Intratumoral chemotherapy with fluorouracil/epinephrine injectable gel: a nonsurgical treatment of cutaneous squamous cell carcinoma

Intralesional Treatments for Invasive Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (cSCC) is the second most frequent cancer in humans and has the potential to progress locally, metastasize, and cause death in a subset of patients. cSCC is especially common in the elderly, and it will probably represent a major health concern in the near future. Surgery is the standard treatment for cSCC, but intralesional therapies can sometimes be considered for certain patients and under certain circumstances. The choice of intralesional treatment depends on the patient's characteristics and the clinician's previous experience and expertise. Here we are reviewing intralesional treatments for cSCC and keratoacanthoma (KA). We have started with some classic drugs, such as methotrexate and 5-fluorouracil, bleomycin, interferon, and cryosurgery, but also comment on electrochemotherapy. Finally, we have focused on novel therapies, some of which are under development, and future perspectives, including intralesional immunotherapy and oncolytic viruses.

Multiple Keratoacanthomas Following Moderna Messenger RNA-1273 COVID-19 Vaccination Resolved With 5-Fluorouracil Treatment: Case Report

Cutaneous reactions have been commonly associated with the Moderna messenger RNA (mRNA) COVID-19 vaccine. Among the reported cutaneous side effects, there have not been any associations reported yet regarding keratoacanthoma development after COVID-19 mRNA vaccination. We report a novel case of an 86-year-old man who experienced an eruption of multiple keratoacanthomas 2 weeks after inoculation with the Moderna mRNA-1273 vaccine that resolved following treatment with intralesional 5-fluorouracil.

Debulking followed by intralesional 5-fluorouracil for the treatment of cutaneous squamous cell carcinoma and keratoacanthoma: A retrospective analysis

Debulking followed by intralesional 5-fluorouracil (deb-IL5FU) is a nonsurgical modality which has been used to treat skin cancer anecdotally for many years. There are few in depth studies examining this technique and success rate of intralesional 5-fluorouracil (IL5FU) for the treatment of cutaneous squamous cell carcinoma (cSCC). To evaluate the response rate of deb-IL5FU for the treatment of cSCC and to determine which patient factors were associated with tumor clearance or treatment failure. A retrospective chart analysis of patients with the diagnosis of cSCC or keratoacanthoma (KA) and subsequent deb-IL5FU treatment. Sixty-one patients with a total of 315 tumors (cSCC and KA), were treated using deb-IL5FU. The overall tumor clearance rate was 89%. This was highest for well-differentiated SCC, SCC, KA-type SCC, and KA. Tumors on the trunk and extremities showed high clearance rates while tumors on the scalp/face/neck/ears showed lower clearance rates. Immunocompetent patients cleared more tumors compared to immunocompromised patients. Limitations included the retrospective nature of this analysis as well as a small sample size. Treatment of cSCC and KA with deb-IL5FU demonstrated high tumor clearance rates. Lower rates of clearance were seen in males, immunosuppressed patients, tumors located on the scalp and face/neck/ears.

Field cancerization: Treatment

The goal of field cancerization treatment is to reduce the risk of developing keratinocyte carcinoma. Selecting the appropriate therapy depends on the degree of field cancerization and the number of invasive cutaneous squamous cell carcinomas. Other considerations include treatment efficacy, cost, side effects, and patient preference. Field therapies are preferred because they address clinically visible disease and subclinical atypia. However, lesion-directed therapies are useful for lesions that are more difficult to treat or those where a histologic diagnosis is required. Patients with extensive field cancerization benefit from a combination of field-directed and lesion-directed treatments. The second article in this continuing medical education series provides a framework to guide evidence-based decision making for field cancerization treatment.

A patient with squamous cell carcinoma in-situ successfully treated with intralesional 5-Fluorouracil and topical trichloroacetic acid

Background: The current gold standard and the first line of treatment for non-melanoma skin cancer is surgical excision. Nevertheless, some patients are not good candidates for surgery when wound healing may be impaired.Methods: A 96-year-old male presented with 1.2 cm by 1.5 cm tumoral lesion with an ill-infiltrated border and central ulceration located on the mid right lower leg. Biopsy confirmed the diagnosis of squamous cell carcinoma (SCC) in situ. The primary lesion was treated centrally to peripherally with multiple intralesional injections of 1.5 mL 5-Fluorouracil (5-FU) (50 mg/mL). The lesion was also treated with a single layer application of 80% Trichloroacetic acid (topical solution). One additional and final treatment of only 80% TCA was performed after three weeks.Results: There was a complete regression of the SCC three weeks after the second treatment.Conclusions: We demonstrate a case of SCC successfully treated with intralesional 5-FU and topical Trichloroacetic acid. Additionally, the SCC in situ was successfully cleared in two treatment sessions with the lowest cumulative dose of 5-FU reported. Intralesional injections of 5-FU and subsequent topical Trichloroacetic acid may be an effective option for patients with SCC who are not eligible for cutaneous surgery.

