Evaluation of polylactic acid nanoparticles safety using Drosophila model

Polylactic acid nanoplastics (PLA-NPLs) induce adverse effects on an in vitro model of the human lung epithelium: The Calu-3 air-liquid interface (ALI) barrier

The expected increments in the production/use of bioplastics, as an alternative to petroleum-based plastics, require a deep understanding of their potential environmental and health hazards, mainly as nanoplastics (NPLs). Since one important exposure route to NPLs is through inhalation, this study aims to determine the fate and effects of true-to-life polylactic acid nanoplastics (PLA-NPLs), using the in vitro Calu-3 model of bronchial epithelium, under air-liquid interphase exposure conditions. To determine the harmful effects of PLA-NPLs in a more realistic scenario, both acute (24 h) and long-term (1 and 2 weeks) exposures were used. Flow cytometry results indicated that PLA-NPLs internalized easily in the barrier (∼10 % at 24 h and ∼40 % after 2 weeks), which affected the expression of tight-junctions formation (∼50 % less vs control) and the mucus secretion (∼50 % more vs control), both measured by immunostaining. Interestingly, significant genotoxic effects (DNA breaks) were detected by using the comet assay, with long-term effects being more marked than acute ones (7.01 vs 4.54 % of DNA damage). When an array of cellular proteins including cytokines, chemokines, and growth factors were used, a significant over-expression was mainly found in long-term exposures (∼20 proteins vs 5 proteins after acute exposure). Overall, these results described the potential hazards posed by PLA-NPLs, under relevant long-term exposure scenarios, highlighting the advantages of the model used to study bronchial epithelium tissue damage, and signaling endpoints related to inflammation.

Are bioplastics safe? Hazardous effects of polylactic acid (PLA) nanoplastics in Drosophila

The expanded uses of bioplastics require understanding the potential health risks associated with their exposure. To address this issue, Drosophila melanogaster as a versatile terrestrial in vivo model was employed, and polylactic acid nanoplastics (PLA-NPLs), as a proxy for bioplastics, were tested as a material model. Effects were determined in larvae exposed for 4 days to different concentrations (25, 100, and 400 μg/mL) of 463.9 ± 129.4 nm PLA-NPLs. Transmission electron microscopy (TEM) and scanning electron microscope (SEM) approaches permitted the detection of PLA-NPLs in the midgut lumen of Drosophila larvae, interacting with symbiotic bacteria. Enzymatic vacuoles were observed as carriers, collecting PLA-NPLs and enabling the crossing of the peritrophic membrane, finally internalizing into enterocytes. Although no toxic effects were observed in egg-to-adult survival, cell uptake of PLA-NPLs causes cytological disturbances and the formation of large vacuoles. The translocation across the intestinal barrier was demonstrated by their presence in the hemolymph. PLA-NPL exposure triggered intestinal damage, oxidative stress, DNA damage, and inflammation responses, as evaluated via a wide set of marker genes. Collectively, these structural and molecular interferences caused by PLA-NPLs generated high levels of oxidative stress and DNA damage in the hemocytes of Drosophila larvae. The observed effects point out the need for further studies aiming to deepen the health risks of bioplastics before adopting their uses as a safe plastic alternative.

Protective effect of San Huang Pill and its bioactive compounds against ulcerative colitis in Drosophila via modulation of JAK/STAT, apoptosis, Toll, and Nrf2/Keap1 pathways

ETHNOPHARMACOLOGICAL RELEVANCE

San Huang Pill (SHP) is a prescription in Dunhuang Ancient Medical Prescription, which has the efficacy of heat-clearing and dampness-drying, and is a traditional formula for the treatment of gastrointestinal diseases. However, its efficacy and mechanism in treating ulcerative colitis (UC) are still unclear.

AIM OF THE STUDY

To investigate the protective effects of SHP and its bioactive compounds against Dextran Sulfate Sodium (DSS)-induced intestinal damage using the Drosophila melanogaster model, and to detect the molecular mechanism of SHP in the treatment of UC.

METHODS

Survival rate, locomotion, feeding, and excretion were used to explore the anti-inflammatory effects of SHP. The pharmacotoxicity of SHP was measured using developmental analysis. Intestinal integrity, intestinal length, intestinal acid-base homeostasis, and Tepan blue assay were used to analyze the protective effect of SHP against DSS-induced intestinal damage. The molecular mechanism of SHP was detected using DHE staining, immunofluorescence, real-time PCR, 16 S rRNA gene sequencing, and network pharmacology analysis. Survival rate, intestinal length, and integrity analysis were used to detect the protective effect of bioactive compounds of SHP against intestinal damage.

