Pearl Powder Fluorescent Carbon Dots Alleviate Neuroinflammation in Cerebral Ischemia/Reperfusion Through Suppression of Anxa2/NF-κB Signaling Pathway

 Will your incompetent? doctor and hospital DO NOTHING to get protocols written up and distributed throughout the world?

Pearl Powder Fluorescent Carbon Dots Alleviate Neuroinflammation in Cerebral Ischemia/Reperfusion Through Suppression of Anxa2/NF-κB Signaling Pathway

uthors Borjigin P , Deng C, Su R, Li J, Ying Y, Chen Y , Wang T 

Received 19 September 2025

Accepted for publication 30 January 2026

Published 11 March 2026 Volume 2026:21 567974

DOI https://doi.org/10.2147/IJN.S567974

Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 2

Editor who approved publication: Prof. Dr. RDK Misra

Pongsigeraxi Borjigin,¹ 

Caixia Deng,² 

Rilaga Su,² 

Juan Li,¹ 

Ying Ying,³ 

Yingsong Chen,⁴ Tegexibaiyin Wang⁵¹College of Mongolian Medicine, Inner Mongolia Minzu University, Tongliao, Inner Mongolia Autonomous Region, People’s Republic of China(,sup>2College of Mongolian Medicine, Inner Mongolia Medical University, Hohhot, Inner Mongolia Autonomous Region, People’s Republic of China; ³College of Chemical Materials, Inner Mongolia Minzu University, Tongliao, Inner Mongolia Autonomous Region, People’s Republic of China; ⁴National and Local Joint Mongolian Medicine R&D Engineering Center, Inner Mongolia Minzu University, Tongliao, Inner Mongolia Autonomous Region, People’s Republic of China; ⁵Affiliated Hospital, Inner Mongolia Minzu University, Tongliao, Inner Mongolia Autonomous Region, People’s Republic of China

Purpose: 

This study aimed to enzymatically synthesize pearl powder fluorescent carbon dots (PFCDs) and investigate their neuroprotective potential against cerebral ischemia/reperfusion injury (CIRI) by modulating the Anxa2/NF-κB signaling pathway.

Methods: 

PFCDs were synthesized through enzymatic digestion and characterized. Neuroprotective effects were assessed using an in vitro oxygen–glucose deprivation/reoxygenation (OGD/R) model in PC12 cells and a middle cerebral artery occlusion/reperfusion (MCAO/R) rat model. Cell viability, neurological function, cerebral infarct volume, and neuronal injury were evaluated. Expression of Anxa2/NF-κB signaling pathway proteins and inflammatory cytokines (TNF-α, IL-6, IL-1β) was analyzed by Western blot, immunofluorescence, and ELISA.

Results: 

The synthesized PFCDs exhibited an organic–inorganic hybrid structure, uniform particle size below 10 nm, and distinctive optical properties. In vitro, PFCDs enhanced cell viability under OGD/R conditions, inhibited phosphorylation of Anxa2 and NF-κB p65, and reduced secretion of pro-inflammatory cytokines (TNF-α, IL-6, IL-1β). In vivo, treatment with PFCDs in MCAO/R rats improved neurological function, reduced cerebral infarct volume, and alleviated neuronal injury. These protective effects were linked to downregulation of the Anxa2/NF-κB signaling pathway and reduced serum levels of inflammatory cytokines.

Conclusion: 

We successfully achieved the enzymatic synthesis of carbon dots from pearl powder, characterized by a unique organic–inorganic hybrid structure. PFCDs effectively alleviated CIRI-induced neuroinflammation by suppressing the Anxa2/NF-κB signaling pathway, highlighting their therapeutic potential as a nanomedicine derived from natural products.

Keywords: pearl powder fluorescent carbon dots, cerebral ischemia/reperfusion, oxygen–glucose deprivation/reoxygenation, middle cerebral artery occlusion/reperfusion, neuroinflammation, Anxa2/NF-κB signaling pathway

