Cytotoxicity of thermo-responsive polymeric nanoparticles based on N-isopropylacrylamide for potential application as a bioscaffold

Switching it Up: The Promise of Stimuli-Responsive Polymer Systems in Biomedical Science

Responsive polymer systems have the ability to change properties or behavior in response to external stimuli. The properties of responsive polymer systems can be fine-tuned by adjusting the stimuli, enabling tailored responses for specific applications. These systems have applications in drug delivery, biosensors, tissue engineering, and more, as their ability to adapt and respond to dynamic environments leads to improved performance. However, challenges such as synthesis complexity, sensitivity limitations, and manufacturing issues need to be addressed for successful implementation. In our review, we provide a comprehensive summary on stimuli-responsive polymer systems, delving into the intricacies of their mechanisms and actions. Future developments should focus on precision medicine, multifunctionality, reversibility, bioinspired designs, and integration with advanced technologies, driving the dynamic growth of sensitive polymer systems in biomedical applications.

pNiPAM-Nanoparticle-Based Antiapoptotic Approach for Pro-Regenerative Capacity of Skeletal Myogenic Cells

The biocompatibility of pNiPAM (Poly N-isopropylacrylamide) copolymers has been examined and they did not exert any cytotoxic effects. Their properties and vulnerable temperature characteristics make them candidates for use in medical applications. We synthesized a well-characterized nanoparticles-based cargo system that would effectively deliver a biological agent to human skeletal myogenic cells (SkMCs); among other aspects, a downregulating apoptotic pathway potentially responsible for poor regeneration of myocardium. We confirmed the size of the pNiPAM based spheres at around 100 nm and the nanomeric shape of nanoparticles (NP) obtained. We confirmed that 33 °C is the adequate temperature for phase transition. We performed the dynamics of cargo release. A small amount of examined protein was detected at 10 min after reaching LCTS (lower critical solution temperature). The presented results of the test with BSA (bovine serum albumin) and doxorubicin loaded into nanoparticles showed a similar release profile for both substances. SkMCs incubated with NP loaded with antiapoptotic agent, BCB (Bax channel blocker), significantly diminished cell apoptosis (p < 0.01). Moreover, the lowest apoptotic level was detected in SkMCs treated with camptothecin and simultaneously incubated with pNiPAMs loaded with BCB. Application of nanoparticles loaded with BCB or subjected to BCB alone did not, however, diminish the amount of apparently necrotic cells.

Biodegradable Polymeric Nanoparticles for Drug Delivery to Solid Tumors

Advances in nanotechnology have favored the development of novel colloidal formulations able to modulate the pharmacological and biopharmaceutical properties of drugs. The peculiar physico-chemical and technological properties of nanomaterial-based therapeutics have allowed for several successful applications in the treatment of cancer. The size, shape, charge and patterning of nanoscale therapeutic molecules are parameters that need to be investigated and modulated in order to promote and optimize cell and tissue interaction. In this review, the use of polymeric nanoparticles as drug delivery systems of anticancer compounds, their physico-chemical properties and their ability to be efficiently localized in specific tumor tissues have been described. The nanoencapsulation of antitumor active compounds in polymeric systems is a promising approach to improve the efficacy of various tumor treatments.

Temperature-Responsive Poly(N-Isopropylacrylamide) Nanogels: The Role of Hollow Cavities and Different Shell Cross-Linking Densities on Doxorubicin Loading and Release

