Biology subjects

Ameer, G. A.

Publications and source records attributed to Ameer, G. A..

4 recordsLinked to original sources

bioRxiv2026

Simultaneous regeneration of skin and bone in full-thickness cranial composite defects

Traumatic cranial defects often involve concurrent loss of soft and hard tissues and can progress to chronic defects due to delayed healing associated with infection or other co-morbidities. Despite autologous reconstruction remaining the clinical standard, it requires staged procedures using heterogeneous tissues, increasing operative time, costs, and surgical risks. Moreover, current tissue engineering approaches focus on single tissues or acute tissue defect models, limiting their clinical applications. Herein, we describe an acellular, material-driven 3D-printed composite scaffold designed to regenerate both bone and skin within composite cranial defects. The scaffold integrates controlled copper ion release from both organic and inorganic components with 3D-printed citrate polymer and citrate polymer-ceramic composites. Integrated thermoresponsive citrate-based hydrogels further enable spatially defined dermoconductive and osteoconductive properties, supporting a one-step surgical approach. At 12 weeks post-implantation, our scaffold enhanced keratinocyte organization, collagen deposition, and defect coverage with mature bone, achieving histological outcomes comparable to autografts. Furthermore, the system suppressed bacterial burden. Thus, this acellular platform represents a clinically promising synchronized strategy to address the complex demands of traumatic craniofacial composite defects.

bioengineering↗

bioRxiv2023

A polydiolcitrate-MoS2 composite for 3D printing Radio-opaque, Bioresorbable Vascular Scaffolds

Implantable polymeric biodegradable devices, such as biodegradable vascular stents or scaffolds, cannot be fully visualized using standard X-ray-based techniques, compromising their performance due to malposition after deployment. To address this challenge, we describe composites of methacrylated poly(1,12 dodecamethylene citrate) (mPDC) and MoS2 nanosheets to fabricate novel X-ray visible radiopaque and photocurable liquid polymer-ceramic composite (mPDC-MoS2). The composite was used as an ink with micro continuous liquid interface production (CLIP) to fabricate bioresorbable vascular scaffolds (BVS). Prints exhibited excellent crimping and expansion mechanics without strut failures and, importantly, required X-ray visibility in air and muscle tissue. Notably, MoS2 nanosheets displayed physical degradation over time in a PBS environment, indicating the potential for producing bioresorbable devices. mPDC-MoS2 is a promising bioresorbable X-ray-visible composite material suitable for 3D printing medical devices, particularly vascular scaffolds or stents, that require non-invasive X-ray-based monitoring techniques for implantation and evaluation. This innovative composite system holds significant promise for the development of biocompatible and highly visible medical implants, potentially enhancing patient outcomes and reducing medical complications. TOC O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=124 SRC="FIGDIR/small/564364v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@58cb6aorg.highwire.dtl.DTLVardef@192d2b1org.highwire.dtl.DTLVardef@4699a3org.highwire.dtl.DTLVardef@110d7f8_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2023

Phase-changing citrate macromolecule combats oxidative pancreatic islet damage, enables islet engraftment and function in the omentum

Clinical outcomes for total-pancreatectomy followed by intraportal islet autotransplantation (TP-IAT) to treat chronic pancreatitis (CP) patients are suboptimal due to the inflammatory state of the patients pancreas, oxidative tissue damage during the isolation process, and the harsh engraftment conditions in the livers vasculature, which include ischemia-reperfusion injury, and instant blood-mediated inflammatory reactions. We describe the use of the thermoresponsive, antioxidant macromolecule poly(polyethylene glycol citrate-co-N-isopropylacrylamide) (PPCN) to protect islet redox status and function in vitro and in vivo and to create a viable extrahepatic islet engraftment site in the abdomen. PPCN in aqueous media transitions from a liquid to an elastic hydrogel when exposed to body temperature via temperature-induced macromolecular self-assembly. Islets entrapped in the PPCN hydrogel and exposed to oxidative stress remain functional and support long-term euglycemia, in contrast to islets entrapped in a biologic scaffold (BS). When applied to the omentum of non-human primates (NHPs), PPCN is well-tolerated, safe, and mostly resorbed without fibrosis at 3 months post-implantation. To obtain autologous islets, a partial pancreatectomy was performed, followed by STZ administration to induce diabetes and destroy any remaining endogenous islets. Application of the autologous islets to the momentum using PPCN restored normoglycemia with minimal insulin requirements for over 100 days. These results support the use of PPCN as a scaffold for minimally invasive delivery of islets to the omentum of pancreatitis patients and highlight the importance of scaffold antioxidant properties as a new mechanism to protect islet function and maximize long-term autologous graft performance. One Sentence SummaryOmentum islet transplantation using a thermoresponsive, antioxidative polymer supports autologous islet viability and function in nonhuman primates.

bioengineering↗

bioRxiv2018

Multimodal interferometric imaging of nanoscale structure and macromolecular motion uncovers UV induced cellular paroxysm

We present a multimodal label-free interferometric imaging platform for measuring intracellular nanoscale structure and macromolecular dynamics in living cells with a sensitivity to macromolecules as small as 20nm and millisecond temporal resolution. We validate this system by pairing experimental measurements of nanosphere phantoms with a novel interferometric theory. Applying this system in vitro, we explore changes in higher-order chromatin structure and dynamics that occur due to cellular fixation, stem cell differentiation, and ultraviolet (UV) light irradiation. Finally, we discover a new phenomenon, cellular paroxysm, a near-instantaneous, synchronous burst of motion that occurs early in the process of UV induced cell death. Given this platforms ability to obtain nanoscale sensitive, millisecond resolved information within live cells without concerns of photobleaching, it has the potential to answer a broad range of critical biological questions about macromolecular behavior in live cells, particularly about the relationship between cellular structure and function.

biophysics↗