Development and in vivo evaluation of papain-functionalized nanoparticles

Future Nanotechnology-Based Strategies for Improved Management of Helicobacter pylori Infection

Helicobacter pylori (H. pylori) is a recalcitrant pathogen, which can cause gastric disorders. During the past decades, polypharmacy-based regimens, such as triple and quadruple therapies have been widely used against H. pylori. However, polyantibiotic therapies can disturb the host gastric/gut microbiota and lead to antibiotic resistance. Thus, simpler but more effective approaches should be developed. Here, some recent advances in nanostructured drug delivery systems to treat H. pylori infection are summarized. Also, for the first time, a drug release paradigm is proposed to prevent H. pylori antibiotic resistance along with an IVIVC model in order to connect the drug release profile with a reduction in bacterial colony counts. Then, local delivery systems including mucoadhesive, mucopenetrating, and cytoadhesive nanobiomaterials are discussed in the battle against H. pylori infection. Afterward, engineered delivery platforms including polymer-coated nanoemulsions and polymer-coated nanoliposomes are poposed. These bioinspired platforms can contain an antimicrobial agent enclosed within smart multifunctional nanoformulations. These bioplatforms can prevent the development of antibiotic resistance, as well as specifically killing H. pylori with no or only slight negative effects on the host gastrointestinal microbiota. Finally, the essential checkpoints that should be passed to confirm the potential effectiveness of anti-H. pylori nanosystems are discussed.

Microparticles and nanoparticles-based approaches to improve oral treatment of Helicobacter pylori infection

Helicobacter pylori is a gram-negative, spiral-shaped, flagellated bacterium that colonizes the stomach of half the world's population. Helicobacter pylori infection causes pathologies of varying severity. Standard oral therapy fails in 15-20% since the barriers of the oral route decrease the bioavailability of antibiotics and the intrinsic factors of bacteria increase the rates of resistance. Nanoparticles and microparticles are promising strategies for drug delivery into the gastric mucosa and targeting H. pylori. The variety of building blocks creates systems with distinct colloidal, surface, and biological properties. These features improve drug-pathogen interactions, eliminate drug depletion and overuse, and enable the association of multiple actives combating H. pylori on several fronts. Nanoparticles and microparticles are successfully used to overcome the barriers of the oral route, physicochemical inconveniences, and lack of selectivity of current therapy. They have proven efficient in employing promising anti-H. pylori compounds whose limitation is oral route instability, such as some antibiotics and natural products. However, the current challenge is the applicability of these strategies in clinical practice. For this reason, strategies employing a rational design are necessary, including in the development of nano- and microsystems for the oral route.

Progress on the pathological tissue microenvironment barrier-modulated nanomedicine

Imbalance in the tissue microenvironment is the main obstacle to drug delivery and distribution in the human body. Before penetrating the pathological tissue microenvironment to the target site, therapeutic agents are usually accompanied by three consumption steps: the first step is tissue physical barriers for prevention of their penetration, the second step is inactivation of them by biological molecules, and the third step is a cytoprotective mechanism for preventing them from functioning on specific subcellular organelles. However, recent studies in drug-hindering mainly focus on normal physiological rather than pathological microenvironment, and the repair of damaged physiological barriers is also rarely discussed. Actually, both the modulation of pathological barriers and the repair of damaged physiological barriers are essential in the disease treatment and the homeostasis maintenance. In this review, we present an overview describing the latest advances in the generality of these pathological barriers and barrier-modulated nanomedicine. Overall, this review holds considerable significance for guiding the design of nanomedicine to increase drug efficacy in the future.

Surface design of nanocarriers: Key to more efficient oral drug delivery systems

As nanocarriers (NCs) can improve the solubility of drugs, prevent their degradation by gastrointestinal (GI) enzymes and promote their transport across the mucus gel layer and absorption membrane, the oral bioavailability of these drugs can be substantially enhanced. All these properties of NCs including self-emulsifying drug delivery systems (SEDDS), solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), liposomes, polymeric nanoparticles, inorganic nanoparticles and polymeric micelles depend mainly on their surface chemistry. In particular, interaction with food, digestive enzymes, bile salts and electrolytes, diffusion behaviour across the mucus gel layer and fate on the absorption membrane are determined by their surface. Bioinert surfaces limiting interactions with gastrointestinal fluid and content as well as with mucus, adhesive surfaces providing an intimate contact with the GI mucosa and absorption enhancing surfaces can be designed. Furthermore, charge converting surfaces shifting their zeta potential from negative to positive directly at the absorption membrane and surfaces providing a targeted drug release are advantageous. In addition to these passive surfaces, even active surfaces cleaving mucus glycoproteins on their way through the mucus gel layer can be created. Within this review, we provide an overview on these different surfaces and discuss their impact on the performance of NCs in the GI tract.

Expanding opportunities to engineer mucosal vaccination with biomaterials

Mucosal vaccines are receiving increasing interest both for protecting against infectious diseases and for inducing therapeutic immune responses to treat non-infectious diseases. However, the mucosal barriers of the lungs, gastrointestinal tract, genitourinary tract, nasal, and oral tissues each present unique challenges for constructing efficacious vaccines. Vaccination through each of these mucosae requires transport through the mucus and across specialized epithelia to reach tissue-specific immune cells and lymphoid structures, necessitating finely tuned and multifunctional strategies. Serving as inspiration for mucosal vaccine design, pathogens have evolved elaborate, diverse, and multipronged approaches to penetrate and infect mucosae. This review is focused on biomaterials-based strategies, many inspired by pathogens, for designing mucosal vaccine platforms. Passive and active technologies are discussed, along with the microbial processes that they seek to mimic.

Mucoadhesive carriers for oral drug delivery

Among the various dosage forms, oral medicine has extensive benefits including ease of administration and patients' compliance, over injectable, suppositories, ocular and nasal. Despite of extensive demand and emerging advantages, over 50% of therapeutic molecules are not available in oral form due to their physicochemical properties. More importantly, most of the biologics, proteins, peptide, and large molecular drugs are mostly available in injectable form. Conventional oral drug delivery system has limitation such as degradation and lack of stability within stomach due to presence of highly acidic gastric fluid, hinders their therapeutic efficacy and demand more frequent and higher dosing. Hence, formulation for controlled, sustained, and targeted drug delivery, need to be designed with feasibility to target the specific region of gastrointestinal (GI) tract such as stomach, small intestine, intestine lymphatic, and colon is challenging. Among various oral delivery approaches, mucoadhesive vehicles are promising and has potential for improving oral drug retention and controlled absorption to treat local diseases within the GI tract, as well systemic diseases. This review provides the overview about the challenges and opportunities to design mucoadhesive formulation for oral delivery of therapeutics in a way to target the specific region of the GI tract. Finally, we have concluded with future perspective and potential of mucoadhesive formulations for oral local and systemic delivery.

