The prevalence of cardiovascular disease, oxidative stress-related complications, and chronic age-related illnesses is gradually increasing worldwide. Several causes include the ineffectiveness of medicinal treatment therapies, their toxicity, their inability to provide radical solutions in some diseases, and the necessity of multiple drug therapy in certain chronic diseases. It is therefore necessary for alternative treatment methods to be sought. In this review, polyphenols were identified and classified according to their chemical structure, and the sources of these polyphenol molecules are indicated. The cardioprotective, ROS scavenging, anti-aging, anticancer properties of polyphenolic compounds have been demonstrated by the results of many studies, and these natural antioxidant molecules are potential alternative therapeutic agents.

Nitrogen-doped arginine carbon dots (Arg CDs) as light-sensitive antibacterial agents were prepared by using citric acid as the carbon source and arginine amino acid as the nitrogen source via a microwave-assisted synthesis method. Dynamic light scattering (DLS) measurements and TEM images revealed that the Arg CDs were in the 1–10 nm size range with a graphitic structure. To improve their antibacterial capability, the Arg CDs were modified with ethyleneimine (EDA), pentaethylenehexamine (PEHA), and polyethyleneimine (PEI) as different amine sources, and the zeta potential value of +2.8 ± 0.6 mV for Arg CDs was increased to +34.4 ± 4.1 mV for PEI-modified Arg CDs. The fluorescence intensity of the Arg CDs was significantly enhanced after the modification with EDA, and the highest antibacterial effect was observed for the PEI-modified Arg CDs. Furthermore, the photodynamic antibacterial capacity of bare and EDA-modified Arg CDs was determined upon light exposure to show their light-induced antibacterial effects. Photoexcited (315–400 nm, UVA, 300 W), EDA-modified Arg CDs at 5 mg/mL concentration were found to inhibit about 49 ± 7% of pathogenic bacteria, e.g., Escherichia coli, with 5 min of light exposure. Furthermore, the biocompatibilities of the bare and modified Arg CDs were also investigated with blood compatibility tests via hemolysis and blood clotting assays and cytotoxicity analysis on L929 fibroblast cells.

Linear polyethyleneimine (L-PEI) was obtained from the acidic hydrolysis of poly(2-ethyl-2-oxazoline) and employed in the synthesis of physically crosslinked L-PEI hydrogel, PC-L-PEI^H, chemically crosslinked L-PEI hydrogel, CC-L-PEI^H, and cryogels, CC-L-PEI^C. The preparation of L-PEI-based hydrogel networks was carried out in two ways: 1) by cooling the L-PEI solution from 90 °C to room temperature, and 2) by crosslinking L-PEI chains with a crosslinker, glycerol diglycidyl ether = 20 °C for CC-L-PEI^C. Furthermore, a polyphenolic compound, tannic acid (TA), with superior antibacterial, antioxidant, and anti-inflammatory properties as an active biomedical functional agent, was encapsulated during the synthesis process within L-PEI-based hydrogels and cryogels, at 10% and 25% (w/w) based on the L-PEI amount. A linear and higher TA release was observed from physically crosslinked PEI-based hydrogels containing 10% and 25% TA-containing PC-L-PEI/TA^H within 6 h, with 9.5 ± 05 mg/g and 60.2 ± 3.8 mg/g cumulative released amounts, respectively. A higher antioxidant activity was observed for 25% TA containing PC-L-PEI/TA^H with 53.6 ± 5.3 µg/mL total phenol content and 0.48 ± 0.01 µmole Trolox equivalent/g. The minimum bactericidal concentration (MBC) of PC-L-PEI^H and CC-L-PEI^C networks against both E. coli (ATCC 8739) and Gram-positive B. subtilis (ATCC 6633) bacteria was determined at 5 mg/mL, whereas the MBC value of 10 mg/mL for CC-L-PEI^H networks against the same bacteria was achieved.

