Impact of Absorption and Transport on Intelligent Therapeutics and Nano-scale Delivery of Protein Therapeutic Agents

Recent Advances in Micro- and Nano-Drug Delivery Systems Based on Natural and Synthetic Biomaterials

Polymeric drug delivery technology, which allows for medicinal ingredients to enter a cell more easily, has advanced considerably in recent decades. Innovative medication delivery strategies use biodegradable and bio-reducible polymers, and progress in the field has been accelerated by future possible research applications. Natural polymers utilized in polymeric drug delivery systems include arginine, chitosan, dextrin, polysaccharides, poly(glycolic acid), poly(lactic acid), and hyaluronic acid. Additionally, poly(2-hydroxyethyl methacrylate), poly(N-isopropyl acrylamide), poly(ethylenimine), dendritic polymers, biodegradable polymers, and bioabsorbable polymers as well as biomimetic and bio-related polymeric systems and drug-free macromolecular therapies have been employed in polymeric drug delivery. Different synthetic and natural biomaterials are in the clinical phase to mitigate different diseases. Drug delivery methods using natural and synthetic polymers are becoming increasingly common in the pharmaceutical industry, with biocompatible and bio-related copolymers and dendrimers having helped cure cancer as drug delivery systems. This review discusses all the above components and how, by combining synthetic and biological approaches, micro- and nano-drug delivery systems can result in revolutionary polymeric drug and gene delivery devices.

Engineered Skin Tissue Equivalents for Product Evaluation and Therapeutic Applications

The current status of skin tissue equivalents that have emerged as relevant tools in commercial and therapeutic product development applications is reviewed. Due to the rise of animal welfare concerns, numerous companies have designed skin model alternatives to assess the efficacy of pharmaceutical, skincare, and cosmetic products in an in vitro setting, decreasing the dependency on such methods. Skin models have also made an impact in determining the root causes of skin diseases. When designing a skin model, there are various chemical and physical considerations that need to be considered to produce a biomimetic design. This includes designing a structure that mimics the structural characteristics and mechanical strength needed for tribological property measurement and toxicological testing. Recently, various commercial products have made significant progress towards achieving a native skin alternative. Further research involve the development of a functional bilayered model that mimics the constituent properties of the native epidermis and dermis. In this article, the skin models are divided into three categories: in vitro epidermal skin equivalents, in vitro full-thickness skin equivalents, and clinical skin equivalents. A description of skin model characteristics, testing methods, applications, and potential improvements is presented.

Guiding protein delivery into live cells using DNA-programmed membrane fusion

Intracellular delivery of proteins provides a direct means to manipulate cell function and probe the intracellular environment. However, direct cytoplasmic delivery of proteins suffers from limited availability of efficient toolsets, and thus remains challenging in research and therapeutic applications. Natural biological cargo delivery processes, like SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complex mediated membrane fusion and other vesicle fusion in live cells, enable targeted delivery with high efficiency. A surrogate of SNARE machinery represents a new direction in intracellular protein delivery. Here, we report a DNA-programmed membrane fusion strategy for guiding the efficient intracellular delivery of proteins into live cells. The inherent programmability of DNA hybridization provides spatiotemporal control of the fusion between protein-encapsulated liposomes and cell membranes, enabling rapid release of proteins directly into the cytoplasm, while still remaining functional due to the bypassing of the endosomal trap. We further demonstrate that delivered exogenous Cytochrome c effectively regulates the cell fate. Hence, this DNA-mediated fusion strategy holds great potential for protein drug delivery, regenerative medicine and gene editing.

Fab on a Package: LTCC Microfluidic Devices Applied to Chemical Process Miniaturization

Microfluidics has brought diverse advantages to chemical processes, allowing higher control of reactions and economy of reagents and energy. Low temperature co-fired ceramics (LTCC) have additional advantages as material for fabrication of microfluidic devices, such as high compatibility with chemical reagents with typical average surface roughness of 0.3154 μm, easy scaling, and microfabrication. The conjugation of LTCC technology with microfluidics allows the development of micrometric-sized channels and reactors exploiting the advantages of fast and controlled mixing and heat transfer processes, essential for the synthesis and surface functionalization of nanoparticles. Since the chemical process area is evolving toward miniaturization and continuous flow processing, we verify that microfluidic devices based on LTCC technology have a relevant role in implementing several chemical processes. The present work reviews various LTCC microfluidic devices, developed in our laboratory, applied to chemical process miniaturization, with different geometries to implement processes such as ionic gelation, emulsification, nanoprecipitation, solvent extraction, nanoparticle synthesis and functionalization, and emulsion-diffusion/solvent extraction process. All fabricated microfluidics structures can operate in a flow range of mL/min, indicating that LTCC technology provides a means to enhance micro- and nanoparticle production yield.

