Tissue response and in vivo degradation of selected polyhydroxyacids: polylactides (PLA), poly(3-hydroxybutyrate) (PHB), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB/VA)

Use of a Biopolymer Polyalkylimide Filler for Facial Lipodystrophy in HIV-Positive Patients Undergoing Treatment with Antiretroviral Drugs

OBJECTIVES

To evaluate the efficacy, overall esthetic effect, and safety of a new permanent, polyalkylimide dermal filler in HIV-infected patients with severe facial lipodystrophy.

METHODS

Eleven subjects with severe facial lipodystrophy secondary to HIV infection were injected bilaterally with 15 and 30 cm3 of a polyalkylimide gel into the buccal, malar, and temporal areas of the face in an attempt to restore their facial contour. The youngest treated subject was 31 years of age and the oldest 73 years of age.

RESULTS

All 11 subjects received an immediately acceptable therapeutic esthetic effect. Injections were generally well tolerated, with only three adverse events (swelling and bruising) recorded. Subjects, assessed at 3 and 18 months after treatment, continued to show improvement.

CONCLUSIONS

The immediate benefits of a polyalkylimide gel in the correction and restoration of facial contour in subjects having severe HIV-related facial lipodystrophy were demonstrated. This improvement was still noted at 18 months. The efficacy, ease of injection, and safety profile of polyalkylimide gel make this filling material a potentially attractive treatment for lipodystrophy. These data must be tempered with the need for significant further safety studies to determine whether this long-term filler has a safety profile consistent with other currently popular fillers.

Reduction of the in vitro pro-inflammatory response by macrophages to poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

This study evaluates the pro-inflammatory response to the thermoplastic biopolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) through the analysis of cellular responses in vitro. The murine macrophage RAW264.7 cell line was cultured on solvent cast PHBV films, which was found to induce pro-inflammatory activity that required direct contact between the material and the macrophages. The identity of the pro-inflammatory stimulus was determined by culturing bone marrow-derived macrophages from bacterial lipopolysaccharide (LPS) hyporesponsive C3H/HeJ mice and CpG non-responsive TLR9-/- mice on PHBV. The lack of a pro-inflammatory response by the C3H/HeJ cells indicates that the pro-inflammatory agent present within PHBV is predominately LPS while the TLR9-/- macrophages confirmed that CpG-containing bacterial DNA is unlikely to contribute to the activity. A series of purification procedures was evaluated and one procedure was developed that utilized hydrogen peroxide treatment in solution. The optimized purification was found to substantially reduce the pro-inflammatory response to PHBV without adversely affecting either the molecular structure or molecular weight of the material thereby rendering it more amenable for use as a biomaterial in vivo.

Safety of Sculptra: a review of clinical trial data

The development of facial lipoatrophy as a result of highly active antiretroviral therapy (HAART) used to treat patients with human immunodeficiency virus (HIV) has adversely affected patient quality of life and compliance with therapy. Thanks to modern pharmacotherapies, HIV can now be viewed as a chronic disease; however, this welcome change has exacerbated the effect of facial lipoatrophy since HIV-infected patients can now expect to live longer and healthier lives but remain subject to public scrutiny of their ongoing disease state. Sculptra (Dermik Laboratories, Berwyn, PA, USA) has recently been introduced in the USA for correction of the appearance of facial lipoatrophy. The device affords long-lasting restoration while still being non-permanent, thus providing an extended but adjustable cosmetic effect. The safety profile of this product has been observed in four investigator-initiated clinical trials of more than 250 HIV patients and in numerous investigator reports, with no serious adverse events or infections deemed associated with the product. Maintenance of the excellent safety profile for this injectable device requires adherence to a novel technique and appreciation of its unique attributes.

Mimicked bioartificial matrix containing chondroitin sulphate on a textile scaffold of poly(3-hydroxybutyrate) alters the differentiation of adult human mesenchymal stem cells

Controlling the differentiation of human mesenchymal stem cells (hMSC) and providing tissue functions in engineered constructs before implantation are major challenges. Beside the additives in culture media, the artificial niches inside a scaffold can serve this purpose. To prepare niches favoring the osteoblastic differentiation of hMSCs, components of the extracellular matrix of bone were immobilized on fabrics of poly(3-hydroxybutyrate). Aqueous gels of fibrillar bovine collagen I, with or without addition of chondroitin sulphate (CS), were immobilized on the textile scaffold, sub-structured in a freeze-drying process, and cross-linked. hMSCs of four donors were isolated from bone marrow. After expansion, the cells were seeded dynamically onto the scaffolds. From thereon, the culture was transferred into perfused vessels and partly submitted to dexamethasone to promote osteogenic differentiation. During their 4 weeks of culture, the cells' distribution and morphology throughout the scaffolds were characterized by laser scanning microscopy (LSM) and scanning electron microscopy (SEM). Photospectrometrically the cells' viability (MTT) and alkaline phosphatase (ALP) production were assessed. The transcription of osteoblast-specific markers was elucidated with polymerase chain reaction (PCR) tests. Cells on CS-containing scaffolds in the presence of dexamethasone showed the highest ALP production. PCR monitored an increase of osteoblastic markers. All scaffolds showed higher calcium deposition than cell-free controls. These results lead to the conclusion that a niche containing CS renders the differentiation of hMSCs toward osteoblastic cells more specific.

Dispelling the myth: appropriate use of poly-l-lactic acid and clinical considerations

OBJECTIVES

Injectable poly-L-lactic acid (PLLA; Sculptra) is widely used throughout Europe and the USA to restore volume in depressed areas of the face by stimulating neocollagenesis. Injectable PLLA was previously marketed as New-Fill, which was often injected incorrectly and at too high a concentration, resulting in some physicians losing confidence in this product. Today, Sculptra is still regarded with a degree of scepticism by some physicians, due to direct or indirect experience with New-Fill. Sculptra, both in formulation and use, is vastly superior to New-Fill and clinical experience with this product dispels the myths associated with the earlier types of injectable PLLA.

RESULTS

PLLA is a very safe, biodegradable compound that has been used in a wide range of medical devices for the last 30 years. In injectable form a good safety profile has been proven; however, when the device is overconcentrated, localized overstimulation of the fibroblasts can result in the formation of small lumps (subcutaneous papules), which are non-pathological but nevertheless palpable by the patient. Physicians must also be trained in the injection of this device, as incorrect injection technique can cause device-related adverse events.

CONCLUSION

New product guidelines have ensured that problems with PLLA concentration have been countered, and tried and tested injection techniques have been shown to ameliorate device-related adverse events, both of which are dispelling the myths associated with modern injectable PLLA.