RESULTS

SHP supplementation significantly increased the survival rate, restored locomotion, increased metabolic rate, maintained intestinal morphological integrity and intestinal homeostasis, protected intestinal epithelial cells, and alleviated intestinal oxidative damage in adult flies under DSS stimulation. Besides, administration of SHP had no toxic effect on flies. Moreover, SHP supplementation remarkably decreased the expression levels of genes related to JAK/STAT, apoptosis, and Toll signaling pathways, increased the gene expressions of the Nrf2/Keap1 pathway, and also reduced the relative abundance of harmful bacteria in DSS-treated flies. Additionally, the ingredients in SHP (palmatine, berberine, baicalein, wogonin, rhein, and aloeemodin) had protection against DSS-induced intestinal injury, such as prolonging survival rate, increasing intestinal length, and maintaining intestinal barrier integrity.

CONCLUSION

SHP had a strong anti-inflammatory function, and remarkably alleviated DSS-induced intestinal morphological damage and intestinal homeostatic imbalance in adult flies by regulating JAK/STAT, apoptosis, Toll and Nrf2/Keap1 signaling pathways, and also gut microbial homeostasis. This suggests that SHP may be a potential complementary and alternative medicine herb therapy for UC, which provides a basis for modern pharmacodynamic evaluation of other prescriptions in Dunhuang ancient medical prescription.

Development of glycan-targeted nanoparticles as a novel therapeutic opportunity for gastric cancer treatment

Chemotherapy resistance remains a major cause of therapeutic failure in gastric cancer. The combination of genetic material such as interference RNAs (iRNAs) to silence cancer-associated genes with chemotherapeutics has become a novel approach for cancer treatment. However, finding the right target genes and developing non-toxic, highly selective nanocarrier systems remains a challenge. Here we developed a novel sialyl-Tn-targeted polylactic acid—didodecyldimethylammonium bromide nanoparticle (PLA-DDAB) nanoparticles (NPs) loaded with dsRNA targeting ST6GalNac-I and/or galectin-3 genes. Using single photon emission computed tomography (SPECT), we have demonstrated that 99mtechnetium radiolabeled sialyl-Tn-targeted nanoparticles can reach the tumor site and downregulate ST6GalNAc-I and galectin-3 RNA expression levels when injected intravenously. Furthermore, using an in vivo gastric tumor model, these nanoparticles increased the effectiveness of 5-FU in reducing tumor growth. Our findings indicate that cancer-associated glycan-targeted NPs loaded with dsRNA targeting ST6GalNAc-I and/or galectin-3 in combination with standard chemotherapy, have the potential to become a novel therapeutic tool for gastric cancer.

The release of polylactic acid nanoplastics (PLA-NPLs) from commercial teabags. Obtention, characterization, and hazard effects of true-to-life PLA-NPLs

This study investigates MNPLs release from commercially available teabags and their effects on both undifferentiated monocultures of Caco-2 and HT29 and in the in vitro model of the intestinal Caco-2/HT29 barrier. Teabags were subjected to mechanical and thermodynamic forces simulating the preparation of a cup of tea. The obtained dispersions were characterized using TEM, SEM, DLS, LDV, NTA, and FTIR. Results confirmed that particles were in the nano-range, constituted by polylactic acid (PLA-NPLs), and about one million of PLA-NPLs per teabag were quantified. PLA-NPLs internalization, cytotoxicity, intracellular reactive oxygen species induction, as well as structural and functional changes in the barrier were assessed. Results show that PLA-NPLs present high uptake rates, especially in mucus-secretor cells, and bio-persisted in the tissue after 72 h of exposure. Although no significant cytotoxicity was observed after the exposure to 100 µg/mL PLA-NPLs during 48 h, a slight barrier disruption could be detected at short-time periods. The present work reveals new insights into the safety of polymer-based teabags, the behavior of true-to-life MNPLs in the human body, as well as new questions on how repeated and prolonged exposures could affect the structure and function of the human intestinal epithelium.

Polylactic acid microparticles in the range of μg/L reduce reproductive capacity by affecting the gonad development and the germline apoptosis in Caenorhabditis elegans

Polylactic acid (PLA) accounts for approximately 45% of the global market of biodegradable plastics. Using Caenorhabditis elegans as an animal model, we examined the effect of long-term exposure to PLA microplastic (MP) on reproductive capacity and the underlying mechanism. Brood size, number of fertilized eggs in uterus, and number of hatched eggs were significantly reduced by exposure to 10 and 100 μg/L PLA MP. Number of mitotic cells per gonad, area of gonad arm, and length of gonad arm were further significantly decreased by exposure to 10 and 100 μg/L PLA MP. In addition, exposure to 10 and 100 μg/L PLA MP enhanced germline apoptosis in the gonad. Accompanied with the enhancement in germline apoptosis, exposure to 10 and 100 μg/L PLA MP decreased expression of ced-9 and increased expressions of ced-3, ced-4, and egl-1. Moreover, the induction of germline apoptosis in PLA MP exposed nematodes was suppressed by RNAi of ced-3, ced-4, and egl-1, and strengthened by RNAi of ced-9. Meanwhile, we did not detect the obvious effect of leachate of 10 and 100 μg/L PLA MPs on reproductive capacity, gonad development, germline apoptosis, and expression of apoptosis related genes. Therefore, exposure to 10 and 100 μg/L PLA MPs potentially reduces the reproductive capacity by influencing the gonad development and enhancing the germline apoptosis in nematodes.