The synthesis and application of nano doxorubicin- indocyanine green matrix metalloproteinase-responsive hydrogel in chemophototherapy for head and neck squamous cell carcinoma

Background

Head and neck squamous cell carcinoma (HNSCC) is one of the most common malignancies, with high rates of mortality and morbidity worldwide. Owing to the special anatomical location of this tumor, an effective, minimally invasive treatment with low systemic toxicity is highly desirable. Hydrogels have shown great potential for tumor-targeting therapy, with excellent performance. However, there have been few reports on co-loading photosensitizers and chemotherapeutic drugs into hydrogels. In this study, we synthesized a nano doxorubicin-indocyanine green matrix metalloproteinase (MMP)-responsive hydrogel (denoted as NDIMH), combining chemotherapy and phototherapy, to achieve superior antitumor efficacy.

Methods

First, NDIMH was synthesized and characterized by scanning electron microscopy and drug-release assays. Second, the photosensitivity properties and antitumor efficiency of this drug delivery system were studied in vivo and in vitro. Last, the imaging and biodistribution of NDIMH were monitored using the Maestro EX in vivo imaging system.

Results

The nanodrugs loaded into the smart hydrogel exhibited uniform size distribution, excellent size stability, and a sustained release in the presence of MMP-2. NDIMH showed ideal photosensitivity characteristics under light. NDIMH with 808 nm near-infrared (NIR) irradiation effectively inhibited the viability, invasion, and metastasis of SCC-15 in vitro. After intratumoral injection of NDIMH with 808 nm NIR illumination, the hydrogels exhibited favorable synergistic antitumor efficacy and acceptable biosafety. Additionally, fluorescence imaging showed that NDIMH could significantly improve the retention of nanodrugs at the tumor site.

Conclusion

The intratumoral injection of NDIMH with 808 nm NIR irradiation could be a promising chemophototherapy alternative for HNSCC.

Skin cancer: symptoms, mechanistic pathways and treatment rationale for therapeutic delivery

Cancer is a group of diseases categorized by abandoning escalation and multiplication of abnormal cells. Current topical treatments for skin cancer are mainly in the semisolid dosage forms of 5-fluorouracil, imiquimod, etc. Many surgical treatments are also available these days for the treatment of skin cancer, for example, photodynamic therapy, which is approved by the US FDA. The stratum corneum is the main barrier against permeation of topical formulations developed for skin cancer treatment. Liposomes, thermosensitive stealth liposomes, nanoemulsions and polymeric lipid nanoparticles have been used by several researchers to increase skin permeability. In the present paper, major aspects of formulations developed for skin cancer, various types of skin cancer, its etiology and pathogenesis have been emphasized.

A programme of research to set priorities and reduce uncertainties for the prevention and treatment of skin disease

Background

Skin diseases are very common and can have a large impact on the quality of life of patients and caregivers. This programme addressed four diseases: (1) eczema, (2) vitiligo, (3) squamous cell skin cancer (SCC) and (4) pyoderma gangrenosum (PG).

Objective

To set priorities and reduce uncertainties for the treatment and prevention of skin disease in our four chosen diseases.

Design

Mixed methods including eight systematic reviews, three prioritisation exercises, two pilot randomised controlled trials (RCTs), three feasibility studies, two core outcome initiatives, four funding proposals for national RCTs and one completed national RCT.

Setting

Secondary care, primary care and the general population.

Participants

Patients (and their caregivers) with eczema, vitiligo, SCC and PG, plus health-care professionals with an interest in skin disease.

Interventions

Our three intervention studies included (1) barrier enhancement using emollients from birth to prevent eczema (pilot RCT); (2) handheld narrowband ultraviolet light B therapy for treating vitiligo (pilot RCT); and (3) oral ciclosporin (Neoral®, Novartis Pharmaceuticals) compared with oral prednisolone for managing PG (pragmatic national RCT).