Poly-L-lactic acid: a new dimension in soft tissue augmentation

Poly-L-lactic acid (PLLA) is a biodegradable, synthetic polymer of L-lactic acid that has been used in a variety of human medical applications for over 40 years. It has recently been approved in the United States for the treatment of HIV-associated facial lipoatrophy. This indication, combined with a European experience that indicates a clinical benefit persisting for up to 2 years, has made PLLA an increasingly popular injectable soft tissue filler in healthy patients. However, controlled clinical studies are necessary to determine whether PLLA benefits healthy patients seeking contour restoration as much as patients seeking treatment for HIV facial lipoatrophy. The present authors reviewed the background and clinical applications of PLLA as treatment for HIV-associated facial lipoatrophy and age-related facial volume loss.

A new option for volumetric restoration: poly-l-lactic acid

OBJECTIVES

The market for products and techniques that correct the visible signs of facial ageing is now huge. There is a diversity of devices and treatments now vying for a share of this growing marketplace, including polymer implants and injectable preparations that are based on an array of substances. The vast majority of these devices can only provide temporary correction of superficial lines and wrinkles, with volumetric augmentation being beyond their capabilities. The products and procedures suitable for the restoration of facial volume are discussed here.

RESULTS

The restoration of facial volume has long been neglected in cosmetic rejuvenation as surgical procedures increase skin tension but do nothing to restore the underlying facial volume, which is a subtle yet important characteristic of the youthful face. Fortunately, devices are now available which can augment facial volume for long periods of time or even permanently. These include implants based on expanded polytetrafluoroethylene and silicone rubber, which provide permanent restoration of volume, but require invasive surgery and do not age with the surrounding tissues eventually resulting in an unnatural appearance. The cosmetic rejuvenation market now abounds with various injectable devices, including: poly-L-lactic acid (PLLA), polymethylmethacrylate, collagens, hyaluronic acids, silicone and calcium hydroxylapatite. The choice of which one to use in practice is physician led, based on facial assessments, product characteristics and the desires of the patient.

CONCLUSION

Although there is a wealth of products available, injectable PLLA (Sculptra) can restore volume to the face providing a natural look. Not only are the results of volume augmentation using this device long lasting, but they are also safe.

Dynamic and Static Light Scattering Studies on Self-Aggregation Behavior of Biodegradable Amphiphilic Poly(ethylene oxide)−Poly[(R)-3-hydroxybutyrate]−Poly(ethylene oxide) Triblock Copolymers in Aqueous Solution

The self-aggregation behavior of two amphiphilic poly(ethylene oxide)-poly[(R)-3-hydroxybutyrate]-poly(ethylene oxide) (PEO-PHB-PEO) triblock copolymer samples with nearly identical PHB block lengths but different PEO block lengths, PEO-PHB-PEO(2000-810-2000) and PEO-PHB-PEO(5000-780-5000), was studied with dynamic and static light scattering (DLS and SLS), in combination with fluorescence spectroscopy and transmission electron microscopy (TEM). The formation of polymeric micelles by the two PEO-PHB-PEO triblock copolymers was confirmed with fluorescence technique and TEM. DLS analysis showed that the hydrodynamic radius (R(h)) of the monodistributed polymeric micelles increased with an increase in PEO block length. The relative thermostability of the triblock copolymer micelles was studied by SLS and DLS at different temperatures. The aggregation number and the ratio of the radius of gyration over hydrodynamic radius were found to be independent of temperature, probably due to the strong hydrophobicity of the PHB block. The combination of DLS and SLS studies indicated that the polymeric micelles were composed of a densely packed core of hydrophobic PHB blocks and a corona shell formed by hydrophilic PEO blocks. The aggregation numbers were found to be approximately 53 for PEO-PHB-PEO(2000-810-2000) micelles and approximately 37 for PEO-PHB-PEO(5000-780-5000) micelles. The morphology of PEO-PHB-PEO spherical micelles determined by DLS and SLS measurements was further confirmed by TEM.

Correction options for lipoatrophy in HIV-infected patients

Lipoatrophy (LA) is a form of lipodystrophy, characterized by volume depletion caused by fat loss in the limbs, buttocks, and face. Facial volume loss is the most obvious outward sign of LA because it alters the facial contours in the cheeks, temples, and orbits. Lipodystrophy and LA are most commonly seen in patients with HIV on highly active antiretroviral therapy (HAART), which was introduced in the mid-1990s for the management of HIV, and is currently considered the mainstay therapy for HIV-infected patients. However, the etiology of LA is likely multifactorial as underlying patient conditions, including duration and severity of HIV and increasing age, have also been found to contribute to its occurrence. The volume loss of LA can be very dramatic with some patients exhibiting no signs of facial fat. As a result, many HIV-infected patients with associated LA suffer from psychological and lifestyle effects, which can lead to noncompliance with HAART. Thus, increases in facial volume and improvement in morphology is anticipated to reduce anxiety caused by LA in HIV-infected patients, and improve quality of life. This review discusses the benefits and limitations of several treatment options available to correct the volume depletion associated with LA, including antiretroviral switching, permanent surgical implants and injectables, poly-L-lactic acid, collagen, and hyaluronic acid derivatives.

Fabrication, characterization, and in vitro degradation of composite scaffolds based on PHBV and bioactive glass

Composite scaffolds of polyhydroxybutyrate-polyhydroxyvalerate (PHBV) with sol-gel-derived bioactive glass (BG, 58S) are fabricated by compression molding, thermal processing, and salt particulate leaching method. Structure and mechanical properties of the scaffolds are determined. The bioactivity of the composites is evaluated by soaking the scaffolds in a simulated body fluid (SBF), and the formation of the apatite layer on the scaffolds is determined by scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). The results show that the PHBV/BG composites are bioactive as they induce the formation of apatite on the composite scaffolds after soaking in SBF for 3 days. In addition, the measurements of the water contact angles suggest that incorporation of BG into PHBV can improve the hydrophilicity of the composites and the enhancement is dependent on the BG content. Furthermore, the degradation assessment of the scaffolds is performed in phosphate-buffered saline (PBS) solution at 37 C. Weight loss and water absorption of the scaffolds, pH of the incubation media, and molecular weight measurements of the PHBV in the scaffolds are used to monitor the degradation of the scaffolds during a nine-week incubation in PBS. It has been found that the incorporation of bioactive glass into the PHBV delayed the degradation of PHBV in the composite scaffolds for the period investigated. The present results show not only a useful method to prepare composite scaffolds with improved properties but also a way of adjusting the in vitro degradation behavior of composite scaffolds by tailoring the content of bioactive glass.

