Targeting the intestinal lymphatic system: a versatile path for enhanced oral bioavailability of drugs

Thoracic lymph collection impacts the level of endogenous macromolecules in rat biological fluids

Lymph collection via insertion of a cannula into a lymphatic vessel is the most commonly used procedure to quantify the transport of pharmaceutical agents into lymph following administration to rodents. Further, lymph is derived from interstitial fluid draining specific organs and tissues such that compositional analysis of lymph collected via cannulation can provide useful information about biochemical and immune cell changes in different patho/physiological states, as well as being a resource for biomarker discovery. Nevertheless, lymph cannulation is a challenging procedure, and continuous collection of lymph for extended periods can lead to lymphocytopenia. Just as important, prolonged lymph collection might deplete other major components in lymph and plasma such as proteins and lipids, yet this has not been reported previously. Therefore, we investigated the effect of thoracic lymph collection in rats on the concentration of protein components (e.g. albumin) and specific lipids (total cholesterol and triglycerides) in lymph and plasma over time for 48 h after lymph cannulation. This study suggests that the level of total protein and albumin, but not lipids, is diminished over time during thoracic lymph collection in rats. We also provide evidence that this depletion impacts the pharmacokinetics of a drug delivery carrier that binds to albumin and lipoproteins. These findings present an important consideration to evaluating the lymphatic transport and pharmacokinetics of pharmaceutical agents that interact with endogenous proteins such as albumin.

Barriers and Strategies for Oral Peptide and Protein Therapeutics Delivery: Update on Clinical Advances

Peptide and protein (PP) therapeutics are highly specific and potent biomolecules that treat chronic and complex diseases. However, their oral delivery is significantly hindered by enzymatic degradation, instability, and poor permeability through the gastrointestinal (GI) epithelium, resulting in low bioavailability. Various strategies have emerged as transformative solutions to address existing challenges, offering enhanced protection, stabilization, and absorption of PPs. These strategies primarily focus on two major challenges: protecting the PP against harsh conditions and enhancing permeation across the intestinal membrane. Innovative approaches such as pH modulation and incorporation of enzyme inhibitors are usually used to mitigate proteolytic degradation of PP during transit across the GI tract. In a similar vein, absorption enhancers and prodrug strategies facilitate epithelial transport, while targeted delivery systems focus on specific areas of the GI tract to enhance absorption. Likewise, mucus-penetrating and mucoadhesive strategies have enhanced retention and interaction with epithelial cells, effectively overcoming barriers like the mucus layer and tight epithelial junctions. Furthermore, structural modifications such as lipidation, peptide cyclization, and polyethylene glycosylation are promising alternatives to render stability, prolong circulation time, and membrane permeability. In particular, functional biomaterials, active targeting, and lymphatic transport strategies have provided new platforms for oral PP delivery. Advancing in materials science, nanotechnology, and the disruption of medical devices holds new frontiers to overcome barriers. Despite substantial advancements, the limited success in clinical translation underscores the urgency of innovative strategies. This review presents oral PPs as a promising platform, highlighting the key barriers and strategies to transform their therapeutic landscapes.

Glucuronidation of orally administered drugs and the value of nanocarriers in strategies for its overcome

The gastrointestinal tract (GIT) plays a pivotal role in the absorption of orally administered drugs, with the small intestine serving as the primary site due to its extensive surface area and specialized cell types, including enterocytes and M cells. After oral administration, drugs are generally transported via the portal vein to the liver, where they undergo first-pass metabolism. This process involves various enzymatic reactions, including glucuronidation, facilitated by uridine diphosphate-glucuronosyltransferase (UGT), a major phase 2 reaction in mammalian metabolism. UGTs conjugate glucuronic acid to a wide array of endogenous and exogenous substrates, enhancing their solubility and excretion, but significantly affecting the bioavailability and therapeutic efficacy of drugs. UGT enzymes are ubiquitously distributed across tissues, prominently in the liver, but also in the GIT, kidneys, brain, and other organs where they play crucial roles in xenobiotic metabolism. Species-specific differences in UGT expression and activity impact the selection of animal models for pharmacological studies. Various experimental models - ranging from computational simulations (in silico) to laboratory experiments (in vitro) and animal studies (in vivo) - are employed throughout drug discovery and development to evaluate drug metabolism, including UGT activity. Effective strategies to counter pre-systemic metabolism are critical for improving drug bioavailability. This review explores several approaches including prodrugs, co-administration of specific molecules or use of inhibiting excipients in formulations. Strategies incorporating these excipients in nanoformulations demonstrate notable increases in drug absorption and bioavailability. This review highlights the importance of targeted delivery systems and excipient selection in overcoming metabolic barriers, aiming to optimize drug efficacy and patient outcomes.

Exploring peptide dendrimers for intestinal lymphatic targeting: formulation and evaluation of peptide dendrimer conjugated liposomes for enhancing the oral bioavailability of Asenapine maleate

Asenapine maleate (ASPM) is a second-generation atypical antipsychotic that is approved for treating acute schizophrenia and bipolar disorder in adults by the US FDA. The major downside of ASPM therapy is rapid, extensive first-pass hepatic metabolism following its oral administration with a very low oral bioavailability of < 2%. In this work, we developed ASPM nanoformulations conjugated with ligands such as arginine-glycine-aspartic acid (RGD) and peptide dendrimers (PDs) with the intention of improving the oral bioavailability of the drug by targeting it to the intestinal lymphatic system (ILS). Peptide dendrimers (PDs), both lipidated and nonlipidated, were synthesized by Fmoc solid phase peptide synthesis (SPPS). Reverse phase high performance chromatography (RP-HPLC) was used to purify the synthesized PDs, and the PDs were characterized by differential scanning calorimetry (DSC) electrospray ionization mass spectroscopy (ESI+-MS), Nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy. The thin film hydration method was used to prepare liposomes, and the process variables affecting the liposome parameters were optimized using the Box‒Behnken design (BBD).Liposomes were PEGylated using DSPE-PEG-COOH2000 and further conjugated with ligands (RGD, PD-1 and PD-2) using EDC-NHS chemistry. The formulation was characterized using different spectroscopic techniques. In vitro, cell line studies, such as cytotoxicity, cell uptake, uptake mechanism, and receptor saturation studies, were performed on both Caco2 and Raji-B cells. The pharmacokinetic parameters of the developed liposomal formulation were evaluated using pharmacokinetic studies on Sprague- Dawley (SD) rats. The psychostimulant-induced hyperactivity model was used to evaluate the pharmacodynamic performance of the developed formulations by measuring the reversal of hyperlocomotor activity induced by levodopa-carbidopa.

[Nanomedicines for the treatment of serious diseases and dual research]

The use of nanotechnologies for the encapsulation of pharmacologically active molecules (nanomedicines) has enhanced the delivery of these molecules within the body after administration. By releasing the active ingredient at the level of pathological cells and tissues, these nanocarriers help reduce toxicity while improving therapeutic efficacy. They also protect fragile molecules from rapid metabolization and can promote their intracellular penetration. Nanomedicines have made significant advances in various therapeutic areas such as oncology, infectious diseases, and several neurological disorders. They have also contributed to groundbreaking discoveries, including the introduction of the first mRNA vaccine (against COVID-19), and have improved certain imaging and diagnostic techniques, too. Depending on the country and therapeutic indications, between 40 to 60 nanomedicines are currently on the market, with over a hundred in clinical trials. This review aims to describe and discuss the characteristics and functionalities of the different generations of nanocarriers, from their inception to the present day, discussing the prospects they offer for the production of therapeutic proteins, for facilitating gene editing (CRISPR/Cas9), and for enabling immune checkpoint blockade in oncology. The potential of extracellular vesicles and exosomes as drug carriers is also explored. These advances compel researchers to consider the dual risks, both conscious and unconscious, that they may pose.

