PEG–PLA–PEG block copolymeric nanoparticles for oral immunization against hepatitis B

Applications of nanoengineered therapeutics and vaccines: special emphasis on COVID-19

Nanomedicine provides innovative strategies that had significantly improved drug and gene delivery and allowed control over the engineering of therapeutics, diagnostics, vaccines, and other medical devices, for a diversity of medical applications. This review focuses on the current attempts to develop potent nanoengineered vaccines and therapeutics against coronaviruses, and the recent fabrication strategies and design principles to control acute infections from the escalating SARS-CoV-2 pandemic. Nanomedical approaches provide versatile platforms that can be utilized to enhance the overall potency, safety, and stability of vaccines, thus augmenting the desired immune response. Their modulable conformational features of size, shape, surface charge, antigen display, and composition allow for precise tuning and optimization of the nanoconstructs for the management of a variety of diseases and pathological conditions. The ability to control the release of their encapsulated cargoes and the possibility of surface decoration with various moieties support the construction of multifunctional nanomaterials that ultimately boost and prolong the immune response elicited and/or therapeutic effects, selectively at the diseased tissues and target sites.

Demystifying particle-based oral vaccines

Introduction: The oral route of vaccination is pain- and needle-free and can induce systemic and mucosal immunity. However, gastrointestinal barriers and antigen degradation impose significant hurdles in the development of oral vaccines. Live attenuated viruses and bacteria can overcome these barriers but at the risk of introducing safety concerns. As an alternative, particles have been investigated for antigen protection and delivery, yet there are no FDA-approved oral vaccines based on particle-based delivery systems. Our objective was to discover underlying determinants that can explain the current inadequacies and identify paradigms that can be implemented in future for successful development of oral vaccines relying on particle-based delivery systems.Areas covered: We reviewed literature related to the use of particles for oral vaccination and placed special emphasis on formulation characteristics and administration schedules to gain an insight into how these parameters impact production of antigen-specific antibodies in systemic and mucosal compartments.Expert opinion: Despite the long history of vaccines, particle-based oral vaccination is a relative new field with the first study published in 1989. Substantial variability exists between different studies with respect to dosing schedules, number of doses, and the amount of vaccine per dose. Most studies have not used adjuvants in the formulations. Better standardization in vaccination parameters is required to improve comparison between experiments, and adjuvants should be used to enhance the systemic and mucosal immune responses and to reduce the number of doses, which will make oral vaccines more attractive.

Nanostrategies to Develop Current Antiviral Vaccines

Infectious diseases are a worldwide concern. They are responsible for increasing the mortality rate and causing economic and social problems. Viral epidemics and pandemics, such as the COVID-19 pandemic, force the scientific community to consider molecules with antiviral activity. A number of viral infections still do not have a vaccine or efficient treatment and it is imperative to search for vaccines to control these infections. In this context, nanotechnology in association with the design of vaccines has presented an option for virus control. Nanovaccines have displayed an impressive immune response using a low dosage. This review aims to describe the advances and update the data in studies using nanovaccines and their immunomodulatory effect against human viruses.

Novel Vaccine Technologies in Veterinary Medicine: A Herald to Human Medicine Vaccines

The success of inactivated and live-attenuated vaccines has enhanced livestock productivity, promoted food security, and attenuated the morbidity and mortality of several human, animal, and zoonotic diseases. However, these traditional vaccine technologies are not without fault. The efficacy of inactivated vaccines can be suboptimal with particular pathogens and safety concerns arise with live-attenuated vaccines. Additionally, the rate of emerging infectious diseases continues to increase and with that the need to quickly deploy new vaccines. Unfortunately, first generation vaccines are not conducive to such urgencies. Within the last three decades, veterinary medicine has spearheaded the advancement in novel vaccine development to circumvent several of the flaws associated with classical vaccines. These third generation vaccines, including DNA, RNA and recombinant viral-vector vaccines, induce both humoral and cellular immune response, are economically manufactured, safe to use, and can be utilized to differentiate infected from vaccinated animals. The present article offers a review of commercially available novel vaccine technologies currently utilized in companion animal, food animal, and wildlife disease control.