Nasal drug delivery: Design of a novel mucoadhesive and in situ gelling polymer

The aim of the present study was to establish a novel polymeric excipient for liquid nasal dosage forms exhibiting viscosity increasing properties, improved mucoadhesion and stability towards oxidation in solution. In order to achieve this goal, 2-mercaptonicotinic acid was first coupled to l-cysteine by disulfide exchange reaction and after purification directly attached to the polymeric backbone of xanthan gum by carbodiimide mediated amide bond formation. The resulting conjugate was characterized with respect to the amount of coupled ligand, the in situ gelling behavior, mucoadhesive properties and stability towards oxidation. Furthermore, the influence of preactivated polymers on ciliary beat frequency (CBF) of porcine nasal epithelial cells was investigated. Results showed, that 252.52±20.54μmol of the ligand was attached per gram polymer. No free thiol groups could be detected on the polymeric backbone indicating entire preactivation. Rheological investigations of polymer mucus mixtures revealed a 1.7-fold and 2.5-fold enhanced mucoadhesion of entirely preactivated xanthan (Xan-Cys-MNA) compared to thiolated xanthan (Xan-Cys) and unmodified xanthan (Xan). Tensile force evaluation reported a 2.87 and 5.11-fold higher total work of adhesion (TWA) as well as a 1.63 and 2.41-fold higher maximum detachement force of Xan-Cys-MNA compared to Xan-Cys and Xan. In the presence of H₂O₂ as an oxidizing agent Xan-Cys-MNA showed unlike Xan-Cys no increase in viscosity, indicating high stability towards oxidation. Addition of CaCl₂ to Xan-Cys-MNA solutions caused a decrease in viscosity at nevertheless higher total viscosity. Results from CBF studies proved nasal safety for the novel conjugate. According to these results, entirely preactivated thiolated xanthan gum seems to be a promising excipient for nasal dosage forms in order to improve drug bioavailability.

Biomedical microelectromechanical systems (BioMEMS): Revolution in drug delivery and analytical techniques

Advancement in microelectromechanical system has facilitated the microfabrication of polymeric substrates and the development of the novel class of controlled drug delivery devices. These vehicles have specifically tailored three dimensional physical and chemical features which together, provide the capacity to target cell, stimulate unidirectional controlled release of therapeutics and augment permeation across the barriers. Apart from drug delivery devices microfabrication technology’s offer exciting prospects to generate biomimetic gastrointestinal tract models. BioMEMS are capable of analysing biochemical liquid sample like solution of metabolites, macromolecules, proteins, nucleic acid, cells and viruses. This review summarized multidisciplinary application of biomedical microelectromechanical systems in drug delivery and its potential in analytical procedures.

Impact of the in vitro gastrointestinal passage of biopolymer-based nanoparticles on insulin absorption

Behavior of insulin-loaded biopolymer-based nanoparticles upon passage through the gastrointestinal tract. Intestinal pH triggered insulin release from nanoparticles, allowing its permeability through cell-based engineered intestinal models.

Core–shell stability of nanoparticles plays an important role for overcoming the intestinal mucus and epithelium barrier

The stability of the core–shell structure plays an important role in the nanoparticles ability to overcome both the mucus and epithelium absorption barrier.

Hybrid responsive hydrogel carriers for oral delivery of low molecular weight therapeutic agents

Hydrogels have been influential in the development of controlled release systems for a wide variety of therapeutic agents. These materials are attractive as carriers for transmucosal and intracellular drug delivery because of their inherent biocompatibility, tunable physicochemical properties, basic synthesis, and ability to be physiologically responsive. Due to their hydrophilic nature, hydrogel-based carrier systems are not always the best systems for delivery of small molecular weight, hydrophobic therapeutic agents. In this work, versatile hydrogel-based carriers composed of copolymers of methyl methacrylate (MMA) and acrylic acid (AA) were designed and synthesized to create formulations for oral delivery of small molecular weight therapeutic agents. Through practical material selection and careful design of copolymer composition and molecular architecture, we engineered systems capable of responding to physiological changes, with tunable physicochemical properties that are optimized to load, protect, and deliver their payloads to their intended site of action. The synthesized carriers' ability to respond to changes in pH, to load and release small molecular weight drugs, and biocompatibility were investigated. Our results suggest these hydrophilic networks have great potential for controlled delivery of small-molecular weight, hydrophobic and hydrophilic agents.