Results

Systematic reviews included two overarching systematic reviews of RCTs of treatments for eczema and vitiligo, an umbrella review of systematic reviews of interventions for the prevention of eczema, two reviews of treatments for SCC (one included RCTs and the second included observational studies), and three reviews of outcome measures and outcome reporting. Three prioritisation partnership exercises identified 26 priority areas for future research in eczema, vitiligo and SCC. Two international consensus initiatives identified four core domains for future eczema trials and seven core domains for vitiligo trials. Two pilot RCTs and three feasibility studies critically informed development of four trial proposals for external funding, three of which are now funded and one is pending consideration by funders. Our pragmatic RCT tested the two commonly used systemic treatments for PG (prednisolone vs. ciclosporin) and found no difference in their clinical effectiveness or cost-effectiveness. Both drugs showed limited benefit. Only half of the participants’ ulcers had healed by 6 months. For those with healed ulcers, recurrence was common (30%). Different side effect profiles were noted for each drug, which can inform clinical decisions on an individual patient basis. Three researchers were trained to PhD level and a dermatology patient panel was established to ensure patient involvement in all aspects of the programme.

Conclusions

Findings from this programme of work have already informed clinical guidelines and patient information resources. Feasibility studies have ensured that large national pragmatic trials will now be conducted on important areas of treatment uncertainty that address the needs of patients and the NHS. There is scope for considerable improvement in terms of trial design, conduct and reporting for RCTs of skin disease, which can be improved through wider collaboration, registration of trial protocols and complete reporting and international consensus over core outcome sets. Three national trials have now been funded as a result of this work. Two international initiatives to establish how best to measure the core outcome domains for eczema and vitiligo are ongoing.

Trial registration

Current Controlled Trials Barrier Enhancement for Eczema Prevention (BEEP) (ISRCTN84854178 and NCT01142999), Study of Treatments fOr Pyoderma GAngrenosum Patients (STOP GAP) (ISRCTN35898459) and Hand Held NB-UVB for Early or Focal Vitiligo at Home (HI-Light Pilot Trial) (NCT01478945).

Funding

This project was funded by the National Institute for Health Research (NIHR) Programme Grants for Applied Research programme and will be published in full inProgramme Grants for Applied Research; Vol. 4, No. 18. See the NIHR Journals Library website for further project information.

Prognostic variables in high-risk cutaneous squamous cell carcinoma: a review

Cutaneous squamous cell carcinoma (SCC) is a growing public health problem in the United States. A subset of high-risk SCC exhibits a more aggressive clinical trajectory including increased local recurrence and lymph node metastasis. However, there are no universally accepted criteria to help define and manage these patients. This review provides an overview of the high-risk features of cutaneous SCC, prognostic stratification of various staging systems and treatment options. It further examines the prognostic factors influencing the staging of cutaneous head and neck SCC.

Phase 2 Study of Intratumoral Cisplatin and Epinephrine Treatment for Locally Recurrent Head and Neck Tumors

Local relapses of head and neck tumors are not often eligible for surgical and/or radiotherapy retreatment, and the efficacy of systemic chemotherapy is poor. A greater accumulation and efficacy of anticancer drugs with lower systemic toxicity is theoretically obtained with intratumoral chemotherapy. In experimental studies, epinephrine has been shown to increase the concentration and antitumor effect of intratumoral cisplatin. Fourteen patients with locally recurrent head and neck tumors (median age, 58.7 years) were included in this phase 2 trial. Recurrent tumors (squamous cell carcinomas) were located on the tongue, oral pharynx, or cervical nodes. Prior therapy was surgery and/or radiotherapy with or without intravenous chemotherapy. Inclusion criteria included an Eastern Cooperative Oncology Group/World Health Organization performance status of 0, 1, or 2, an anticipated survival of >3 months, adequate cardiac, kidney, liver, and bone marrow function, and no coagulopathy or carotid invasion. Fifty intratumoral injections of cisplatin-epinephrine (average, 3.6 injections per patient; range, 1 to 5 injections) were given to the 14 patients from November 1998 to July 2000. Patients were treated with cisplatin (1 mg/mL; maximum dose, 50 mg) at an injection volume corresponding to the tumor volume (1 mL/cm3 of tumor; maximum volume, 50 mL). Epinephrine was added at a concentration of 0.02 mg/mL. Intratumoral injections were repeated every 2 to 3 weeks at different locations in the tumors to obtain a homogeneous distribution. Tumor response was evaluated by clinical examination and computed tomography. Eight objective responses were registered among the 14 patients. Four were complete responses, and 4 were partial responses. The average time to disease progression was 11.5 ± 8.9 weeks. Local adverse effects were transient pain, swelling, and erythema at the site of the injection. No nephrotoxicity, neurotoxicity, or ototoxicity was observed. Intratumoral injection of cisplatin and epinephrine in an aqueous solution has a definite antitumor activity in recurrent head and neck cancer with acceptable local tolerance and no major systemic toxic effects except for transient tachycardia and high blood pressure at the time of injection.