Chitosan modified poly (lactic acid) nanoparticles increased the ursolic acid oral bioavailability

Ursolic acid (UA) is a naturally occurring triterpene that has been investigated for its antitumor activity. However, its lipophilic character hinders its oral bioavailability, and therapeutic application. To overcome these limitations, chitosan (CS) modified poly (lactic acid) (PLA) nanoparticles containing UA were developed, characterized, and had their oral bioavailability assessed. The nanoparticles were prepared by emulsion-solvent evaporation technique and presented a mean diameter of 330 nm, zeta potential of +28 mV, spherical shape and 90% encapsulation efficiency. The analysis of XRD and DSC demonstrated that the nanoencapsulation process induced to UA amorphization. The in vitro release assay demonstrated that 53% of UA was released by diffusion after 144 h, following a second-order release kinetics. In simulated gastrointestinal fluids and mucin interaction tests, CS played an important role in stability and mucoadhesiveness improvement of PLA nanoparticles, respectively. In the presence of erythrocytes, nanoparticles proved their hemocompatibility. In tumor cells, nanoparticles presented lower cytotoxicity than free UA, due to slow UA release. After a single oral dose in rats, CS modified PLA nanoparticles increased the UA absorption, reduced its clearance and elimination, resulting in increased bioavailability. The results show the potential application of these nanoparticles for UA oral delivery for cancer therapy.

Direct Synthesis and Characterization of Photo-Crosslinkable Biodegradable PLA-PEG-PLA Ttiblock Copolymer with Methacrylates Functions by Green Montmorillonite Clay Catalyst

Di-methacrylated PLA-PEG-PLA triblock copolymers of polylactide and polyethylene glycol were synthesized in one-step process by bulk cationic polymerization of lactide in the presence of PEG with different average molecular weights, using Maghnite-H+, an acidic montmorillonite clay, as a solid non-toxic catalyst. The obtained di-methacrylated copolymer was analyzed by 1H NMR and DSC. The effect of Maghnite-H+ proportions and PEG average molecular weight on the copolymerization and methacrylation yields and on average molecular weight of the resulting copolymers was studied.

Development of Rifapentine-Loaded PLGA-Based Nanoparticles: In vitro Characterisation and in vivo Study in Mice

Background

Tuberculosis (TB) is a leading cause of death amongst infectious diseases. The poor response to antitubercular agents necessitates the long-term use of high drug doses, resulting in low patient compliance, which is the main reason for chemotherapy failure and contributes to the development of multidrug-resistant TB. Patient non-compliance has been a major obstacle in the successful management of TB. The aim of this work was to develop and characterise rifapentine (RPT)-loaded PLGA-based nanoparticles (NPs) for reducing dosing frequency.

Methods

RPT-loaded PLGA and PLGA–PEG NPs were prepared using premix membrane homogenisation combined with solvent evaporation method. The resulting NPs were characterised in terms of physicochemical characteristics, toxicity, cellular uptake and antitubercular activity. NPs were further evaluated for pharmacokinetic and biodistribution studies in mice.

Results

The resulting NPs showed suitable and safe physicochemical characteristics and could be taken up by macrophages. RPT-loaded NPs were more effective against Mycobacterium tuberculosis than free RPT. In vivo studies revealed that NPs could improve pharmacokinetic parameters, particularly for RPT/PLGA–PEG NPs. Moreover, both formulations had no toxicity to the organs of mice and could reduce hepatotoxicity.

Conclusion

The application of PLGA-based NPs as sustained-release delivery vehicles for RPT could prolong drug release, modify pharmacokinetics, increase antitubercular activity and diminish toxicity, thereby allowing low dosage and frequency.

Rational application of nanoadjuvant for mucosal vaccine delivery system

The surface of the mucosa is the biggest path through which pathogens enter the human body. We need an understanding of mucosal immune systems to use vaccines that generate protective mucosal and systemic immunity to regulate the outbreak of various infectious diseases. The better impact of the mucosal vaccine over traditional injectable vaccines are that not only do they induce efficient immune reactions to the mucosa but they are also comfortable in physical aspect & psychological aspect. The material of the vaccine includes pathogens antigens and adjuvants, which enable vaccination to be effective. Vaccines are classified into different criteria, including the used vaccine material and method of administration. Vaccines have traditionally been injected through a needle. However, as most of the pathogens first infect the mucosal surfaces, and growing interest is expressed in establishing protective immunity from the mucosa, which is accomplished through mucosal paths through vaccinosis. To improve the existing vaccines further, innovative strategies derived from interdisciplinary scientific research will need to develop new vaccine production, storage, and delivery systems. A distinctive & vast research and development platform has been set up for the growth of the next generation of mucosal vaccinations. The latest science and technological advancement in the areas of molecular biology, bio and chemical engineering, genome and system biology has provided accumulated understanding of the inborn and acquired multi-dimensional immune system. This review summarizes recent developments in the use of mucosal vaccines and their associated nanoadjuvants for the control of infectious diseases.