Intestinal Lymphatic Biology, Drug Delivery, and Therapeutics: Current Status and Future Directions

Historically, the intestinal lymphatics were considered passive conduits for fluids, immune cells, dietary lipids, lipid soluble vitamins, and lipophilic drugs. Studies of intestinal lymphatic drug delivery in the late 20th century focused primarily on the drugs' physicochemical properties, especially high lipophilicity, that resulted in intestinal lymphatic transport. More recent discoveries have changed our traditional view by demonstrating that the lymphatics are active, plastic, and tissue-specific players in a range of biological and pathological processes, including within the intestine. These findings have, in turn, inspired exploration of lymph-specific therapies for a range of diseases, as well as the development of more sophisticated strategies to actively deliver drugs or vaccines to the intestinal lymph, including a range of nanotechnologies, lipid prodrugs, and lipid-conjugated materials that "hitchhike" onto lymphatic transport pathways. With the increasing development of novel therapeutics such as biologics, there has been interest in whether these therapeutics are absorbed and transported through intestinal lymph after oral administration. Here we review the current state of understanding of the anatomy and physiology of the gastrointestinal lymphatic system in health and disease, with a focus on aspects relevant to drug delivery. We summarize the current state-of-the-art approaches to deliver drugs and quantify their uptake into the intestinal lymphatic system. Finally, and excitingly, we discuss recent examples of significant pharmacokinetic and therapeutic benefits achieved via intestinal lymphatic drug delivery. We also propose approaches to advance the development and clinical application of intestinal lymphatic delivery strategies in the future. SIGNIFICANCE STATEMENT: This comprehensive review details the understanding of the anatomy and physiology of the intestinal lymphatic system in health and disease, with a focus on aspects relevant to drug delivery. It highlights current state-of-the-art approaches to deliver drugs to the intestinal lymphatics and the shift toward the use of these strategies to achieve pharmacokinetic and therapeutic benefits for patients.

Enteral Route Nanomedicine for Cancer Therapy

With the in-depth knowledge of the pathological and physiological characteristics of the intestinal barrier-portal vein/intestinal lymphatic vessels-systemic circulation axis, oral targeted drug delivery is frequently being renewed. With many advantages, such as high safety, convenient administration, and good patient compliance, many researchers have begun to explore targeted drug delivery from intravenous injections to oral administration. Over the past few decades, the fields of materials science and nanomedicine have produced various drug delivery platforms that hold great potential in overcoming the multiple barriers associated with oral drug delivery. However, the oral transport of particles into the systemic circulation is extremely difficult due to immune rejection and biochemical invasion in the intestine, which limits absorption and entry into the bloodstream. The feasibility of the oral delivery of targeted drugs to sites outside the gastrointestinal tract (GIT) is unknown. This article reviews the biological barriers to drug absorption, the in vivo fate and transport mechanisms of drug carriers, the theoretical basis for oral administration, and the impact of carrier structural evolution on oral administration to achieve this goal. Finally, this article reviews the characteristics of different nano-delivery systems that can enhance the bioavailability of oral therapeutics and highlights their applications in the efficient creation of oral anticancer nanomedicines.

Fabrication of Luteolin Nanoemulsion by Box-Behnken Design to Enhance its Oral Absorption Via Lymphatic Transport

Intestinal lymphatic transport offers an alternative and effective way to deliver drugs, such as avoiding first-pass metabolism, enhancing oral bioavailability, and facilitating the treatment of targeted lymphoid-related diseases. However, the clinical use of luteolin (LUT) is limited by its poor water solubility and low bioavailability, and enhancing lymphatic transport by nanoemulsion may be an efficient way to enhance its oral bioavailability. The objective of this work is to prepare the luteolin nanoemulsions (LUT NEs), optimized its preparation parameters by using Box-Behnken design optimization (BBD) and evaluated it in vitro and in vivo. An Caco-2 / Raji B cell co-incubation monolayer model was established to simulate the M-cell pathway, and the differences in the transmembrane transport of LUT and NEs were compared. Cycloheximide (CHX) was utilized to establish rat chylomicron (CM) blocking model, and for investigating the influence of pharmacokinetic parameters in rats thereafter. The results showed that LUT NEs have good stability, the particle sizes were about 23.87 ± 0.57 nm. Compared with LUT suspension, The Papp of LUT NEs was enhanced for 3.5-folds, the oral bioavailability was increased by about 2.97-folds. In addition, after binding with chylomicron, the oral bioavailability of LUT NEs was decreased for about 30% (AUC 0-∞ (μg/L*h): 5.356 ± 1.144 vs 3.753 ± 0.188). These results demonstrated that NEs could enhance the oral absorption of luteolin via lymphatic transport routes.

Understanding lymphatic drug delivery through chylomicron blockade: A retrospective and prospective analysis

Scientists have developed and employed various models to investigate intestinal lymphatic uptake. One approach involves using specific blocking agents to influence the chylomicron-mediated lymphatic absorption of drugs. Currently utilized models include pluronic L-81, puromycin, vinca alkaloids, colchicine, and cycloheximide. This review offers a thorough analysis of the diverse models utilized, evaluating existing reports while delineating the gaps in current research. It also explores pharmacokinetic related aspects of intestinal lymphatic uptake pathway and its blockage through the discussed models. Pluronic L-81 has a reversible effect, minimal toxicity, and unique mode of action. Yet, it lacks clinical reports on chylomicron pathway blockage, likely due to low concentrations used. Puromycin and vinca alkaloids, though documented for toxicity, lack information on their application in drug intestinal lymphatic uptake. Other vinca alkaloids show promise in affecting triglyceride profiles and represent possible agents to test as blockers. Colchicine and cycloheximide, widely used in pharmaceutical development, have demonstrated efficacy, with cycloheximide preferred for lower toxicity. However, further investigation into effective and toxic doses of colchicine in humans is needed to understand its clinical impact. The review additionally followed the complete journey of oral lymphatic targeting drugs from intake to excretion, provided a pharmacokinetic equation considering the intestinal lymphatic pathway for assessing bioavailability. Moreover, the possible application of urinary data as a non-invasive way to measure the uptake of drugs through intestinal lymphatics was illustrated, and the likelihood of drug interactions when specific blockers are employed in human subjects was underscored.