Intralesional 5-fluorouracil (FU) as a treatment for nonmelanoma skin cancer (NMSC): A review

The treatment paradigm for nonmelanoma skin cancer remains surgical. This fact combined with its remarkably high incidence positions it as the fifth most costly cancer to treat in the Medicare population. To address this, consideration of alternative medical therapeutics is warranted. Intralesional 5-fluorouracil is a potentially affordable option that may demand further investigation. This literature review examines current data on its efficacy and adverse effects.

Therapeutic Evaluation of Intralesional 5% 5-Fluorouracil in Condyloma Acuminata

Condyloma acumianata is one of the most common virally transmitted diseases. Its prevalence has increased many fold throughout the world. Because all the currently available treatments yield low cure rates with side effects, the search for a new alternative continues. Topically, 5-fluorouracil (5-FU) has been in used for many years to treat various skin diseases. When applied topically in condyloma acuminata, 5-FU results in low cure rates with high recurrences. Therefore, intralesional 5% 5-FU is being evaluated to determine its therapeutic efficacy in condyloma acuminata.

Injectable in situ forming controlled release implant composed of a poly-ether-ester-carbonate and applications in the field of chemotherapy

Polymeric controlled delivery systems hold great promise in the field of modern medicine. Such technology has already been converted into commercially viable products in a myriad of fields. Chemotherapy is an example of such an area where constant efficacious levels of drug can greatly enhance clinical outcomes. The key to designing such therapies is the preparation of the proper delivery system. To this end, a series of bioresorbable polyether-ester-carbonate copolymers have been developed, which when combined with a diluent, are capable injection into the body and consistently forming a drug delivery depot. The study delineated here aimed at producing a more effective treatment of a common drug, paclitaxel, using the polymeric carrier. The polymer carrier system exhibited controlled release of paclitaxel both in vitro and in vivo. Drug concentrations were analyzed by high performance liquid chromatography and apoptotic activity was confirmed through flow cytometry. Relevant success was exhibited by the regression of tumor size following a multiple injection treatment regimen in a murine xenograft model. This multiple injection treatment shows promising results when compared to the traditional paclitaxel paradigm of a single injection for a period of 3 weeks.

Non-surgical treatments of primary, non-melanoma eyelid malignancies: a review

The diagnosis and management of periocular cutaneous malignancies are essential components of an ophthalmologist's practice. Skin cancers comprise nearly one-third of newly diagnosed malignancies. Furthermore, the incidence of skin cancer appears to be increasing. Multiple treatment modalities exist for periocular cutaneous malignancy. Surgical extirpation, often with the combined expertise of a Mohs micrographic surgeon, is typically the first line therapy and is often curative in the periocular region, depending on a variety of factors, including tumour histology, specific location, depth of invasion and surgical technique. However, there are instances where a less invasive, non-surgical treatment option is warranted, including patients who are poor surgical risks or those with diffuse disease. The purpose of this article is to review the literature and describe the non-surgical treatment options, indications and efficacies for non-melanoma primary eyelid malignancies.