Nanoparticles for mucosal vaccine delivery

Mucosal surfaces represent important routes of entry into the human body for the majority of pathogens, and they constitute unique sites for targeted vaccine delivery. Nanoparticle-based drug delivery systems are emerging technologies for delivering and improving the efficacy of mucosal vaccines. Recent studies have provided new insights into formulation and delivery aspects of importance for the design of safe and efficacious mucosal subunit vaccines based on nanoparticles. These include novel nanomaterials, their physicochemical properties and formulation approaches, nanoparticle interaction with immune cells in the mucosa, and mucosal immunization and delivery strategies. Here, we present recent progress in the application of nanoparticle-based approaches for mucosal vaccine delivery and discuss future research challenges and opportunities in the field.

Study on the biodegradability of modified starch/polylactic acid (PLA) composite materials

In this work, polylactic acid/thermoplastic acetylated starch (PLA/TPAS) composites were prepared using PLA as a matrix material and TPAS as a modifier. TPAS is based on acetylated starch, which is plasticized using glycerin. Analysis of the mechanical, thermal, and dynamic mechanical properties, and morphological structures of the PLA/TPAS composites shows that with an increase in the TPAS content, the toughness of the PLA/TPAS composites significantly improves. When the amount of TPAS added is 40% by weight, the elongation at break is increased 4 times. At the same time, the addition of TPAS has little effect on the thermal stability of the composites. Differential scanning calorimetry (DSC), dynamic mechanical analysis and scanning electron microscopy (SEM) analysis results show that PLA is incompatible with TPAS. The addition of TPAS promotes the crystallization of PLA, resulting in a decrease in the thermal stability but limits the degradation behavior during the processing of the material, which has little effect on the performance of the material. High temperature and high humidity soil degradation and ultraviolet radiation aging experiments on PLA/TPAS composites show that the PLA/TPAS composites have good biodegradability. In soil burial degradation experiments, the degradation rate of the pure PLA material is slow, and its final mass retention rate is high. The PLA/TPAS composites degrade fast. In ultraviolet radiation aging experiments, the tensile strength of the PLA/TPAS composites was improved to a certain extent after exposure to ultraviolet radiation. With an increase in the ultraviolet irradiation time, the tensile properties of the PLA/TPAS composites gradually decreased.

In this work, polylactic acid/thermoplastic acetylated starch (PLA/TPAS) composites were prepared using PLA as a matrix material and TPAS as a modifier.

A CRISPR/Cas9 based polymeric nanoparticles to treat/inhibit microbial infections

The latest breakthrough towards the adequate and decisive methods of gene editing tools provided by CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeat/CRISPR Associated System), has been repurposed into a tool for genetically engineering eukaryotic cells and now considered as the major innovation in gene-related disorders. Nanotechnology has provided an alternate way to overcome the conventional problems where methods to deliver therapeutic agents have failed. The use of nanotechnology has the potential to safe-side the CRISPR/Cas9 components delivery by using customized polymeric nanoparticles for safety and efficacy. The pairing of two (CRISPR/Cas9 and nanotechnology) has the potential for opening new avenues in therapeutic use. In this review, we will discuss the most recent advances in developing nanoparticle-based CRISPR/Cas9 gene editing cargo delivery with a focus on several polymeric nanoparticles including fabrication proposals to combat microbial infections.

A nano-sized blending system comprising identical triblock copolymers with different hydrophobicity for fabrication of an anticancer drug nanovehicle with high stability and solubilizing capacity

