Collagen-based materials, renowned for their biocompatibility and minimal immunogenicity, serve as exemplary substrates in a myriad of biomedical applications. Collagen-based micro/nanogels, in particular, are valued for their increased surface area, tunable degradation rates, and ability to facilitate targeted drug delivery, making them instrumental in advanced therapeutics and tissue engineering endeavors. Although extensive reviews on micro/nanogels exist, they tend to cover a wide range of biomaterials and lack a specific focus on collagen-based materials. The current review offers an in-depth look into the manufacturing technologies, drug release mechanisms, and biomedical applications of collagen-based micro/nanogels to address this gap. First, we provide an overview of the synthetic strategies that allow the precise control of the size, shape, and mechanical strength of these collagen-based micro/nanogels by controlling the degree of cross-linking of the materials. These properties are crucial for their performance in biomedical applications. We then highlight the environmental responsiveness of these collagen-based micro/nanogels, particularly their sensitivity to enzymes and pH, which enables controlled drug release under various pathological conditions. The discussion then expands to include their applications in cancer therapy, antimicrobial treatments, bone tissue repair, and imaging diagnosis, emphasizing their versatility and potential in these critical areas. The challenges and future perspectives of collagen-based micro/nanogels in the field are discussed at the end of the review, with an emphasis on the translation to clinical practice. This comprehensive review serves as a valuable resource for researchers, clinicians, and scientists alike, providing insights into the current state and future directions of collagen-based micro/nanogel research and development.
Collagen/chemistry* ; Drug Delivery Systems/methods* ; Humans ; Tissue Engineering/methods* ; Animals ; Biocompatible Materials/chemistry*

Objective:To investigate and summarize the imaging and pathological features of non-acute occlusion following flow diverter (FD) implantation in animal models.Methods:Four experimental pigs (experimental group) that experienced non-acute occlusion (occlusion time exceeding 24 hours) within the FD stent implanted in the common carotid artery, and 19 pigs (control group) that did not experience stent occlusion during the same period were involved. Using an interventional approach under digital subtraction angiography (DSA), the 4 occluded FD lumens were mechanically opened. Optical coherence tomography (OCT), intravascular ultrasound (IVUS) and histopathological examinations were performed to evaluate the intraluminal composition and characteristics of the occlusive tissues. These findings were compared with non-occluded FD stents to summarize the imaging and pathological changes within the occluded FD lumen.Results:The occlusion times of the FD stents in the 4 experimental pigs were 16 weeks, 20 weeks, 20 weeks, and 24 weeks postoperatively. All occluded stents were successfully recanalized under DSA, with a technical success rate of 4/4. Among the 19 non-occluded FD stents, OCT and IVUS revealed uniform (16 stents) or non-uniform (3 stents) neointimal coverage of the stent struts, presenting as homogeneous high/slightly high signal intensity or medium echogenicity. Histopathological examination indicated that the neointima was primarily composed of smooth muscle cells and a small amount of fibrous connective tissues. In contrast, the 4 occluded FD stents demonstrated excessive neointimal proliferation and plaque formation, leading to luminal loss, as shown by OCT and IVUS. The occlusion tissues predominantly presented as homogeneous high signal intensity with weak attenuation (fibrous plaques) on OCT, with some regions showing blurred low signal intensity and strong attenuation (lipid plaques). IVUS presented homogeneous echogenicity (fibrous plaques) and hypoechogenic zones (lipid plaques). Histopathological examination showed that the occlusion tissues mainly consisted of smooth muscle cells, fibrous connective tissues, and lipids, accompanied by numerous foam cells and a minor presence of inflammatory cells.Conclusions:Histopathological examinations confirm that non-acute occlusion of FD is mainly caused by excessive hyperplasia of intima along with the formation of fibrous plaques and lipid plaques. OCT and IVUS have typical finding in imaging that can assist in determining the cause of stent occlusion as well as the lesion's nature, thereby providing crucial guidance for subsequent clinical treatment and drug selection.