Surface Modification of Lipid-Based Nanoparticles

There is a growing interest in the development of lipid-based nanocarriers for multiple purposes, including the recent increase of these nanocarriers as vaccine components during the COVID-19 pandemic. The number of studies that involve the surface modification of nanocarriers to improve their performance (increase the delivery of a therapeutic to its target site with less off-site accumulation) is enormous. The present review aims to provide an overview of various methods associated with lipid nanoparticle grafting, including techniques used to separate grafted nanoparticles from unbound ligands or to characterize grafted nanoparticles. We also provide a critical perspective on the usefulness and true impact of these modifications on overcoming different biological barriers, with our prediction on what to expect in the near future in this field.

Emerging technologies to increase gastrointestinal transit times of drug delivery systems

Apart from already established technologies to increase gastrointestinal transit times, including devices rapidly increasing in size once they have reached the stomach in order to retard the passage through the pylorus, formulations that float on gastric fluids and mucoadhesive drug delivery systems adhering to the gastrointestinal mucosa, there are new technologies emerging that might be game changing. They include mucus permeating nanocarriers that are able to diffuse deeply into the mucus gel layer of the gastric and intestinal mucosa remaining there for a prolonged time period (i), charge-converting nanocarriers that shift their zeta potential from negative to positive within the mucus gel layer providing strong ionic bonds with anionic mucus glycoproteins (ii) and thiolated nanocarriers and cyclodextrins form even covalent bonds with cysteine-rich subdomains of mucus glycoproteins (iii). Within this review we will provide an overview about these emerging new technologies and will critically discuss their potential and shortcomings.

Barrier properties of ex vivo porcine intestinal mucus are highly independent of isolation and storage conditions

Porcine intestinal mucus (PIM) is often utilized as an ex vivo mucus model in mucus interaction studies. However, numerous isolation procedures and storage conditions for PIM are reported, yet their potential impact on preserving the critical properties of PIM remains unknown. This study investigated the effect of isolation procedures (rinsing and anatomical site of mucus isolation) and storage conditions (-20°C, -80°C, snap frozen in liquid nitrogen prior to storage at -80°C, or freeze-dried followed by storage at room temperature and reconstitution) of PIM in regard to the permeation of fluorescein-isothiocyanate-labelled dextran (FD) macromolecules of 4, 40 and 150 kDa, rheological properties as well as pH, osmolality, protein and water content. Rinsing intestines with tap water or phosphate-buffered saline as well as isolating PIM from different regions of the first five meters of the proximal jejunum did not affect the pH or osmolality of isolated PIM. The permeation of FD4, FD40 and FD150 through stored PIM was similar to permeation through fresh PIM. The rheological properties of stored PIM were similar to properties of fresh PIM. Osmolality, protein and water content were similar in stored and fresh PIM whereas pH decreased with 0.3 unit for all stored PIMs. Overall, PIM samples stored at -20°, -80°C, snap frozen or freeze-dried were found to have similar properties to freshly isolated PIM and can all be considered good alternatives to fresh PIM for mucus studies.

Purified mucins in drug delivery research

One of the main challenges in the field of drug delivery remains the development of strategies to efficiently transport pharmaceuticals across mucus barriers, which regulate the passage and retention of molecules and particles in all luminal spaces of the body. A thorough understanding of the molecular mechanisms, which govern such selective permeability, is key for achieving efficient translocation of drugs and drug carriers. For this purpose, model systems based on purified mucins can contribute valuable information. In this review, we summarize advances that were made in the field of drug delivery research with such mucin-based model systems: First, we give an overview of mucin purification procedures and discuss the suitability of model systems reconstituted from purified mucins to mimic native mucus. Then, we summarize techniques to study mucin binding. Finally, we highlight approaches that made use of mucins as building blocks for drug delivery platforms or employ mucins as active compounds.

Modulation of Gastrointestinal Mucus Properties with Ionic Liquids for Drug Delivery

The mucus barrier lining the gastrointestinal tract poses a significant barrier to the oral delivery of macromolecular drugs. Successful approaches to overcoming this barrier have primarily focused on reducing drug and carrier interactions with mucus or disrupting the mucus layer directly. Choline-based ionic liquids (ILs) such as choline geranate and choline glycolate (CGLY) have recently been shown to be effective in enhancing the intestinal absorption of macromolecules such as insulin and immunoglobulin (IgG), respectively. Herein, the use of choline-based ILs as mucus-modulating agents for safely improving drug penetration through mucus is described. Choline-based ILs significantly increase the diffusion rates of cationic dextrans through mucin solution. Choline-maleic acid (CMLC 2:1) enhances the diffusion of 4 kDa cationic dextran in mucin solution by more than fourfold when compared to phosphate-buffered saline control. Choline-based ILs also reduce mucus viscosity without significantly impacting the native mucus gel structure. In vitro studies in a mucus-secreting coculture model with Caco-2 and HT29MTX-E12 cells further demonstrate the effectiveness of ILs in improving transport of cationic molecules in the presence of secreted mucus. This work demonstrates the potential for choline-based ionic liquids to be used as nondestructive mucus-modulating agents for enabling enhanced oral delivery of macromolecular drugs.

Ocular drug delivery to the anterior segment using nanocarriers: A mucoadhesive/mucopenetrative perspective

There is a growing demand for effective treatments for ocular conditions that improve patient compliance and reduce side-effects. While methods such as implants and injections have proven effective, topical administration remains the method of choice for the delivery of therapeutics to the anterior segment of the eye. However, topical administration suffers from multiple drawbacks including low bioavailability of the target therapeutic, systemic toxicity, and the requirement for high therapeutic doses due to the effective clearance mechanisms that exist in the eye. Nanoparticles that have tunable mucoadhesion and/or mucopenetration offer outstanding potential to overcome the anatomical and physiological barriers present to improve ocular bioavailability, reduce toxicity, and increase ocular retention, among other benefits. The current review highlights recent advances in the field of developing nanocarriers with tunable mucoadhesion and mucopenetration for drug delivery to the eye.