Goblet cell targeting nanoparticle containing drug-loaded micelle cores for oral delivery of insulin

Oral administration of insulin remains a challenge due to its poor enzymatic stability and inefficient permeation across epithelium. We herein developed a novel self-assembled polyelectrolyte complex nanoparticles by coating insulin-loaded dodecylamine-graft-γ-polyglutamic acid micelles with trimethyl chitosan (TMC). The TMC material was also conjugated with a goblet cell-targeting peptide to enhance the affinity of nanoparticles with epithelium. The developed nanoparticle possessed significantly enhanced colloid stability, drug protection ability and ameliorated drug release profile compared with graft copolymer micelles or ionic crosslinked TMC nanoparticles. For in vitro evaluation, Caco-2/HT29-MTX-E12 cell co-cultures, which composed of not only enterocyte-like cells but also mucus-secreting cells and secreted mucus layer, were applied to mimic the epithelium. Intracellular uptake and transcellular permeation of encapsulated drug were greatly enhanced for NPs as compared with free insulin or micelles. Goblet cell-targeting modification further increased the affinity of NPs with epithelium with changed cellular internalization mechanism. The influence of mucus on the cell uptake was also investigated. Ex vivo performed with rat mucosal tissue demonstrated that the nanoparticle could facilitate the permeation of encapsulated insulin across the intestinal epithelium. In vivo study preformed on diabetic rats showed that the orally administered nanoparticles elicited a prolonged hypoglycemic response with relative bioavailability of 7.05%.

Self-emulsifying drug delivery systems in oral (poly)peptide drug delivery

INTRODUCTION

Oral administration of most therapeutic peptides and proteins is mainly restricted due to the enzymatic and absorption membrane barrier of the GI tract. In order to overcome these barriers, various technologies have been explored. Among them, self-emulsifying drug delivery systems (SEDDS) received considerable attention as potential carriers to facilitate oral peptide and protein delivery in recent years.

AREAS COVERED

This review article intends to summarize physiological barriers which limit the bioavailability of orally administrated peptide and protein drugs. Furthermore, the potential of SEDDS to protect incorporated peptides and proteins towards peptidases and proteases and to penetrate the mucus layer is reviewed. Their permeation-enhancing properties and their ability to release the drug in a controlled way are described. Moreover, this review covers the results of in vivo studies providing evidence for this promising approach.

EXPERT OPINION

As SEDDS can: i) provide a protective effect towards a presystemic metabolism; ii) efficiently permeate the intestinal mucus gel layer in order to reach the absorption membrane; and iii) be produced in a very simple and cost-effective manner, they are a promising tool for oral peptide and protein drug delivery.

Penetratin derivative-based nanocomplexes for enhanced intestinal insulin delivery

Sufficient mucosal permeability is the bottleneck problem in developing an efficient intestinal delivery system of insulin. Cell-penetrating peptide-based nanocomplexes for the enhanced mucosal permeation of insulin were developed in this study. Penetratin, a cell-penetrating peptide was site-specifically modified with a bis-β-cyclodextrin group. Insulin-loaded nanocomplexes were prepared by self-assembly using penetratin or its bis-β-cyclodextrin modified derivative (P-bis-CD). A stronger intermolecular interaction and higher complex stability were observed for P-bis-CD nanocomplexes than the penetratin nanocomplexes. P-bis-CD nanocomplexes were significantly more efficient for the permeation of insulin as compared to the penetratin nanocomplexes both in vitro and in situ. Interestingly, different cellular internalization mechanisms were observed for the two nanocomplexes. In diabetic rats, intestinal administration of P-bis-CD nanocomplexes resulted in a prominent hypoglycemic effect which lasted for 6 h with maximum inhibitory rate at 60%. The relative pharmacological availability and bioavailability of P-bis-CD nanocomplexes were 10.6% and 7.1%, which were 3.0-fold and 2.3-fold higher than that of penetratin nanocomplexes, respectively. In addition, no sign of toxicity was observed after 7 consecutive days of administration of P-bis-CD nanocomplexes with endotoxin. These results demonstrated that P-bis-CD was a promising epithelium permeation enhancer for insulin and suggested that the chemical modification of cell penetration peptides was a feasible strategy to enhance their potential.