Polyester nanoparticles delivering chemotherapeutics: Learning from the past and looking to the future to enhance their clinical impact in tumor therapy

Polymeric nanoparticles (NPs), specifically those comprised of biodegradable and biocompatible polyesters, have been heralded as a game-changing drug delivery platform. In fact, poly(α-hydroxy acids) such as polylactide (PLA), poly(lactide-co-glycolide) (PLGA), and poly(ε-caprolactone) (PCL) have been heavily researched in the past three decades as the material basis of polymeric NPs for drug delivery applications. As materials, these polymers have found success in resorbable sutures, biodegradable implants, and even monolithic, biodegradable platforms for sustained release of therapeutics (e.g., proteins and small molecules) and diagnostics. Few fields have gained more attention in drug delivery through polymeric NPs than cancer therapy. However, the clinical translational of polymeric nanomedicines for treating solid tumors has not been congruent with the fervor or funding in this particular field of research. Here, we attempt to provide a comprehensive snapshot of polyester NPs in the context of chemotherapeutic delivery. This includes a preliminary exploration of the polymeric nanomedicine in the cancer research space. We examine the various processes for producing polyester NPs, including methods for surface-functionalization, and related challenges. After a detailed overview of the multiple factors involved with the delivery of NPs to solid tumors, the crosstalk between particle design and interactions with biological systems is discussed. Finally, we report state-of-the-art approaches toward effective delivery of NPs to tumors, aiming at identifying new research areas and re-evaluating the reasons why some research avenues have underdelivered. We hope our effort will contribute to a better understanding of the gap to fill and delineate the future research work needed to bring polyester-based NPs closer to clinical application. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Novel First-Generation Dissolution Models to Investigate the Release and Uptake of Oral Lymphotropic Drug Products

Conventional dissolution tests only assess the aqueous release of drugs to ensure quality and performance, without indicating whether absorption occurs through the portal or the lymphatic circulation. To address this issue, this study aimed to develop novel first-generation dissolution models that could investigate the release and uptake of oral lymphotropic drugs and examine relevant formulation issues. Dissolution of three commercial lymphotropic drug products (Terbinafina, Apo-terbinafine, and Lamisil) was done using modified versions of USP Apparatus II and IV. The developed models contained a lymphatic compartment filled with artificial chylomicrons to account for absorption through intestinal lymphatic pathway. The various products exhibited different release profiles into the aqueous media and the lymphatic media across the two tested models. The modified USP IV apparatus demonstrated greater distinction in aqueous release patterns. However, the release pattern into the lymphatic media remained similar in both models. This work represents a progress in meeting the challenges posed by the increasing complexity of pharmaceutical products containing lipophilic drugs or formulations, and has the potential to contribute towards the development of in-vitro bioequivalence standards for formulations targeting intestinal lymphatics.

2-Monoacylglycerol Mimetic Liposomes to Promote Intestinal Lymphatic Transport for Improving Oral Bioavailability of Dihydroartemisinin

Purpose

Reducing the first-pass hepatic effect via intestinal lymphatic transport is an effective way to increase the oral absorption of drugs. 2-Monoacylglycerol (2-MAG) as a primary digestive product of dietary lipids triglyceride, can be assembled in chylomicrons and then transported from the intestine into the lymphatic system. Herein, we propose a biomimetic strategy and report a 2-MAG mimetic nanocarrier to target the intestinal lymphatic system via the lipid absorption pathway and improve oral bioavailability.

Methods

The 2-MAG mimetic liposomes were designed by covalently bonding serinol (SER) on the surface of liposomes named SER-LPs to simulate the structure of 2-MAG. Dihydroartemisinin (DHA) was chosen as the model drug because of its disadvantages such as poor solubility and high first-pass effect. The endocytosis and exocytosis mechanisms were investigated in Caco-2 cells and Caco-2 cell monolayers. The capacity of intestinal lymphatic transport was evaluated by ex vivo biodistribution and in vivo pharmacokinetic experiments.

Results

DHA loaded SER-LPs (SER-LPs-DHA) had a particle size of 70 nm and a desirable entrapment efficiency of 93%. SER-LPs showed sustained release for DHA in the simulated gastrointestinal environment. In vitro cell studies demonstrated that the cellular uptake of SER-LPs primarily relied on the caveolae- rather than clathrin-mediated endocytosis pathway and preferred to integrate into the chylomicron assembly process through the endoplasmic reticulum/Golgi apparatus route. After oral administration, SER-LPs efficiently promoted drug accumulation in mesenteric lymphatic nodes. The oral bioavailability of DHA from SER-LPs was 10.40-fold and 1.17-fold larger than that of free DHA and unmodified liposomes at the same dose, respectively.

Conclusion

SER-LPs improved oral bioavailability through efficient intestinal lymphatic transport. These findings of the current study provide a good alternative strategy for oral delivery of drugs with high first-pass hepatic metabolism.

Oral targeted drug delivery to post-gastrointestinal sites

As an essential branch of targeted drug delivery, oral targeted delivery is attracting growing attention in recent years. In addition to site-specific delivery for the treatment of locoregional diseases in the gastrointestinal tract (GIT), oral targeted delivery to remote sites beyond the GIT emerges as a cutting-edge research topic. This review aims to provide an overview of the fundamental concepts and most recent advances in this field. Owing to the physiological barriers existing in the GIT, carrier systems should be transported across the enteric epithelia to target remote sites. Recently, pioneer investigations have validated the transport of intact micro- or nanocarriers across gastrointestinal barriers and subsequently to various distal organs and tissues. The microfold (M) cell pathway is the leading mechanism underlying the oral absorption of particulates, but the contribution of the transcellular and paracellular pathways should not be neglected either. In addition to well-acknowledged physicochemical and biological factors, the formation of a protein corona may also influence the biological fate of carrier systems. Although in an early stage of conceptualization, oral targeted delivery to remote diseases has demonstrated promising potential for the treatment of inflammation, tumors, and diseases inflicting the lymphatic and mononuclear phagocytosis systems.

Quality by design (QbD) approach-based development of optimized nanocarrier to achieve quality target product profile (QTPP)-targeted lymphatic delivery

Background.Insulin, commonly used for diabetes treatment, needs better ways to improve its effectiveness and safety due to its challenges with poor permeability and stability. Various system has been developed for oral peptide delivery. The non-targeted system can prevent gastric and enzymatic degradation of peptides but cannot increase the bulk transport of peptides across the membrane. However, the non-selectivity is the limitation of the existing system. Numerous carbohydrate-binding receptors overexpressed on intestinal macrophage cells (M-cells) of gut-associated lymphoid tissue. It is the most desirable site for receptor-mediated endocytosis and lymphatic drug delivery of peptides.Objective. The prime objective of the study was to fabricate mannose ligand conjugated nanoparticles (MNPs) employing a quality-by-design approach to address permeability challenges after oral administration. Herein, the study's secondary objective of this study is to identify the influencing factor for producing quality products. Considering this objective, the Lymphatic uptake of NPs was selected as a quality target product profile (QTPP), and a systematic study was conducted to identify the critical formulation attributes (CFAs) and critical process parameters (CPP) influencing critical quality attributes (CQAs). Mannosylated Chitosan concentrations (MCs) and TPP concentrations were identified as CFAs, and stirring speed was identified as CPP.Methods. MNPs were prepared by the inotropic gelation method and filled into the enteric-coated capsule to protect from acidic environments. The effect of CFAs and CPP on responses like particle size (X) and entrapment (Y) was observed by Box-Behnken design (BBD). ANOVA statistically evaluated the result to confirm a significant level (p< 0.05). The optimal conditions of NPs were obtained by constructing an overlay plot and determining the desirability value. HPLC and zeta-seizer analysis characterized the lyophilized NPs. Cell-line studies were performed to confirm the safety and M-cell targeting of NPs to enhance Insulin oral bioavailability.Results. The morphology of NPs was revealed by SEM. The developed NPs showed a nearly oval shape with the average size, surface potential, and % drug entrapment were 245.52 ± 3.37 nm, 22.12 ± 2.13 mV, and 76.15 ± 1.3%, respectively. MTT assay result exhibited that MNPs safe and Confocal imaging inference that NPs selectively uptake by the M-cell.Conclusion. BBD experimental design enables the effective formulation of optimized NPs. The statistical analysis estimated a clear assessment of the significance of the process and formulation variable. Cell line study confirms that NPs are safe and effectively uptake by the cell.