Facial volumetric correction with injectable poly-L-lactic acid

BACKGROUND

Polymers of lactic acid'have been widely used for many years in different types of medical devices, such as resorbable sutures, intrabone implants, and soft tissue implants. Injectable poly-L-lactic acid (PLLA; Sculptra), a synthetic, biodegradable polymer, has gained widespread popularity in Europe for the treatment of facial changes associated with aging.

OBJECTIVE

To provide background information on injectable PLLA and to describe clinical experience with its use in Europe for facial volume enhancement.

METHODS

Technique varies with site of injection. Generally, the product is implanted subcutaneously or intradermally in a series of treatments. No allergy testing is required.

RESULTS

Based on experience in more than 2,500 patients, injectable PLLA has been used successfully for the correction of nasolabial folds, mid- and lower facial volume loss, jawline laxity, and other signs of facial aging. Correction lasts for 18 to 24 months in most patients.

CONCLUSIONS

Injectable PLLA treatment provides an excellent and prolonged correction of a variety of facial wrinkles, depressions, and laxity with a minimally invasive procedure that does not require allergy testing or a recovery period.

Introducing Amine Functionalities on a Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Surface: Comparing the Use of Ammonia Plasma Treatment and Ethylenediamine Aminolysis

Amine functionalities were introduced onto the surface of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films by applying radio frequency ammonia plasma treatment and wet ethylenediamine treatment. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS) for chemical composition and Raman microspectroscopy for the spatial distribution of the chemical moieties. The relative amount of amine functionalities introduced onto the PHBV surface was determined by exposing the treated films to the vapor of trifluoromethylbenzaldehyde (TFBA) prior to XPS analysis. The highest amount of amino groups on the PHBV surface could be introduced by use of ammonia plasma at short treatment times of 5 and 10 s, but no effect of plasma power within the range of 2.5-20 W was observed. Ethylenediamine treatment yielded fewer surface amino groups, and in addition an increase in crystallinity as well as degradation of PHBV was evident from Fourier transform infrared spectroscopy. Raman maps showed that the coverage of amino groups on the PHBV surfaces was patchy with large areas having no amine functionalities.

NMR relaxometry and imaging of water absorbed in biodegradable polymer scaffolds

Porous substrates made of poly(3-hydroxybutyrate-3-hydroxyvalerate) (PHBHV) were prepared by a particulate leaching method. After removing the salt by extraction in water, proton nuclear magnetic resonance (NMR) relaxometry and imaging were performed on sets of PHBHV substrates immersed in phosphate-buffered solution during 3 months at different time points. Polarized optical microscopy studies were performed on thin sections, 25 and 5 mum, of the PHBHV samples. The results of NMR relaxometry showed two (1)H nuclei populations, well distinguishable on the free induction decay (FID), due to the different decay time constants, a factor of 10(2) apart. Thus, it was possible to separate the two populations, giving separate distributions of T(1) relaxation times. One population could be associated with water protons in the pores and the other to macromolecular protons. The distributions of T(1) and T(2) of the water proton shifted to lower values with increasing immersion time to a constant value after 30 days. The results obtained by NMR imaging showed an initial increase in the apparent porosity, reaching a plateau after 25 days of immersion. This increase is attributed mainly to the absorption of water in the microporosity as supported by the results of the relaxometry measurements and shown by scanning electron microscopy. The average porosity measured by NMR imaging at the plateau, 78+/-3%, is slightly higher than that determined by optical microscopy, 73+/-9%, which may be due to the fact that the latter method did not resolve the microporosity. Overall, the results suggest that at early stages after immersing the scaffolds in the aqueous medium, first 30 days approximately, NMR imaging could underestimate the porosity of the substrate.

Caring for HIV-positive and aging patients with associated facial lipoatrophy

Facial lipoatrophy is characterized by fat loss and redistribution. It is a natural, biological phenomenon that occurs over time, presenting as mild-to-moderate volume depletion that gives the skin the appearance of sagging. More recently, highly active antiretroviral therapy, introduced for the management of human immunodeficiency virus, has been associated with moderate-to-severe facial lipoatrophy, and is characterized by sunken cheeks, accentuated nasolabial folds, and protruding musculature and bones. Furthermore, the consequences of facial lipoatrophy have been found to substantially impact patient quality of life. Nurses play an integral role in the treatment of facial lipoatrophy by educating the patients on available therapies and assisting them in making informed treatment decisions. It is important that treating nurses conduct a well-organized interview to understand patient treatment goals. This article will discuss several treatment options available to correct facial lipoatrophy-associated volume deficits, including collagen, hyaluronic acid, calcium hydroxylapatite, poly-L-lactic acid, and permanent implants and injectables.

Enhanced vascular-related cellular affinity on surface modified copolyesters of 3-hydroxybutyrate and 3-hydroxyhexanoate (PHBHHx)

Random copolyester of 3-hydroxybutyrate and 3-hydroxyhexanoate, short as PHBHHx, was surface modified by ammonia plasma treatment and/or fibronectin coating, respectively. The improved results were demonstrated by better growth of human umbilical vein endothelial cells (HUVECs) and rabbit aorta smooth muscle cells (SMCs) on the surface of ammonia plasma-treated PHBHHx coated with fibronectin (PFn-PHBHHx), compared with the fibronectin-coated (Fn-PHBHHx) or uncoated PHBHHx, respectively, although XPS analysis and ELISA demonstrated higher fibronectin adsorption on Fn-PHBHHx than on PFn-PHBHHx. Confocal microscopy observation showed that the specific co-localization of fibronectin with F-actin was impaired on PFn-PHBHHx, while it was almost lost on Fn-PHBHHx compared with pristine PHBHHx or plasma-treated PHBHHx (P-PHBHHx). These were attributed to the generation of new nitrogen- and oxygen-containing groups on the PHBHHx surface by the ammonia plasma treatment, which led to increased polar components that enhanced polymer surface energy and hydrophilic properties on P-PHBHHx. The most prominent effect of PFn-PHBHHx was its stimulation of HUVECs proliferation. HUVECs on PFn-PHBHHx formed a confluent monolayer after 3 days of incubation, while SMCs were unable to form a sub-confluent layer. The above evidences revealed that PFn-PHBHHx would benefit endotheliazation rather than SMCs proliferation. We therefore believed that PFn-PHBHHx would be a promising material as a luminal surface of vascular grafts.