Background: A very common and simple method (known as the blending method) to formulate drug delivery systems with required properties is to physically mix amphiphilic block copolymers with different hydrophobicity. In addition to its simplicity, this blending strategy could help avoid the time and effort involved in the synthesis of block copolymers with the desired structure required for specific drug formulations. Purpose: We used the blending strategy to design a system that could overcome the problem of high hydrophobicity and be a good candidate for drug product development using PEG-PLA-PEG triblock copolymers. Methods: Two types of PEG-PLA-PEG triblock copolymers with similar (long) PLA molecular weights (MWs) and different PEG MWs were synthesized. The micellar formulations were prepared by blending the two block copolymers in various ratios. The size and stability of the blending systems were subsequently investigated to optimize the formulations for further studies. The loading properties of doxorubicin or paclitaxel into the optimized blending system were compared to that in mono systems (systems composed of only a single type of triblock copolymer). In vitro and in vivo anti-cancer effects of the preparations were evaluated to assess the use of the blending system as an optimal nanomedicine platform for insoluble anticancer agents. Results: The blending system (B20 system) with an optimized ratio of the triblock copolymers overcame the drawbacks of mono systems. Drug uptake from the drug-loaded B20 system and its anticancer effects against KB cells were superior compared to those of free drugs (doxorubicin hydrochloride and free paclitaxel). In particular, doxorubicin-loaded B20 resulted in extensive doxorubicin accumulation in tumor tissues and significantly higher in vivo anti-cancer effects compared to free doxorubicin. Conclusion: The blending system reported here could be a potential nanoplatform for drug delivery due to its simplicity and efficiency for pharmaceutical application.

Mucosal vaccines and technology

There is an urgent and unmet need to develop effective vaccines to reduce the global burden of infectious disease in both animals and humans, and in particular for the majority of pathogens that infect via mucosal sites. Here we summarise the impediments to developing mucosal vaccines and review the new and emerging technologies aimed at overcoming the lack of effective vaccine delivery systems that is the major obstacle to developing new mucosal vaccines.

Antiretroviral Hydrophobic Core Graft-Copolymer Nanoparticles: The Effectiveness against Mutant HIV-1 Strains and in Vivo Distribution after Topical Application

PURPOSE

Developing and testing of microbicides for pre-exposure prophylaxis and post-exposure protection from HIV are on the list of major HIV/AIDS research priorities. To improve solubility and bioavailability of highly potent anti-retroviral drugs, we explored the use of a nanoparticle (NP) for formulating a combination of two water-insoluble HIV inhibitors.

METHODS

The combination of a non-nucleoside HIV reverse transcriptase inhibitor (NNRTI), Efavirenz (EFV), and an inhibitor of HIV integrase, Elvitegravir (ELV) was stabilized with a graft copolymer of methoxypolyethylene glycol-polylysine with a hydrophobic core (HC) composed of fatty acids (HC-PGC). Formulations were tested in TZM-bl cells infected either with wild-type HIV-1_IIIB, or drug-resistant HIV-1 strains. In vivo testing of double-labeled NP formulations was performed in female rats after a topical intravaginal administration using SPECT/CT imaging and fluorescence microscopy.

RESULTS

We observed a formation of stable 23-30 nm NP with very low cytotoxicity when EFV and ELV were combined with HC-PGC at a 1:10 weight ratio. For NP containing ELV and EFV (at 1:1 by weight) we observed a remarkable improvement of EC50 of EFV by 20 times in the case of A17 strain. In vivo imaging and biodistribution showed in vivo presence of NP components at 24 and 48 h after administration, respectively.

CONCLUSIONS

insoluble orthogonal inhibitors of HIV-1 life cycle may be formulated into the non-aggregating ultrasmall NP which are highly efficient against NNRTI-resistant HIV-1 variant.

The Chlamydia M278 Major Outer Membrane Peptide Encapsulated in the Poly(lactic acid)-Poly(ethylene glycol) Nanoparticulate Self-Adjuvanting Delivery System Protects Mice Against a Chlamydia muridarum Genital Tract Challenge by Stimulating Robust Systemic and Local Mucosal Immune Responses

Recently, we reported that our PPM chlamydial nanovaccine [a biodegradable co-polymeric PLA-PEG (poly(lactic acid)-poly(ethylene glycol))-encapsulated M278 peptide (derived from the major outer membrane protein (MOMP) of Chlamydia)] exploits the caveolin-mediated endocytosis pathway for endosomal processing and MHC class II presentation to immune-potentiate Chlamydia-specific CD4⁺ T-cell immune effector responses. In the present study, we employed the Chlamydia muridarum mouse infection model to evaluate the protective efficacy of PPM against a genital tract challenge. Our results show that mice immunized with PPM were significantly protected against a homologous genital tract challenge evidently by reduced vaginal bacterial loads. Protection of mice correlated with enhanced Chlamydia-specific adaptive immune responses predominated by IFN-γ along with CD4⁺ T-cells proliferation and their differentiation to CD4⁺ memory (CD44^high CD62L^high) and effector (CD44^high CD62L^low) T-cell phenotypes. We observed the elevation of M278- and MOMP-specific serum antibodies with high avidity in the ascending order IgG1 > IgG2b > IgG2a. A key finding was the elevated mucosal IgG1 and IgA antibody titers followed by an increase in MOMP-specific IgA after the challenge. The Th1/Th2 antibody titer ratios (IgG2a/IgG1 and IgG2b/IgG1) revealed that PPM evoked a Th2-directed response, which skewed to a Th1-dominated antibody response after the bacterial challenge of mice. In addition, PPM immune sera neutralized the infectivity of C. muridarum in McCoy cells, suggesting the triggering of functional neutralizing antibodies. Herein, we reveal for the first time that subcutaneous immunization with the self-adjuvanting biodegradable co-polymeric PPM nanovaccine immune-potentiated robust CD4⁺ T cell-mediated immune effector responses; a mixed Th1 and Th2 antibody response and local mucosal IgA to protect mice against a chlamydial genital tract challenge.