Introduction

Ischemic stroke (IS), which accounts for approximately 87% of all strokes, remains a major contributor to mortality and long-term disability worldwide.¹ Reperfusion therapy has marked a milestone in acute cerebral infarction management; however, in certain patients, re-establishing cerebral blood flow through recombinant tissue-type plasminogen activator (rt-PA) thrombolysis or interventional thrombectomy leads to aggravated brain injury. This phenomenon, known as cerebral ischemia/reperfusion (CIRI) injury, involves multiple pathological processes, including oxidative stress, autophagy, inflammation, and glial cell activation.^2,3 However, less than 5% of patients benefit from tissue plasminogen activator (tPA) due to its narrow therapeutic window and high bleeding risk, and approximately 30% of survivors experience neurological deficits caused by ischemia-reperfusion injury.^4,5 Despite this, no effective drug currently exists to protect against CIRI injury, emphasizing the need to clarify its mechanisms and develop effective treatment strategies.⁶ Nanomedicine, with its ability to cross the blood-brain barrier (BBB) and selectively target the ischemic penumbra surrounding the infarct core, has emerged as a promising approach for cerebrovascular diseases.^7,8 Carbon dots (CDs), a novel class of carbon nanomaterials following graphene, carbon nanotubes, and fullerenes, have attracted considerable attention for biotherapeutic applications. Their ultra-small size (<10 nm), stable surface charge, diverse functional chemical moieties, and favorable biocompatibility contribute to their biomedical potential^9,10 Previous studies indicate that CDs are non-toxic to tissues, organs, or genetic material.¹¹ Various natural sources, including straw, ginger, coffee, candle ash, eggs, and graphene, have been used for CD synthethis.^12,13 Notably, CDs have demonstrated antioxidant activity and inhibitory effects against hepatocellular, lung, breast, and cervical cancers.^11,14

In this study, we developed and reported a novel method for the preparation of CDs derived from pearl powder. To the best of our knowledge, the enzymatic synthesis of carbon dots from pearl powder has not been previously described in the literature. Pearl powder originates from bivalve mollusks, where epithelial cells secrete calcium carbonate to encapsulate foreign substances. Its composition is dominated by inorganic calcium carbonate crystals (~95 wt%), with a small but essential proportion of organic matter (~5 wt%), including proteins and polysaccharides, which govern biomineralization and contribute to its biological activity.¹⁵ Modern studies have demonstrated that pearl powder enhances immunity, exhibits anti-inflammatory and anti-aging effects, promotes central inhibition, improves skin appearance, and serves as a calcium supplement.¹⁶ Owing to its fine particle dimensions and extensive surface area, pearl powder shows high bioavailability, facilitating the release and absorption of active ingredients.¹⁷ Evidence further indicates that particle size influences therapeutic efficacy, leading to the development of nano-pearl powder, which releases more active proteins with enhanced activity.¹⁸ In this study, we employed enzymatic digestion to synthesize pearl powder fluorescent carbon dots (PFCDs), which exhibit excellent water solubility, fluorescence, and biocompatibility.¹⁹

Annexin A2 (Anxa2) is a multifunctional phospholipid-binding protein with Ca²⁺ dependence, expressed in a wide range of cell types. It contributes to the development of atherosclerosis (AS) by regulating inflammatory pathways, endothelial homeostasis, and lipid metabolism.^20,21 Anxa2 deficiency is strongly associated with enhanced inflammatory responses. Notably, Anxa2(-/-) mice show increased NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome activation in dendritic cells, elevated production of cytokines such as tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), interleukin-1β (IL-1β), and interferon-γ (IFN-γ), decreased macrophage-mediated bacterial clearance, excessive superoxide release, and increased pulmonary neutrophil infiltration.^22–24 Nuclear factor kappa-B (NF-κB), a dimeric transcription factor, further regulates key physiological processes, including inflammation, immunity, apoptosis, and the cell cycle.²⁵ When NF-κB signaling is initiated, phosphorylation of NF-κB p65 promotes its translocation into the nucleus, where it binds to specific DNA sequences and triggers the expression of proinflammatory mediators. This process drives the release of cytokines such as TNF-α, IL-1β, and IL-6, thereby promoting the recruitment and accumulation of inflammatory cells.^26,27 In the complex pathological context of neural injury, critical inflammatory signaling pathways, including Anxa2/NF-κB are prone to dysregulation.²⁸ Evidence indicates that Anxa2, when stimulated by damage-associated signals, can directly interact with components of the inhibitor of κB kinase (IKK) complex to trigger NF-κB phosphorylation and subsequent nuclear translocation.²⁹ However, the altered intracellular environment following neural injury may compromise Anxa2’s ability to precisely modulate NF-κB activity. Conversely, excessive or prolonged NF-κB activation can further disrupt Anxa2 expression and function, undermining regulatory feedback. This maladaptive interplay exacerbates neuroinflammation, diminishes neuronal survival, and impedes neural repair.³⁰ Although nanomedicines hold promise for targeted delivery, their nanoscale properties and neuroprotective mechanisms remain poorly understood. In this study, we report that PFCDs mitigate CIRI by exerting anti-neuroinflammatory effects via the Anxa2/NF-kB signaling pathway.

Moreat link.