High loading of lipophilic compounds in mesoporous silica for improved solubility and dissolution performance

Loading poorly soluble active pharmaceutical ingredients (API) into mesoporous silica can enable API stabilization in non-crystalline form, which leads to improved dissolution. This is particularly beneficial for highly lipophilic APIs (log D7.4 > 8) as these drugs often exhibit limited solubility in dispersion forming carrier polymers, resulting in low drug load and reduced solid state stability. To overcome this challenge, we loaded the highly lipophilic natural products coenzyme Q10 (CoQ10) and astaxanthin (ASX), as well as the synthetic APIs probucol (PB) and lumefantrine (LU) into the mesoporous silica carriers Syloid® XDP 3050 and Silsol® 6035. All formulations were physically stable in their non-crystalline form and drug loads of up to 50 % were achieved. At increasing drug loads, a marked increase in equilibrium solubility of the active ingredients in biorelevant medium was detected, leading to improved performance during biorelevant biphasic dissolution studies (BiPHa + ). Particularly the natural products CoQ10 and ASX showed substantial benefits from being loaded into mesoporous carrier particles and clearly outperformed currently available commercial formulations. Performance differences between the model compounds could be explained by in silico calculations of the mixing enthalpy for drug and silica in combination with an experimental chromatographic method to estimate molecular interactions.

Dihydroquercetin-Loaded Liposomes Change Fibrous Tissue Distribution in the Bleomycin-Induced Fibrosis Model

The effects of the antioxidant dihydroquercetin (DHQ) were studied in a model of pulmonary fibrosis. DHQ penetration into the lesion was facilitated by encapsulation into liposomes. Pulmonary fibrosis was modeled in rats by intratracheal injection of bleomycin. For the first 7 days, the rats in the treatment group received a liposomal emulsion with DHQ, while in the comparator group rats received saline. In the control group, intact rats did not receive any exposure. Thirty days after the initiation, lung function and the pathological lesion volume were assessed by 7T 1H MRI and the lungs were taken for histologic examination. The proportion of fibrous tissue was counted by Masson's trichrome staining. Both experimental groups were characterized by a significant functional pulmonary deficiency, with low mortality and a small lesion area. In the rats treated with DHQ, the distribution of fibrous tissue was significantly altered. Significantly more fibrous tissue was found in the center of the lesion, while significantly less was in the interstitial space of alveoli. Lung density at the same time was lower in the treated lungs. Dihydroquercetin encapsulated in liposomes affects the mechanisms of bleomycin-induced pulmonary fibrosis progression in rats. While accelerated fibrosis of the lesion can restrict inflammatory processes, delayed fibrosis of the interstitium can further improve the functional state of the lungs.

State-of-the-art drug delivery system to target the lymphatics

PRIMARY OBJECTIVE

The primary objective of the review is to assess the potential of lymphatic-targeted drug delivery systems, with a particular emphasis on their role in tumour therapy and vaccination efficacy.

REASON FOR LYMPHATIC TARGETING

The lymphatic system's crucial functions in maintaining bodily equilibrium, regulating metabolism, and orchestrating immune responses make it an ideal target for drug delivery. Lymph nodes, being primary sites for tumour metastasis, underscore the importance of targeting the lymphatic system for effective treatment.

OUTCOME

Nanotechnologies and innovative biomaterials have facilitated the development of lymphatic-targeted drug carriers, leveraging endogenous macromolecules to enhance drug delivery efficiency. Various systems such as liposomes, micelles, inorganic nanomaterials, hydrogels, and nano-capsules demonstrate significant potential for delivering drugs to the lymphatic system.

CONCLUSION

Understanding the physiological functions of the lymphatic system and its involvement in diseases underscores the promise of targeted drug delivery in improving treatment outcomes. The strategic targeting of the lymphatic system presents opportunities to enhance patient prognosis and advance therapeutic interventions across various medical contexts, indicating the importance of ongoing research and development in this area.

Linoleate-pazopanib conjugation as active pharmacological ingredient to abolish hepatocellular carcinoma growth

Small molecule compounds targeting multiple kinases involved in neoangiogenesis have shown survival benefits in patients with unresectable hepatocellular carcinoma (HCC). Nonetheless, despite the beneficial effects of multikinase inhibitors (MKIs), a lack of boosting adjuvant limits their objective response rate. Lipid conjugates have been used to improve delivery efficacy or pharmaceutical benefits for decades. However, the feasibility of utilizing lipid-drug conjugates (LDCs) in HCC regimens remains untested. In this study, oral feeding of linoleate-fluorescein isothiocyanate conjugates showed that the compound was well distributed in a spontaneous HCC mouse model. Therefore, a rationale design was developed for chemically synthesizing a linoleate-pazopanib conjugate (LAPC). The LAPC showed a significantly improved cytotoxicity compared to the parental drug pazopanib. Pazopanib's angiogenic suppressing signals were not observed in LAPC-treated HCC cells, potentially suggesting an altered mechanism of action (MOA). In an efficacy trial comparing placebo, oral pazopanib, and LAPC treatments in the hepatitis B virus transgene-related spontaneous HCC mouse model (HBVtg-HCC), the LAPC treatment demonstrated superior tumor ablating capacity in comparison to both placebo and pazopanib treatments, without any discernible systemic toxicity. The LAPC exposure is associated with an apoptosis marker (Terminal deoxynucleotidyl transferase dUTP nick end labeling [TUNEL]) and an enhanced ferroptosis (glutathione peroxidase 4 [GPX4]) potential in HBVtg-HCC tumors. Therefore, the LAPC showed excellent HCC ablative efficacy with altered MOA. The molecular mechanisms of the LAPC and LDCs for HCC therapeutics are of great academic interest. Further comprehensive preclinical trials (e.g., chemical-manufacture-control, toxicity, distribution, and pharmacokinetics/pharmacodynamics) are expected.

The Chimera of TPGS and Nanoscale Lipid Carriers as Lymphatic Drug Delivery Vehicles to Fight Metastatic Cancers

The lymphatic system (LS) plays a crucial role in fluid balance, transportation of macromolecules, and immune response. Moreover, LS is a channel for microbial invasion and cancer metastasis. Particularly, solid tumors, including lung, breast, melanoma, and prostate cancers, are metastasized across highways of LS. Subsequently, the fabrication of chimeric lymphatic drug delivery systems (LDDS) is a promising strategy to fight cancer metastasis and control microbial pandemics. In this regard, LDDS, in terms of PEG-nanoscaled lipid carriers, elicited a revolution during the COVID-19 pandemic as cargoes for mRNA vaccines. The drug delivered by the lymphatic pathway escapes first-pass metabolism and enhances the drug's bioavailability. Ample approaches, including synthesis of prodrugs, trigging of chylomicron biosynthesis, and fabrication of nanocarriers, facilitate lymphatic drug delivery. Specifically, nanoscales lipid cargoes have the propensity to lymphatic trafficking. Interestingly, TPGSengineered nanoscale lipid cargoes enhance lymphatic trafficking, increase tissue permeation, and, specifically, uptake. Moreover, they overcome biological barriers, control biodistribution, and enhance organelles localization. Most anticancer agents are non-specific, have low bioavailability, and induced drug resistance. Therefore, TPGS-engineered nanoscale lipid chimeras improve the therapeutic impact of anticancer agents. This review highlights lymphatic cancer metastasis, nanoscales lipid cargoes as LDDS, and their influence on lymphatic trafficking, besides the methods of LDD studies.