Stereocomplexed microparticles loaded with Salvia cadmica Boiss. extracts for enhancement of immune response towards Helicobacter pylori

Controlled delivery of therapeutic substance gives numerous advantages (prevents degradation, improves uptake, sustains concentration, lowers side effects). To encapsulate Salvia cadmica extracts (root or aerial part), enriched with polyphenols with immunomodulatory activity, in stereocomplexed microparticles (sc-PLA), for using them to enhance the immune response towards gastric pathogen Helicobacter pylori. Microparticles were made of biodegradable poly(lactic acid) (PLA) and poly(D-lactic acid) (PDLA). Their stereocomplexation was used to form microspheres and enhance the stability of the obtained particles in acidic/basic pH. The release of Salvia cadmica extracts was done in different pH (5.5, 7.4 and 8.0). The obtained polymers are safe in vitro and in vivo (guinea pig model). The sc-PLA microparticles release of S. cadmica extracts in pH 5.5, 7.4, and 8.0. S. cadmica extracts enhanced the phagocytic activity of guinea pig bone marrow-derived macrophages, which was diminished by H. pylori, and neutralized H. pylori driven enhanced production of tumor necrosis factor (TNF)-α and interleukin (IL)-10. The sc-PLA encapsulated S. cadmica extracts can be recommended for further in vivo study in guinea pigs infected with H. pylori to confirm their ability to improve an immune response towards this pathogen.

Structural composite based on 3D printing polylactic acid/carbon fiber laminates (PLA/CFRC) as an alternative material for femoral stem prosthesis

In recent years, surgical procedures for hip prostheses have increased. These implants are manufactured with materials with high stiffness compared to the bone, causing bone loss or aseptic loosening. This research proposes an alternative structural composite consisting of 3D-printing polylactic acid layers and carbon fiber laminates (PLA/CFRC) with potential application in prosthetic implants. Fourier-transform infrared spectroscopy (FTIR) achieved to characterize starting materials and structural composites revealed secondary chemical interactions between the carbonyl group of PLA with the hydroxyl group of epoxy resin from CFRC. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) results show both components (PLA and CFRC) influence the structural composite's thermal behavior, observed in the temperatures of degradation, glass transition, and melting. Furthermore, the composite reached cell viability above 80%, a tensile modulus of 19.29 ± 0.48 GPa and tensile strength of 238.91 ± 25.95 MPa, with mechanical properties very similar to the bone. The results of this study demonstrated that the proposed PLA/CFRC composite can be used as candidate base material for the manufacturing of a hip femoral stem prostheses.

Chronic exposure to the star polycation (SPc) nanocarrier in the larval stage adversely impairs life history traits in Drosophila melanogaster

BACKGROUND

Nanomaterials are widely used as pesticide adjuvants to increase pesticide efficiency and minimize environmental pollution. But it is increasingly recognized that nanocarrier is a double-edged sword, as nanoparticles are emerging as new environmental pollutants. This study aimed to determine the biotoxicity of a widely applied star polycation (SPc) nanocarrier using Drosophila melanogaster, the fruit fly, as an in vivo model.

RESULTS

The lethal concentration 50 (LC₅₀) value of SPc was identified as 2.14 g/L toward third-instar larvae and 26.33 g/L for adults. Chronic exposure to a sub lethal concentration of SPc (1 g/L) in the larval stage showed long-lasting adverse effects on key life history traits. Exposure to SPc at larval stage adversely impacted the lifespan, fertility, climbing ability as well as stresses resistance of emerged adults. RNA-sequencing analysis found that SPc resulted in aberrant expression of genes involved in metabolism, innate immunity, stress response and hormone production in the larvae. Orally administrated SPc nanoparticles were mainly accumulated in intestine cells, while systemic responses were observed.

CONCLUSIONS

These findings indicate that SPc nanoparticles are hazardous to fruit flies at multiple levels, which could help us to develop guidelines for further large-scale application.