Intralesional agents in the management of cutaneous malignancy: a review

Intralesional agents have a role in the management of cutaneous malignancies. In this article, the efficacy, side effects, strengths, limitations, costs, and practical considerations regarding the use of intralesional agents to treat basal cell carcinoma, squamous cell carcinoma, selected cutaneous lymphomas, and even metastatic melanoma are reviewed. Intralesional administration of 5-fluorouracil, interferon, interleukin-2, bleomycin with electrochemotherapy, and aminolevulinic acid with photodynamic therapy are discussed as treatment modalities in basal cell carcinoma. Interferon (∼1.5 M IU, 3 times weekly × 3 weeks) is perhaps the most widely used regimen for basal cell carcinoma. With regard to squamous cell carcinoma, treatment with 5-fluorouracil, methotrexate, interferon, and bleomycin are reviewed. Methotrexate (∼0.3-2.0 mL of 12.5 or 25 mg/mL, two injections ∼2 weeks apart) was perhaps the most widely used agent. Interferon (3 M IU × 3 times weekly for ∼8.5 weeks) and rituximab (10-30 mg per lesion, 3 times weekly for 1 week, possibly repeated 4 weeks later) are sometimes used in the management of primary cutaneous B-cell lymphomas, whereas in primary cutaneous CD30(+) lymphoma intralesional methotrexate (0.4-0.5 mL of 50 mg/mL weekly for 2 weeks) has been used. Finally, the roles of BCG vaccine, cidofovir, rose bengal, and bleomycin with electrochemotherapy for the palliation of metastatic melanoma are reviewed. Intralesional management appears most useful when surgical intervention is not a viable option, for cases in which the cosmetic outcome may be superior, or for situations in which the side effects from systemic chemotherapeutic agents are to be minimized.

[Precancerous and early invasive carcinomas: non-surgical treatment of head and facial skin]

Chronic exposure to sunlight with its high proportion of high energy ultraviolet light is the main cause of the common cutaneous precancerous lesions and carcinomas of the head and neck. This causes a field cancerization effect frequently with multiple actinic keratoses (AKs), basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs). Although demonstrating the best cure rates and lowest recurrence rates, surgical excision rapidly progresses to its limits. Field cancerization requires field therapy. Non-specific caustic agents may remove superficial lesions, however, the modern therapeutic modalities such as topical cytotoxic treatment with 5-fluorouracil, photodynamic therapy with 5-aminolevulinic acid (ALA) or its methyl ester (MeALA), the topical immune response modifier imiquimod or the local application of the cyclooxygenase inhibitor diclofenac are more specific and effective. Intralesional and perilesional injections of cytotoxic agents and interferons as well as the new targeted anti-cancer drugs are further alternatives. The most important aspect, however, is the prophylaxis of chronic photodamage.

Squamous cell carcinoma growth in mice and in culture is regulated by c-Jun and its control of matrix metalloproteinase-2 and -9 expression

Squamous cell carcinoma (SCC) is an invasive malignancy of epidermal keratinocytes. Surgical excision is currently the main treatment; however, this can cause scarring and disfigurement. There is accordingly, an acute need for alternative strategies to treat SCC. The transcription factor c-Jun is expressed in human SCC and another common form of invasive skin cancer, basal cell carcinoma together with the mitogenic marker-proliferating cell nuclear antigen. Here, we have employed DNAzymes (catalytic DNA molecules) targeting c-Jun (Dz13) to inhibit c-Jun expression in SCC cells. Dz13 inhibits SCC proliferation and suppresses solid SCC tumor growth and tumor angiogenesis in severe combined immunodeficient mice. We further demonstrate that Dz13 inhibits c-Jun, together with matrix metalloproteinase (MMP)-2 and MMP-9 expression in the tumors, consistent with DNAzyme inhibition of MMP-2 and MMP-9 gelatinolytic activity by zymography. Dz13 also suppressed the expression of vascular endothelial growth factor and fibroblast growth factor-2 in the tumors. These findings demonstrate that c-Jun regulates SCC growth and suggest that DNAzymes targeting this transcription factor may potentially be useful as inhibitors of cutaneous carcinoma.

Formes galéniques nouvelles en cancérologie

Despite recent emergence of novel therapeutic agents the major progress achieved in cancer treatments results from conventional drugs used for cytotoxic or hormone therapy. Over the past 20 years, a more rational and more pharmacological-based approach to chemotherapy has led to major successes. One of the most promising avenues of research is to improve the pharmacokinetic properties of well-known anticancer drugs (bioavailability, distribution, targeting, drug carriers) by modifications of their formulations (new drug delivery systems). As an example, new pharmaceutical forms of analogs of LH-RH, (microparticles or implants) permitting sustained release of the drug for months, are now largely used in the routine chemotherapy for prostate cancers. Improvement of the oral bioavailabilty of drugs previously administered only by the parenteral route is simplifying treatment protocols. Parenteral delivery of doxorubicine entrapped in liposomes (pegylated liposomes) decreases the cardiotoxicity and increases the half-live of this drug widely used in the treatment of breast carcinomas. Molecular targeting using immunocarriers such as immunoliposomes is also a very strong field of research.