Polymer encapsulated clinical ICG nanoparticles for enhanced photothermal therapy and NIR fluorescence imaging in cervical cancer

Photothermal therapy (PTT) is a popular tumor therapy method, which is based on efficient photothermal nanoagents (PTNs). Clinical Indocyanine Green (ICG), as a Food and Drug Administration (FDA) approved agent, is an often-used PTN, meanwhile it is also a good near-infrared (NIR) fluorescence contrast agent. However, the further applications of ICG in biomedical fields are limited due to its poor stability. In this study, ICG was encapsulated by the amphiphilic polymer poly(styrene-co-maleic anhydride) (PSMA) to form ICG@PSMA nanoparticles. Furthermore, optical and thermal characteristics of ICG@PSMA nanoparticles were studied in detail. Strong NIR fluorescence and excellent photothermal properties of ICG@PSMA nanoparticles under 808 nm laser irradiation were measured. Besides, favorable biocompatibility of ICG@PSMA nanoparticles was demonstrated on a human cervical cancer cell line (HeLa) via cell viability studies. Hence, ICG@PSMA nanoparticles were further applied to enhanced PTT of living HeLa cells under 808 nm excitation, and a high PTT efficiency of ∼70% was obtained. The novel ICG nanoparticles as a promising PTT nanoplatform could offer an opportunity for further tumour treatments.

PSMA encapsulated Clinical ICG to form ICG@PSMA nanoparticles. ICG@PSMA nanoparticles showed strong NIR fluorescence and excellent photothermal properties.

Design and Testing of Efficient Mucus-Penetrating Nanogels-Pitfalls of Preclinical Testing and Lessons Learned

Mucosal surfaces pose a challenging environment for efficient drug delivery. Various delivery strategies such as nanoparticles have been employed so far; yet, still yielding limited success. To address the need of efficient transmucosal drug delivery, this report presents the synthesis of novel disulfide-containing dendritic polyglycerol (dPG)-based nanogels and their preclinical testing. A bifunctional disulfide-containing linker is coupled to dPG to act as a macromolecular crosslinker for poly-N-isopropylacrylamide (PNIPAM) and poly-N-isopropylmethacrylamide (PNIPMAM) in a precipitation polymerization process. A systematic analysis of the polymerization reveals the importance of a careful polymer choice to yield mucus-degradable nanogels with diameters between 100 and 200 nm, low polydispersity, and intact disulfide linkers. Absorption studies in porcine intestinal tissue and human bronchial epithelial models demonstrate that disulfide-containing nanogels are highly efficient in overcoming mucosal barriers. The nanogels efficiently degrade and deliver the anti-inflammatory biomacromolecule etanercept into epithelial tissues yielding local anti-inflammatory effects. Over the course of this work, several problems are encountered due to a limited availability of valid test systems for mucosal drug-delivery systems. Hence, this study also emphasizes how critical a combined and multifaceted approach is for the preclinical testing of mucosal drug-delivery systems, discusses potential pitfalls, and provides suggestions for solutions.

Biochemical Properties and Anti-Biofilm Activity of Chitosan-Immobilized Papain

Chitosan, the product of chitin deacetylation, is an excellent candidate for enzyme immobilization purposes. Here we demonstrate that papain, an endolytic cysteine protease (EC: 3.4.22.2) from Carica papaya latex immobilized on the matrixes of medium molecular (200 kDa) and high molecular (350 kDa) weight chitosans exhibits anti-biofilm activity and increases the antimicrobials efficiency against biofilm-embedded bacteria. Immobilization in glycine buffer (pH 9.0) allowed adsorption up to 30% of the total protein (mg g chitosan⁻¹) and specific activity (U mg protein⁻¹), leading to the preservation of more than 90% of the initial total activity (U mL⁻¹). While optimal pH and temperature of the immobilized papain did not change, the immobilized enzyme exhibited elevated thermal stability and 6–7-fold longer half-life time in comparison with the soluble papain. While one-half of the total enzyme dissociates from both carriers in 24 h, this property could be used for wound-dressing materials design with dosed release of the enzyme to overcome the relatively high cytotoxicity of soluble papain. Our results indicate that both soluble and immobilized papain efficiently destroy biofilms formed by Staphylococcus aureus and Staphylococcus epidermidis. As a consequence, papain, both soluble and immobilized on medium molecular weight chitosan, is capable of potentiating the efficacy of antimicrobials against biofilm-embedded Staphylococci. Thus, papain immobilized on medium molecular weight chitosan appears a presumably beneficial agent for outer wound treatment for biofilms destruction, increasing antimicrobial treatment effectiveness.

In Vivo T Cell-Targeting Nanoparticle Drug Delivery Systems: Considerations for Rational Design

T cells play an important role in immunity and repair and are implicated in diseases, including blood cancers, viral infections, and inflammation, making them attractive targets for the treatment and prevention of diseases. Over recent years, the advent of nanomedicine has shown an increase in studies that use nanoparticles as carriers to deliver therapeutic cargo to T cells for ex vivo and in vivo applications. Nanoparticle-based delivery has several advantages, including the ability to load and protect a variety of drugs, control drug release, improve drug pharmacokinetics and biodistribution, and site- or cell-specific targeting. However, the delivery of nanoparticles to T cells remains a major technological challenge, which is primarily due to the nonphagocytic nature of T cells. In this review, we discuss the physiological barriers to effective T cell targeting and describe the different approaches used to deliver cargo-loaded nanoparticles to T cells for the treatment of disease such as T cell lymphoma and human immunodeficiency virus (HIV). In particular, engineering strategies that aim to improve nanoparticle internalization by T cells, including ligand-based targeting, will be highlighted. These nanoparticle engineering approaches are expected to inspire the development of effective nanomaterials that can target or manipulate the function of T cells for the treatment of T cell-related diseases.

Models to evaluate the barrier properties of mucus during drug diffusion

Mucus is widely disseminated in the nasal cavity, oral cavity, respiratory tract, eyes, gastrointestinal tract, and reproductive tract to prevent the invasion of pathogenic bacteria and toxins. The mucus layer through its continuous secretion can prevent the passage of macromolecular substances such as pathogenic bacteria and toxins, thereby reducing the occurrence of inflammation. Without a doubt, mucus also hinders oral absorption. The physiological and biochemical properties of intestinal mucus and the different types of mucus barrier models need to be predominated. To find ways to increase the bioavailability of drugs in the future, this article summarizes mucus composition, barrier properties, mucus models, and mucoadhesive/mucopenetrating particles to highlight the information they can afford. Collectively, the review seeks to provide a state-of-the-art roadmap for researchers who must contend with this critical barrier to drug delivery.