Promoting Immune Efficacy of the Oral Helicobacter pylori Vaccine by HP55/PBCA Nanoparticles against the Gastrointestinal Environment

The immunogenicity of oral subunit vaccines is poor partly as a result of the harsh milieu of the gastrointestinal (GI) tract. For some pathogens that restrictedly inhabit the GI tract, a vaccine that works in situ may provide more potent protection than vaccines that operate parenterally. Yet, no appropriate delivery system is available for oral subunit vaccines. In this study, we designed HP55/poly( n-butylcyanoacrylate) (PBCA) nanoparticles (NPs) to carry Helicobacter pylori ( H. pylori) subunit vaccine CCF for oral administration in a prophylactic mice model. These NPs, which are synthesized using an interfacial polymerization method, protected the CCF antigen not only from the acidic pH in simulated gastric fluid (SGF, pH 1.2) but also from the proteolysis in simulated intestinal fluid (SIF, pH 7.4). Oral vaccination of mice with HP55/PBCA-CCF NPs promoted the production of serum antigen-specific antibodies, mucosal secretory IgA, and proinflammatory cytokines. Moreover, a Th1/Th17 response and augmented lymphocytes were found in the gastric tissue of HP55/PBCA-CCF NP-immunized mice, which might eventually limit H. pylori colonization. Collectively, these results indicate that HP55/PBCA NPs are promising carriers against the severe situation of the GI tract and thereby may be further utilized for other orally administrated vaccines or drugs.

Properties and applications of nanoparticle/microparticle conveyors with adjuvant characteristics suitable for oral vaccination

Vaccination is one of the most effective approaches in the prevention and control of disease worldwide. Oral vaccination could have wide applications if effective protection cannot be achieved through traditional (eg, parenteral) routes of vaccination. However, oral administration is hampered by the difficulties in transferring vaccines in vivo. This has led to the development of materials such as carriers with potential adjuvant effects. Considering the requirements for selecting adjuvants for oral vaccines as well as the advantages of nanoparticle/microparticle materials as immune effectors and antigen conveyors, synthetic materials could improve the efficiency of oral vaccination. In this review, nanoparticles and microparticles with adjuvant characteristics are described with regard to their potential importance for oral immunization, and some promising and successful modification strategies are summarized.

Fc-modified exenatide-loaded nanoparticles for oral delivery to improve hypoglycemic effects in mice

To improve the oral efficiency of exenatide, we prepared polyethylene glycol-poly(lactic-co-glycolic acid) (PEG-PLGA) NPs modified with Fc (NPs-Fc) for exenatide oral delivery. Exenatide was encapsulated into the NPs by the w/o/w emulsion-solvent evaporation method. The particle size of the NPs-Fc was approximately 30 nm larger than that of the unmodified NPs with polydispersity indices in a narrow range (PDIs; PDI < 0.3) as detected by DLS, and the highest encapsulation efficiency of exenatide in the NPs was greater than 80%. Fc-conjugated NPs permeated Caco-2 cells faster and to a greater extent compared to unmodified NPs, as verified by CLSM and flow cytometry. Hypoglycemic effect studies demonstrated that oral administration of exenatide-loaded PEG-PLGA NPs modified by an Fc group extended the hypoglycemic effects compared with s.c. injection of the exenatide solution. Fluorescence-labeled NPs were used to investigate the effects of Fc targeting, and the results demonstrated that the NPs-Fc stayed in the gastrointestinal tract for a longer time in comparison with the unmodified NPs, as shown by the whole-body fluorescence images and fluorescence images of the dissected organs detected by in vivo imaging in live mice. Therefore, Fc-targeted nano-delivery systems show great promise for oral peptide/protein drug delivery.