Objective:To compare the efficacies of endovascular therapy (EVT) and standard medical therapy in acute ischemic stroke (AIS) patients aged ≥85 years, and analyze the independent influencing factors for poor prognosis of AIS patients after EVT.Methods:Sixty-nine AIS patients aged ≥85 years admitted to Department of Neurology, Xi'an Third Hospital from January 2018 to April 2024, including 40 accepted EVT and 28 accepted standard medicinal therapy, were enrolled. Modified Rankin scale (mRS) was used to evaluate the prognosis of the patients 90 days after onset. General data, prognosis and complications between the EVT group and standard medical therapy group were compared. General data, treatment processes and complications between patients with good prognosis and poor prognosis in the EVT group were compared. Multivariate Logistic regression was used to analyze the independent influencing factors for poor prognosis in AIS patients after EVT.Results:Compared with the standard medical therapy, the EVT group had significantly lower NIHSS score at discharge, greater improvement in NIHSS score (NIHSS score at admission-NIHSS score at discharge), lower mRS score 90 days after onset, higher good prognosis rate, lower mortality rate within 90 days of onset, and longer hospital stay ( P<0.05). In the EVT group, 11 patients (27.5%) had good prognosis and 29 patients (72.5%) had poor prognosis 90 days after onset. Compared with the good prognosis group, the poor prognosis group had significantly higher blood glucose level and lower Alberta Stroke Program Early CT Score (ASPECT) on admission ( P<0.05). Multivariate Logistic regression analysis showed that blood glucose on admission ( OR=2.363, 95% CI: 1.134-4.928, P=0.022) and ASPECT score on admission ( OR=0.273, 95% CI: 0.088-0.854, P=0.026) were independent influencing factors for poor prognosis in AIS patients after EVT. Conclusion:AIS patients aged ≥85 years received EVT have better prognosis compared with those accepted standard medical therapy; these patients with high glucose level and low ASPECT score on admission have poor prognosis.

Objective:To investigate the impact of flow diverter (FD) malapposition at the aneurysm neck on clinical outcomes and complications of intracranial aneurysms, and identify the influencing factors for intraoperative FD malapposition.Methods:A retrospective study was performed; 153 patients with unruptured saccular aneurysms at the C4-C7 segments of the internal carotid artery accepted single FD implantation at Department of Interventional Radiology, First Affiliated Hospital of Zhengzhou University from June 2022 to March 2024 were chosen. Intraoperative high-resolution C-arm CT was utilized to assess FD apposition at the aneurysm neck. (1) Based on FD apposition at the aneurysm neck as shown, these 153 patients were divided into a malapposition group ( n=23, including 16 patients with malapposition being identified as residual malapposition after intraoperative corrective measures such as microwire massage and 7 patients with malapposition being newly detected in this study) and a complete apposition group ( n=130). Perioperative and follow-up complications were recorded. Clinical outcomes were assessed using modified Rankin Scale (mRS) at the final follow-up (mRS score of 0-2 as favorable outcome), and angiographic outcomes were evaluated by DSA at the final follow-up. Differences in clinical and angiographic outcomes and complication rate were compared between the malapposition group and complete apposition group. (2) Based on FD apposition at the aneurysm neck as shown, these 153 patients were divided into an intraoperative malapposition group ( n=74, including 67 patients with malapposition being detected during surgery and 7 patients with malapposition being newly detected in this study) and an intraoperative complete apposition group ( n=79). Univariate analysis was performed to compare the clinical variables between the intraoperative malapposition group and intraoperative complete apposition group; multivariate Logistic regression was further employed to identify the independent influencing factors for FD malapposition at the aneurysm neck. Results:(1) Four patients (all from the malapposition group) developed perioperative acute in-stent thrombosis. Nine patients experienced ischemic or hemorrhagic stroke during the follow-up, including 6 from the malapposition group and 3 from the complete apposition group; the complication rate in the malapposition group (6/23, 26.1%) was significantly higher than that in the complete apposition group (3/130, 2.3%) during the follow-up ( P<0.05). At the final follow-up, 2 patients (both from the malapposition group) had poor clinical outcome, while the remaining 151 patients had favorable outcome. Proportion of patients with favorable outcome between the two groups was statistically different (91.3%[21/23] vs. 100.0%[130/130], P<0.05). Delayed occlusion was detected in 46 patients (12 from the malapposition group and 34 from the complete apposition group) at the final angiographic follow-up. FD restenosis/re-occlusion was noted in 10 patients, including 6 from the malapposition group and 4 from the complete apposition group. Significant difference in delayed occlusion rate (52.2%[12/23] vs. 26.2%[34/130]) and long-term in-stent stenosis/occlusion rate (26.1%[6/23] vs. 3.1%[4/130]) was observed between the two groups ( P<0.05). (2) Significant difference in aneurysm neck diameter, FD angulation, parent artery stenosis, parent artery diameter ratio>1.2, and presence of branching vessels at the FD implantation site was noted between the intraoperative complete apposition group and intraoperative malapposition group ( P<0.05). Multivariate Logistic regression indicated that aneurysm neck diameter ( OR=1.431, 95% CI: 1.096-1.868, P=0.008), parent artery diameter ratio>1.2 ( OR=2.199, 95% CI: 1.083-4.463, P=0.029), and FD angulation ( OR=1.019, 95% CI: 1.002-1.036, P=0.027) were independent influencing factors for FD malapposition at the aneurysm neck. Conclusion:In FD implantation for intracranial aneurysms, FD malapposition at the aneurysm neck adversely affects delayed occlusion rate and complication rate; aneurysms with wider aneurysm neck diameter, parent artery diameter ratio>1.2, and greater FD angulation are trend to have FD malapposition at the aneurysm neck.

