotropin releasing hormone (TRH), a water soluble drug used for treating suicidal patients, was incorporated into a fast degrading poly(sebacic anhydride) (PSA) NPs. NPs were prepared by a solvent-antisolvent process under strict anhydrous environment to obtain high TRH loading and to avoid premature PSA degradation and TRH release. PSA and TRH were dissolved in a mixture of dichloromethane and ethanol and added dropwise to a dispersion of mannitol particles in heptane as an antisolvent. Mannitol powder was included in the antisolvent, so that formed NPs adhered to the mannitol microparticles for easy isolation and immediate dispersion in water prior to use. The size, surface charge, and morphology of the TRH-PSA NPs were determined using dynamic light scattering (DLS), zeta-potential, and Scanning Electron Microscopy (SEM), respectively. The NPs prepared were uniform and spherical of ~250 nm. Further, the in vitro release profile of TRH from NPs lasted for 12 h with most TRH released within the first hour in water. Concentration dependent cell toxicity studies revealed low toxicity level at low concentrations of the NPs. Surface adsorption of the NPs was also uniform on the cell surface as examined through the odyssey near infrared fluorescence (NIR) images using Indocyanine green (ICG). The NPs are designed to enable direct delivery to the olfactory epithelium using a refillable nasal atomizer that deposits mist onto the olfactory neuro-epithelium.

Topical Application of TGF-β-Activating Peptide, KRFK, Prevents Inflammatory Manifestations in the TSP-1-Deficient Mouse Model of Chronic Ocular Inflammation

Chronic inflammation of the ocular surface poses a risk of vision impairment. The understanding of the molecular mechanisms that are involved in the inflammatory response is critical to identify novel molecular targets. Recently, thrombospondin-1 (TSP-1) has emerged as a key player in ocular surface homeostasis that efficiently activates the TGF-β2 isoform that is predominantly expressed in the ocular mucosa. Here, the potential of the peptide derived from TSP-1 (KRFK), that can activate TGF-β, is proposed as a potentially applicable therapeutic for chronic ocular surface inflammatory disorders. Our in vitro results confirm that the chosen peptide activates TGF-β, reducing the expression of co-stimulatory molecules on dendritic cells, driving them towards a tolerogenic phenotype. For the in vivo studies, the TSP-1-/- mouse is used as a pre-clinical model of chronic ocular inflammation. We observe that the topical application of KRFK alters the peripheral balance of effectors by reducing the proportion of pathogenic Th1 and Th17 cells while increasing Treg cell proportion in cervical lymph nodes. In line with these findings, the development of chronic ocular surface inflammation is significantly prevented in KRFK-treated TSP-1-/- mice, as assessed by clinical parameters and inflammatory cytokine expression in conjunctival and lacrimal gland tissues. Together, our results identify the KRFK peptide as a novel therapeutic option to prevent the development of chronic inflammatory manifestations of the ocular surface.

Uniform Core-Shell Nanoparticles with Thiolated Hyaluronic Acid Coating to Enhance Oral Delivery of Insulin

Oral delivery of protein drugs is an attractive route of administration due to its convenience for repeated dosing and good patient compliance. However, currently oral protein therapeutics show very low bioavailability mainly due to the existence of hostile gastrointestinal (GI) environments, including mucus layers and intestinal epithelial barriers. Herein, using insulin as a model protein therapeutic, the core-shell nanoparticles with thiolated hyaluronic acid (HA-SH) coating (NP_HA-SH ) are produced utilizing a two-step flash nanocomplexation process to enhance oral delivery efficiency of insulin. A positively charged nanoparticle core is first generated by electrostatic complexation between insulin and N-(2-hydroxypropyl)-3-trimethyl ammonium chloride modified chitosan (HTCC), followed by surface coating with HA-SH. The optimized NP_HA-SH shows an average size of 100 nm with high encapsulation efficiency (91.1%) and loading capacity (38%). In vitro and ex vivo results confirm that NP_HA-SH shows high mucus-penetration ability, improved intestinal retention and transepithelial transport property due to its thiolated surface and the ability of HA-SH coating to dissociate from the nanoparticle surface when across the mucosal layer. Oral administration of NP_HA-SH to Type 1 diabetic rats yields high efficacy and an average relative bioavailability of 11.3%. These results demonstrate that the HA-SH coated core-shell nanoparticles are a promising oral delivery vehicle for protein therapeutics.

Carriers for the targeted delivery of aerosolized macromolecules for pulmonary pathologies

INTRODUCTION

Macromolecules with unique effects and potency are increasingly being considered for application in lung pathologies. Numerous delivery strategies for these macromolecules through the lung have been investigated to improve the targeting and overall efficacy.

AREAS COVERED

Targeting approaches from delivery devices, formulation strategies and specific targets are discussed.

EXPERT OPINION

Although macromolecules are a heterogeneous group of molecules, a number of strategies have been investigated at the macro, micro, and nanoscopic scale for the delivery of macromolecules to specific sites and cells of lung tissues. Targeted approaches are already in use at the macroscopic scale through inhalation devices and formulations, but targeting strategies at the micro and nanoscopic scale are still in the laboratory stage. The combination of controlling lung deposition and targeting after deposition, through a combination of targeting strategies could be the future direction for the treatment of lung pathologies through the pulmonary route.