Bioresorbable polymers: heading for a new generation of spinal cages

The use of polymer-based bioresorbable materials is now expanding to the realm of spinal interbody fusion. Bioresorbable polymers have important advantages over metals, because they are temporary, much less stiff, and radiolucent. Most promising is a group of alpha-polyesters, in particular polylactide acids (PLAs). Their biocompatibility is excellent, and they have sufficient stiffness and strength to provide initial and intermediate-term stability required for bone healing. However, polylactides have characteristics that make them vulnerable to complications if not properly controlled. Degradation rate strongly depends on polymer type, impurities, manufacturing process, sterilization, device size, and the local environment. The fact that larger implants degrade faster is contra-intuitive, and should be considered in the design process. Also optimal surgical techniques, such as careful bone bed preparation, are required for a successful application of these materials. The purpose of this paper is to highlight the specific properties of these bioresorbable polymers and to discuss their potential and limitations. This is illustrated with early preclinical and clinical data.Bioresorbable cage technology is just emerging: their time-engineered degradation characteristics allow controlled dynamization in interbody applications, facilitating spinal fusion. Their radiolucency improves image assessment of fusion healing. Acceptance and use of bioresorbable implants may increase as further research and clinical studies report on their safety, efficacy, and proper usage.

Polymeric grafting of acrylic acid onto poly(3-hydroxybutyrate-co-3-hydroxyvalerate): surface functionalization for tissue engineering applications

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) melt processed disks and solvent cast films were modified by graft co-polymerization with acrylic acid (AAc) in methanol solution at ambient temperature using gamma irradiation (dose rate of 4.5 kGy/h). To assess the presence of carboxylic acid groups on the surface, reaction with pentafluorophenol was performed prior to X-ray photoelectron spectroscopy analysis. The grafting yield for all samples increased with monomer concentration (2-15%), and for the solvent cast films, it also increased with dose (2-9 kGy). However, the grafting yield of the melt processed disks was largely independent of the radiation dose (2-8 kGy). Toluidine blue was used to stain the modified materials facilitating visual information about the extent of carboxylic acid functionalization and depth penetration of the grafted copolymer. Covalent linking of glucosamine to the functionalized surface was achieved using carbodiimide chemistry verifying that the modified substrates are suitable for biomolecule attachment.

Preparation and Interfacial Properties of a Novel Biodegradable Polymer Surfactant: Poly(ethylene oxide monooleate-block-DL-lactide)

In this paper, we report a novel synthesis of poly(ethylene oxide monooleate-block-DL-lactide) (MOPEO-PLA) in the presence of stannous 2-ethylhexanoate catalyst. By utilizing the surfactant property and the reactive double bond of the amphiphilic MOPEO-PLA, various characteristics of PLA microspheres, such as surface and internal structure, surface morphology, release property, and so on, may potentially be controlled. MOPEO-PLA was found to be hydrophobic enough to prevent loss by dissolution into aqueous solution, which is often a problem for MOPEO. Furthermore, the interfacial tension measurements of a MOPEO-PLA/toluene/water system revealed that MOPEO-PLA had a good surface activity almost equal to that of MOPEO. The MOPEO-PLA/PLA blend films were prepared by solvent casting on a water layer. Contact-angle measurements of MOPEO-PLA/PLA blend films confirmed that the hydrophilic PEO segments were selectivity accumulated at the oil/water interface. Moreover, the surface free energy on the 'water side' of the MOPEO-PLA/PLA blend films was increased because of the increase in polar components as a result of the ether bonds of the PEO segments. Schematic illustration of the adsorption property of a) MOPEO-PLA with a high-molecular-weight PLA segment and b) MOPEO-PLA with a low-molecular-weight PLA segment at an ethyl acetate/water interface.

Micellization phenomena of biodegradable amphiphilic triblock copolymers consisting of poly(beta-hydroxyalkanoic acid) and poly(ethylene oxide)

This paper reports the studies on micelle formation of new biodegradable amphiphilic poly(ethylene oxide)-poly[(R)-3-hydroxybutyrate]-poly(ethylene oxide) (PEO-PHB-PEO) triblock copolymer with various PHB and PEO block lengths in aqueous solution. Transmission electron microscopy showed that the micelles took an approximately spherical shape with the surrounding diffuse outer shell formed by hydrophilic PEO blocks. The size distribution of the micelles formed by one triblock copolymer was demonstrated by dynamic light scattering technique. The critical micellization phenomena of the copolymers were extensively studied using the pyrene fluorescence dye absorption technique, and the (0,0) band changes of pyrene excitation spectra were used as a probe for the studies. For the copolymers studied in this report, the critical micelle concentrations ranged from 1.3 x 10(-5) to 1.1 x 10(-3) g/mL. For the same PEO block length of 5000, the critical micelle concentrations decreased with an increase in PHB block length, and the change was more significant in the short PHB range. It was found that the micelle formation of the biodegradable amphiphilic triblock copolymers consisting of poly(beta-hydroxyalkanoic acid) and PEO was relatively temperature-insensitive, which is quite different from their counterparts consisting of poly(alpha-hydroxyalkanoic acid) and PEO.

Morphological and functional evaluation of leg-muscle reinnervation after coupler coaptation of the divided rat sciatic nerve

Mechanical couplers are successfully used for microvascular venous anastomoses. The advantages include a simple and fast technique and a high patency rate. Couplers offer a secluded coaptation site, and might also be of use in peripheral nerve repair. The present study was designed to investigate coupler coaptation of the rat sciatic nerve, evaluating the number and locations of motor and sensory neurons projecting to the selected muscles as well as stimulation-induced muscle contraction force. Adult rats underwent either suture or coupler repair after left sciatic nerve transection. In all rats, the experimental side was compared to the healthy right side. Evaluation after 20 weeks included retrograde labeling of motoneurons and dorsal root ganglion neurons projecting to the tibial anterior muscle and to the tibial posterior muscle, histology, muscle contraction force (tibial anterior muscle and gastrocnemius muscle), and a pinch reflex test. The results show that the suture and the coupler groups did not differ significantly regarding the examined parameters, except for discrete signs of nerve compression at the coaptation site after coupler repair due to fibrous tissue ingrowth. However, this did not impair axonal regeneration. Importantly, axonal outgrowth from the repair site to the surrounding tissue was not observed after coupler coaptation, but it was observed after suture repair. These results suggest that couplers may be of value for repair of nerves in adjacency to avoid axonal crisscrossing between nerves during regeneration.

Resorbable Polylactic Acid Interbody Spacers with Vertebral Autograft for Anterior Cervical Discectomy and Fusion

OBJECTIVE:

Resorbable polylactic acid spinal implants have recently become commercially available. These spacers carry the advantages of allowing for clear visualization of new bone growth, eliminating the risk of pathogen transmission, and providing for consistent biomechanical quality. However, previously published reports on the use of these spacers have all utilized bone morphogenetic proteins to supplement the fusion. This report describes our early experience with the use of these devices for interbody reconstruction in anterior cervical discectomy with fusion.