Current state and challenges in developing oral vaccines

While vaccination remains the most cost effective strategy for disease prevention, communicable diseases persist as the second leading cause of death worldwide. There is a need to design safe, novel vaccine delivery methods to protect against unaddressed and emerging diseases. Development of vaccines administered orally is preferable to traditional injection-based formulations for numerous reasons including improved safety and compliance, and easier manufacturing and administration. Additionally, the oral route enables stimulation of humoral and cellular immune responses at both systemic and mucosal sites to establish broader and long-lasting protection. However, oral delivery is challenging, requiring formulations to overcome the harsh gastrointestinal (GI) environment and avoid tolerance induction to achieve effective protection. Here we address the rationale for oral vaccines, including key biological and physicochemical considerations for next-generation oral vaccine design.

Recent developments in nanocarrier-aided mucosal vaccination

To date, most of the licensed vaccines for mucosal delivery are based on live-attenuated viruses which carry the risk of regaining their pathogenicity. Therefore, the development of efficient nonviral vectors allowing the induction of potent humoral and cell-mediated immunity is regarded as an imperative scientific challenge as well as a commercial breakthrough for the pharma industries. For a successful translation to the clinic, such nanocarriers should protect the antigens from mucosal enzymes, facilitate antigen uptake by microfold cells and allow the copresentation of robust, safe for human use, mucosal adjuvants to antigen-presenting cells. Finally, the developed formulations should exhibit accuracy regarding the administered dose, a major drawback of mucosal vaccines in comparison with parenteral ones.

Poly(lactic acid)-based particulate systems are promising tools for immune modulation

Poly(lactic acid) (PLA) is one of the most successful and versatile polymers explored for controlled delivery of bioactive molecules. Its attractive properties of biodegradability and biocompatibility in vivo have contributed in a meaningful way to the approval of different products by the FDA and EMA for a wide range of biomedical and pharmaceutical applications, in the past two decades. This polymer has been widely used for the preparation of particles as delivery systems of several therapeutic molecules, including vaccines. These PLA vaccine carriers have shown to induce a sustained and targeted release of different bacterial, viral and tumor-associated antigens and adjuvants in vivo, triggering distinct immune responses. The present review intends to highlight and discuss the major advantages of PLA as a promising polymer for the development of potent vaccine delivery systems against pathogens and cancer. It aims to provide a critical discussion based on preclinical data to better understand the major effect of PLA-based carrier properties on their interaction with immune cells and thus their role in the modulation of host immunity.

STATEMENT OF SIGNIFICANCE

During the last decades, vaccination has had a great impact on global health with the control of many severe diseases. Polymeric nanosystems have emerged as promising strategies to stabilize vaccine antigens, promoting their controlled release to phagocytic cells, thus avoiding the need for multiple administrations. One of the most promising polymers are the aliphatic polyesters, which include the poly(lactic acid). This is a highly versatile biodegradable and biocompatible polymer. Products containing this polymer have already been approved for all food and some biomedical applications. Despite all favorable characteristics presented above, PLA has been less intensively discussed than other polymers, such as its copolymer PLGA, including regarding its application in vaccination and particularly in tumor immunotherapy. The present review discusses the major advantages of poly(lactic acid) for the development of potent vaccine delivery systems, providing a critical view on the main properties that determine their effect on the modulation of immune cells.

Chemical Synthesis, Versatile Structures and Functions of Tailorable Adjuvants for Optimizing Oral Vaccination

Oral vaccines have become a recent focus because of their potential significance in disease prevention and therapy. In the development of oral vaccine-based therapeutics, synthetic materials with tailorable structures and versatile functions can act as antigen conveyers with adjuvant effects, reduce the time cost for vaccine optimization, and provide high security and enhanced immunity. This review presents an overview of the current status of tailoring synthetic adjuvants for oral vaccination, modification strategies for producing effectors with specific structures and functions, enhancement of immune-associated efficiencies, including the barrier-crossing capability to protect antigens in the gastrointestinal tract, coordination of the antigens penetrating mucosa and cell barriers, targeting of concentrated antigens to immune-associated cells, and direct stimulation of immune cells. Finally, we focus on prospective synthetic adjuvants that facilitate the use of oral vaccines via two approaches, namely, in vivo antigen expression and cancer immunotherapy.