Objective:To investigate the efficacy and safety of different endovascular interventional treatments for extracranial carotid artery pseudoaneurysms.Method:The clinical data of 48 patients with extracranial carotid artery pseudoaneurysms treated with multiple endovascular procedures were retrospectively analyzed in the First Affiliated Hospital of Zhengzhou University from February 2012 to February 2024. The patients presented with a total of 48 extracranial carotid pseudoaneurysms, ranging in diameter from 2.5 to 34.2 mm [mean (12.0±9.6) mm]. The lesions were distributed as follows: 25 in the internal carotid artery, 16 in the external carotid artery and 7 in the common carotid artery. The selection of endovascular interventional techniques was tailored to individual cases according to the pseudoaneurysm size, anatomical location, morphological configuration, and specific features of the parent artery. Perioperative adverse events were monitored, and the efficacy of individualized endovascular interventional therapy was evaluated based on immediate postoperative and 6-month follow-up digital subtraction angiography (DSA) findings, including aneurysm occlusion and in-stent patency.Result:The treatment modalities included parent artery coiling occlusion ( n=16), overlapping braided carotid stent implantation ( n=3), covered stent placement ( n=23), combined implantation of covered stent and braided carotid stent implantation ( n=4) and flow-diverting stent implantation ( n=2) based on the characteristics of the pseudoaneurysms. Endovascular interventional procedures were successfully completed in 47 patients (technical success rate: 97.9%). Immediate postoperative DSA revealed residual pseudoaneurysm at the distal end of the stent in 1 case. Among the remaining cases, complete aneurysm obliteration or faint opacification was observed, with stent lumen patency confirmed in 31 cases and complete parent artery occlusion achieved in 16 cases. In one case involving a patient who underwent flow-diverting stent implantation, a pulsatile vascular murmur reappeared in the neck one week postoperatively. Follow-up DSA revealed stent migration into the aneurysm sac. After retrieval and removal of the displaced stent, combined implantation of a covered stent and a braided carotid artery stent was performed. Postoperative angiography confirmed complete aneurysm occlusion and patent parent artery blood flow. No severe perioperative adverse events (e.g., aneurysm rupture) were observed. During a postoperative follow-up period of 6.2-24.2 months, DSA at 6 months revealed mild in-stent or distal segment stenosis in 2 patients who underwent covered stent implantation. The remaining 46 patients exhibited complete aneurysm occlusion with no significant stenosis observed within the stent lumen. At the final follow-up, all patients demonstrated resolution or significant alleviation of clinical symptoms. Conclusion:Individualized endovascular interventional therapy demonstrates favorable safety and efficacy profiles in managing extracranial carotid artery pseudoaneurysms.

