Jet injection into polyacrylamide gels: investigation of jet injection mechanics

Jet injectors employ high-velocity liquid jets that penetrate into human skin and deposit drugs in the dermal or subdermal region. Although jet injectors have been marketed for a number of years, relatively little is known about the interactions of high-speed jets with soft materials such as skin. Using polyacrylamide gels as a model system, the mechanics of jet penetration, including the dependence of jet penetration on mechanical properties, was studied. Jets employed in a typical commercial injector, (orifice diameter: 152 microm, velocity: 170-180 m/s) were used to inject fluid into polyacrylamide gels possessing Young's moduli in the range of 0.06-0.77 MPa and hardness values in the range of 4-70 H(OO). Motion analysis of jet entry into polyacrylamide gels revealed that jet penetration can be divided into three distinct events: erosion, stagnation, and dispersion. During the erosion phase, the jet removed the gel at the impact site and led to the formation of a distinct cylindrical hole. Cessation of erosion induced a period of jet stagnation ( approximately 600 micros) characterized by constant penetration depth. This stage was followed by dispersion of the liquid into the gel. The dispersion took place by crack propagation and was nearly symmetrical with the exception of injections into 10% acrylamide (Young's modulus of 0.06 MPa). The penetration depth of the jets as well as the rate of erosion decreased with increasing Young's modulus. The mechanics of jet penetration into polyacrylamide gels provides an important tool for understanding jet injection into skin.     

The crossflow injection technique: an improvement of the ethanol injection method

A novel scalable liposome preparation technique for pharmaceutical application is presented. Previous experiments have shown that the concept of continuous crossflow injection is a promising approach. For the characterization of the process, we focus on the influencing parameters like the lipid concentration, the injection hole diameter, the injection pressure, the buffer flow rate, and system performance. These experiments demonstrate that the injection hole diameter and the system performance do not influence the vesicle forming process and that a minimum of buffer flow rate is required to affect batch homogeneity. In contrast, strongly influencing parameters are lipid concentration in combination with increasing injection pressures. After exceeding the upper pressure limit of the linear range, where injection velocities remain constant, the vesicle batches are narrowly distributed, also when injecting higher lipid concentrations. Reproducibility and scalability data show similar results with respect to vesicle size and size distribution and demonstrate the stability and robustness of the novel continuous liposome preparation technique.     

两种不同的静脉注射方法对血管的影响

目的：比较两种给药方法对血管损伤的程度。方法：采用自身对照法进行注射泵（实验组）和手推（对照组）静脉注射,指压止血,光镜下观察局部血管及周围组织的变化。结果：注射泵指压止血时间较短,静脉炎发生率低（P〈0.01）,差异具有高度显著性。结论：注射中血流动力学的改变可加重血管的损伤,使指压止血时间延长。     

Mouse bladder wall injection

Mouse bladder wall injection is a useful technique to orthotopically study bladder phenomena, including stem cell, smooth muscle, and cancer biology. Before starting injections, the surgical area must be cleaned with soap and water and antiseptic solution. Surgical equipment must be sterilized before use and between each animal. Each mouse is placed under inhaled isoflurane anesthesia (2-5% for induction, 1-3% for maintenance) and its bladder exposed by making a midline abdominal incision with scissors. If the bladder is full, it is partially decompressed by gentle squeezing between two fingers. The cell suspension of interest is intramurally injected into the wall of the bladder dome using a 29 or 30 gauge needle and 1 cc or smaller syringe. The wound is then closed using wound clips and the mouse allowed to recover on a warming pad. Bladder wall injection is a delicate microsurgical technique that can be mastered with practice.     

Fibreoptic injection of oesophageal varices.

A new technique for injecting sclerosant into oesophageal varices uses a flexible gastroscope. Once the gastroscope has been inserted a flexible tube with a window cut into its distal end is pushed down over the gastroscope until a varix protrudes through the window. The varix can then be injected with a needle passed down the biopsy channel of the gastroscope. Once the varices have all been injected in this way the tube is advanced to compress the injection sites and so help control bleeding. This method, using a flexible gastroscope, has proved easier and safer than the traditional method using a rigid gastroscope.     

Migration of monocytes after intracerebral injection

Recently, we monitored green fluorescent protein (GFP)-expressing monocytes after injection at the entorhinal cortex lesion (ECL) site in mice. We followed their migration out of the central nervous system (CNS) along olfactory nerve fibers penetrating the lamina cribrosa, within the nasal mucosa, and their subsequent appearance within the deep cervical lymph nodes (CLN), with numbers peaking at day 7. This is the same route activated T cells use for reaching the CLN, as we have shown before. Interestingly, GFP cells injected into the brain and subsequently found in the CLN exhibited ramified morphologies, which are typical of microglia and dendritic cells. To gain more insight into immunity and regeneration within the CNS we want to monitor injected monocytes using magnetic resonance imaging (MRI) after labeling with very small superparamagnetic iron oxide particles (VSOP). Due to their small size, nanoparticles have huge potential for magnetic labeling of different cell populations and their MRI tracking in vivo. So far we have verified that incubation with VSOP particles does not alter their migration pattern after ECL.     

Migration of monocytes after intracerebral injection

Recently, we monitored green fluorescent protein (GFP)-expressing monocytes after injection at the entorhinal cortex lesion (ECL) site in mice. We followed their migration out of the central nervous system (CNS) along olfactory nerve fibers penetrating the lamina cribrosa, within the nasal mucosa, and their subsequent appearance within the deep cervical lymph nodes (CLN), with numbers peaking at day 7. This is the same route activated T cells use for reaching the CLN, as we have shown before. Interestingly, GFP cells injected into the brain and subsequently found in the CLN exhibited ramified morphologies, which are typical of microglia and dendritic cells. To gain more insight into immunity and regeneration within the CNS we want to monitor injected monocytes using magnetic resonance imaging (MRI) after labeling with very small superparamagnetic iron oxide particles (VSOP). Due to their small size, nanoparticles have huge potential for magnetic labeling of different cell populations and their MRI tracking in vivo. So far we have verified that incubation with VSOP particles does not alter their migration pattern after ECL.     

Refinement of intrathymic injection in mice

Direct intrathymic injection is a common procedure used in several types of experimental protocols in the mouse. Currently available approaches involve major surgical procedures that expose the thoracic cavity, resulting in an increased risk of poor recovery and postsurgical complications. The authors sought to refine this surgery to reduce animal pain and distress without compromising overall efficiency of the technique. Using a minimally invasive method that does not expose the thoracic cavity, the authors gave accurately placed intrathymic injections, as confirmed by analyses with a reporter dye. They describe this new approach for intrathymic injection in mice that reduces complications associated with lengthy periods of anesthesia and thoracic cavity exposure.