Photonic and magnetic materials for on-demand local drug delivery

Nanomedicine has been considered a promising tool for biomedical research and clinical practice in the 21st century because of the great impact nanomaterials could have on human health. The generation of new smart nanomaterials, which enable time- and space-controlled drug delivery, improve the limitations of conventional treatments, such as non-specific targeting, poor biodistribution and permeability. These smart nanomaterials can respond to internal biological stimuli (pH, enzyme expression and redox potential) and/or external stimuli (such as temperature, ultrasound, magnetic field and light) to further the precision of therapies. To this end, photonic and magnetic nanoparticles, such as gold, silver and iron oxide, have been used to increase sensitivity and responsiveness to external stimuli. In this review, we aim to report the main and most recent systems that involve photonic or magnetic nanomaterials for external stimulus-responsive drug release. The uniqueness of this review lies in highlighting the versatility of integrating these materials within different carriers. This leads to enhanced performance in terms of in vitro and in vivo efficacy, stability and toxicity. We also point out the current regulatory challenges for the translation of these systems from the bench to the bedside, as well as the yet unresolved matter regarding the standardization of these materials.

Mucosal Adjuvants Delivered by a Mucoadhesive Patch for Sublingual Administration of Subunit Vaccines

Among mucosal administration routes for vaccines, the sublingual route has been proven capable of inducing a potent systemic and mucosal immune response. However, the absence of a simple and compliant delivery system and the lack of robust mucosal adjuvants impede the development of sublingual vaccines. Here, we describe a mucoadhesive patch made of a layer-by-layer assembly of polysaccharides, chitosan, and hyaluronic acid. The mucoadhesive patch was covered by adjuvanted nanoparticles carrying viral proteins. We showed that the nanoparticles effectively cross the outer layers of the sublingual mucosa to reach the epithelium. Furthermore, the encapsulated adjuvants, 3M-052 and mifamurtide, targeting toll-like receptor (TLR) 7/8 and nucleotide-binding oligomerization domain-2 (NOD2), respectively, remain fully active after encapsulation into nanoparticles and exhibit a cytokine/chemokine signature similar to the mucosal gold-standard adjuvant, the cholera toxin. However, the particulate adjuvants induced more moderate levels of proinflammatory interleukin (IL)-6 and keratinocyte chemoattractant (KC), suggesting a controlled activation of the innate immune response.

Flos puerariae ameliorates the intestinal inflammation of Drosophila via modulating the Nrf2/Keap1, JAK-STAT and Wnt signaling

Gut homeostasis is important for human health, and its disruption can lead to inflammatory bowel disease (IBD). Flos Puerariae is a herb with a wide variety of pharmacological activities including antioxidant, antidiabetic, antialcoholismic and anti-inflammatory properties. However, the role of Flos Puerariae on treating IBD remains obscure. Here, we employed Drosophila melanogaster as a model organism to investigate the protective effect of Flos Puerariae extract (FPE) against sodium dodecyl sulfate (SDS)-induced intestinal injury. Our data showed that FPE had no toxic effect in flies, and significantly extended lifespan in SDS-inflamed flies, reduced stem cell proliferation in the midgut, and maintained intestinal morphological integrity. Furthermore, FPE remarkably recused the altered expression level of genes and proteins in Nrf2/Keap1 signaling, JAK-STAT signaling and Wnt signaling pathways in gut of inflammation flies. Thus, FPE has a protective effect against intestinal injury possibly via increasing the Nrf2/keap1 pathway and suppressing the JAK-STAT and Wnt signaling pathways, which would have tremendous potential for treating IBD.

Bioinspired silk fibroin nano-delivery systems protect against 5-FU induced gastrointestinal mucositis in a mouse model and display antitumor effects on HT-29 colorectal cancer cells in vitro

Colorectal cancer (CRC), is the second cause of cancer-related deaths worldwide is one of the most prevalent types of cancers. Conventional treatment continues to rely on surgery, chemotherapy, and radiotherapy, but for advanced cases, adjuvant chemotherapy remains the main approach for improving surgical outcomes and lower the disease recurrence probability. Chemotherapy-induced gastrointestinal (GI) toxicity is the main dose-limiting factor for many chemotherapeutic regimens, including 5-FU, and one of the biggest oncological challenges. Up to 40% of the patients receiving 5-FU get mucositis, 10-15% of which develop severe symptoms. In this context, our study aimed to develop a bioinspired nanosized drug delivery system as a strategy to reduce 5-FU associated side effects, such as GI mucositis. To this end, SF-based nanoparticles were prepared and characterized in terms of size and morphology, as well as in terms of in vitro antitumoral activity on a biomimetic colorectal cancer model by investigation of apoptosis, DNA fragmentation, and release of reactive oxygen species. Additionally, the capacity of the SF-based nanocarriers to offer intestinal protection against 5-FU-induced GI mucositis was evaluated in vivo using a mouse model that mimics the chemotherapy-associated gut mucositis occurring in colorectal cancer. Our studies show that silk fibroin nanoparticles efficiently deliver 5-FU to tumor cells in vitro while protecting against drug-induced GI mucositis in a mouse model.