Carboxymethyl chitosan (CMCh) is a unique polysaccharide with functional groups that can develop positive and negative charges due to the abundant numbers of amine and carboxylic acid groups. CMCh is widely used in different areas due to its excellent biocompatibility, biodegradability, water solubility, and chelating ability. CMCh microgels were synthesized in a microemulsion environment using divinyl sulfone (DVS) as a crosslinking agent. CMCh microgel with tailored size and zeta potential values were obtained in a single stem by crosslinking CMCh in a water-in-oil environment. The spherical microgel structure is confirmed by SEM analysis. The sizes of CMCh microgels varied from one micrometer to tens of micrometers. The isoelectric point of CMCh microgels was determined as pH 4.4. Biocompatibility of CMCh microgels was verified on L929 fibroblasts with 96.5 ± 1.5% cell viability at 1 mg/mL concentration. The drug-carrying abilities of CMCh microgels were evaluated by loading Vancomycin (Van) antibiotic as a model drug. Furthermore, the antibacterial activity efficiency of Van-loaded CMCh microgels (Van@CMCh) was investigated. The MIC values of the released drug from Van@CMCh microgels were found to be 68.6 and 7.95 µg/mL against E. coli and S. aureus, respectively, at 24 h contact time. Disk diffusion tests confirmed that Van@CMCh microgels, especially for Gram-positive (S. aureus) bacteria, revealed long-lasting inhibitory effects on bacteria growth up to 72 h.

Neurodegenerative diseases occur due to progressive and sometimes irreversible loss of function and death of nerve cells. A great deal of effort is being made to understand the pathogenesis of neurodegenerative diseases. In particular, the prevalence of Alzheimer’s disease (AD) is quite high, and only symptomatic therapy is available due to the absence of radical treatment. The aim of this review is to try to elucidate the general pathogenesis of AD, to provide information about the limit points of symptomatic treatment approaches, and to emphasize the potential neurologic effects of phytocompounds as new tools as therapeutic agents for disease prevention, retardation, and therapy. This survey also covers the notable properties of herbal compounds such as their effects on the inhibition of an enzyme called acetylcholinesterase, which has significant value in the treatment of AD. It has been proven that phytopharmaceuticals have long-term effects that could protect nervous system health, eliminate inflammatory responses, improve cognitive damage, provide anti-aging effects in the natural aging process, and alleviate dementia sequelae. Herbal-based therapeutic agents can afford many advantages and can be used as potentially as new-generation therapeutics or complementary agents with high compliance, fewer adverse effects, and lower cost in comparison to the traditional pharmaceutical agents in the fight against AD.

Glycol chitosan (GC) is a chitosan (CH) derivative with improved water solubility with regards to CH which affords significant solubility advantages. In this study, microgels of GC as p(GC) were synthesized by a microemulsion technique at various crosslinking ratios e.g., 5%, 10%, 50%, 75%, and 150% based on the repeating unit of GC using divinyl sulfone (DVS) as a crosslinker. The prepared p(GC) microgels were tested for blood compatibility and it was found that p(GC) microgels at 1.0 mg/mL concentration possessed a 1.15 ± 0.1% hemolysis ratio and 89 ± 5% blood clotting index value confirming their hemocompatibility. In addition, p(GC) microgels were found biocompatible with 75.5 ± 5% cell viability against L929 fibroblasts even at a 2.0 mg/mL concentration. By loading and releasing tannic acid (TA) (a polyphenolic compound with high antioxidant activity) as an active agent, p(GC) microgels’ possible drug delivery device application was examined. The TA loading amount of p(GC) microgels was determined as 323.89 mg/g, and TA releases from TA loaded microgels (TA@p(GC)) were found to be linear within 9 h and a total amount of TA released was determined as 42.56 ± 2 mg/g within 57 h. According to the Trolox equivalent antioxidant capacity (TEAC) test, 400 µL of the sample added to the ABTS+ solution inhibited 68.5 ± 1.7% of the radicals. On the other hand, the total phenol content (FC) test revealed that 2000 μg/mL of TA@p(GC) microgels resulted in 27.5 ± 9.5 mg/mL GA eq antioxidant properties.