Current Advancements on Oral Protein and Peptide Drug Delivery Approaches to Bioavailability: Extensive Review on Patents

Protein and peptide-based drugs have greater therapeutic efficacy and potential application and lower toxicity compared to chemical entities in long-term use within optimum concentration as they are easily biodegradable due to biological origin. While oral administration is preferable, most of these substances are currently administered intravenously or subcutaneously. This is primarily due to the breakdown and poor absorption in the GI tract. Hence, ongoing research is focused on investigating absorption enhancers, enzyme inhibitors, carrier systems, and stability enhancers as potential strategies to facilitate the oral administration of proteins and peptides. Investigations have been directed towards advancing novel technologies to address gastrointestinal (GI) barriers associated with protein and peptide medications. The current review intensifies formulation and stability approaches for oral protein & peptide drug delivery systems with all significant parameters intended for patient safety. Notably, certain innovative technologies have been patented and are currently undergoing clinical trials or have already been introduced into the market. All the approaches stated for the administration of protein and peptide drugs are critically discussed, having their current status, future directions, and recent patents published in the last decades.

Enhanced tissue distribution of ritonavir-loaded nanostructured lipid carriers-recommending its dose reduction

Human immunodeficiency virus (HIV) mainly attacks lymphocytes of the human immune system. The untreated infection leads to acquired immune deficiency syndrome (AIDS). Ritonavir (RTV) belongs to protease inhibitors (PIs), the crucial contributors of the combination therapy used in the treatment of HIV that is called highly active antiretroviral therapy (HAART). Formulations targeting the lymphatic system (LS) play a key role in delivering and maintaining therapeutic drug concentrations in HIV reservoirs. In our previous study, we developed RTV-loaded nanostructured lipid carriers (NLCs), which contain the natural antioxidant alpha-tocopherol (AT). In the current study, the cytotoxicity of the formulation was studied in HepG2, MEK293, and H9C2 cell lines. The formulation efficacy to reach the LS was evaluated through a cycloheximide-injected chylomicron flow blockade model in Wistar rats. Biodistribution and toxicity studies were conducted in rodents to understand drug distribution patterns in various organs and to establish the safety profile of the optimized formulation (RTV-NLCs). From the MTT assay, it was found that the cell viability of the formulation is comparable with the pure drug (RTV-API). More than 2.5-folds difference in AUC was observed in animals treated with RTV-NLCs with and without cycloheximide injection. Biodistribution studies revealed higher drug exposure in the lymphoidal organs with the RTV-NLCs. No significant increase in serum biomarkers for hepatotoxicity was observed in rats dosed with the RTV-NLCs. The current study reveals the lymphatic uptake of the RTV-NLCs and their safety in rodents. As the tissue distribution of RTV-NLCs is high, hence re-adjusting the RTV-NLCs dose to get the response equivalent to RTV-API may be more beneficial with respect to its safety and efficacy.

Pharmacokinetics of vitamin dosage forms: A complete overview

Vitamins are crucial for sustaining life because they play an essential role in numerous physiological processes. Vitamin deficiencies can lead to a wide range of severe health issues. In this context, there is a need to administer vitamin supplements through appropriate routes, such as the oral route, to ensure effective treatment. Therefore, understanding the pharmacokinetics of vitamins provides critical insights into absorption, distribution, and metabolism, all of which are essential for achieving the desired pharmacological response. In this review paper, we present information on vitamin deficiencies and emphasize the significance of understanding vitamin pharmacokinetics for improved clinical research. The pharmacokinetics of several vitamins face various challenges, and thus, this work briefly outlines the current issues and their potential solutions. We also discuss the feasibility of enhanced nanocarrier-based pharmaceutical formulations for delivering vitamins. Recent studies have shown a preference for nanoformulations, which can address major limitations such as stability, solubility, absorption, and toxicity. Ultimately, the pharmacokinetics of pharmaceutical dosage forms containing vitamins can impede the treatment of diseases and disorders related to vitamin deficiency.

Nanocarriers transport across the gastrointestinal barriers: The contribution to oral bioavailability via blood circulation and lymphatic pathway

Oral administration is the preferred route of drug delivery in clinical practice due to its noninvasiveness, safety, convenience, and high patient compliance. The gastrointestinal tract (GIT) plays a crucial role in facilitating the targeted delivery of oral drugs. However, the GIT presents multiple barriers that impede drug absorption, including the gastric barrier in the stomach and the mucus and epithelial barriers in the intestine. In recent decades, nanotechnology has emerged as a promising approach for overcoming these challenges by utilizing nanocarrier-based drug delivery systems such as liposomes, micelles, polymeric nanoparticles, solid lipid nanoparticles, and inorganic nanoparticles. Encapsulating drugs within nanocarriers not only protects them from degradation but also enhances their transport and absorption across the GIT, ultimately improving oral bioavailability. The aim of this review is to elucidate the mechanisms underlying nanocarrier-mediated transportation across the GIT into systemic circulation via both the blood circulation and lymphatic pathway.

Development of a Novel In Vitro Model to Study Lymphatic Uptake of Drugs via Artificial Chylomicrons

The lymphatic system plays a crucial role in the absorption of lipophilic drugs, making it an important route for drug delivery. In this study, an in vitro model using Intralipid® was developed to investigate the lymphatic uptake of drugs. The model was validated using cannabidiol, halofantrine, quercetin, and rifampicin. Remarkably, the uptake of these drugs closely mirrored what would transpire in vivo. Furthermore, adding peanut oil to the model system significantly increased the lymphatic uptake of rifampicin, consistent with meals containing fat stimulating lymphatic drug uptake. Conversely, the inclusion of pluronic L-81 was observed to inhibit the lymphatic uptake of rifampicin in the model. This in vitro model emerges as a valuable tool for investigating and predicting drug uptake via the lymphatic system. It marks the first phase in developing a physiologically based predictive tool that can be refined further to enhance the precision of drug interaction predictions with chylomicrons and their subsequent transport via the lymphatic system. Moreover, it can be employed to explore innovative drug formulations and excipients that either enhance or hinder lymphatic drug uptake. The insights gained from this study have significant implications for advancing drug delivery through the lymphatic system.

Cracking the intestinal lymphatic system window utilizing oral delivery vehicles for precise therapy

Oral administration is preferred over other drug delivery methods due to its safety, high patient compliance, ease of ingestion without discomfort, and tolerance of a wide range of medications. However, oral drug delivery is limited by the poor oral bioavailability of many drugs, caused by extreme conditions and absorption challenges in the gastrointestinal tract. This review thoroughly discusses the targeted drug vehicles to the intestinal lymphatic system (ILS). It explores the structure and physiological barriers of the ILS, highlighting its significance in dietary lipid and medication absorption and transport. The review presents various approaches to targeting the ILS using spatially precise vehicles, aiming to enhance bioavailability, achieve targeted delivery, and reduce first-pass metabolism with serve in clinic. Furthermore, the review outlines several methods for leveraging these vehicles to open the ILS window, paving the way for potential clinical applications in cancer treatment and oral vaccine delivery. By focusing on targeted drug vehicles to the ILS, this article emphasizes the critical role of these strategies in improving therapeutic efficacy and patient outcomes. Overall, this article emphasizes the critical role of targeted drug vehicles to the ILS and the potential impact of these strategies on improving therapeutic efficacy and patient outcomes.