Smart polymers with extraordinary characteristics are studied in drug-delivery applications. In the current study, temperature-responsive hybrid core-shell nanoparticles were synthesized by precipitation polymerization of N-isopropylacrylamide and vinyl-modified silica nanoparticles. These temperature-responsive hybrid core-shells were prepared with different cross-linking densities by using 2, 4, and 8 mol % of N,N-methylene bisacrylamide (MBA). Hydrolysis of the silica cores of the hybrid core-shells resulted in hollow poly(N-isopropylacrylamide) (PNIPAM) nanogels. Functionalization of silica nanoparticles with vinyl-containing silane modifier of 3-(trimethoxysilyl) propyl methacrylate (MPS) in two different contents was proven by Fourier transform infrared spectroscopy. Preparation of the hybrid PNIPAM nanogels and etching of the silica cores were studied using thermogravimetric analysis and also electron microscopy imaging. Sensitivity of the PNIPAM nanogel samples to temperature was studied using ultraviolet-visible (UV-vis) spectroscopy. In addition, dynamic light scattering was used for investigation of the squeezing and expansion of the hybrid and hollow samples against variation of temperature. The UV-vis spectroscopy results display higher absorption intensities in higher contents of MPS modifier and MBA cross-linker. The swelling content of the nanogels with hollow cavities was higher than that of the hybrid samples. The hybrid nanogels with 2 and 8 wt % silica content and different cross-linking densities and also their hollow nanoparticles were used for loading and release of doxorubicin (DOX). The release characteristics of the DOX-loaded nanogels were studied at different temperatures using UV-vis spectroscopy. The DOX release was higher at temperatures lower than the gel collapse temperature of the PNIPAM network. Although the nanogels with hollow cavities displayed higher loading capacities, the release percentage was higher for the hybrid PNIPAM nanogels, which was confirmed by the experimental release profiles and mathematical models. The most appropriate fitting of the DOX release data from the PNIPAM nanogel samples was observed for the Korsmeyer-Peppas model. Cytotoxicity studies on HeLa cell line showed that drug-loaded hollow samples showed higher toxicity due to loading of a higher amount of DOX.

A study of digital image analysis on the acrylamide derivative monomers induced apoptosis in rat cerebrum

Nowadays, apoptosis is mostly evaluated visually in histological studies. By using the quantitative digital image analysis, this study aimed to investigate the effect of acrylamide-based monomers (acrylamide [AAm], methacrylamide [MAAm], N-isopropylacrylamide [NIPAm]) on the cerebrum tissues in rats, which are the most common water-soluble monomers in the production of polymeric hydrogels used as biomaterials. The Wistar albino rats weighing ~220-240 g were divided into control and three test groups. The control group received 1 mL of saline, and the test groups received 1 mL of aqueous 50 mg/kg/day intramuscular injection of AAm, MAAm, and NIPAm, respectively. At the end of the experiments, brain tissues of all rats euthanized by intramuscular injection of sodium pentobarbital were removed. Terminal deoxynucleotide transferase dUTP nick and labeling (TUNEL) method was applied to brain tissue sections. The monomers have been shown to cause apoptosis due to oxidative stress in cerebrum tissue. Based on apoptosis by tunneling method, quantitative digital image analysis of cell fragments was performed with Olympus cellSens Dimension 1.15 software, and the number, total count area, selected area, average area, and ROI% values of the fragments were found. In addition, the total area and ROI% values of the fragments increased linearly with increasing the molar mass of monomers from the digital image analysis data. Quantitative digital image analysis can facilitate the monitoring of apoptosis caused by the oxidative stress of monomers used in the production of the biomaterials.

Exploring the anomalous cytotoxicity of commercially-available poly(N-isopropyl acrylamide) substrates

Poly(N-isopropyl acrylamide) (pNIPAM) is a stimulus-responsive polymer that has been of great interest to the bioengineering community. When the temperature is lowered below its lower critical solution temperature (∼32 °C), pNIPAM rapidly hydrates, and adherent cells detach as intact cell sheets. This cell-releasing behavior in a physiologically relevant temperature range has led to NIPAM's use for engineered tissues and other devices. In a previous study, however, the authors found that although most techniques used to polymerize NIPAM yield biocompatible films, some formulations from commercially-available NIPAM (cpNIPAM) can be cytotoxic. In this work, the authors investigate the reasons underlying this anomaly. The authors evaluated the response of a variety of cell types (e.g., bovine aortic endothelial cells, BAECs; monkey kidney epithelial cells, Vero cells; and mouse embryonic fibroblasts, 3T3s) after culture on substrates spin-coated with sol-gel (spNIPAM) and commercially-prepared (cpNIPAM). The relative biocompatibility of each cell type was evaluated using observations of its cell morphology and function (e.g., XTT and Live/Dead assays) after 48 and 96 h in culture. In addition, the substrates themselves were analyzed using NMR, goniometry, and XPS. The authors find that all the cell types were compromised by 96 h in culture with cpNIPAM, although the manner in which the cells are compromised differs; in particular, while Vero and 3T3 cells appear to be undergoing cytotoxic death, BAECs undergo apoptic death. The authors believe that this result is due to a combination of factors, including the presence of short chain oligomers of NIPAM in the commercially-available preparation. This work will provide valuable insights into the cytotoxicity of commercially-prepared polymer substrates for this type of bioengineering work and therefore into the applicability of cells grown on such surfaces for human subjects.