Molecular and cellular cues governing nanomaterial-mucosae interactions: from nanomedicine to nanotoxicology

Mucosal tissues constitute the largest interface between the body and the surrounding environment and they regulate the access of molecules, supramolecular structures, particulate matter, and pathogens into it. All mucosae are characterized by an outer mucus layer that protects the underlying cells from physicochemical, biological and mechanical insults, a mono-layered or stratified epithelium that forms tight junctions and controls the selective transport of solutes across it and associated lymphoid tissues that play a sentinel role. Mucus is a gel-like material comprised mainly of the glycoprotein mucin and water and it displays both hydrophilic and hydrophobic domains, a net negative charge, and high porosity and pore interconnectivity, providing an efficient barrier for the absorption of therapeutic agents. To prolong the residence time, absorption and bioavailability of a broad spectrum of active compounds upon mucosal administration, mucus-penetrating and mucoadhesive particles have been designed by tuning the chemical composition, the size, the density, and the surface properties. The benefits of utilizing nanomaterials that interact intimately with mucosae by different mechanisms in the nanomedicine field have been extensively reported. To ensure the safety of these nanosystems, their compatibility is evaluated in vitro and in vivo in preclinical and clinical trials. Conversely, there is a growing concern about the toxicity of nanomaterials dispersed in air and water effluents that unintentionally come into contact with the airways and the gastrointestinal tract. Thus, deep understanding of the key nanomaterial properties that govern the interplay with mucus and tissues is crucial for the rational design of more efficient drug delivery nanosystems (nanomedicine) and to anticipate the fate and side-effects of nanoparticulate matter upon acute or chronic exposure (nanotoxicology). This review initially overviews the complex structural features of mucosal tissues, including the structure of mucus, the epithelial barrier, the mucosal-associated lymphatic tissues and microbiota. Then, the most relevant investigations attempting to identify and validate the key particle features that govern nanomaterial-mucosa interactions and that are relevant in both nanomedicine and nanotoxicology are discussed in a holistic manner. Finally, the most popular experimental techniques and the incipient use of mathematical and computational models to characterize these interactions are described.

Advanced materials for drug delivery across mucosal barriers

Mucus is a viscoelastic gel that traps pathogens and other foreign particles to limit their penetration into the underlying epithelium. Dosage forms containing particle-based drug delivery systems are trapped in mucosal layers and will be removed by mucus turnover. Mucoadhesion avoids premature wash-off and prolongs the residence time of drugs on mucus. Moreover, mucus penetration is essential for molecules to access the underlying epithelial tissues. Various strategies have been investigated to achieve mucoadhesion and mucus penetration of drug carriers. Innovations in materials used for the construction of drug-carrier systems allowed the development of different mucoadhesion and mucus penetration delivery systems. Over the last decade, advances in the field of materials chemistry, with a focus on biocompatibility, have led to the expansion of the pool of materials available for drug delivery applications. The choice of materials in mucosal delivery is generally dependent on the intended therapeutic target and nature of the mucosa at the site of absorption. This review presents an up-to-date account of materials including synthesis, physical and chemical modifications of mucoadhesive materials, nanocarriers, viral mimics used for the construction of mucosal drug delivery systems.

Comparing the permeability of human and porcine small intestinal mucus for particle transport studies

The gastrointestinal mucus layer represents the last barrier between ingested food or orally administered pharmaceuticals and the mucosal epithelium. This complex gel structure plays an important role in the process of small intestinal absorption. It provides protection against hazardous particles such as bacteria but allows the passage of nutrients and drug molecules towards the intestinal epithelium. In scientific research, mucus from animal sources is usually used to simulate difficult-to-obtain human small intestinal mucus for investigating the intramucus transport of drug delivery systems or food nanoparticles. However, there is a lack of evidence the human mucus can be reliably substituted by animal counterparts for human-relevant transport models. In this report, a procedure for collecting human mucus has been described. More importantly, the permeability characteristics of human and porcine small intestinal mucus secretions to sub-micron sized particles have been compared under simulated intestinal conditions. Negatively charged, 500 nm latex beads were used in multiple-particle tracking experiments to examine the heterogeneity and penetrability of mucus from different sources. Diffusion of the probe particles in adult human ileal mucus and adult pig jejunal and ileal mucus revealed no significant differences in microstructural organisation or microviscosity between the three mucus types (P > 0.05). In contrast to this interspecies similarity, the intraspecies comparison of particle diffusivity in the mucus obtained from adult pigs vs. 2-week old piglets showed better penetrability of the piglet mucus. The mean Stokes–Einstein viscosity of the piglet jejunal mucus was approx. two times lower than the viscosity of the pig jejunal mucus (P < 0.05). All mucus structures were also visualised by scanning electron microscopy. This work validates the use of porcine small intestinal mucus collected from fully-grown pigs for studying colloidal transport of sub-micron sized particles in mucus under conditions mimicking the adult human small intestinal environment.

Addressing the challenges to increase the efficiency of translating nanomedicine formulations to patients

INTRODUCTION

Nanotechnology is in a growth phase for drug delivery and medical imaging. Nanomaterials with unique properties present opportunities for encapsulation of therapeutics and imaging agents, along with conjugation to ligands for targeting. Favorable chemistry of nanomaterials can create formulations that address critical challenges for therapeutics, such as insolubility and a low capacity to cross the blood-brain-barrier (BBB) and intestinal wall.

AREAS COVERED

The authors investigate challenges faced during translation of nanomedicines while suggesting reasons as to why some nanoformulations have under-performed in clinical trials. They assess physiological barriers such as the BBB and gut mucus that nanomedicines must overcome to deliver cargos. They also provide an overview with examples of how nanomedicines can be designed to improve localization and site-specific delivery (e.g., encapsulation, bioconjugation, and triggered-release).

EXPERT OPINION

There are examples where nanomedicines have demonstrated improved efficacy of payload in humans; however, most of the advantages conferred were in improved pharmacokinetics and reduced toxicity. Problematic data show susceptibility of nanoformulations against natural protective mechanisms present in the body, including distribution impediment by physiological barriers and activation of the reticuloendothelial system. Further initiatives should address current challenges while expanding the scope of nanomedicine into advanced biomedical imaging and antibiotic delivery.

Enteric-Coated Strategies in Colorectal Cancer Nanoparticle Drug Delivery System

Colorectal cancer is one of the most common cancer diseases with the increase of cases prevalence >5% every year. Multidrug resistance mechanisms and non-localized therapy become primary problems of chemotherapy drugs for curing colorectal cancer disease. Therefore, the enteric-coated nanoparticle system has been studied and proved to be able to resolve those problems with good performance for colorectal cancer. The highlight of our review aims to summarize and discuss the enteric-coated nanoparticle drug delivery system specific for colorectal cancer disease. The main and supporting literatures were collected from published research articles of journals indexed in Scopus and PubMed databases. In the oral route of administration, Eudragit pH-sensitive copolymer as a coating agent prevents the degradation of the nanoparticle system from the gastric fluid and releases drug to intestinal-colon track. Therefore, it provides a colon-specific targeting ability. Impressively, enteric-coated nanoparticles having a sustained release profile significantly increase the cytotoxic effect of chemotherapeutic drugs and achieve cell-specific target delivery. The enteric-coated nanoparticle drug delivery system represents an excellent modification to improve the effectiveness and performance of anticancer drugs for colorectal cancer disease in terms of the oral route of administration.