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

Alginate-Based Oral Delivery Systems to Enhance Protection, Release, and Absorption of Catalase

Oxidative stress, overproduction of reactive oxygen species (ROS), plays an important role in the development of inflammatory bowel diseases. Catalase has great therapeutic potential by scavenging hydrogen peroxide, one of the ROSs produced in cellular metabolisms. However, in vivo application to scavenge ROS is currently limited especially in oral administrations. Here, we introduced an alginate-based oral drug delivery system that effectively protected catalase from the simulated harsh conditions of the gastrointestinal (GI) tract, released it in the small intestine mimicked condition, and enhanced its absorption via M cells, highly specialized epithelium cells in the small intestine. First of all, catalase was encapsulated in alginate-based microparticles with different amounts of polygalacturonic acid or pectin, which achieved an encapsulation efficiency of more than 90%. It was further shown that catalase was released from alginate-based microparticles in a pH-dependent manner. Results indicated that alginate-polygalacturonic acid microparticles (60 wt % Alg:40 wt % Gal) released 79.5 ± 2.4% of encapsulated catalase at pH 9.1 in 3 h, while they only released 9.2 ± 1.5% of encapsulated catalase at pH 2.0. Even when catalase was encapsulated in microparticles (60 wt % Alg:40 wt % Gal) and exposed to pH 2.0 followed by pH 9.1, it still retained 81.0 ± 11.3% enzyme activity compared to that in microparticles prior to the pH treatment. We then investigated the efficiency of RGD conjugation to catalase on the catalase uptake by M-like cells, the coculturing of human epithelial colorectal adenocarcinoma; Caco-2 cells and B lymphocyte; Raji cells. RGD-catalase protected M-cells more efficiently from the cytotoxicity of H₂O₂, a typical ROS. RGD conjugation to catalase enhanced the uptake by M-cells with 87.6 ± 0.8% RGD-catalase, whereas 11.5 ± 9.2% of RGD-free catalase passed across M-cells. From the results of protection, release, and absorption of model therapeutic proteins from the harsh pH conditions, alginate-based oral drug delivery systems will have numerous applications for the controlled release of drugs that are easily degradable in the GI tract.

Encapsulation of resveratrol within size-controlled nanoliposomes: Impact on solubility, stability, cellular permeability, and oral bioavailability

This study examined the influence of the nanoliposomes (LPs) particle size on the solubility, antioxidant stability, in vitro release profile, Caco-2 cellular transport activity, cellular antioxidant activity, and in vivo oral bioavailability of resveratrol (RSV). LPs with sizes of 300, 150, and 75 nm were prepared using the thin-lipid film hydration method, followed by ultrasonication for 0, 2, and 10 min, respectively. Formulating small LPs (< 100 nm) was effective to enhance the solubility, in vitro release profile, cellular permeability, and cellular antioxidant activity of RSV. A similar pattern was observed for in vivo oral bioavailability. However, the size reduction of RSV-loaded LPs did not promote the antioxidant stability of RSV, owing to their large surface area used to interact with harsh environments. This study provides the better understanding of the appropriate particle size range of LPs to improve their in vitro and in vivo performances of RSV as an effective carrier for oral administration.

Structure modification: a successful tool for prodrug design

Prodrug strategy is critical for innovative drug development. Structural modification is the most straightforward and effective method to develop prodrugs. Improving drug defects and optimizing the physical and chemical properties of a drug, such as lipophilicity and water solubility, changing the way of administration can be achieved through specific structural modification. Designing prodrugs by linking microenvironment-responsive groups to the prototype drugs is of great help in enhancing drug targeting. In the meantime, making connections between prodrugs and suitable drug delivery systems could realize drug loading increases, greater stability, bioavailability and drug release control. In this paper, lipidic, water-soluble, pH-responsive, redox-sensitive and enzyme-activatable prodrugs are reviewed on the basis of structural modification.

Engineered Nano-carrier Systems for the oral targeted delivery of Follicle Stimulating Hormone: Development, characterization, and, assessment of in vitro and in vivo performance and targetability

Follicle stimulating hormone (FSH) is widely used for the treatment of female infertility, where the level of FSH is suboptimal due to which arrest in follicular development and anovulation takes place. Currently, only parenteral formulations are available for FSH in the market. Due to the drawbacks of parenteral administration and the high market shares of FSH, there is a need for easily accessible oral formulation. Therefore, enteric coated capsules filled with FSH loaded nanostructured lipid carriers (NLCs) or liposomes were prepared. Preliminary studies such as circular dichroism, SDS-PAGE, FTIR and ELISA were conducted to analyze FSH. Prepared formulations were optimized with respect to the size, polydispersity index, zeta potential, and entrapment efficiency using the design of experiments. Optimized formulations were subjected to particle counts and distribution analysis, TEM analysis, in vitro drug release, dissolution of enteric coated capsules, cell line studies, everted sac rat's intestinal uptake study, pharmacokinetics, pharmacodynamics, and stability studies. In the case of liposomes, RGD conjugation was done by carbodiimide chemistry and conjugation was confirmed by FTIR, ¹HNMR and Raman spectroscopy. The prepared formulations were discrete and spherical. The release of FSH from enteric coated capsules was slow and sustained. The increased permeability of nano-formulations was observed in Caco-2 monoculture as well as in Caco-2 and Raji-B co-culture models. NLCs and liposomes showed an improvement in oral bioavailability and efficacy of FSH in rats. This may be due to mainly chylomicron-assisted lymphatic uptake of NLCs; whereas, in the case of liposomes, RGD-based targeting of β1 integrins of M cells on Peyer's patches may be the main reason for the better effect by FSH. FSH was found to be stable chemically and conformationally. Overall, the study reveals the successful development and evaluation of FSH loaded NLCs and liposomes.

Surface-modified nanoparticles of docetaxel for chemotherapy of lung cancer: An intravenous to oral switch

Despite being potent, the marketed formulations of Docetaxel (DX) are associated with numerous side effects and are meant for intravenous administration. Advanced pharmaceutical nanotechnology has a significant potential to facilitate the 'intravenous (i.v) to oral switch'. The present research work deals with the development of an orally administrable, folate-receptor-targeted Nanostructured lipid carriers (NLCs) of DX (FA-DX-NLCs) for facilitating oral chemotherapy of lung cancer while overcoming the bioavailability and toxicity issues. The nanoformulation prepared to employ high-pressure homogenization and lyophilization, was evaluated and statistically analyzed for various in-vitro and in-vivo formulation characteristics. The lyophilized nanoparticles were observed to be spherical with a particle size of 183.4 ± 2.13 (D90), Pdi of 0.358 ± 0.03, % EE of 82.41 ± 2.44, % DL of 4.41 ± 0.54 and a zeta potential of -3.3 ± 0.7 mv. The increased oral in-vivo bioavailability of DX was evident from the plasma-concentration area under the time curve (AUC_0-t), which was ∼ 27-fold greater for FA-DX-NLCs as compared to DX suspension. The orally administered FA-DX-NLCs exhibited excellent antitumor efficacy in a pre-clinical model of lung carcinoma. Tumor staging, histopathology, and immunostaining of the tumors suggested greater anti-proliferative, apoptotic, anti-metastatic, and anti-angiogenic potential as compared to DX-suspension. The pre-clinical toxicity studies affirmed the excellent safety and bio-compatibility of FA-DX-NLCs. The research work presents immense translational potential for switching the DX-based chemotherapy for lung cancer from 'hospital to home.'

Transporter-Mediated Drug Delivery

Transmembrane transport of small organic and inorganic molecules is one of the cornerstones of cellular metabolism. Among transmembrane transporters, solute carrier (SLC) proteins form the largest, albeit very diverse, superfamily with over 400 members. It was recognized early on that xenobiotics can directly interact with SLCs and that this interaction can fundamentally determine their efficacy, including bioavailability and intertissue distribution. Apart from the well-established prodrug strategy, the chemical ligation of transporter substrates to nanoparticles of various chemical compositions has recently been used as a means to enhance their targeting and absorption. In this review, we summarize efforts in drug design exploiting interactions with specific SLC transporters to optimize their therapeutic effects. Furthermore, we describe current and future challenges as well as new directions for the advanced development of therapeutics that target SLC transporters.