PLA micro- and nano-particles

Poly(d,l-lactic acid) (PLA) has been widely used for various biomedical applications for its biodegradable, biocompatible, and nontoxic properties. Various methods, such as emulsion, salting out, and precipitation, have been used to make better PLA micro- and nano-particle formulations. They are widely used as controlled drug delivery systems of therapeutic molecules, including proteins, genes, vaccines, and anticancer drugs. Even though PLA-based particles have challenges to overcome, such as low drug loading capacity, low encapsulation efficiency, and terminal sterilization, continuous innovations in particulate formulations will lead to development of clinically useful formulations.

Mitochondrion: A Promising Target for Nanoparticle-Based Vaccine Delivery Systems

Vaccination is one of the most popular technologies in disease prevention and eradication. It is promising to improve immunization efficiency by using vectors and/or adjuvant delivery systems. Nanoparticle (NP)-based delivery systems have attracted increasing interest due to enhancement of antigen uptake via prevention of vaccine degradation in the biological environment and the intrinsic immune-stimulatory properties of the materials. Mitochondria play paramount roles in cell life and death and are promising targets for vaccine delivery systems to effectively induce immune responses. In this review, we focus on NPs-based delivery systems with surfaces that can be manipulated by using mitochondria targeting moieties for intervention in health and disease.

Poly(d,l-lactic acid)-block-poly(N-(2-hydroxypropyl)methacrylamide) nanoparticles for overcoming accelerated blood clearance and achieving efficient anti-tumor therapy

The substitution of PEG with PHPMA maintained the long circulation of PDLLA-b-PEG and alleviated the accelerated blood clearance (ABC).

What's Next for Gastrointestinal Disorders: No Needles?

A myriad of pathologies affect the gastrointestinal tract, citing this affected area as a significant target for therapeutic intervention. One group of therapeutic agents, antisense and oligonucleotides and small interfering RNAs, offer a promising platform for treating a wide variety of diseases ranging from cancer to auto-immune diseases. Current delivery methods are carried out either systemically or locally into diseased areas, both of which involve needles. The challenge in orally administering this type of treatment lies in the complications that arise due to the vast environmental extremes found within the gastrointestinal tract, owing to the fact that, as the drug travels down the gastrointestinal tract, it is subjected to pH changes and interactions with bacteria and a variety of digestive and protective enzymes including proteases, DNAses, and RNAses. Overcoming these challenges to allow the practical application of these drugs is a priority that has invoked a multitude of research in the chemical, biological, and material sciences. In this review, we will address common gastrointestinal pathologies, the barriers to oral-based therapies and antisense-interfering technologies, the approaches that have already been applied for their delivery, and the current status of antisense drug therapy clinical trials for gastrointestinal-related disorders.

Micelle-Based Adjuvants for Subunit Vaccine Delivery

In the development of subunit vaccines with purified or recombinant antigens for cancer and infectious diseases, the design of improved and safe adjuvants able to efficiently target the antigen presenting cells, such as dendritic cells, represents a crucial challenge. Nanoparticle-based antigen delivery systems have been identified as an innovative strategy to improve the efficacy of subunit vaccines. Among them, self-assembled micellar nanoparticles from amphiphilic (macro)molecules have recently emerged as promising candidates. In this short review, we report on the recent research findings highlighting the versatility and potential of such systems in vaccine delivery.

Intranasal and oral vaccination with protein-based antigens: advantages, challenges and formulation strategies

Most pathogens initiate their infections at the human mucosal surface. Therefore, mucosal vaccination, especially through oral or intranasal administration routes, is highly desired for infectious diseases. Meanwhile, protein-based antigens provide a safer alternative to the whole pathogen or DNA based ones in vaccine development. However, the unique biopharmaceutical hurdles that intranasally or orally delivered protein vaccines need to overcome before they reach the sites of targeting, the relatively low immunogenicity, as well as the low stability of the protein antigens, require thoughtful and fine-tuned mucosal vaccine formulations, including the selection of immunostimulants, the identification of the suitable vaccine delivery system, and the determination of the exact composition and manufacturing conditions. This review aims to provide an up-to-date survey of the protein antigen-based vaccine formulation development, including the usage of immunostimulants and the optimization of vaccine delivery systems for intranasal and oral administrations.

Preparation and characterization of N-phthaloyl-chitosan-g-(PEO–PLA–PEO) as a potential drug carrier

Synthesis of N-phthaloyl-chitosan-g-(PEO–PLA–PEO) and its drug loading capacities and drug release profiles of IMC.