Biosafety of the Novel Vancomycin-loaded Bone-like Hydroxyapatite/Poly-amino Acid Bony Scaffold

BACKGROUND

Recently, local sustained-release antibiotics systems have been developed because they can increase local foci of concentrated antibiotics without increasing the plasma concentration, and thereby effectively decrease any systemic toxicity and side effects. A vancomycin-loaded bone-like hydroxyapatite/poly-amino acid (V-BHA/PAA) bony scaffold was successfully fabricated with vancomycin-loaded poly lactic-co-glycolic acid microspheres and BHA/PAA, which was demonstrated to exhibit both porosity and perfect biodegradability. The aim of this study was to systematically evaluate the biosafety of this novel scaffold by conducting toxicity tests in vitro and in vivo.

METHODS

According to the ISO rules for medical implant biosafety, for in vitro tests, the scaffold was incubated with L929 fibroblasts or rabbit noncoagulant blood, with simultaneous creation of positive control and negative control groups. The growth condition of L929 cells and hemolytic ratio were respectively evaluated after various incubation periods. For in vivo tests, a chronic osteomyelitis model involving the right proximal tibia of New Zealand white rabbits was established. After bacterial identification, the drug-loaded scaffold, drug-unloaded BHA/PAA, and poly (methyl methacrylate) were implanted, and a blank control group was also set up. Subsequently, the in vivo blood drug concentrations were measured, and the kidney and liver functions were evaluated.

RESULTS

In the in vitro tests, the cytotoxicity grades of V-BHA/PAA and BHA/PAA-based on the relative growth rate were all below 1. The hemolysis ratios of V-BHA/PAA and BHA/PAA were 2.27% and 1.42%, respectively, both below 5%. In the in vivo tests, the blood concentration of vancomycin after implantation of V-BHA/PAA was measured at far below its toxic concentration (60 mg/L), and the function and histomorphology of the liver and kidney were all normal.

CONCLUSION

According to ISO standards, the V-BHA/PAA scaffold is considered to have sufficient safety for clinical utilization.

Thermally triggered release of the bacteriophage endolysin CHAPK and the bacteriocin lysostaphin for the control of methicillin resistant Staphylococcus aureus (MRSA)

Staphylococcus aureus infections of the skin and soft tissue pose a major concern to public health, largely owing to the steadily increasing prevalence of drug resistant isolates. As an alternative mode of treatment both bacteriophage endolysins and bacteriocins have been shown to possess antimicrobial efficacy against multiple species of bacteria including otherwise drug resistant strains. Despite this, the administration and exposure of such antimicrobials should be restricted until required in order to discourage the continued evolution of bacterial resistance, whilst maintaining the activity and stability of such proteinaceous structures. Utilising the increase in skin temperature during infection, the truncated bacteriophage endolysin CHAP_K and the staphylococcal bacteriocin lysostaphin have been co-administered in a thermally triggered manner from Poly(N-isopropylacrylamide) (PNIPAM) nanoparticles. The thermoresponsive nature of the PNIPAM polymer has been employed in order to achieve the controlled expulsion of a synergistic enzybiotic cocktail consisting of CHAP_K and lysostaphin. The point at which this occurs is modifiable, in this case corresponding to the threshold temperature associated with an infected wound. Consequently, bacterial lysis was observed at 37 °C, whilst growth was maintained at the uninfected skin temperature of 32 °C.