Objective:To investigate the efficacy and safety of different endovascular interventional treatments for extracranial carotid artery pseudoaneurysms.Method:The clinical data of 48 patients with extracranial carotid artery pseudoaneurysms treated with multiple endovascular procedures were retrospectively analyzed in the First Affiliated Hospital of Zhengzhou University from February 2012 to February 2024. The patients presented with a total of 48 extracranial carotid pseudoaneurysms, ranging in diameter from 2.5 to 34.2 mm [mean (12.0±9.6) mm]. The lesions were distributed as follows: 25 in the internal carotid artery, 16 in the external carotid artery and 7 in the common carotid artery. The selection of endovascular interventional techniques was tailored to individual cases according to the pseudoaneurysm size, anatomical location, morphological configuration, and specific features of the parent artery. Perioperative adverse events were monitored, and the efficacy of individualized endovascular interventional therapy was evaluated based on immediate postoperative and 6-month follow-up digital subtraction angiography (DSA) findings, including aneurysm occlusion and in-stent patency.Result:The treatment modalities included parent artery coiling occlusion ( n=16), overlapping braided carotid stent implantation ( n=3), covered stent placement ( n=23), combined implantation of covered stent and braided carotid stent implantation ( n=4) and flow-diverting stent implantation ( n=2) based on the characteristics of the pseudoaneurysms. Endovascular interventional procedures were successfully completed in 47 patients (technical success rate: 97.9%). Immediate postoperative DSA revealed residual pseudoaneurysm at the distal end of the stent in 1 case. Among the remaining cases, complete aneurysm obliteration or faint opacification was observed, with stent lumen patency confirmed in 31 cases and complete parent artery occlusion achieved in 16 cases. In one case involving a patient who underwent flow-diverting stent implantation, a pulsatile vascular murmur reappeared in the neck one week postoperatively. Follow-up DSA revealed stent migration into the aneurysm sac. After retrieval and removal of the displaced stent, combined implantation of a covered stent and a braided carotid artery stent was performed. Postoperative angiography confirmed complete aneurysm occlusion and patent parent artery blood flow. No severe perioperative adverse events (e.g., aneurysm rupture) were observed. During a postoperative follow-up period of 6.2-24.2 months, DSA at 6 months revealed mild in-stent or distal segment stenosis in 2 patients who underwent covered stent implantation. The remaining 46 patients exhibited complete aneurysm occlusion with no significant stenosis observed within the stent lumen. At the final follow-up, all patients demonstrated resolution or significant alleviation of clinical symptoms. Conclusion:Individualized endovascular interventional therapy demonstrates favorable safety and efficacy profiles in managing extracranial carotid artery pseudoaneurysms.

Objective:To investigate and summarize the imaging and pathological features of non-acute occlusion following flow diverter (FD) implantation in animal models.Methods:Four experimental pigs (experimental group) that experienced non-acute occlusion (occlusion time exceeding 24 hours) within the FD stent implanted in the common carotid artery, and 19 pigs (control group) that did not experience stent occlusion during the same period were involved. Using an interventional approach under digital subtraction angiography (DSA), the 4 occluded FD lumens were mechanically opened. Optical coherence tomography (OCT), intravascular ultrasound (IVUS) and histopathological examinations were performed to evaluate the intraluminal composition and characteristics of the occlusive tissues. These findings were compared with non-occluded FD stents to summarize the imaging and pathological changes within the occluded FD lumen.Results:The occlusion times of the FD stents in the 4 experimental pigs were 16 weeks, 20 weeks, 20 weeks, and 24 weeks postoperatively. All occluded stents were successfully recanalized under DSA, with a technical success rate of 4/4. Among the 19 non-occluded FD stents, OCT and IVUS revealed uniform (16 stents) or non-uniform (3 stents) neointimal coverage of the stent struts, presenting as homogeneous high/slightly high signal intensity or medium echogenicity. Histopathological examination indicated that the neointima was primarily composed of smooth muscle cells and a small amount of fibrous connective tissues. In contrast, the 4 occluded FD stents demonstrated excessive neointimal proliferation and plaque formation, leading to luminal loss, as shown by OCT and IVUS. The occlusion tissues predominantly presented as homogeneous high signal intensity with weak attenuation (fibrous plaques) on OCT, with some regions showing blurred low signal intensity and strong attenuation (lipid plaques). IVUS presented homogeneous echogenicity (fibrous plaques) and hypoechogenic zones (lipid plaques). Histopathological examination showed that the occlusion tissues mainly consisted of smooth muscle cells, fibrous connective tissues, and lipids, accompanied by numerous foam cells and a minor presence of inflammatory cells.Conclusions:Histopathological examinations confirm that non-acute occlusion of FD is mainly caused by excessive hyperplasia of intima along with the formation of fibrous plaques and lipid plaques. OCT and IVUS have typical finding in imaging that can assist in determining the cause of stent occlusion as well as the lesion's nature, thereby providing crucial guidance for subsequent clinical treatment and drug selection.