Radiopaque poly(ε-caprolactone) as additive for X-ray imaging of temporary implantable medical devices

A family of radiopaque PCL, poly(ε-caprolactone-co-α-triiodobenzoate-ε-caprolactone), has been designed, used and evaluated as macromolecular contrast agent for X-ray imaging of implantable polymeric biomaterials.

Optimization of entrapping conditions to improve the release of BMP-2 from PELA carriers by response surface methodology

A microcapsule prepared from triblock copolymer poly(lactic acid)-poly(ethylene glycol)-poly(lactic acid) (PLA-PEG-PLA, PELA) was investigated as a controlled release carrier for recombinant human bone morphogenetic protein-2 (rhBMP-2). The rhBMP-2/PELA microspheres were prepared using the water-in-oil-in-water (W/O/W) solvent evaporation method. This work was conducted to optimize the entrapping conditions of the rhBMP-2 loaded PELA copolymer. The effects on encapsulation efficiency (EE) of different molecular weights (MW) of PEG in the copolymer, the amount of PELA, the amount of rhBMP-2, the span-20 concentration, the polyvinyl alcohol (PVA) concentration and stirring time were tested. On the basis of single-factor experiments, the optimum parameters were achieved using response surface methodology (RSM). The results showed that the highest EE of BMP-2 was achieved with a span-20 concentration of 0.5%, PEG MW 4000 Da, a stirring time of 30 min at 800 rpm min(-1), 282.3 mg of PELA, 1 μg of rhBMP-2 and PVA concentration 0.79%. Under these optimal conditions, it was predicted that the highest EE to be achieved would be 76.5%; the actual EE achieved was 75%.

Polymer nanotechnology based approaches in mucosal vaccine delivery: challenges and opportunities

Mucosal sites serve as the main portal for the entry of pathogens and thus immunization through mucosal routes can greatly improve the immunity. Researchers are continuously exploring the vaccination strategies to engender protective mucosal immune responses. Unearthing of mucosal adjuvants, that are safe and effective, is enhancing the magnitude and quality of the protective immune response. Use of nanotechnology based polymeric nanocarrier systems which encapsulate vaccine components for protection of sensitive payload, incorporate mucosal adjuvants to maximize the immune responses and target the mucosal immune system is a key strategy to improve the effectiveness of mucosal vaccines. These advances promise to accelerate the development and testing of new mucosal vaccines against many human diseases. This review focuses on the need for the development of nanocarrier based mucosal vaccines with emphases on the polymeric nanoparticles, their clinical status and future perspectives. This review focuses on the need and new insights for the development of nanoarchitecture governed mucosal vaccination with emphases on the various polymeric nanoparticles, their clinical status and future perspectives.

Oral delivery of nanoparticle-based vaccines

Most infectious diseases are caused by pathogenic infiltrations from the mucosal tract. Therefore, vaccines delivered to the mucosal tissues can mimic natural infections and provide protection at the first site of infection. Thus, mucosal, especially, oral delivery is becoming the most preferred mode of vaccination. However, oral vaccines have to overcome several barriers such as the extremely low pH of the stomach, the presence of proteolytic enzymes and bile salts as well as low permeability in the intestine. Several formulations based on nanoparticle strategies are currently being explored to prepare stable oral vaccine formulations. This review briefly discusses several molecular mechanisms involved in intestinal immune cell activation and various aspects of oral nanoparticle-based vaccine design that should be considered for improved mucosal and systemic immune responses.

Investigation of 3-D ordered materials with a high adsorption capacity for BSA and their potential application as an oral vaccine adjuvant

3-D ordered macroporous (3DOM) materials were customized for BSA adsorption and further oral immunization. These carriers have a high adsorption capacity and our customized carrier showed a distinctive double-plateau adsorption behavior. Different BSA release rates (between the two plateaus) could be obtained by adjusting the ratio of the protein adsorbed on the internal surface and the external surface. This suggests that the release pattern was determined by the adsorption state. One benefit is that the same carrier could have different release profiles making it possible to study the relationship between the release behavior and adjuvant effects without any distractions. Compared with free BSA alone, a significantly higher level of serum IgG, IgA induced by BSA/3DOM was observed and the release profile had an effect on the immunity. The IgG1 and IgG2a titers suggesting that both the Th1 and Th2 mediated immune response were induced. Therefore, this research could help in the development of a novel inorganic oral adjuvant and provide a new avenue for the administration of oral vaccine.