Green tea catechin loaded niosomes: formulation and their characterization for food fortification

The main aim of this study was to deliver green tea catechins with enhanced bioavailability using niosomal system. Catechins-loaded niosomes were prepared using food grade surfactant, Tween 60 and membrane stabilizers namely, lauryl alcohol, cetyl alcohol and cholesterol by thin film hydration technique. Catechins-loaded niosomes exhibited a hydrodynamic diameter of 58.48 nm with a narrow size distribution (PDI = 0.13) and zeta potential of - 31.75 mV, suggestive for homogeneity and good stability. Niosomes entrapped about 85.82% of catechin and showed sustained release under simulated GI conditions. Morphology of niosomal vesicles were carried out using scanning electron microscopy-energy X-ray dispersion spectroscopy, transmission electron microscopy and atomic force microscopy. Fourier-transform infrared spectroscopy and High-performance liquid chromatography analysis confirmed successful encapsulation of catechins. Antioxidant activity of catechins was retained in the niosomal form. Fortification of milk with catechins loaded niosomes showed no significant changes on sensory, physicochemical properties and exhibited higher antioxidant property.

Natural Kinase Inhibitors for the Treatment and Management of Endometrial/Uterine Cancer: Preclinical to Clinical Studies

Endometrial cancer (EC) is the sixth most prevalent type of cancer among women. Kinases, enzymes mediating the transfer of adenosine triphosphate (ATP) in several signaling pathways, play a significant role in carcinogenesis and cancer cells’ survival and proliferation. Cyclin-dependent kinases (CDKs) are involved in EC pathogenesis; therefore, CDK inhibitors (CDKin) have a noteworthy therapeutic potential in this type of cancer, particularly in EC type 1. Natural compounds have been used for decades in the treatment of cancer serving as a source of anticancer bioactive molecules. Many phenolic and non-phenolic natural compounds covering flavonoids, stilbenoids, coumarins, biphenyl compounds, alkaloids, glycosides, terpenes, and terpenoids have shown moderate to high effectiveness against CDKin-mediated carcinogenic signaling pathways (PI3K, ERK1/2, Akt, ATM, mTOR, TP53). Pharmaceutical regimens based on two natural compounds, trabectedin and ixabepilone, have been investigated in humans showing short and midterm efficacy as second-line treatments in phase II clinical trials. The purpose of this review is twofold: the authors first provide an overview of the involvement of kinases and kinase inhibitors in the pathogenesis and treatment of EC and then discuss the existing evidence about natural products’ derived kinase inhibitors in the management of the disease and outline relevant future research.

Drug delivery to the intestinal lymph by oral formulations

Oral drug delivery systems (DDS) targeting lymphocytes in intestinal lymphatic vessels, ducts, and nodes are useful for treating diverse diseases. The intestinal lymph harbors numerous lymphocyte subsets, and DDS containing lipids such as triglycerides and fatty acids can deliver drugs to the lymph through the chylomicron pathway. DDS are efficient, thus allowing the administration of reduced drug doses, which mitigate systemic adverse effects. Here we review orally administered lipid formulations comprising oil solutions, suspensions, micro/nanoemulsions, self-micro/nano emulsifying DDS, liposomes, micelles, solid lipid nanoparticles, and nanostructured lipid carriers for targeting drugs to the lymph. We first describe the structures of lymphatic vessels and lymph nodes and the oral absorption of lipids and drugs into the intestinal lymph. We next summarize the effects of the properties and amounts of lipids and drugs delivered into the lymph and lymphocytes, as well as their effects on drug delivery ratios of lymph to blood. Finally, we describe lymphatic DDS containing saquinavir, tacrolimus, and methotrexate, and their potency that reduce drug concentrations in blood, which are associated with systemic adverse effects.

Relative bioavailability enhancement of simvastatin via dry emulsion systems: comparison of spray drying and fluid bed layering technology

Comprehensive comparisons of similar lipid based drug delivery systems produced by different technologies are scarce. Spray drying and fluid bed layering technologies were compared with respect to the process and product characteristics of otherwise similar simvastatin loaded dry emulsion systems. Fluid bed layering provided higher process yield (83.3% vs 71.5%), encapsulation efficiency (80.0% vs 68.4 %), relative one month product stability (93.8% vs 85.5%), larger and more circular particles (336 µm vs 56 µm) and lower median oil droplet size after product reconstitution in water (2.85 µm vs 4.27 µm), compared to spray drying. However, spray dried products exhibited higher drug content (22.2 mg/g vs 9.34 mg/g). An in-vivo pharmacokinetic study in rats was performed and a pharmacokinetic model was developed in order to compare the optimised simvastatin loaded dry emulsion systems, a simvastatin glyceride mimetic loaded in the dry emulsion and a simvastatin loaded SMEDDS with a reference physical mixture. Of the formulation tested, fluid bed layered pellets excelled and provided a 115% relative increase in bioavailability. Among the two technologies, fluid bed layering provided dry emulsion products with higher relative bioavailability and better product characteristics for further processing into final dosage forms.

Smart design approaches for orally administered lipophilic prodrugs to promote lymphatic transport

Challenges to effective delivery of drugs following oral administration has attracted growing interest over recent decades. Small molecule drugs (<1000 Da) are generally absorbed across the gastrointestinal tract into the portal blood and further transported to the systemic circulation via the liver. This can result in a significant reduction to the oral bioavailability of drugs that are metabolically labile and ultimately lead to ineffective exposure and treatment. Targeting drug delivery to the intestinal lymphatics is attracting increased attention as an alternative route of drug transportation providing multiple benefits. These include bypassing hepatic first-pass metabolism and selectively targeting disease reservoirs residing within the lymphatic system. The particular physicochemical requirements for drugs to be able to access the lymphatics after oral delivery include high lipophilicity (logP>5) and high long-chain triglyceride solubility (> 50 mg/g), properties required to enable drug association with the lipoprotein transport pathway. The majority of small molecule drugs, however, are not this lipophilic and therefore not substantially transported via the intestinal lymph. This has contributed to a growing body of investigation into prodrug approaches to deliver drugs to the lymphatic system by chemical manipulation. Optimised lipophilic prodrugs have the potential to increase lymphatic transport thereby improving oral pharmacokinetics via a reduction in first pass metabolism and may also target of disease-specific reservoirs within the lymphatics. This may provide advantages for current pharmacotherapy approaches for a wide array of pathological conditions, e.g. immune disease, cancer and metabolic disease, and also presents a promising approach for advanced vaccination strategies. In this review, specific emphasis is placed on medicinal chemistry strategies that have been successfully employed to design lipophilic prodrugs to deliberately enable lymphatic transport. Recent progress and opportunities in medicinal chemistry and drug delivery that enable new platforms for efficacious and safe delivery of drugs are critically evaluated.

Engineering Nano- and Microparticles as Oral Delivery Vehicles to Promote Intestinal Lymphatic Drug Transport

Targeted oral delivery of a drug via the intestinal lymphatic system (ILS) has the advantages of protecting against hepatic first-pass metabolism of the drug and improving its pharmacokinetic performance. It is also a promising route for the oral delivery of vaccines and therapeutic agents to induce mucosal immune responses and treat lymphatic diseases, respectively. This article describes the anatomical structures and physiological characteristics of the ILS, with an emphasis on enterocytes and microfold (M) cells, which are the main gateways for the transport of particulate delivery vehicles across the intestinal epithelium into the lymphatics. A comprehensive overview of recent advances in the rational engineering of particulate vehicles, along with the challenges and opportunities that they present for improving ILS drug delivery, is provided, and the mechanisms by which such vehicles target and transport through enterocytes or M cells are discussed. The use of naturally sourced materials, such as yeast microcapsules and their derived polymeric β-glucans, as novel ILS-targeting delivery vehicles is also reviewed. Such use is the focus of an emerging field of research. Their potential use in the oral delivery of nucleic acids, such as mRNA vaccines, is proposed.