Enhanced bioavailability of poorly absorbed hydrophilic compounds through drug complex/in situ gelling formulation

BCS class III hydrophilic compounds are often associated with low oral bioavailability due to their poor epithelial permeability in the gastrointestinal tract. In this study, we reported an approach of incorporating a drug complex into an in situ gelling muco-adhesive carrier to achieve an improved bioavailability of a poorly absorbed hydrophilic compound. A new molecular entity (RWJ-445167) from Johnson and Johnson was used as a model compound. The compound was first complexed with sodium lauryl sulfate (SLS). The complex was then incorporated into an in situ gelling muco-adhesive carrier Cremophor for formulation characterization and rat pharmacokinetic (PK) studies. The study results showed that RWJ-445167 bound to SLS at a stoichiometric ratio. By complexing with SLS, the compound became lipophilic. The aqueous solubility of RWJ-445167 dropped to 0.58 mg/mL for the complex from 61 mg/mL for the free compound, while the partitioning coefficient of the complex increased to 7.59, compared with 0.05 of the free compound. In the rat PK study, with duodenal administration, the complex in the in situ-gelling formulation achieved 28.24% of bioavailability, compared to 4.26% of the free compound solution. The enhanced bioavailability was also significantly higher than those in the RWJ-445167/SLS physical mixture in Cremophor (14.91%), the complex in non-gelling carrier PEG 400 (9.95%) and the RWJ-445167/SLS physical mixture in PEG 400 carrier (8.60%). The study demonstrates that incorporation of a drug complex into an in situ gelling formulation provides a new approach to improving bioavailability of BCS class III drugs.

Microfabrication technologies for oral drug delivery

Micro-/nanoscale technologies such as lithographic techniques and microfluidics offer promising avenues to revolutionalize the fields of tissue engineering, drug discovery, diagnostics and personalized medicine. Microfabrication techniques are being explored for drug delivery applications due to their ability to combine several features such as precise shape and size into a single drug delivery vehicle. They also offer to create unique asymmetrical features incorporated into single or multiple reservoir systems maximizing contact area with the intestinal lining. Combined with intelligent materials, such microfabricated platforms can be designed to be bioadhesive and stimuli-responsive. Apart from drug delivery devices, microfabrication technologies offer exciting opportunities to create biomimetic gastrointestinal tract models incorporating physiological cell types, flow patterns and brush-border like structures. Here we review the recent developments in this field with a focus on the applications of microfabrication in the development of oral drug delivery devices and biomimetic gastrointestinal tract models that can be used to evaluate the drug delivery efficacy.

Intestinal patches with an immobilized solid-in-oil formulation for oral protein delivery

Oral administration of biomolecular drugs such as peptides, proteins, and DNA is an attractive delivery method because of the safety and convenience of delivery in contrast to injection administration. However, oral delivery of biomolecules has several potential barriers such as enzymatic degradation in the gastrointestinal tract and low permeability across an intestinal membrane. In this study, we proposed an intestinal patch system that included surfactant-coated insulin for oral delivery. The intestinal patches, which have mucoadhesive and drug-impermeable layers, induced sustained unidirectional insulin release toward intestinal mucosa and inhibition of insulin leakage from the patches. Moreover, the surfactant-coated insulin, which has high compatibility with cell membranes, enhanced insulin transport across the intestinal membrane. This study demonstrates that the intestinal patches might improve protein permeability in the intestinal mucosa, thereby offering an innovative therapeutic strategy.

Tissue engineered human skin equivalents

Human skin not only serves as an important barrier against the penetration of exogenous substances into the body, but also provides a potential avenue for the transport of functional active drugs/reagents/ingredients into the skin (topical delivery) and/or the body (transdermal delivery). In the past three decades, research and development in human skin equivalents have advanced in parallel with those in tissue engineering and regenerative medicine. The human skin equivalents are used commercially as clinical skin substitutes and as models for permeation and toxicity screening. Several academic laboratories have developed their own human skin equivalent models and applied these models for studying skin permeation, corrosivity and irritation, compound toxicity, biochemistry, metabolism and cellular pharmacology. Various aspects of the state of the art of human skin equivalents are reviewed and discussed.

The oral delivery of proteins using interpolymer polyelectrolyte complexes

In spite of the numerous barriers inherent in the oral delivery of therapeutically active proteins, research into the development of functional protein-delivery systems is still intense. The effectiveness of such oral protein-delivery systems depend on their ability to protect the incorporated protein from proteolytic degradation in the GI tract and enhance its intestinal absorption without significantly compromising the bioactivity of the protein. Among these delivery systems are polyelectrolyte complexes (PECs) which are composed of polyelectrolyte polymers complexed with a protein via coulombic and other interactions. This review will focus on the current status of PECs with a particular emphasis on the potential and limitations of multi- or inter-polymer PECs used to facilitate oral protein delivery.