Reactive oxygen species: the root cause of nanoparticle-induced toxicity in Drosophila melanogaster

Nanotechnology is a rapidly developing technology in the twenty-first century. Nanomaterials are extensively used in numerous industries including cosmetics, food, medicines, industries, agriculture, etc. Along with its wide application toxicity is also reported from studies of various model organisms including Drosophila. The toxicity reflects cytotoxicity, genotoxicity, and teratogenicity. The current study correlates the toxicity as a consequence of reactive oxygen species (ROS) generated owing to the presence of nanoparticles with the living cell. ROS mainly includes hydroxyl ions, peroxide ions, superoxide anions, singlet oxygen, and hypochlorous acids. An elevated level of ROS can damage the cells by various means. To protect the body from excess ROS, living cells possess a set of antioxidant enzymes which includes peroxidase, glutathione peroxidase, and catalase. If the antioxidant enzymes cannot nullify the elevated ROS level than DNA damage, cell damage, cytotoxicity, apoptosis, and uncontrolled cell regulations occur resulting in abnormal physiological and genotoxic conditions. Herewith, we are reporting various morphological and physiological defects caused after nanoparticle treatment as a function of redox imbalance.

LipoParticles: Lipid-Coated PLA Nanoparticles Enhanced In Vitro mRNA Transfection Compared to Liposomes

The approval of two mRNA vaccines as urgent prophylactic treatments against Covid-19 made them a realistic alternative to conventional vaccination methods. However, naked mRNA is rapidly degraded by the body and cannot effectively penetrate cells. Vectors capable of addressing these issues while allowing endosomal escape are therefore needed. To date, the most widely used vectors for this purpose have been lipid-based vectors. Thus, we have designed an innovative vector called LipoParticles (LP) consisting of poly(lactic) acid (PLA) nanoparticles coated with a 15/85 mol/mol DSPC/DOTAP lipid membrane. An in vitro investigation was carried out to examine whether the incorporation of a solid core offered added value compared to liposomes alone. To that end, a formulation strategy that we have named particulate layer-by-layer (pLbL) was used. This method permitted the adsorption of nucleic acids on the surface of LP (mainly by means of electrostatic interactions through the addition of LAH4-L1 peptide), allowing both cellular penetration and endosomal escape. After a thorough characterization of size, size distribution, and surface charge- and a complexation assessment of each vector-their transfection capacity and cytotoxicity (on antigenic presenting cells, namely DC2.4, and epithelial HeLa cells) were compared. LP have been shown to be significantly better transfecting agents than liposomes through pLbL formulation on both HeLa and DC 2.4 cells. These data illustrate the added value of a solid particulate core inside a lipid membrane, which is expected to rigidify the final assemblies and makes them less prone to early loss of mRNA. In addition, this assembly promoted not only efficient delivery of mRNA, but also of plasmid DNA, making it a versatile nucleic acid carrier that could be used for various vaccine applications. Finally, if the addition of the LAH4-L1 peptide systematically leads to toxicity of the pLbL formulation on DC 2.4 cells, the optimization of the nucleic acid/LAH4-L1 peptide mass ratio becomes an interesting strategy-essentially reducing the peptide intake to limit its cytotoxicity while maintaining a relevant transfection efficiency.

Surface charge modulation of rifampicin-loaded PLA nanoparticles to improve antibiotic delivery in Staphylococcus aureus biofilms

Background

After the golden age of antibiotic discovery, bacterial infections still represent a major challenge for public health worldwide. The biofilm mode of growth is mostly responsible for chronic infections that current therapeutics fail to cure and it is well-established that novel strategies must be investigated. Particulate drug delivery systems are considered as a promising strategy to face issues related to antibiotic treatments in a biofilm context. Particularly, poly-lactic acid (PLA) nanoparticles present a great interest due to their ability to migrate into biofilms thanks to their submicronic size. However, questions still remain unresolved about their mode of action in biofilms depending on their surface properties. In the current study, we have investigated the impact of their surface charge, firstly on their behavior within a bacterial biofilm, and secondly on the antibiotic delivery and the treatment efficacy.