Improving Curcumin Bioavailability: Current Strategies and Future Perspectives

Curcumin possesses a plethora of interesting pharmacological effects. Unfortunately, it is also characterized by problematic drug delivery and scarce bioavailability, representing the main problem related to the use of this compound. Poor absorption, fast metabolism, and rapid systemic clearance are the most important factors contributing to low curcumin levels in plasma and tissues. Accordingly, to overcome these issues, numerous strategies have been proposed and are investigated in this article. Due to advances in the drug delivery field, we describe here the most promising strategies for increasing curcumin bioavailability, including the use of adjuvant, complexed/encapsulated curcumin, specific curcumin formulations, and curcumin nanoparticles. We analyze current strategies, already available in the market, and the most advanced technologies that can offer a future perspective for effective curcumin formulations. We focus the attention on the effectiveness of curcumin-based formulations in clinical trials, providing a comprehensive summary. Clinical trial results, employing various delivery methods for curcumin, showed that improved bioavailability corresponds to increased therapeutic efficacy. Furthermore, advances in the field of nanoparticles hold great promise for developing curcumin-based complexes as effective therapeutic agents. Summarizing, suitable delivery methods for this polyphenol will ensure the possibility of using curcumin-derived formulations in clinical practice as preventive and disease-modifying therapeutics.

Lymphatic Drug Transport and Associated Drug Delivery Technologies: A Comprehensive Review

Lymphatic system is the secondary circulation system of the human body after the systemic circulation. Various problems, including the first-pass metabolism through oral administration of medicines, can be resolved by lymphatic targeting. Lymphatic absorption has been explored in detail, and studies reveal the improved bioavailability of medicines. In the case of cancer, AIDS, and various other health problems, lymphatic targeting has been focused on due to the fact that lymph nodes are involved greatly in tumor metastasis. This article reviews lymphatic absorption and its exploration in the treatment of various health problems. The physiology of the lymphatic system, the mechanisms of absorption, and the various formulation systems suitable for lymphatic absorption have been discussed. Some recent novel approaches like hydrodynamically driven device (HDD) and carbon nanotubes for lymphatic delivery have also been appraised.

Liposomes as Versatile Platform for Cancer Theranostics: Therapy, Bio-imaging, and Toxicological Aspects

Liposomes are nano-sized formulations having the benefits of site-specificity, biocompatibility, and biodegradability, which make them useful for the therapy and diagnosis of major diseases like cancer. In this review, various synthetic strategies of liposomes and their biomedical application in special concern to cancer are discussed. In context to the biomedical application, this article gives a detailed insight into subcellular targeted therapy and several therapeutic modifications like immunotherapy, receptor-based therapy, phototherapy, and combination therapy. The review also describes the liposome-based imaging platforms and the toxicity associated with liposomes. Owing to a significant amount of benefits of this carrier system, several products have been approved to be launched in the market and several others have already been marketed for clinical use.

Oral delivery of proteins and peptides: Challenges, status quo and future perspectives

Proteins and peptides (PPs) have gradually become more attractive therapeutic molecules than small molecular drugs due to their high selectivity and efficacy, but fewer side effects. Owing to the poor stability and limited permeability through gastrointestinal (GI) tract and epithelia, the therapeutic PPs are usually administered by parenteral route. Given the big demand for oral administration in clinical use, a variety of researches focused on developing new technologies to overcome GI barriers of PPs, such as enteric coating, enzyme inhibitors, permeation enhancers, nanoparticles, as well as intestinal microdevices. Some new technologies have been developed under clinical trials and even on the market. This review summarizes the history, the physiological barriers and the overcoming approaches, current clinical and preclinical technologies, and future prospects of oral delivery of PPs.

An update on oral drug delivery via intestinal lymphatic transport

Orally administered drug entities have to survive the harsh gastrointestinal environment, penetrate the enteric epithelia and circumvent hepatic metabolism before reaching the systemic circulation. Whereas the gastrointestinal stability can be well maintained by taking proper measures, hepatic metabolism presents as a formidable barrier to drugs suffering from first-pass metabolism. The pharmaceutical academia and industries are seeking alternative pathways for drug transport to circumvent problems associated with the portal pathway. Intestinal lymphatic transport is emerging as a promising pathway to this end. In this review, we intend to provide an updated overview on the rationale, strategies, factors and applications involved in intestinal lymphatic transport. There are mainly two pathways for peroral lymphatic transport-the chylomicron and the microfold cell pathways. The underlying mechanisms are being unraveled gradually and nowadays witness increasing research input and applications.

Re-Assessing PK/PD Issues for Oral Protein and Peptide Delivery

Due to a lack of safe and effective oral delivery strategies for most protein and peptide therapeutics, pharmaceutical drug developers have focused on parenteral routes to administer these agents. Recent advances in delivery technologies have now shown clinical validation for a few of these biopharmaceuticals following oral administration. While these initial opportunities have provided more than just a glimmer of hope within the industry, there are important aspects of oral biopharmaceutical delivery that do not completely align with pharmacokinetic (PK) parameters and pharmacodynamics (PD) outcomes that have been learned from parenteral administrations. This commentary examines some of these issues with the goal of presenting a rationale for re-assessing methods, models, and success criteria to better measure oral protein or peptide delivery outcomes related to PK/PD events.

All-trans retinoic acid in anticancer therapy: how nanotechnology can enhance its efficacy and resolve its drawbacks

Introduction: All-trans retinoic acid (ATRA, tretinoin) is the main drug used in the treatment of acute promyelocytic leukemia (APL). Despite its impressive activity against APL, the same could not be clinically observed in other types of cancer. Nanotechnology can be a tool to enhance ATRA anticancer efficacy and resolve its drawbacks in APL as well as in other malignancies.Areas covered: This review covers ATRA use in APL and non-APL cancers, the problems that were found in ATRA therapy and how nanoencapsulation can aid to circumvent them. Pre-clinical results obtained with nanoencapsulated ATRA are shown as well as the two ATRA products based on nanotechnology that were clinically tested: ATRA-IV® and Apealea®.Expert opinion: ATRA presents interesting properties to be used in anticancer therapy with a notorious differentiation and antimetastatic activity. Bioavailability and resistance limitations impair the use of ATRA in non-APL cancers. Nanotechnology can circumvent these issues and provide tools to enhance its anticancer activities, such as co-loading of multiple drug and active targeting to tumor site.

New insight into function and dysfunction of gut microfold cells

Microfold cells (M cells), derived from intestinal crypt Lgr5⁺ stem cells, are distributed in gut-associated lymphoid tissue (GALT), nasopharyngeal-associated lymphoid tissue (NALT), and bronchial-associated lymphoid tissue (BALT). The basement membrane of mature M cells protrudes upward, showing a "pocket-like" shape. M cell differentiation is mainly regulated by two pathways, one is the non-canonical NF-κB pathway, and the other is the canonical NF-κB pathway. The differentiation and maturation of M cells are closely related to RANKL and S100A4. M cells can not only transport antigens and trigger an immune response, but also are the gateway for various pathogens to invade the body. The occurrence and development of tuberculosis, prion disease, and Crohn's disease are closely related to M cells.