Enhancing the Furosemide Permeability by Papain Minitablets Through a Triple Co-culture In Vitro Intestinal Cell Model

The administration of medicines by the oral route is the most used approach for being very convenient. Although it is the most popular, this route also has absorption, and consequently, bioavailability limitations. In this sense, several pharmacotechnical strategies have been used to improve drug absorption, one of which is the use of permeation promoters. Papain is a very versatile plant enzyme that can be used as a permeation promoter of various active compounds. This study aimed to evaluate the safety of papain and the formulation of native papain minitablets to promote in vitro permeation of furosemide through an innovative biomimetic triple co-culture model of Caco-2, HT29-MTX, and Raji cells. Regarding permeation, furosemide and metaprolol concentrations are determined with HPLC; those are used to calculate P_app. Monolayer integrity was evaluated using TEER and Lucifer Yellow. In the presence of papain, TEER decreased two-fold and the P_app of furosemide increased six-fold. The results suggest that native papain minitablets can be used as therapeutic adjuvants to enhance the permeation of drugs significantly improving bioavailability.

Transformation of Nanomaterials and Its Implications in Gut Nanotoxicology

Ingestion of engineered nanomaterials (ENMs) is inevitable due to their widespread utilization in the agrifood industry. Safety evaluation has become pivotal to identify the consequences on human health of exposure to these ingested ENMs. Much of the current understanding of nanotoxicology in the gastrointestinal tract (GIT) is derived from studies utilizing pristine ENMs. In reality, agrifood ENMs interact with their microenvironment, and undergo multiple physicochemical transformations, such as aggregation/agglomeration, dissolution, speciation change, and surface characteristics alteration, across their life cycle from synthesis to consumption. This work sieves out the implications of ENM transformations on their behavior, stability, and reactivity in food and product matrices and through the GIT, in relation to measured toxicological profiles. In particular, a strong emphasis is given to understand the mechanisms through which these transformations can affect ENM induced gut nanotoxicity.

Silica Nanoparticles in Transmucosal Drug Delivery

Transmucosal drug delivery includes the administration of drugs via various mucous membranes, such as gastrointestinal, nasal, ocular, and vaginal mucosa. The use of nanoparticles in transmucosal drug delivery has several advantages, including the protection of drugs against the harsh environment of the mucosal lumens and surfaces, increased drug residence time, and enhanced drug absorption. Due to their relatively simple synthetic methods for preparation, safety profile, and possibilities of surface functionalisation, silica nanoparticles are highly promising for transmucosal drug delivery. This review provides a description of silica nanoparticles and outlines the preparation methods for various core and surface-functionalised silica nanoparticles. The relationship between the functionalities of silica nanoparticles and their interactions with various mucous membranes are critically analysed. Applications of silica nanoparticles in transmucosal drug delivery are also discussed.

Ternary nanoparticle complex of antibiotic, polyelectrolyte, and mucolytic enzyme as a potential antibiotic delivery system in bronchiectasis therapy

Antibiotic-polyelectrolyte nanoparticle complex (or nanoplex in short) has been recently demonstrated as a superior antibiotic delivery system to the native antibiotic in bronchiectasis therapy owed to its ability to overcome the lung's mucus barrier and generate high localized antibiotic exposure in the infected sites. The present work aimed to further improve the mucus permeability, hence the antibacterial efficacy of the nanoplex, by incorporating mucolytic enzyme papain (PAP) at the nanoplex formation step to produce PAP-decorated antibiotic-polyelectrolyte nanoplex exhibiting built-in mucolytic capability. Ciprofloxacin (CIP) and dextran sulfate (DXT) were used as the models for antibiotics and polyelectrolyte, respectively. The results showed that the PAP inclusion had minimal effects on the physical characteristics, preparation efficiency, and dissolution of the CIP-DXT nanoplex. The optimal CIP-(DXT-PAP) nanoplex exhibited size and zeta potential of approximately 200 nm and -50 mV with CIP and PAP payloads of 60% and 32% (w/w), respectively. The nanoplex was prepared at high efficiency with larger than 80% CIP and PAP utilization rates. The CIP-(DXT-PAP) nanoplex exhibited tenfold improvement in the mucus permeability compared to its CIP-DXT nanoplex counterpart, resulting in the former's superior bactericidal activity against clinical Pseudomonas aeruginosa biofilm in the presence of mucus barrier. A trade-off, nevertheless, existed between antibacterial efficacy and cytotoxicity towards human lung epithelium cells upon the incorporation of PAP above a certain concentration threshold. Therefore, the optimal dosing of the CIP-(DXT-PAP) nanoplex must be carefully determined.

Developing Biodegradable Nanoparticles Loaded with Mometasone Furoate for Potential Nasal Drug Delivery

Intranasal drug administration is considered a routine in the treatment of many nasal conditions including chronic rhinosinusitis (CRS), which is a common disease involving long-term inflammation of the nasal mucosa. Topical nasal steroid treatment is safe and easy to use and plays a basic role in both nonsurgical and surgical treatments for CRS. Intranasal steroid therapy for various time intervals is commonly used before and after endoscopic CRS nasal surgeries to reduce inflammation and edema and to improve mucosal healing. The medication is currently administered via conventional nasal sprays; therefore, there is an incentive to develop more efficient drug delivery systems for the controlled release of topical steroids into the sinonasal cavities over a prolonged period of time. In this study, poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) loaded with mometasone furoate (MF) were generated using the nanoprecipitation method and characterized physicochemically and morphologically. MF NPs exhibited adequate physicochemical properties and high drug encapsulation efficiency and loading content. MF exhibited sustained release from NPs over 7 days in vitro with an initial burst release; various mathematical models were applied to determine the kinetics of drug release. Having demonstrated the ability to load MF in PLGA-NPs using the nanoprecipitation method for the first time, these NPs urge the need for additional investigations to demonstrate their therapeutic potential in nasal delivery applications.

