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This study aimed to investigate the impact of plastic particles on cell viability and tissue toxicity. The cells were subjected to incubation with plastic particles immobilized in agar gels, resulting in minimal cell death and cytotoxicity. Furthermore, direct exposure of various cell types to suspended plastic particles showed negligible effects on cell viability, with no observed lysis or growth inhibition. Staining techniques revealed minimal plastic particle‐induced cell death, with the majority of cells remaining viable. However, histological evaluations of mouse tissues demonstrated that the nondegradable low‐density poly(ethylene) (LDPE) groups exhibited severe irritation, characterized by an excessive presence of macrophages, neutrophils, fibrosis, fat infiltration, and increased blood vessel formation in subcutaneous tissue. In contrast, biodegradable neat poly(butylene succinate) (KRICT‐PBS) and cellulose nanocrystals/PBS nanocomposite (CNC‐PBS) groups induced minimal toxicity. Interestingly, the intravenous injection of KRICT‐PBS and CNC‐PBS degradate solutions in mice exhibited mild toxicity, suggesting no significant damage to normal kidney and liver function. [ABSTRACT FROM AUTHOR]

In this study, we have developed pH‐dependent nanogels based on hyaluronic acid (HA) to specifically target acidic tumors. Our initial approach involved modifying HA through the grafting of 3‐(diethylamino)propylamine (DEAP), a molecule known for its responsiveness to changes in pH. This modified HA was termed as HDEA. Subsequently, we performed chemical crosslinking of HDEA using adipic acid dihydrazide (ADH), a crosslinking molecule, resulting in the formation of nanogels referred to as cHDEA. Importantly, the non‐ionized DEAP molecules (with a pKb value of ~pH 7.0) at pH 7.4 support the formation of deswellable cHDEA. This property enables the encapsulation of a photodynamic model drug, chlorin e6 (Ce6), into cHDEA. However, when the DEAP molecules become protonated at pH 6.8, they induce a change in the nanogel structure, causing it to swell due to electrostatic repulsion. As a result, Ce6 is rapidly released from the nanogels. By modulating the pH, we can continuously control the nanogel structure, alternating between swelling and deswelling states. We anticipate that this system offers the advantage of facilitating drug release specifically under acidic tumor conditions while inhibiting drug release under normal pH conditions (i.e., pH 7.4). This approach will serve as an effective strategy for mitigating side effects by efficiently controlling drug release in specific disease areas. [ABSTRACT FROM AUTHOR]

In this study, we reported pH‐responsive microparticles consisting of poly(D,L‐lactide‐co‐glycolide) (PLGA), aminated hyaluronic acid (aHA) conjugated with 2,3‐dimethylmaleic anhydride (DMA, as a pH‐responsive cleavable molecule) (aHA‐DMA), and doxorubicin (DOX, as an antitumor drug) for local tumor treatment. The DOX‐loaded microparticles, denoted as PLGA(aHA‐DMA)/DOX MPs, were fabricated using the W1/O/W2 multi‐emulsification method. These PLGA(aHA‐DMA)/DOX MPs (~10 μm in diameter) accelerated the rate of DOX release at pH 6.8 due to the acidic pH‐responsive cleavage of the DMA moieties followed by electrostatic‐repulsion between aHA and DOX. This event caused the structural destabilization and collapse of the MPs, leading to the rapid release of DOX. Consequently, the PLGA(aHA‐DMA)/DOX MPs resulted in significant inhibition of tumor growth, demonstrating their ability for acidic tumor‐specific treatment. [ABSTRACT FROM AUTHOR]