Results

Rifampicin-loaded PLA nanoparticles were synthetized by nanoprecipitation and characterized. A high and superficial loading of rifampicin, confirmed by an in silico simulation, enabled to deliver effective antibiotic doses with a two-phase release, appropriate for biofilm-associated treatments. These nanoparticles were functionalized with poly-l-lysine, a cationic peptide, by surface coating inducing charge reversal without altering the other physicochemical properties of these particles. Positively charged nanoparticles were able to interact stronger than negative ones with Staphylococcus aureus, under planktonic and biofilm modes of growth, leading to a slowed particle migration in the biofilm thickness and to an improved retention of these cationic particles in biofilms. While rifampicin was totally ineffective in biofilms after washing, the increased retention capacity of poly-l-lysine-coated rifampicin-loaded PLA nanoparticles has been associated with a better antibiotic efficacy than uncoated negatively charged ones.

Conclusions

Correlating the carrier retention capacity in biofilms with the treatment efficacy, positively charged rifampicin-loaded PLA nanoparticles are therefore proposed as an adapted and promising approach to improve antibiotic delivery in S. aureus biofilms.

Recombinant Haemagglutinin Derived From the Ciliated Protozoan Tetrahymena thermophila Is Protective Against Influenza Infection

Current influenza vaccines manufactured using eggs have considerable limitations, both in terms of scale up production and the potential impact passaging through eggs can have on the antigenicity of the vaccine virus strains. Alternative methods of manufacture are required, particularly in the context of an emerging pandemic strain. Here we explore the production of recombinant influenza haemagglutinin using the ciliated protozoan Tetrahymena thermophila. For the first time we were able to produce haemagglutinin from both seasonal influenza A and B strains. This ciliate derived material was immunogenic, inducing an antibody response in both mice and non-human primates. Mice immunized with ciliate derived haemagglutinin were protected against challenge with homologous influenza A or B viruses. The antigen could also be combined with submicron particles containing a Nod2 ligand, significantly boosting the immune response and reducing the dose of antigen required. Thus, we show that Tetrahymena can be used as a manufacturing platform for viral vaccine antigens.

Hazard Assessment of Polymeric Nanobiomaterials for Drug Delivery: What Can We Learn From Literature So Far

The physicochemical properties of nanobiomaterials, such as their small size and high surface area ratio, make them attractive, novel drug-carriers, with increased cellular interaction and increased permeation through several biological barriers. However, these same properties hinder any extrapolation of knowledge from the toxicity of their raw material. Though, as suggested by the Safe-by-Design (SbD) concept, the hazard assessment should be the starting point for the formulation development. This may enable us to select the most promising candidates of polymeric nanobiomaterials for safe drug-delivery in an early phase of innovation. Nowadays the majority of reports on polymeric nanomaterials are focused in optimizing the nanocarrier features, such as size, physical stability and drug loading efficacy, and in performing preliminary cytocompatibility testing and proving effectiveness of the drug loaded formulation, using the most diverse cell lines. Toxicological studies exploring the biological effects of the polymeric nanomaterials, particularly regarding immune system interaction are often disregarded. The objective of this review is to illustrate what is known about the biological effects of polymeric nanomaterials and to see if trends in toxicity and general links between physicochemical properties of nanobiomaterials and their effects may be derived. For that, data on chitosan, polylactic acid (PLA), polyhydroxyalkanoate (PHA), poly(lactic-co-glycolic acid) (PLGA) and policaprolactone (PCL) nanomaterials will be evaluated regarding acute and repeated dose toxicity, inflammation, oxidative stress, genotoxicity, toxicity on reproduction and hemocompatibility. We further intend to identify the analytical and biological tests described in the literature used to assess polymeric nanomaterials toxicity, to evaluate and interpret the available results and to expose the obstacles and challenges related to the nanomaterial testing. At the present time, considering all the information collected, the hazard assessment and thus also the SbD of polymeric nanomaterials is still dependent on a case-by-case evaluation. The identified obstacles prevent the identification of toxicity trends and the generation of an assertive toxicity database. In the future, in vitro and in vivo harmonized toxicity studies using unloaded polymeric nanomaterials, extensively characterized regarding their intrinsic and extrinsic properties should allow to generate such database. Such a database would enable us to apply the SbD approach more efficiently.

Molecular modelling of TLR agonist Pam3CSK4 entrapment in PLA nanoparticles as a tool to explain loading efficiency and functionality