METHODS:

Twenty patients underwent an anterior cervical discectomy with fusion at 30 levels during an 18-month period. All patients were implanted with polylactic acid interbody spacers using the Smith-Robinson technique. Supplementary anterior cervical plating was applied using unicortical semiconstrained screws, and the spacers were filled with vertebral endplate autograft bone shavings. Seven of the patients were smokers, and three were diabetics. Radiographic fusion was determined with dynamic cervical spine x-rays, and clinical responses were determined using the Medical Outcomes Study Short-Form 36-Item Health Survey, Odom's criteria, Nurick scores, and functional outcome swallowing score dysphagia scores. Follow-up averaged 11.6 months.

RESULTS:

Of the 9 patients with myelopathy, all experienced clinical improvement, with the mean Nurick score improving from 2.7 to 1.3. Of the 14 patients who had radiculopathy, 9 had complete resolution of symptoms, 4 experienced some improvement, and 1 had no improvement. All 20 patients demonstrated radiographic fusion at last follow-up as demonstrated by bridging bone between the vertebral bodies and the absence of motion on dynamic x-rays.

CONCLUSION:

Resorbable polylactic acid interbody spacers are safe and effective for anterior cervical discectomy and fusion. Use of locally harvested vertebral endplate bone packed within the spacer is sufficient to promote fusion in anterior cervical discectomy with fusion.

Mechanical Properties of Laser Cut Poly(L-Lactide) Micro-Specimens: Implications for Stent Design, Manufacture, and Sterilization

Background: The development of endoluminal stents from polymeric materials requires an understanding of the basic mechanical properties of the polymer and the effects of manufacturing and sterilization on those properties. Methods: Pure poly(L-lactide) (PLLA) and PLLA containing varying amounts of triethylcitrate (TEC) as a plasticizer (5-10-15%) were studied. The specimens were solution-cast and CO2 laser-cut. Specimen dimensions were adapted to the strut size of polymeric vascular stents. The properties of the PLLA micro-specimens were assessed before and after sterilization (EtO cold gas, H2O2-plasma, beta- and gamma-irradiation). Tensile tests, and creep and recovery tests were carried out at 37°C. Additionally the thermal and thermo-mechanical characteristics were investigated using dynamic-mechanical analysis (DMA) and differential scanning calorimetry (DSC). Results: The results showed the dramatic influence of the plasticizer content and sterilization procedure on the mechanical properties of the material. Laser cutting had a lesser effect. Hence the effects of processing and sterilization must not be overlooked in the material selection and design phases of the development process leading to clinical use. Altogether, the results of these studies provide a clearer understanding of the complex interaction between the laser machining process and terminal sterilization on the primary mechanical properties of PLLA and PLLA plasticized with TEC.

A novel osteotropic biomaterial OG-PLG: Synthesis andin vitro release

Statins (e.g., simvastatin) have shown to induce expression of the bone morphogenic protein-2 gene in bone cells, but they are not used clinically because of a lack of a suitable delivery device. The overall objective is to develop optimized statin delivery devices for bone regeneration. The specific objective was to determine the effect of grafting statins to biodegradable poly[lactide-co-glycolide] (PLG) on release kinetics. Simvastatin was grafted to PLG (OG-PLG) and characterized using contact-angle measurements, attenuated total reflectance-Fourier transform infrared, and ultraviolet-visible spectroscopy to determine success of the synthesis. An ultraviolet-visible assay for measuring release of statins and degraded OG-PLG in media was also developed. In vitro release studies using films and scaffolds made with PLG, PLG blended with simvastatin (PLG + Sim), and OG-PLG (simvastatin grafted to PLG) blended into PLG at different concentrations showed that release rate of OG-PLG from films was significantly greater than that of PLG + Sim. However, release rate from scaffolds showed PLG + Sim to be significantly higher than that of OG-PLG. The diffusion-controlled release kinetics of simvastatin from PLG + Sim seems to be more heavily affected by device morphology, whereas the degradation-controlled release kinetics seem to be less affected. In short, release kinetics can be modulated by grafting statins to PLG.

Effects of monopolar radiofrequency treatment over soft-tissue fillers in an animal model: Part 1

BACKGROUND AND OBJECTIVES

Monopolar radiofrequency (RF) treatment is used by physicians to tighten and contour the skin of their patients. In many cases, patients have received prior treatment with other aesthetic modalities such as soft-tissue augmentation or they may wish to receive these treatment modalities simultaneously. Together, soft-tissue augmentation and monopolar RF treatment have the potential to restore tissue volume and improve facial laxity. To date, no published studies have documented the effects of RF treatment directly over soft-tissue fillers.

STUDY DESIGN/MATERIALS AND METHODS

We examined the tissue interactions of monopolar RF heating with five commonly injected fillers in a juvenile pig model. This is the first part of a two-part study. In this study, the interaction of monopolar RF and filler substances was examined over a period of 4 months. The five soft-tissue fillers examined were cross-linked human collagen (Cosmoplast), hyaluronic acid (Restylane), calcium hydroxylapatite (Radiesse), polylactic acid (Sculptra), and liquid injectable silicone (Silikon 1000).

RESULTS

There was no apparent increase in the risk of local burns and no observable effect of RF treatment on filler persistence in the tissue. With monopolar RF treatment, an increase in fibroplasia and collagen deposition surrounding Restylane, Radiesse, and Sculptra was observed. When scored in a blinded fashion, the increase in collagen deposition was statistically significant for Radiesse.

CONCLUSIONS

In this animal study, RF treatment had no observed adverse effect on filler collagen responses or persistence. Filler presence did not increase the risk of undesirable thermal effects with monopolar RF treatment. Further clinical studies are required to evaluate the effect of monopolar RF treatment over dermal fillers with respect to aesthetic outcome.