Objective:To compare the efficacies of endovascular therapy (EVT) and standard medical therapy in acute ischemic stroke (AIS) patients aged ≥85 years, and analyze the independent influencing factors for poor prognosis of AIS patients after EVT.Methods:Sixty-nine AIS patients aged ≥85 years admitted to Department of Neurology, Xi'an Third Hospital from January 2018 to April 2024, including 40 accepted EVT and 28 accepted standard medicinal therapy, were enrolled. Modified Rankin scale (mRS) was used to evaluate the prognosis of the patients 90 days after onset. General data, prognosis and complications between the EVT group and standard medical therapy group were compared. General data, treatment processes and complications between patients with good prognosis and poor prognosis in the EVT group were compared. Multivariate Logistic regression was used to analyze the independent influencing factors for poor prognosis in AIS patients after EVT.Results:Compared with the standard medical therapy, the EVT group had significantly lower NIHSS score at discharge, greater improvement in NIHSS score (NIHSS score at admission-NIHSS score at discharge), lower mRS score 90 days after onset, higher good prognosis rate, lower mortality rate within 90 days of onset, and longer hospital stay ( P<0.05). In the EVT group, 11 patients (27.5%) had good prognosis and 29 patients (72.5%) had poor prognosis 90 days after onset. Compared with the good prognosis group, the poor prognosis group had significantly higher blood glucose level and lower Alberta Stroke Program Early CT Score (ASPECT) on admission ( P<0.05). Multivariate Logistic regression analysis showed that blood glucose on admission ( OR=2.363, 95% CI: 1.134-4.928, P=0.022) and ASPECT score on admission ( OR=0.273, 95% CI: 0.088-0.854, P=0.026) were independent influencing factors for poor prognosis in AIS patients after EVT. Conclusion:AIS patients aged ≥85 years received EVT have better prognosis compared with those accepted standard medical therapy; these patients with high glucose level and low ASPECT score on admission have poor prognosis.

Objective:To investigate the impact of flow diverter (FD) malapposition at the aneurysm neck on clinical outcomes and complications of intracranial aneurysms, and identify the influencing factors for intraoperative FD malapposition.Methods:A retrospective study was performed; 153 patients with unruptured saccular aneurysms at the C4-C7 segments of the internal carotid artery accepted single FD implantation at Department of Interventional Radiology, First Affiliated Hospital of Zhengzhou University from June 2022 to March 2024 were chosen. Intraoperative high-resolution C-arm CT was utilized to assess FD apposition at the aneurysm neck. (1) Based on FD apposition at the aneurysm neck as shown, these 153 patients were divided into a malapposition group ( n=23, including 16 patients with malapposition being identified as residual malapposition after intraoperative corrective measures such as microwire massage and 7 patients with malapposition being newly detected in this study) and a complete apposition group ( n=130). Perioperative and follow-up complications were recorded. Clinical outcomes were assessed using modified Rankin Scale (mRS) at the final follow-up (mRS score of 0-2 as favorable outcome), and angiographic outcomes were evaluated by DSA at the final follow-up. Differences in clinical and angiographic outcomes and complication rate were compared between the malapposition group and complete apposition group. (2) Based on FD apposition at the aneurysm neck as shown, these 153 patients were divided into an intraoperative malapposition group ( n=74, including 67 patients with malapposition being detected during surgery and 7 patients with malapposition being newly detected in this study) and an intraoperative complete apposition group ( n=79). Univariate analysis was performed to compare the clinical variables between the intraoperative malapposition group and intraoperative complete apposition group; multivariate Logistic regression was further employed to identify the independent influencing factors for FD malapposition at the aneurysm neck. Results:(1) Four patients (all from the malapposition group) developed perioperative acute in-stent thrombosis. Nine patients experienced ischemic or hemorrhagic stroke during the follow-up, including 6 from the malapposition group and 3 from the complete apposition group; the complication rate in the malapposition group (6/23, 26.1%) was