Designing potent and safe-of-use therapies against cancers and infections remains challenging despite the emergence of novel molecule classes like checkpoint inhibitors or Toll-Like-Receptor ligands. The latest therapeutic perspectives under development for immune modulator administration exploits vectorization, and biodegradable delivery systems are one of the most promising vehicles. Nanoparticles based on Poly (D,L) Lactic Acid (PLA) as polymer for formulation are widely investigated due to its bioresorbable, biocompatible and low immunogen properties. We propose a PLA-based nanoparticle delivery system to vectorize Pam₃CSK₄, a lipopeptide TLR1/2 ligand and a potent activator of the proinflammatory transcription factor NF-κB that shows a self-assembling behavior from 30 µg/mL onwards. We demonstrate successful encapsulation of Pam₃CSK₄ in PLA nanoparticles by nanoprecipitation in a 40-180 µg/mL concentration range, with 99% of entrapment efficiency. By molecular modelling, we characterize drug/carrier interactions and conclude that Pam₃CSK₄ forms clusters onto the nanoparticle and is not encapsulated into the hydrophobic core. In silico predictions provide nanoprecipitation optimization and the mechanistic understanding of the particle dynamics. The loaded-Pam₃CSK₄ maintains bioactivity on TLR2, confirmed by in vitro experiments using reporter cell line HEK-Blue hTLR2. Our presented data and results are convincing evidence that Pam₃CSK₄-loaded in PLA nanoparticles represent a promising immune modulating system.

Poly(D,L-Lactic Acid) Nanoparticle Size Reduction Increases Its Immunotoxicity

Polylactic acid (PLA), a biodegradable and biocompatible polymer produced from renewable resources, has been widely used as a nanoparticulate platform for antigen and drug delivery. Despite generally regarded as safe, its immunotoxicological profile, when used as a polymeric nanoparticle (NP), is not well-documented. Thus, this study intends to address this gap, by evaluating the toxicity of two different sized PLA NPs (PLA_A NPs and PLA_B NPs), produced by two nanoprecipitation methods and extensively characterized regarding their physicochemical properties in in vitro experimental conditions. After production, PLA_A NPs mean diameter (187.9 ± 36.9 nm) was superior to PLA_B NPs (109.1 ± 10.4 nm). Interestingly, when in RPMI medium, both presented similar mean size (around 100 nm) and neutral zeta potential, possibly explaining the similarity between their cytotoxicity profile in PBMCs. On the other hand, in DMEM medium, PLA_A NPs presented smaller mean diameter (75.3 ± 9.8 nm) when compared to PLA_B NPs (161.9 ± 8.2 nm), which may explain its higher toxicity in RAW 264.7. Likewise, PLA_A NPs induced a higher dose-dependent ROS production. Irrespective of size differences, none of the PLA NPs presented an inflammatory potential (NO production) or a hemolytic activity in human blood. The results herein presented suggest the hypothesis, to be tested in the future, that PLA NPs presenting a smaller sized population possess increased cytotoxicity. Furthermore, this study emphasizes the importance of interpreting results based on adequate physicochemical characterization of nanoformulations in biological medium. As observed, small differences in size triggered by the dispersion in cell culture medium can have repercussions on toxicity, and if not correctly evaluated can lead to misinterpretations, and subsequent ambiguous conclusions.

Poly(lactic acid) nanoparticles and cell-penetrating peptide potentiate mRNA-based vaccine expression in dendritic cells triggering their activation

Messenger RNA-based vaccines have the potential to trigger robust cytotoxic immune responses, which are essential for fighting cancer and infectious diseases like HIV. Dendritic Cells (DCs) are choice targets for mRNA-based vaccine strategies, as they link innate and adaptive immune responses and are major regulators of cytotoxic and humoral adaptive responses. However, efficient delivery of antigen-coding mRNAs into DC cytosol has been highly challenging. In this study, we developed an alternative to lipid-based mRNA delivery systems, using poly(lactic acid) nanoparticles (PLA-NPs) and cationic cell-penetrating peptides as mRNA condensing agent. The formulations are assembled in two steps: (1) formation of a polyplex between mRNAs and amphipathic cationic peptides (RALA, LAH4 or LAH4-L1), and (2) adsorption of polyplexes onto PLA-NPs. LAH4-L1/mRNA polyplexes and PLA-NP/LAH4-L1/mRNA nanocomplexes are taken up by DCs via phagocytosis and clathrin-dependent endocytosis, and induce strong protein expression in DCs in vitro. They modulate DC innate immune response by activating both endosome and cytosolic Pattern Recognition Receptors (PRRs), and induce markers of adaptive responses in primary human DCs in vitro, with prevalent Th1 signature. Thus, LAH4-L1/mRNA and PLA-NP/LAH4-L1/mRNA represent a promising platform for ex vivo treatment and mRNA vaccine development.

Rotary jet-spun porous microfibers as scaffolds for stem cells delivery to central nervous system injury

Stem cell transplantation is a promising strategy to treat brain injuries. However, cell-based therapies are limited because poor local cell engraftment. Here, we present a polylactic acid (PLA) scaffold to support mesenchymal stem cells (MSCs) delivery in stroke. We isolated bone marrow MSCs from adult C57/Bl6 mice, cultured them on PLA polymeric rough microfibrous (PRM) scaffolds obtained by rotary jet spinning, and transplanted over the brains of adult C57/Bl6 mice, carrying thermocoagulation-induced cortical stroke. No inflammatory response to PRM was found. MSCs transplantation significantly reduced the area of the lesion and PRM delivery increased MSCs retention at the injury site. In addition, PRM upregulated α6-integrin and CXCL12 production, which may be the cause for greater cell retention at the lesion site and may provide additional benefit to MSCs transplantation procedures. We conclude that PRM scaffolds offer a promising new system to deliver stem cells to injured areas of the brain.