Oligo-3-hydroxybutyrates as potential carriers for drug delivery

In the present paper we describe the synthesis and toxicity studies of well-defined tailor made oligo-[R,S]-3-hydroxybutyrates (OHBs). The results indicate potential applicability of these nano-polymers as drug delivery carriers. Several OHBs of number average molecular weight (M(n)) ranging from 800 to 2400 have been synthesized and tested on transformed hamster V79 fibroblasts and murine melanoma B16(F10) cells using the 3-[4,5-dimethylthiazol-2-yl]2,5-diphenyltetrazolium bromide (MTT) based drug resistance and clonogenic survival assays. We show that 96-h incubation of cells with 1-9 microg/ml of OHBs did not affect cell viability. Incubation of OHBs with rat hepatoma FTO-2B cells stably transfected with chloramphenicol acetyltransferase (CAT) gene ligated to heat-inducible hsp70i gene promoter demonstrated that OHBs did not induce cellular stress response. Finally, we demonstrate that doxorubicin conjugated with OHB is effectively taken up by murine melanoma B16(F10) cells in vitro and localizes in the cytoplasm. These data show for the first time that tailor-made biodegradable and biocompatible oligomers of 3-hydroxybutyric acid can be taken into consideration as effective, non-toxic vectors for delivery of drugs in a conjugated form.

New polymers for drug delivery systems in orthopaedics: in vivo biocompatibility evaluation

The use of biodegradable polymers for drug delivery systems excluded the need for a second operation to remove the carrier. However, the development of an avascular fibrous capsule, reducing drug release, has raised concern about these polymers in terms of tissue-implant reaction. Five novel polymers were evaluated in vivo after implantation in the rat dorsal subcutis and compared to the reference polycaprolactone (PCL). Poly(cyclohexyl-sebacate) (PCS), poly(L-lactide-b-1,5-dioxepan-2-one-b-L-lactide) (PLLA-PDXO-PLLA), two 3-hydroxybutyrate-co-3-hydroxyvalerate copolymers (D400G and D600G), and a poly(organo)phosphazene (POS-PheOEt:Imidazole) specimens were histologically evaluated in terms of the inflammatory tissue thickness and vascular density at 4 and 12 weeks from surgery. The highest values of inflammatory tissue thickness were observed in D600G (P < 0.01), PCS (P < 0.001) and PLLA-PDXO-PLLA (P < 0.001) at 4 weeks, while POP-PheOEt:Imidazole showed the lowest value of inflammatory tissue thickness (P < 0.05) at 12 weeks. D400G, D600G, PLLA-PDXO-PPLA and POP-PheOEt:Imidazole showed higher (P < 0.001) values of vascular density near the implants in comparison to PCL at 4 weeks. Finally, D400G and D600G increased their vessel densities while POP-PheOEt:Imidazole and the synthetic polyester PLLA-PDXO-PLLA presented similar vessel density values during experimental times. These different behaviours to improve neoangiogenesis without severe inflammatory tissue-responses could be further investigated with drugs in order to obtain time-programmable drug delivery systems for musculoskeletal therapy.

MacroPore resorbable devices in craniofacial surgery

Resorbable polymer implants have become a compelling option in the treatment of acquired and congenital craniofacial deformities. The resorbable polylactide (PLa) and polyglycolide (PGa) polymers in particular have demonstrated excellent safety profile sin multiple in vitro, animal, and clinical studies and are currently being used in a wide variety of craniofacial applications. In this article, the authors discuss the biomaterial properties of PLa and PGa resorbable implants and provide an overview of the use of these polymers in craniofacial surgery. They conclude by relating their experience with an ongoing clinical series using MacroPore PLDLa and FRP implants for various applications,including Le Fort osteotomies, midface/monobloc internal distraction, and craniosynostosis reconstruction.

Orbital floor reconstruction with poly-L/D-lactide implants: clinical, radiological and immunohistochemical study in sheep

In this study the reconstruction capacity of orbital wall in sheep was evaluated when poly-L/D-lactide (PLDLA96) implants were used for large blow-out defects in 18 sheep. The contralateral side, where the defects healed spontaneously, served as controls. The follow-up was 12, 16, 22 and 36 weeks. Healing was evaluated clinically, radiologically, histologically and immunohistochemically. Physiochemical properties of the implants were also studied. At first, the implants were surrounded by elastic capsules, which gradually ossified. At 36 weeks, 60% were still visible and deformed but surrounded by bone. Light microscopy revealed a low grade inflammatory reaction. Expression of Tn-c and cFn was intense throughout the study. Shear strength decreased gradually and was not measurable after 16 weeks. Crystallinity increased steadily from 1.5 to 29.30% and molecular weight decreased from 49,000 to 4186. In CT, the final bony defect was smaller in the reconstructed sides than in the controls. Based on this study it can be concluded that PLDLA96 implant provokes a local inflammation, which does not prevent bone healing. The deformation of the implant, however, indicates that this PLDLA96 plate is not suitable for orbital floor reconstruction.

Biodegradable poly(ether-ester) multiblock copolymers for controlled release applications: Anin vivoevaluation

Multiblock poly(ether-ester)s based on poly(ethylene glycol), butylene terephthalate, and butylene succinate segments were evaluated for their in vivo degradation and biocompatibility in order to establish a correlation with previously reported in vitro results. Porous polymer sheets were implanted subcutaneously for 32 weeks in rats. The degradation was monitored visually (histology), by molecular weight (GPC), and by copolymer composition (NMR). Substitution of the aromatic terephthalate units by aliphatic succinate units was shown to accelerate the degradation rate of the copolymers. Direct correlation of the in vivo and in vitro degradation of the porous implants showed a slightly faster initial molecular weight decrease in vivo. Besides hydrolysis, oxidation occurs in vivo due to the presence of radicals produced by inflammatory cells. In addition, the higher molecular weight plateau of the residue found in vivo indicated a higher solubility of the oligomers in the extracellular fluid compared to a phosphate buffer. Minor changes in the poly(ether-ester) compositions were noted due to degradation. Microscopically, fragmentation of the porous implants was observed in time. At later stages of degradation, macrophages were observed phagocytozing small polymer particles. Both in vitro cytotoxicity studies and histology on in vivo samples proved the biocompatibility of the poly(ether-ester)s.

Bone generation on PHBV matrices: an in vitro study

Bone formation was investigated in vitro by culturing rat marrow stromal osteoblasts in biodegradable, macroporous poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) matrices over a period of 60 days. Foams were prepared after solvent evaporation and solute leaching. PHBV solutions with different concentrations were prepared in chloroform: dichloromethane (1:2, v/v). In order to create a matrix with high porosity and uniform pore sizes, sieved sucrose crystals (300-500 microm) were used. PHBV foams were treated with rf-oxygen plasma (100 W 10 min) to modify their surface chemistry and hydrophilicity with the aim of increasing the reattachment of osteoblasts. Osteoblasts were isolated from rat bone marrow and seeded onto PHBV foams. The cell density on and in the foams was determined with MTS assay. MTS results showed that osteoblasts proliferated on PHBV. Twenty-one days after seeding of incubation, growth of osteoblasts on matrices and initiation of mineralization were observed by confocal laser scanning microscopy. Increasing ALP and osteocalcin secretion during 60 days confirmed the osteoblastic phenotype of the derived stromal cells. SEM, histological evaluations and confocal laser scanning microscopy showed that osteoblasts could grow inside the matrices and lead to mineralization. Cells exhibited spindle-like morphology and had a diameter of 10-30 microm. Based on these, it could confidently be stated that PHBV seems to be a promising polymeric matrix material for bone tissue engineering.