WITHDRAWN: The safety of synthetic paclitaxel by intralesional delivery with OncoGeltrade mark into skin breast cancer metastases: method and results of a clinical pilot trial

Ahead of Print article withdrawn by publisher

Therapieoptionen bei epithelialen Hauttumoren

There has been worldwide a significant rise in the incidence of epithelial skin tumors and their precursors in the past years with an increased number of younger patients affected. The risk factors are identified. The choice of the appropriate treatment for each individual is crucial. Major consideration include high cure rate, low long-term recurrence rate and few side effects. In the following article different therapeutic approaches for actinic keratoses, Bowen's disease, basal cell carcinoma and squamous cell carcinoma are presented and analysed.

Intralesional 5-fluorouracil, lidocaine and epinephrine mixture for the treatment of verrucae: a prospective placebo-controlled, single-blind randomized study

BACKGROUND

The treatment of viral warts remains challenging. A variety of treatment modalities have been used with a range of success. Fluorouracil has been shown to be effective in treating warts but the method of its delivery directly onto the affected tissue has been of little efficacy. We evaluated the safety and efficacy of intralesional 5-fluorouracil in the treatment of verrucae.

METHODS

Seventy-six patients with a total 315 verrucae were randomized to receive either a 5-fluorouracil, lidocaine and epinephrine (5-FU + LE) mixture or serum saline injection into the paired verrucae in the same patient. The mixture of 5-FU (4 cm(3), 50 mg/mL), lidocaine (1 cm(3), 20 mg/mL) and epinephrine (0.0125 mg/mL) was injected into the base of the wart using a mantoux needle. Each lesion was infiltrated with either of the solutions once a week for up to a maximum of 4 weeks, and the patients were followed up for 6 months.

RESULTS

Complete response was noted in an average of 70% of the verrucae treated with the 5-FU + LE mixture and in 29% of those in the placebo group (P < 0.001). No clinically significant systemic and local adverse effects occurred. Pain and burning were noted as an immediate injection pain. Recurrence rates were evaluated and no statistically significant difference between the two groups was found.

CONCLUSIONS

The results demonstrate that treatment of verrucae with 5-FU + LE mixture is safe and effective.

Intralesional chemotherapy for head and neck carcinoma: a review of the literature

In the last decade chemotherapy has gained widespread acceptance in the treatment of oral and pharyngeal cancer. Current standard treatment for advanced lesions consists of concomitant radiation and chemotherapy. This approach has provided marginal improvement of prognosis for Stage III-IV disease. Recent studies have explored the idea that locally delivered cytotoxic drugs could further improve prognosis in this patient population. We review this literature with the objective of popularizing these data and suggesting future directions for treatment and clinical research for head and neck cancer.

Treatment of squamous cell carcinoma with intralesional 5-Fluorouracil

BACKGROUND

5-Fluorouracil (5-FU) has been used topically and intralesionally to treat lesions related to squamous cell carcinoma (SCC) such as actinic keratosis, Bowen's disease, and keratoacanthoma.

OBJECTIVE

We sought to determine whether intralesional 5-FU might be effective in treating a patient with SCC.

METHODS

A patient with SCC at the junction of the right alar crease and right nasolabial fold was treated with eight weekly injections of 5-FU, with doses ranging from 0.8 to 2.4 mL.

RESULTS

A repeat biopsy after the eighth treatment showed total clearance of the cancer, and the patient has remained free of recurrence during a 5-month follow-up period.

CONCLUSION

This modality may provide patients with SCC in cosmetically important locations or in areas that require complex surgery the advantage of a nonsurgical cure.

Modeling of drug release from collagen matrices

Drug release from collagen matrices is in most cases governed by diffusion from swollen matrices but also enzymatic matrix degradation or hydrophobic drug/collagen interactions may contribute. To reduce water uptake and to prolong the release, insoluble collagen matrices have been chemically or dehydrothermally crosslinked. Assuming Fickian diffusion a one-dimensional model was developed and tested that allows description of water penetration, swelling and drug release and that may be expanded considering a subsequent erosion process or interactions. Swelling is described by a volume balance. For dry collagen matrices crosslinked by thermal treatment the existence of a moving front separating the polymer from a gel phase was considered, and a convective term induced by the volume expansion was incorporated. The resulting moving boundary problem was solved using a method based on biquadratic finite elements in both space and time that is stable, shows high accuracy, and is suitable for solving problems with a singularity at the initial time point. The model was verified for insoluble collagen matrices at different crosslinking degrees for both chemical and thermal treatment. For constant diffusion coefficients a close form of the solution was derived yielding equivalent results to the numerical approach.