Facilitated nanoscale delivery of insulin across intestinal membrane models

The effect of nanoparticulate delivery system on enhancing insulin permeation through intestinal membrane was evaluated in different intestinal epithelial models using cell cultures and excised intestinal tissues. Multilayered nanoparticles were formulated by encapsulating insulin within a core consisting of alginate and dextran sulfate nucleating around calcium and binding to poloxamer, stabilized by chitosan, and subsequently coated with albumin. Insulin permeation through Caco-2 cell monolayer was enhanced 2.1-fold, facilitated by the nanoparticles compared with insulin alone, 3.7-fold through a mucus-secreting Caco-2/HT29 co-culture, and 3.9-fold through excised intestinal mucosa of Wistar rats. Correlation of Caco-2/HT29 co-culture cells with the animal-model intestinal membrane demonstrates that the mucus layer plays a significant role in determining the effectiveness of oral nanoformulations in delivering poorly absorbed drugs. Albumin was applied to the nanoparticles as outermost coat to protect insulin through shielding from proteolytic degradation. The effect of the albumin layering on insulin permeation was compared with albumin-free nanoparticles that mimic the result of albumin being enzymatically removed during gastric and intestinal transport. Results showed that albumin layering is important toward improving insulin transport across the intestinal membrane, possibly by stabilizing insulin in the intestinal conditions. Transcellular permeation was evidenced by internalization of independently labeled insulin and nanoparticles into enterocytes, in which insulin appeared to remain associated with the nanoparticles. Transcellular transport of insulin through rat intestinal mucosa may represent the predominant mechanism by which nanoparticles facilitate insulin permeation. Nanoformulations demonstrated biocompatibility with rat intestinal mucosa through determination of cell viability via monitoring of mitochondrial dehydrogenases. Insulin permeation facilitated by the biocompatible nanoparticles suggests a potential carrier system in delivering protein-based drugs by the oral route.

Topical and mucosal liposomes for vaccine delivery

Mucosal (and in minor extent transcutanous) stimulation can induce local or distant mucosa secretory IgA. Liposomes and other vesicles as mucosal and transcutaneous adjuvants are attractive alternatives to parenteral vaccination. Liposomes can be massively produced under good manufacturing practices and stored for long periods, at high antigen/vesicle mass ratios. However, their uptake by antigen-presenting cells (APC) at the inductive sites remains as a major challenge. As neurotoxicity is a major concern in intranasal delivery, complexes between archaeosomes and calcium as well as cationic liposomes complexed with plasmids encoding for antigenic proteins could safely elicit secretory and systemic antigen-specific immune responses. Oral bilosomes generate intense immune responses that remain to be tested against challenge, but the admixing with toxins or derivatives is mandatory to reduce the amount of antigen. Most of the current experimental designs, however, underestimate the mucus blanket 100- to 1000-fold thicker than a 100-nm diameter liposome, which has first to be penetrated to access the underlying M cells. Overall, designing mucoadhesive chemoenzymatic resistant liposomes, or selectively targeted to M cells, has produced less relevant results than tailoring the liposomes to make them mucus penetrating. Opposing, the nearly 10 µm thickness stratum corneum interposed between liposomes and underlying APC can be surpassed by ultradeformable liposomes (UDL), with lipid matrices that penetrate up to the limit with the viable epidermis. UDL made of phospholipids and detergents, proved to be better transfection agents than conventional liposomes and niosomes, without the toxicity of ethosomes, in the absence of classical immunomodulators.

Nanocarriers for pulmonary administration of peptides and therapeutic proteins

Peptides and therapeutic proteins have been the target of intense research and development in recent years by the pharmaceutical and biotechnology industry. Preferably, they are administered through the parenteral route, which is associated with reduced patient compliance. Formulations for noninvasive administration of peptides and therapeutic proteins are currently being developed. Among them, inhalation appears as a promising alternative for the administration of such products. Several formulations for pulmonary delivery are in various stages of development. Despite positive results, conventional formulations have some limitations such as reduced bioavailability and side effects. Nanocarriers may be an alternative way to overcome the problems of conventional formulations. Some nanocarrier-based formulations of peptides and therapeutic proteins are currently under development. The results obtained are promising, revealing the usefulness of these systems in the delivery of such drugs.