A randomized open-label study of immediate versus delayed polylactic acid injections for the cosmetic management of facial lipoatrophy in persons with HIV infection

BACKGROUND

Polylactic acid (PLA, New-Fill; Medifill, London, UK and Dermic Labs, a division of Eventis, Strasbourg, France) injections into the deep dermis increase fibroblast numbers and collagen production. The substance is widely used in medical applications including cosmetic procedures.

METHODS

HIV-positive individuals with facial lipoatrophy (based on physician assessment) were randomized to immediate (weeks 0, 2 and 4) or delayed (weeks 12, 14 and 16) PLA given as three bilateral injections 2 weeks apart into the deep dermis overlying the buccal fat pad. Assessments included facial ultrasound, visual analogue scales, the Hospital Anxiety and Depression Scale (HADS) and assessment using photographs at weeks 0, 12 and 24.

RESULTS

All 30 patients completed 24 weeks of treatment. The median age of the patients was 41 years, with a mean of 80 months of nucleoside reverse transcriptase inhibitor (NRTI) therapy and a mean of 44 months of prior protease inhibitor (PI) therapy. The median CD4 count was 428-460 cells/microL, with 47% of patients in the immediate-treatment group and 93% of patients in the delayed-treatment groups with <50 HIV-1 RNA copies/mL at baseline. No differences in immunological, virological, biochemical, haematological or metabolic parameters emerged during the study. Injections were well tolerated with only two adverse events (cellulitis and bruising) recorded, one of which delayed treatment by 1 week. There were no discontinuations. Patient visual analogue assessments, photographic assessments, and anxiety and depression scores improved with treatment. At week 12, immediate-treatment patients had significantly better visual analogue scores (7 vs. 1, P<0.001) and lower anxiety scores (6 vs. 9, P=0.056) than delayed-treatment patients. Benefits on visual analogue and HADS scores persisted until week 24.

CONCLUSIONS

PLA injections led to improvements in patient self-perception, anxiety and depression scores in individuals with facial lipoatrophy. Adverse events were uncommon. The benefits of PLA persisted for at least 18 weeks beyond the last injection.

[Conservative treatment of facial wrinkles in the hands of the plastic surgeon]

The conservative treatment of facial wrinkles is an integral part of the growing market for aesthetic surgery. Unfortunately, physicians of any specialty and even nonphysicians tried to occupy this lucrative field without providing serious information and knowledge about a holistic plastic surgical concept, which includes second- and third-step aesthetic surgical procedures when conservative treatment does not suffice. The following article outlines and critically evaluates the current state of knowledge.

Local delivery of IL-1 alpha polymeric microspheres for the immunotherapy of an experimental fibrosarcoma

The immunotherapeutic effects of interleukin-1 alpha (IL-1 alpha) encapsulated within 1-5 microns-diameter poly (D, L-lactide) microspheres and delivered intratumorally into fibrosarcoma-bearing mice were investigated. Such microspheres are avidly taken up by macrophages, and directing IL-1 alpha into these cells may activate them to participate in antitumor responses in vivo. Treating of tumor-bearing mice with IL-1 alpha microspheres has increased their survival rate, as compared with control mice, untreated or treated with microspheres containing bovine serum albumin (BSA). In 20% of the IL-1 alpha-treated mice, a complete tumor regression was observed. The timing of treatment with IL-1 alpha microspheres was crucial; optimal survival and regression rates were observed in mice treated 24 hr postinjection of the tumor cells. Administration of three doses of IL-1 alpha microspheres on days 1, 8, and 15 postinjection of tumor cells resulted in longer survival rates. Histopathology studies on regressed tumors revealed extensive areas of tumor cell degeneration and necrotic tissue surrounded by a large number of inflammatory cells. A similar picture was observed when IL-1 alpha microspheres were administered into the footpad of control mice, whereas the tissue reaction to BSA microspheres was much milder. Thus, it appears that tumor regression is mainly due to the antitumor effects of IL-1 alpha. Further studies are being aimed at increasing the immunotherapeutic efficiency of microspheric IL-1 alpha, used as a single treatment or in combination with other treatment modalities.

Polylactic acid implants (New-Fill) to correct facial lipoatrophy in HIV-infected patients: results of the open-label study VEGA

BACKGROUND

In the absence of currently available therapy to manage facial lipoatrophy, strategies used to compensate for facial fat loss warrant clinical evaluation.

METHODS

The goal of this open-label, single-arm, pilot study was to evaluate the efficacy and safety of facial injections of poly-L-lactic acid (PLA) (New-Fill) in HIV-infected patients with severe facial lipoatrophy. Patients received four sets of injection at day 0 and then every 2 weeks for 6 weeks. Patients were evaluated by clinical examination, facial ultrasonography, and photography at screening and at weeks 6, 24, 48, 72, and 96.

RESULTS

Fifty patients were enrolled. At entry, the median facial fat thickness was equal to zero (range, 0.0-2.1 mm). The median total cutaneous thickness (TCT) increased significantly from baseline : +5.1 mm (range, 2.2-8.6 mm) at week 6, +6.4 mm (range, 3.1-9.1 mm) at week 24, +7.2 mm (range, 4.2-9.6 mm) at week 48, +7.2 mm (range, 3.5-9.6 mm) at week 72 and +6.8 mm (range, 3.9-10.1 mm) at week 96 (P < 0.001). The proportion of patients with TCT > 10 mm was observed in 19% at week 6, 41% at week 24, 61% at week 48, 52% at week 72 and 43% at week 96. In 22 (44%) patients, palpable but non-visible subcutaneous micronodules were observed with a spontaneous resolution in six patients at week 96.

CONCLUSION

The benefit of PLA for the correction of the facial lipoatrophy in HIV-infected patients was clearly demonstrated, with an evident aesthetic and quality of life improvement. The efficacy, safety profile, and the simplicity of the injection schedule of PLA make this filling material a potentially attractive treatment.