Population Effects of Calcium Phosphate Nanoparticles in Drosophila melanogaster: The Effects of Phase Composition, Crystallinity, and the Pathway of Formation

Unpredictable biological response due to the finest nanostructural variations is one of the hallmarks of nanoparticles. Because of this erratic behavior of nanoparticles in living systems, thorough analyses of biosafety must precede the analyses of the pharmacotherapeutic efficacy and simple animal models are ideal for such purposes. Drosophila melanogaster, the common fruit fly, is an animal model capable of giving a fast, high-throughput response as to the safety and efficacy of drug delivery carriers and other pharmacological agents, while minimizing the suffering imposed onto animals in more complex in vivo models. Here we studied the effects on the viability and fertility of D. melanogaster due to variations in phase composition, crystallinity, and the pathway of formation of four different calcium phosphate (CP) nanopowders consumed orally. To minimize the effect of other nanostructural variables, CP nanopowders were made to possess highly similar particle sizes and morphologies. The composition of CP affected the fecundity of flies, but so did crystallinity and the pathway of formation. Both the total number of eclosed viable flies and pupae in populations challenged with hydroxyapatite (HAP) greatly exceeded those in control populations. Viability was adversely affected by the only pyrophosphate tested (CPP) and by the metastable and the most active of all CP nanopowders analyzed: the amorphous CP (ACP). The pupation peak was delayed and the viable fly to-pupa ratio increased in all the CP-challenged populations. F1 CPP population, whose viability was most adversely affected by the CP consumption, when crossed, produced the largest number of F2 progeny under regular conditions, possibly pointing to stress as a positive evolutionary drive. The positive effect of HAP on fertility of fruit flies may be due to its slow absorption and the activation of calmodulin during the transit of oocytes through the reproductive tract of fertilized females. Exerted in the prepupation stage, the effect of CP is thus traceable beyond the instar larval stage and to the oogenesis stage of the Drosophila lifecycle.

Poly(Lactic Acid) Nanoparticles Targeting α5β1 Integrin as Vaccine Delivery Vehicle, a Prospective Study

Biodegradable polymeric nanoparticles are vehicles of choice for drug delivery and have the ability to encapsulate and present at their surface different molecules of interest. Among these bio-nanocarriers, poly(lactic acid) (PLA) nanoparticles have been used as adjuvant and vehicle for enhanced vaccine efficacy. In order to develop an approach to efficient vaccine delivery, we developed nanoparticles to target α5β1 positive cells. We first overproduced, in bacteria, human fibronectin FNIII9/10 recombinant proteins possessing an integrin α5β1 binding site, the RGDS sequence, or a mutated form of this site. After having confirmed the integrin binding properties of these recombinant proteins in cell culture assays, we were able to formulate PLA nanoparticles with these FNIII9/10 proteins at their surface. We then confirmed, by fluorescence and confocal microscopy, an enhanced cellular uptake by α5β1+ cells of RGDS-FNIII9/10 coated PLA nanoparticles, in comparison to KGES-FNIII9/10 coated or non-coated controls. As a first vaccination approach, we prepared PLA nanoparticles co-coated with p24 (an HIV antigen), and RGDS- or KGES-FNIII9/10 proteins, followed by subcutaneous vaccine administration, in mice. Although we did not detect improvements in the apparent humoral response to p24 antigen in the serum of RGDS/p24 nanoparticle-treated mice, the presence of the FNIII proteins increased significantly the avidity index of anti-p24 antibodies compared to p24-nanoparticle-injected control mice. Future developments of this innovative targeted vaccine are discussed.

Novel biodegradable nanocarriers for enhanced drug delivery

With the refinement of functional properties, the interest around biodegradable materials, in biorelated applications and, in particular, in their use as controlled drug-delivery systems, increased in the last decades. Biodegradable materials are an ideal platform to obtain nanoparticles for spatiotemporal controlled drug delivery for the in vivo administration, thanks to their biocompatibility, functionalizability, the control exerted on delivery rates and the complete degradation. Their application in systems for cancer treatment, brain and cardiovascular diseases is already a consolidated practice in research, while the bench-to-bedside translation is still late. This review aims at summarizing reported applications of biodegradable materials to obtain drug-delivery nanoparticles in the last few years, giving a complete overview of pros and cons related to degradable nanomedicaments.