Preparation of mesoporous silica microparticles by sol-gel/emulsion route for protein release

Encapsulation of therapeutic proteins into particles from appropriate material can improve both stability and delivery of the drugs, and the obtained particles can serve as a platform for development of their new oral formulations. The main goal of this work was development of sol-gel/emulsion method for preparation of silica microcapsules capable of controlled release of encapsulated protein without loss of its native structure. For this purpose, the reported in literature direct sol-gel/W/O/W emulsion method of protein encapsulation was used with some modifications, because the original method did not allow to prepare silica microcapsules capable for protein release. The particles were synthesized using sodium silicate and tetraethoxysilane as silica precursors and different compositions of oil phase. In vitro kinetics of bovine serum albumin (BSA) release in buffer (pH 7.4) was studied by Fourier transform infrared (FTIR) and fluorescence spectrometry, respectively. Structural state of encapsulated BSA and after release was evaluated. It was found that the synthesis conditions influenced substantially the porous structure of the unloaded silica particles, release properties of the BSA-loaded silica particles and structural state of the encapsulated and released protein. The modified synthesis conditions made it possible to obtain the silica particles capable of controlled release of the protein during a week without loss of the protein native structure.

Encapsulation, protection, and delivery of bioactive proteins and peptides using nanoparticle and microparticle systems: A review

There are many examples of bioactive proteins and peptides that would benefit from oral delivery through functional foods, supplements, or medical foods, including hormones, enzymes, antimicrobials, vaccines, and ACE inhibitors. However, many of these bioactive proteins are highly susceptible to denaturation, aggregation or hydrolysis within commercial products or inside the human gastrointestinal tract (GIT). Moreover, many bioactive proteins have poor absorption characteristics within the GIT. Colloidal systems, which contain nanoparticles or microparticles, can be designed to encapsulate, retain, protect, and deliver bioactive proteins. For instance, a bioactive protein may have to remain encapsulated and stable during storage and passage through the mouth and stomach, but then be released within the small intestine where it can be absorbed. This article reviews the application of food-grade colloidal systems for oral delivery of bioactive proteins, including microemulsions, emulsions, nanoemulsions, solid lipid nanoparticles, multiple emulsions, liposomes, and microgels. It also provides a critical assessment of the characteristics of colloidal particles that impact the effectiveness of protein delivery systems, such as particle composition, size, permeability, interfacial properties, and stability. This information should be useful for the rational design of medical foods, functional foods, and supplements for effective oral delivery of bioactive proteins.

Impact of change of matrix crystallinity and polymorphism on ovalbumin release from lipid-based implants

The objectives of this study were to prepare lipid-based implants by hot melt extrusion (HME) for the prolonged release of ovalbumin (OVA), and to relate protein release to crystallinity and polymorphic changes of the lipid matrix. Two lipids, glycerol tristearate and hydrogenated palm oil, with different composition and degree of crystallinity were studied. Solid OVA was dispersed within the lipid matrixes, which preserved its stability during extrusion. This was partially attributed to a protective effect of the lipidic matrix. The incorporation of OVA decreased the mechanical strength of the implants prepared with the more crystalline matrix, glycerol tristearate, whereas it remained comparable for the hydrogenated palm oil because of stronger physical and non-covalent interactions between the protein and this lipid. This was also the reason for the faster release of OVA from the glycerol tristearate matrix when compared to the hydrogenated palm oil (8 vs. 28 weeks). Curing induced and increased crystallinity, and changes in the release rate, especially for the more crystalline matrix. In this case, both an increase and a decrease in release, were observed depending on the tempering condition. Curing at higher temperatures induced a melt-mediated crystallization and solid state transformation of the glycerol tristearate matrix and led to rearrangements of the inner structure with the formation of larger pores, which accelerated the release. In contrast, changes in the hydrogenated palm oil under the same curing conditions were less noticeable leading to a more robust formulation, because of less polymorphic changes over time. This study helps to understand the effect of lipid matrix composition and crystallinity degree on the performance of protein-loaded implants, and to establish criteria for the selection of a lipid carrier depending on the release profile desired.

Improved in vitro corneal delivery of a thrombospondin-1-derived peptide using a liposomal formulation

Peptide delivery to and through ocular sites is a growing field of research interest. However, several barriers restrict the permeation and bioavailability of these molecules to target tissues. The main pharmacological barriers of topical administration are the tear film, rapid drainage of the tear film, and poor corneal permeation. If the administered molecule is a peptide, instability and enzymatic degradation can be significant. Novel approaches such as the design and development of nanocarriers to overcome these drawbacks have been investigated with promising results. Therefore, in continuation of our previous study using a liposome-based (LP) formulation as topical drug delivery system, the aim of this work was to efficiently encapsulate a thrombospondin-1-derived peptide, KRFK, in this formulation and to assess peptide permeability through different ocular surface epithelia. LPs were prepared by the solvent evaporation technique and the labeled peptide FITC-KRFK was incorporated in the aqueous core. Different sonication times were used to optimize encapsulation efficiency. The selected formulation was further analyzed in terms of size, pH, osmolarity, and corneal epithelial cytotoxicity. The permeabilities of the LP-encapsulated and free labeled KRFK peptides were assessed with in vitro models of conjunctival and corneal epithelia. Our results provide a proof of concept that the LP formulation efficiently encapsulates the KRFK peptide and improves corneal permeation. Data reported in this study strongly support that this formulation could be a more effective therapeutic approach than free peptide instillation and warrant further analysis using experimental in vivo models.