Retinal pigment epithelium cell culture on surface modified poly(hydroxybutyrate-co-hydroxyvalerate) thin films

There is currently no effective treatment for the retinal disorders caused by retinal pigment epithelium (RPE) degeneration. Transplantation of allografts is the main strategy towards correction of this malady. Tissue engineering could offer hope and involve the use of biodegradable polymeric templates to replace diseased or lost RPE. In this study PHBV8 film was chosen as a temporary substrate for growing retinal pigment epithelium cells as an organized monolayer before their subretinal transplantation. The surface of the PHBV8 film was rendered hydrophilic by oxygen plasma treatment to increase the reattachment of D407 cells on the film surface. Power and duration was changed, from 50 W, 10 min to 100 W, 20 min during plasma treatment. The effect of these two parameters on surface hydrophilicity, morphology, topography, surface composition of PHBV8 thin films was studied using AFM, SEM, and phase contrast microscopy. The effect of changes in surface characteristics on cell reattachment, spreading and cell growth rate was investigated. It was found that as the treatment level was increased the surface hydrophilicity increased and roughness was decreased probably due to ablation. The PHBV8 film treated with 100 W 10 min was found to be the most suitable for 24 h reattachment of D407 cells. The cells were also grown to confluency as an organized monolayer suggesting PHBV8 film as a potential temporary substrate for subretinal transplantation to replace diseased or damaged retinal pigment epithelium.

Biodegradation and in vivo biocompatibility of rosin: a natural film-forming polymer

The specific aim of the present study was to investigate the biodegradation and biocompatibility characteristics of rosin, a natural film-forming polymer. Both in vitro as well as in vivo methods were used for assessment of the same. The in vitro degradation of rosin films was followed in pH 7.4 phosphate buffered saline at 37 degrees C and in vivo by subdermal implantation in rats for up to 90 days. Initial biocompatibility was followed on postoperative days 7, 14, 21, and 28 by histological observations of the surrounding tissues around the implanted films. Poly (DL-lactic-co-glycolic acid) (PLGA) (50:50) was used as reference material for biocompatibility. Rate and extent of degradation were followed in terms of dry film weight loss, molecular weight (MW) decline, and surface morphological changes. Although the rate of in vitro degradation was slow, rosin-free films showed complete degradation between 60 and 90 days following subdermal implantation in rats. The films degraded following different rates, in vitro and in vivo, but the mechanism followed was primarily bulk degradation. Rosin films demonstrated inflammatory reactions similar to PLGA, indicative of good biocompatibility. Good biocompatibility comparable to PLGA is demonstrated by the absence of necrosis or abscess formation in the surrounding tissues. The study provides valuable insight, which may lead to new applications of rosin in the field of drug delivery.

Tramadol encapsulated into polyhydroxybutyrate microspheres: in vitro release and epidural analgesic effect in rats

BACKGROUND

Controlled release techniques are used to increase the duration of action and decrease the toxicity of drugs. Any controlled release form of tramadol in spinal or epidural blocks has not been studied previously. Tramadol was encapsulated into polyhydroxybutyrate (PHB) microspheres and release kinetics was studied. The epidural analgesic effect of this solution in rats was also compared with free tramadol.

METHODS

Controlled release of tramadol from PHB microspheres into 10 ml of phosphate buffer solution at pH 7.4 and 37 degrees C was studied in vitro. In vivo studies were performed in 40 rats. Epidural catheters were placed during general anaesthesia. Rats were randomly allocated into one of the four study groups to receive normal saline, 4 mg of tramadol, PHB microspheres without tramadol, or 4 mg of tramadol encapsulated into PHB microspheres. Analgesia was evaluated with tail flick tests performed at 52.5 +/- 0.5 degrees C before injection and at intervals up to 30 h after injection. Catalepsy and loss of corneal reflexes were considered as signs of supraspinal toxicity.

RESULTS

In vitro drug release was observed for more than 6 days. Epidural analgesic effects of tramadol released from PHB microspheres were observed for 21 h, whereas an equal dose of free tramadol was effective for less than 5 h. No signs of toxicity were observed.

CONCLUSION

Controlled release of tramadol from PHB microspheres is possible, and pain relief during epidural analgesia is prolonged by this drug formulation compared with free tramadol.

Study of the biodegradation and in vivo biocompatibility of novel biomaterials

The degradation of two rosin-based biomaterials, the glycerol ester of maleic rosin (GMR) and the pentaerythritol ester of maleic rosin (PMR), was examined in vitro in phosphate-buffered saline at pH 7.4 and in vivo in a subcutaneous rat model. Free films of the two biomaterials with mean thickness 0.4+/-0.02 mm were used for the study. The initial biocompatibility was followed by microscopic examination of the inflammatory tissue response to the implanted films. Sample weight loss and molecular weight decline of the free films was used to monitor the degradation quantitatively, while surface morphological changes were analysed for qualitative estimation. Biocompatibility response was followed on post-operative days 7, 14, 21 and 28 and compared with those of poly(DL-lactic-co-glycolic acid) (PLGA) (50:50) films. Both biomaterials showed slow in vitro degradation when compared with the in vivo rate. The mechanism followed was, however, bulk degradation of the films. The penta-esterified form of maleic rosin was observed to degrade more rapidly than glycerol esterified maleic rosin. The acute and subacute inflammatory reactions were characterized by fibrosis at the end of 28 days. The biomaterials showed reasonable tissue tolerance to the extent evaluated. There was a total absence of tissue necrosis or abscess formation for all implanted films. The response, although not identical to that of PLGA, is reasonable, promising new drug delivery applications for rosin biomaterials.

Fabrication of Polymer Root Form Scaffolds to Be Utilized for Alveolar Bone Regeneration

Engineering dental tissues and organs is primarily motivated by a clinical need to restore these lost or diseased structures, in contrast to the use of harvested tissue. The present work focused on designing and characterizing scaffolds suitable for cultivation and implantation into the fresh extraction sockets of teeth, for the purpose of alveolar bone regeneration at a rate and quality higher than that of normal tissue healing for subsequent treatment with dental implants. Three-dimensional hollow root form scaffolds were prepared from poly-L-lactic acid/polyglycolic acid composites (50/50, 65/35, and 75/25 ratios), using the solvent casting compression molding particulate leaching technique. Two different salt particle sizes were used, 150-180 and 180-300 microm, to effect porogenesis. The scaffolds were characterized in vitro and in vivo. The highest percent porosity recorded was 75% with interconnectivity shown by scanning electron microscopy. The scaffolds demonstrated viscoelastic behavior and average strain in response to both static and dynamic forces that were suitable for them under bite-force magnitude anteriorly. The degradation of the root scaffolds depended on composite type, and on salt particle size. Tissue reaction favored samples made with large salt particle size.