significantly higher than that in the complete apposition group (3/130, 2.3%) during the follow-up ( P<0.05). At the final follow-up, 2 patients (both from the malapposition group) had poor clinical outcome, while the remaining 151 patients had favorable outcome. Proportion of patients with favorable outcome between the two groups was statistically different (91.3%[21/23] vs. 100.0%[130/130], P<0.05). Delayed occlusion was detected in 46 patients (12 from the malapposition group and 34 from the complete apposition group) at the final angiographic follow-up. FD restenosis/re-occlusion was noted in 10 patients, including 6 from the malapposition group and 4 from the complete apposition group. Significant difference in delayed occlusion rate (52.2%[12/23] vs. 26.2%[34/130]) and long-term in-stent stenosis/occlusion rate (26.1%[6/23] vs. 3.1%[4/130]) was observed between the two groups ( P<0.05). (2) Significant difference in aneurysm neck diameter, FD angulation, parent artery stenosis, parent artery diameter ratio>1.2, and presence of branching vessels at the FD implantation site was noted between the intraoperative complete apposition group and intraoperative malapposition group ( P<0.05). Multivariate Logistic regression indicated that aneurysm neck diameter ( OR=1.431, 95% CI: 1.096-1.868, P=0.008), parent artery diameter ratio>1.2 ( OR=2.199, 95% CI: 1.083-4.463, P=0.029), and FD angulation ( OR=1.019, 95% CI: 1.002-1.036, P=0.027) were independent influencing factors for FD malapposition at the aneurysm neck. Conclusion:In FD implantation for intracranial aneurysms, FD malapposition at the aneurysm neck adversely affects delayed occlusion rate and complication rate; aneurysms with wider aneurysm neck diameter, parent artery diameter ratio>1.2, and greater FD angulation are trend to have FD malapposition at the aneurysm neck.

Objective:To assess the efficacy and safety of overlapping braided carotid artery stent (Wallstent) implantation in large extracranial internal carotid artery aneurysms (15 mm≤diameter<25 mm) and giant ones (diameter≥25 mm).Methods:A retrospective study was performed; the clinical data of 23 patients with large or giant extracranial internal carotid artery aneurysms accepted overlapping Wallstent stent implantation in Department of Interventional Radiology, First Affiliated Hospital of Zhengzhou University from August 2015 to June 2023 were collected. Immediately after implantation, DSA was used to evaluate the retention of contrast agent within the aneurysms and high-resolution C-arm CT (HR-CBCT) was used to detect the apposition between the two stents and between the stents and inner wall of the blood vessel. Perioperative complications were recorded. Clinical follow-up was performed bi-monthly via outpatient visits or telephone, and modified Rankin scale (mRS) was used to assess the prognoses (mRS scores of 0-2 as good prognosis) at the last follow-up; aneurysm occlusion was evaluated in a 6-month follow-up by DSA and in-stent restenosis in a final imaging follow-up by DSA or CTA according to the OKM grading. Results:Twenty-two patients had successful overlapping implantation of 2 Wallstent stents; blood flow was restricted in one patient due to carotid artery dissection at the distal end of the aneurysm during stent implantation and restored after a Neuroform EZ stent and 2 Wallstent stent implantation from the distal-proximal lesion; technical success rate of 95.7% (22/23) was obtained. DSA immediately after implantation showed obvious contrast medium retention in all aneurysms. HR-CBCT indicated good stent apposition in 21 patients and mild incomplete stent apposition in 2. Clinical follow-up was finished in 23 patients, ranged 6-31 months (mean 11.5±6.3 months); all patients had good prognosis at the last follow-up. Imaging follow-up, including at least once DSA, was conducted for all patients, with intervals ranging from 6 to 15 months (mean 10.4±3.4 months); DSA 6 months after implantation showed complete aneurysm occlusion in 19 patients (OKM grading D) and a bit of residual contrast in 4 patients (OKM grading C); final imaging follow-up (DSA in 2 and CTA in 21) revealed in-stent stenosis in 2 patients (stenosis rates of 51% and 87%) with obvious improved stenosis after balloon angioplasty and patent stents in 21 patients without evidence of aneurysm opacification.Conclusion:Overlapping braided carotid artery stent (Wallstent) implantation is an effective and safe approach for managing large or giant extracranial carotid artery aneurysms.