Newer approaches and novel drugs for inhalational therapy for pulmonary arterial hypertension

Introduction: Pulmonary arterial hypertension (PAH) is a progressive disease characterized by remodeling of small pulmonary arteries leading to increased pulmonary arterial pressure. Existing treatments acts to normalize vascular tone via three signaling pathways: the prostacyclin, the endothelin-1, and the nitric oxide. Although over the past 20 years, there has been considerable progress in terms of treatments for PAH, the disease still remains incurable with a disappointing prognosis.Areas covered: This review summarizes the pathophysiology of PAH, the advantages and disadvantages of the inhalation route, and assess the relative advantages various inhaled therapies for PAH. The recent studies concerning the development of controlled-release drug delivery systems loaded with available anti-PAH drugs have also been summarized.Expert opinion: The main obstacles of current pharmacotherapies of PAH are their short half-life, stability, and formulations, resulting in reducing the efficacy and increasing systemic side effects and unknown pathogenesis of PAH. The pulmonary route has been proposed for delivering anti-PAH drugs to overcome the shortcomings. However, the application of approved inhaled anti-PAH drugs is limited. Inhalational delivery of controlled-release nanoformulations can overcome these restrictions. Extensive studies are required to develop safe and effective drug delivery systems for PAH patients.

A synergistic optical strategy for enhanced deep-tumor penetration and therapy in the second near-infrared window

A mesoporous core–shell nanohybrid allows delivery of thermophilic enzymes for stromal depletion and high photothermal conversion efficiency for tumor therapy.

Improved Intestinal Mucus Permeation of Vancomycin via Incorporation Into Nanocarrier Containing Papain-Palmitate

The aim of this study was to improve intestinal mucus permeation of a peptide antibiotic via incorporation into papain-palmitate-modified self-emulsifying drug delivery systems (SEDDS) as nanocarrier. Vancomycin as a peptide antibiotic was lipidized by hydrophobic ion pair formation using sodium bis-2-ethylhexyl-sulphosuccinate before incorporation in SEDDS comprising Capmul MCM, propylenglycol, and Kolliphor EL (2:1:2). As mucolytic agent, 0.5% papain-palmitate was introduced in SEDDS formulation containing the vancomycin-sodium bis-2-ethylhexyl-sulphosuccinate ion pair. The formulation was evaluated regarding droplet size, zeta potential, and cytotoxicity using Caco-2 cells previous to intestinal mucus permeation studies using Transwell diffusion and rotating tube method. The hydrophobic ion pair product yielded from surfactant to drug ratio of 3:1 provided a 25-fold increase in lipophilicity, drug payload in SEDDS of 5%, and log D_{SEDDS/release medium} of 2.2. The formulation exhibited a droplet size and zeta potential of 221.5 ± 14.8 nm and -4.2 ± 0.8 mV, respectively. Cytotoxicity study showed that SEDDS formulations were not toxic. Introducing 0.5% papain-palmitate increased the mucus permeability of SEDDS 2.8-fold and 3.3-fold in Transwell diffusion and rotating tube studies, respectively. According to these results, papain decorated SEDDS might be a potential strategy to improve the mucus permeating properties of peptide antibiotics.

Multifunctional oral delivery systems for enhanced bioavailability of therapeutic peptides/proteins

In last few years, therapeutic peptides/proteins are rapidly growing in drug market considering their higher efficiency and lower toxicity than chemical drugs. However, the administration of therapeutic peptides/proteins is mainly limited in parenteral approach. Oral therapy which was hampered by harsh gastrointestinal environment and poorly penetrating epithelial barriers often results in low bioavailability (less than 1%-2%). Therefore, delivery systems that are rationally designed to overcome these challenges in gastrointestinal tract and ameliorate the oral bioavailability of therapeutic peptides/proteins are seriously promising. In this review, we summarized various multifunctional delivery systems, including lipid-based particles, polysaccharide-based particles, inorganic particles, and synthetic multifunctional particles that achieved effective oral delivery of therapeutic peptides/proteins.

Crossing biological barriers with nanogels to improve drug delivery performance

The current limitations in the use of nanocarriers to treat constantly evolving diseases call for the design of novel and smarter drug delivery systems (DDS). Nanogels (NGs) are three-dimensional crosslinked polymers with dimensions on the nanoscale and with a great potential for use in the biomedical field. Particular interest focuses on their application as DDS to minimize severe toxic effects and increase the therapeutic index of drugs. They have recently gained attention, since they can include responsive modalities within their structure, which enable them to excerpt a therapeutic function on demand. Their bigger sizes and controlled architecture and functionality, when compared to non-crosslinked polymers, make them particularly interesting to explore novel modalities to cross biological barriers. The present review summarizes the most significant developments of NGs as smart carriers, with focus on smart modalities to cross biological barriers such as cellular membrane, tumor stroma, mucose, skin, and blood brain barrier. We discuss the properties of each barrier and highlight the importance that the NG design has on their capability to overcome them and deliver the cargo at the site of action.

Encapsulated functionalized stereocomplex PLA particles: An effective system to support mucolytic enzymes

In this work, the preparation of a novel enzyme carrier based on a polymer multicomponent system was assessed. Indeed, the design of the above system considered several issues that are the need of applying a biodegradable polymer carrier, characterized by a nanometric dimension, thus suitable to diffuse into the dense mucus structure, with functionalities capable of interacting/reacting with enzymes but resistant to enzymatic degradation. The particles were prepared from solutions containing equimolar amount of high-molecular-weight poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) and by applying the nanoprecipitation method. Dynamic Light Scattering (DLS) measurements allowed to establish the optimal preparation conditions to obtain polymer particles characterized by diameters lower than 1 μm, which dimensions were confirmed by Field Emission Scanning Electron Microscope (FE-SEM) analysis. In order to produce surface functionalization, necessary for anchoring enzymes, the stereocomplexed particles, whose structuration was confirmed by Differential Scanning Calorimetry (DSC) measurements, underwent an amminolysis reaction by using a diamine as reactant. The treated particles were characterized by means of FE-SEM, Fourier-Transform Infrared Spectroscopy (FTIR), DLS and zeta potential measurements and their characteristics were compared with those of the neat PLLA/PDLA particles. The degree of functionalization turned out to depend on the applied conditions, it increasing by enhancing the reaction time. The activity of enzymes, i.e. papain and alginate lyase, anchored to the particles, was evaluated by Quartz Crystal Microbalance (QCM) and UV measurements. Moreover, with the aim at exploiting the material for an inhalation administration, a method to encapsulate the enzyme-particles systems was assessed. Conversely to free enzymes, the developed systems were found to be capable of diminishing the viscosity of two hydrogels, ad hoc prepared and based on the main constituents of the real mucus.

Self-emulsifying drug delivery system: Mucus permeation and innovative quantification technologies

Mucus is a dynamic barrier which covers and protects the underlying mucosal epithelial membrane against bacteria and foreign particles. This protection mechanism extends to include therapeutic macromolecules and nanoparticles (NPs) through trapping of these particles. Mucus is not only a physical barrier that limiting particles movements based on their sizes but it selectively binds with particles through both hydrophilic and lipophilic interactions. Therefore, nano-carriers for mucosal delivery should be designed to eliminate entrapment by the mucus barrier. For this reason, different strategies have been approached for both solid nano-carriers and liquid core nano-carriers to synthesise muco-diffusive nano-carrier. Among these nano-strategies, Self-Emulsifying Drug Delivery System (SEDDS) was recognised as very promising nano-carrier for mucus delivery. The system was introduced to enhance the dissolution and bioavailability of orally administered insoluble drugs. SEDDS has shown high stability against intestinal enzymatic activity and more importantly, relatively rapid permeation characteristics across mucus barrier. The high diffusivity of SEDDS has been tested using various in vitro measurement techniques including both bulk and individual measurement of droplets diffusion within mucus. The selection and processing of an optimum in vitro technique is of great importance to avoid misinterpretation of the diffusivity of SEDDS through mucus barrier. In conclusion, SEDDS is a system with high capacity to diffuse through intestinal mucus even though this system has not been studied to the same extent as solid nano-carriers.

Efficacy and safety concerns over the use of mucus modulating agents for drug delivery using nanoscale systems

Drug delivery to the mucus covered mucosae is fraught with difficulties and many different approaches have been developed to permeate the mucus barrier. Generally by modifying the delivery system to avoid interaction with the mucus. These modifications are reviewed here in terms of efficacy and safety. These are particular problems for oral delivery the pharmaceutical industry's favoured route for drug administration. For effective delivery through the gastrointestinal tract a drug must pass through three barriers in sufficient amounts to yield a biological effect. These barriers are the digestive barrier in the lumen, the mucus barrier, and the epithelial barrier. Other approaches involve mucolytic agents added with or prior to the delivery system or agents regulating mucus production and are reviewed here. In terms of safety, a key property of a mucus modulating delivery system is that it must not damage the protective function of the mucus layer.

Enzyme decorated drug carriers: Targeted swords to cleave and overcome the mucus barrier

The use of mucus permeating drug carrier systems being able to overcome the mucus barrier can lead to a remarkable enhancement in bioavailability. One promising approach is the design of mucolytic enzyme decorated carrier systems (MECS). These systems include micro- and nanoparticles as well as self-emulsifying drug delivery systems (SEDDS) decorated with mucin cleaving enzymes such as papain (PAP) or bromelain (BRO). MECS are able to cross the mucus barrier in a comparatively efficient manner by cleaving mucus substructures in front of them on their way to the epithelium. Thereby these enzymes hydrolyze peptide bonds of mucus glycoproteins forming tiny holes or passages through the mucus. In various in vitro and in vivo studies MECS proved to be superior in their mucus permeating properties over nanocarriers without enzyme decoration. PAP decorated nanoparticles, for instance, remained 3h after oral administration to an even 2.5-fold higher extend in rat small intestine than the corresponding undecorated nanoparticles permeating the intestinal mucus gel layer to a much lower degree. As MECS break up the mucus network only locally without destroying its overall protective barrier function, even long term treatments with such systems seem feasible. Within this review article we address different drug carrier systems decorated with various types of enzymes, their particular pros and cons and potential applications.

Beyond PEGylation: Alternative surface-modification of nanoparticles with mucus-inert biomaterials

Mucus is a highly hydrated viscoelastic gel present on various moist surfaces in our body including the eyes, nasal cavity, mouth, gastrointestinal, respiratory and reproductive tracts. It serves as a very efficient barrier that prevents harmful particles, viruses and bacteria from entering the human body. However, the protective function of the mucus also hampers the diffusion of drugs and nanomedicines, which dramatically reduces their efficiency. Functionalisation of nanoparticles with low molecular weight poly(ethylene glycol) (PEGylation) is one of the strategies to enhance their penetration through mucus. Recently a number of other polymers were explored as alternatives to PEGylation. These alternatives include poly(2-alkyl-2-oxazolines), polysarcosine, poly(vinyl alcohol), other hydroxyl-containing non-ionic water-soluble polymers, zwitterionic polymers (polybetaines) and mucolytic enzymes. This review discusses the studies reporting the use of these polymers or potential application to facilitate mucus permeation of nanoparticles.

Engineering nanomaterials to overcome the mucosal barrier by modulating surface properties

Although nanotechnology has been investigated during recent years to increase the bioavailability and therapeutic effects of mucosal administrated drugs, numerous barriers (e.g., pH environment, enzymes and mucus) still limit the delivery efficiency. And the epithelium would also affect the systemic mucosal drug delivery. Amongst all the barriers, the protective mucus has drawn more and more attention, which strongly hinders the accessibility of nanovehicles to epithelium. Therefore, trials to conquer the mucus barrier have been designed using two controversial strategies: mucoadhesion and mucus-penetration. This review summarizes the influence of mucus layer on nanomaterials and introduces the modification strategies by modulating surface properties (i.e., hydrophilicity/hydrophobicity and surface charge) to overcome mucus barriers. Furthermore, it also reviews advanced modification methods to meet the different surface requirements of nanovehicles to overcome mucus and epithelium barriers in systemic mucosal delivery.

The role of mucus as an invisible cloak to transepithelial drug delivery by nanoparticles

Mucosal administration of drugs and drug delivery systems has gained increasing interest. However, nanoparticles intended to protect and deliver drugs to epithelial surfaces require transport through the surface-lining mucus. Translation from bench to bedside is particularly challenging for mucosal administration since a variety of parameters will influence the specific barrier properties of the mucus including the luminal fluids, the microbiota, the mucus composition and clearance rate, and the condition of the underlying epithelia. Besides, after administration, nanoparticles interact with the mucosal components, forming a biomolecular corona that modulates their behavior and fate after mucosal administration. These interactions are greatly influenced by the nanoparticle properties, and therefore different designs and surface-engineering strategies have been proposed. Overall, it is essential to evaluate these biomolecule-nanoparticle interactions by complementary techniques using complex and relevant mucus barrier matrices.

Mucus-penetrating solid lipid nanoparticles for the treatment of cystic fibrosis: Proof of concept, challenges and pitfalls

Nanocarrier-mediated transmucosal drug delivery based on conventional mucoadhesive, muco-inert or mucus-penetrating nanoparticles (NPs) is a growing field especially in challenging diseases like cystic fibrosis (CF). Efficacy of such systems dictates profound investigation of particle-mucus interaction and factors governing the whole process. Although variable techniques studying particle diffusion in mucus have been introduced, standardized procedures are lacking. The study comprised different methods based on micro- and macro-displacement as well as colloidal stability and turbidimetric experiments. Artificial sputum medium (ASM), CF sputum and mucus-secreting cell line (Calu-3 air interface culture, AIC) were applied. Solid lipid nanoparticles (SLNs) coated with variable hydrophilic sheath (poloxamer, Tween 80 or PVA) represented the nanocarriers under investigation. Both micro-displacement studies based on single particle tracking and macro-displacement experiments based on 3D-time laps confocal imaging revealed faster diffusion of poloxamer- > Tween- > PVA-coated SLNs. Compared to ASM, CF sputum showed not only lower diffusion rates but also remarkable discrepancies in particle-mucus diffusion rate due to sputum heterogenicity. Meanwhile, in case of Calu-3 AIC, thickness of the mucosal layer as well as density of mucus network were key determinants in the diffusion process. The points emphasized in this study highlight the road towards in vivo relevant particle-mucus interaction research.

Mucopenetrating micelles with a PEG corona

Crossing the intestinal mucus layer is a long-standing challenge for orally delivered nanoparticles carrying therapeutic cargo. We report the assembly of mucopenetrating cargo-loaded micelles using block copolymers consisting of either linear poly(ethylene glycol) (PEG) or bottle-brush poly(oligo(ethylene glycol)methacrylate) (PEG_b) as the hydrophilic block and poly(caprolactone) (PCL) or poly(cholesteryl methacrylate) (PCMA) as the hydrophobic extension. The micelles were shown to preserve their stability and retain ∼50% of their cargo in simulated gastric fluid. The ability of micelles to diffuse through reconstituted porcine mucus was assessed in a microfluidic set-up. Finally, the delivery of Nile Red as a hydrophobic model cargo across a mucus layer produced by epithelial cells was demonstrated. These engineered mucopenetrating micelles have potential to be developed into efficient absorption enhancers, contributing a nanotechnology solution to oral drug delivery.

Mucus permeating self-emulsifying drug delivery systems (SEDDS): About the impact of mucolytic enzymes

This study aimed to improve the mucus permeating properties of self-emulsifying drug delivery systems (SEDDS) by anchoring lipidized bromelain, papain and trypsin using palmitoyl chloride. SEDDS containing enzyme-palmitate conjugates were characterized regarding droplet size and zeta potential. Their mucus permeating properties were evaluated by Transwell diffusion and rotating tube method using fluorescein diacetate (FDA) as marker. Degree of substitution of modified enzymes was 35.3%, 47.8% and 38.5% for bromelain-palmitate, papain-palmitate and trypsin-palmitate, respectively. SEDDS as control and SEDDS containing enzyme-palmitate conjugates displayed a droplet size less than 50nm and 180-312nm as well as a zeta potential of -3 to -4 and -4 to -5mV, respectively. The highest percentage of permeation was achieved by introducing 5% papain-palmitate into SEDDS. It could enhance the mucus permeation of SEDDS in porcine intestinal mucus 4.6-fold and 2-fold as evaluated by Transwell diffusion and rotating tube method, respectively. It is concluded that mucus permeation of SEDDS can be strongly improved by incorporation of enzyme-palmitate conjugates.

Protease-functionalized mucus penetrating microparticles: In-vivo evidence for their potential

The focus of the current study was to explore whether immobilization of proteases to microparticles could result in their enhanced penetration into mucus. The proteases papain (PAP) and bromelain (BROM) were covalently attached to a polyacrylate (PAA; Carbopol 971P) via amide bond formation based on carbodiimide reaction. Microparticles containing these conjugates were generated via ionic gelation with calcium chloride and were characterized regarding size, surface charge, enzymatic activity and fluorescein diacetate (FDA) loading efficiency. Furthermore, mucus penetration potential of these microparticles was evaluated in-vitro on freshly collected porcine intestinal mucus, on intact intestinal mucosa and in-vivo in Sprague-Dawley rats. Results showed mean diameter of microparticles ranging between 2-3μm and surface charge between -8 to -18mV. The addition of PAA-microparticles to porcine intestinal mucus led to a 1.39-fold increase in dynamic viscosity whereas a 3.10- and 2.12-fold decrease was observed in case of PAA-PAP and PAA-BROM microparticles, respectively. Mucus penetration studies showed a 4.27- and 2.21- fold higher permeation of FDA loaded PAA-PAP and PAA-BROM microparticles as compared to PAA microparticles, respectively. Extent of mucus diffusion determined via silicon tube assay illustrated 3.96- fold higher penetration for PAA-PAP microparticles and 1.99- fold for PAA-BROM microparticles. An in-vitro analysis on porcine intestinal mucosa described up to 16- and 7.35-fold higher degree of retention and furthermore, during in-vivo evaluation in Sprague-Dawley rats a 3.35- and 2.07-fold higher penetration behavior was observed in small intestine for PAA-PAP and PAA-BROM microparticles as compared to PAA microparticles, respectively. According to these results, evidence for microparticles decorated with proteases in order to overcome the mucus barrier and to reach the absorption lining has been provided that offers wide ranging applications in mucosal drug delivery.

Thermoresponsive Elastin-b-Collagen-Like Peptide Bioconjugate Nanovesicles for Targeted Drug Delivery to Collagen-Containing Matrices

Over the past few decades, (poly)peptide block copolymers have been widely employed in generating well-defined nanostructures as vehicles for targeted drug delivery applications. We previously reported the assembly of thermoresponsive nanoscale vesicles from an elastin-b-collagen-like peptide (ELP-CLP). The vesicles were observed to dissociate at elevated temperatures, despite the LCST-like behavior of the tethered ELP domain, which is suggested to be triggered by the unfolding of the CLP domain. Here, the potential of using the vesicles as drug delivery vehicles for targeting collagen-containing matrices is evaluated. The sustained release of an encapsulated model drug was achieved over a period of 3 weeks, following which complete release could be triggered via heating. The ELP-CLP vesicles show strong retention on a collagen substrate, presumably through collagen triple helix interactions. Cell viability and proliferation studies using fibroblasts and chondrocytes suggest that the vesicles are highly cytocompatible. Additionally, essentially no activation of a macrophage-like cell line is observed, suggesting that the vesicles do not initiate an inflammatory response. Endowed with thermally controlled delivery, the ability to bind collagen, and excellent cytocompatibility, these ELP-CLP nanovesicles are suggested to have significant potential in the controlled delivery of drugs to collagen-containing matrices and tissues.